This is not so much either homework, or me asking for help. Rather, because it's an attempt at improving my learning in my one subject at uni, because I've missed a lot of lectures this semester due to work, and want to make sure I actually learn the subject.
So I thought I would write out summaries on each lecture (I have copies of all the powerpoints) as well summaries on related topics, and if people have any questions at all in relation to my summaries, or ecology in general, I will answer them as well. I don't mind if the questions are not ones I know the answer too, because then I can do some more research, and I'll reference everything as well.
So lecture 1;
Introduction to Ecology - Erik Wapstra
Types of Data - Stewart Nicol
What is ecology?
Ecology is the study of the interactions between organisms and their environments. It can be broken down into a number of different fields. Behavioural ecology is the study of the behaviour of organisms in response to their environment. It addresses questions like how behaviour contributes to the ability of organisms to survive and reproduce, as well as how behaviour can affect population growth. This links into the next field of ecology - population ecology - which is the study of populations and the factors that influence changes (or stability) in populations. Population ecologists try to answer questions like what controls the growth of populations and why are some species more abundant than others. The third sub-discipline of ecology is community ecology. This is not cheap public funded ecology, but rather the study of interactions between organisms and their environments. This is linked strongly with conservation ecology and understanding the best ways of preserving biodiversity. The fourth sub-discipline is ecosystem ecology, which is looking at the ecology of whole ecosystems. It looks at the way energy and nutrients pass through the system, and various nutrient cycles.
Ecologists work across a big range of spatial and temporal scales. Ecologists can study the space that a single species occupies, all the way up to global spaces, such as the effects of changes to the thermohaline cycle on various ecosystems. * In terms of temporal scales, ecologists look at time spans varying from particular moments in a species life, to the change and evolution of an ecosystem over time.
An example of the work of an ecologist.
The Tasmanian Devil (Sacrophilus harrisii) is a small dog sized marsupial carnivore, that is now only found in Tasmania, Australia, although it was once found in much of Australia. Due to the sudden spread of an unusual facial cancer (first discovered in 1996), Tasmanian Devils are now listed as endangered, and have dropped in numbers by around 60%, with drops in the area where the disease first emerged at around 95%. Ecologists are studying the populations of devils and the changes of their populations. They are looking at the habitats of devils and their interactions with other species. Reproductive output and the limits to their potential reproductive output is also an important area being studied. Ecologists are working closely with spatial mathematicians to map and predict the spread of the disease across Tasmania and the interaction between population density and the rate of infection, as well as predicting the successfulness of various proposed responses to the disease. They are also studying how the overall ecosystems will change with declining devil numbers, and the possibility of extinction. There are only two major native carnivores in Tasmania; the Tasmanian devil and the wedge tailed eagle (Aquila audax fleayi), both of which are now seriously endangered (there are less than 200 breeding pairs of wedge tailed eagles left in Tasmania) and the loss of major carnivores could have a significant effect on ecosystems, including rises in populations of herbivores, resulting in further losses of habitat, or possibly rises in populations of herbivores resulting in rises in numbers of other predators, especially snakes, which could result in greater conflicts between animals and humans.
* The thermohaline cycle is the large scale ocean circulation that is driven by temperature and salinity differences in water - especially from the Arctic. It's the circulation system that has been predicted by some people to shut down if there is too much fresh water in the Atlantic ocean due to Greenland melting, causing an ice age in the Northern Hemisphere, and it's currently responsible for pushing warm ocean currents up along the East Coast of the US, as well as along the bottom of Australia. It has a major impact on all weather patterns.
Ecology
Ok so starting some more serious study. I've decided not to do the lectures in order, but rather in order of who took them, as that's how they're presented on the student website.
Behavioural and Evolutionary Ecology
In this field we try to answer questions like: why is a particular animal feeding where it is? Why does it feed alone or in flock? Which direction will it move in? Does it collect all the food it finds? When does it decide to return to a nest. Why did it build a nest there? Why did it lay that number of eggs? Do the parents share food responsibilities? Why do the chicks make so much noise? Are they competing? What determines which ones survive? Etc.
Behaviour is intrinsic to all animals. All animals exhibit some kind of behaviour. It is fundamental to understanding biology as a whole. There is a strong evolutionary aspect to the subject. I.E. how do behaviours relate to success and how did they evolve over time?
Animal behaviour is "all observable processes by which an an animal responds to perceived changes in the internal state of its body or in the external world" - B.F. Skinner or "What and animal does and how it does it" (text book) - also why it does it.
Examples of behaviours include:
Running away from predators
Rejecting foul tasting food
Attracting a mate (and being attracted to good looking mates)
Avoiding hot or cold areas
Migrating to the Northern Hemisphere
Pain avoidance
Singing in the morning (birds more so than people in the shower)
Crying for attention
Marking territory
Feeding offspring
It can also include physiological responses such as secretion from sweat glands and pupil dilation.
Behaviour is extremely diverse within and between species. For example wolves exhibit a variety of social interactions, scent marking, maternal care, howling etc.
An example of animal behaviour is in what Erik Wapstra studies - Sand lizards (Lacerta agilis) in Sweden. He's looking at things like; Why are males green and girls grey/brown? Why aren't all males equally green? Why are some males "sexier" than others? Why do females have sex with multiple partners? Do boys choose girls? Do girls choose boys? Why do males "guard" females?
He is also studying the spotted snow skink (Niveoscincus ocellatus) in Tasmanian - comparing the behaviour of the animal at a cold high altitude site to a warm coastal site. He's been studying this behaviour for over 8 years now and especially looking at the number of offspring in the breeding season and how this correlates to temperature. This has significant impacts for global warming as the gender of these lizards appears to relate to the temperature - as it gets warmer more girls are born. However this relationship was only noticeable at the coastal site. At the significantly colder site there was no such observed relationship.
Another example of behaviour ecology research is investigating the impact of foxes on native species in Australia (and especially Tasmania). i.e. Do native animals have behavioural responses to be able to respond to the risk of foxes? How much variation is there in the native species ability to respond?
Other people at the university are studying behavioural ecology in Antarctica. There is also significant research going into Tasmanian devils and also how their behaviour impacts on the devil facial tumour disease.
The lecture goes on to mention a bunch of other research, but I don't think it's important for me to remember all that
Behavioural and Evolutionary Ecology
In this field we try to answer questions like: why is a particular animal feeding where it is? Why does it feed alone or in flock? Which direction will it move in? Does it collect all the food it finds? When does it decide to return to a nest. Why did it build a nest there? Why did it lay that number of eggs? Do the parents share food responsibilities? Why do the chicks make so much noise? Are they competing? What determines which ones survive? Etc.
Behaviour is intrinsic to all animals. All animals exhibit some kind of behaviour. It is fundamental to understanding biology as a whole. There is a strong evolutionary aspect to the subject. I.E. how do behaviours relate to success and how did they evolve over time?
Animal behaviour is "all observable processes by which an an animal responds to perceived changes in the internal state of its body or in the external world" - B.F. Skinner or "What and animal does and how it does it" (text book) - also why it does it.
Examples of behaviours include:
Running away from predators
Rejecting foul tasting food
Attracting a mate (and being attracted to good looking mates)
Avoiding hot or cold areas
Migrating to the Northern Hemisphere
Pain avoidance
Singing in the morning (birds more so than people in the shower)
Crying for attention
Marking territory
Feeding offspring
It can also include physiological responses such as secretion from sweat glands and pupil dilation.
Behaviour is extremely diverse within and between species. For example wolves exhibit a variety of social interactions, scent marking, maternal care, howling etc.
An example of animal behaviour is in what Erik Wapstra studies - Sand lizards (Lacerta agilis) in Sweden. He's looking at things like; Why are males green and girls grey/brown? Why aren't all males equally green? Why are some males "sexier" than others? Why do females have sex with multiple partners? Do boys choose girls? Do girls choose boys? Why do males "guard" females?
He is also studying the spotted snow skink (Niveoscincus ocellatus) in Tasmanian - comparing the behaviour of the animal at a cold high altitude site to a warm coastal site. He's been studying this behaviour for over 8 years now and especially looking at the number of offspring in the breeding season and how this correlates to temperature. This has significant impacts for global warming as the gender of these lizards appears to relate to the temperature - as it gets warmer more girls are born. However this relationship was only noticeable at the coastal site. At the significantly colder site there was no such observed relationship.
Another example of behaviour ecology research is investigating the impact of foxes on native species in Australia (and especially Tasmania). i.e. Do native animals have behavioural responses to be able to respond to the risk of foxes? How much variation is there in the native species ability to respond?
Other people at the university are studying behavioural ecology in Antarctica. There is also significant research going into Tasmanian devils and also how their behaviour impacts on the devil facial tumour disease.
The lecture goes on to mention a bunch of other research, but I don't think it's important for me to remember all that
Lecture 2 (EW)
The basics of studying behaviour.
Because behaviour is so diverse, a range of different techniques are needed to study it. Behaviour can range from the twitch of muscles to sophisticated social interactions.
Repeatability and functionality.
A behaviour is consistent and allows repeated observation. This means it can be measured reliably and used to test hypotheses. It can be broken down into recognisable and measurable units (patterns). Individuals perform the same way each time (for example; scratching or nest building). It should be recognisable and convey a meaning (functionality). Behaviour must have a function or purpose. This should be conveyed by behavioural ecologists in their description of the behaviour.
How could you quantify "laughter?" What kind of hypotheses could you set up? It can be seen in many species, not just humans. Alternatively so can grief and sadness.
Purpose is a difficult concept in studying animal behaviour. All behaviours can be assigned a purpose and meaning and it could be said that animals have a sense of what needs to be achieved but that does not imply that they wake up in the morning and think "what do I need to achieve today?" It is important not to assign human emotions and motivations to animals (anthropomorphism). However all behaviours do have a purpose in terms of survival and ultimately reproductive output (i.e. fitness). This leads to the question of what is the purpose of a behaviour and why does the animal do it?
The Dutch zoologist and ethologist Nikolass Tinbergen (who won a Nobel prize in 1973 for physiology for discoveries in the organisation and elicitation of individual and social behaviour patterns in animals, and also taught Richard Dawkins) proposed that there are 4 questions we should ask about any animal behaviour.
The first two are proximate mechanisms - they relate to the specific behaviour being observed.
1. Causation (mechanism): What are the stimuli that elicit the observed response and how has it been modified through learning? How does the behaviour function on a molecular, physiological, neuro-ethological, cognitive and social level and what are the relationships between each level?
2. Development (Ontogeny): How does the behaviour change as the animal ages? What early experiences are necessary for the behaviour to be shown? Which developmental steps and environmental factors play a role in the behaviour and how?
The second pair are ultimate mechanism - looking at the behaviour as a whole and how it came about.
3. Evolution (phylogeny): How does the behaviour compare to similar behaviour in related species? How might it have arisen through the process of phylogeny? Why did it evolve in this manner and not another manner?
4. Function (Adaptation): How does the behaviour impact on the animals chances of survival and reproduction?
For example Antechinus sp. exhibits the behaviour of selectively feeding towards the most energetically rewarding food. We can apply these four questions to this behaviour.
Function; Antechinus sp. feeds selectively so as to only take the most nutritious prey to maximise foraging efficiency. It can save energy by not eating and digesting less nutritious prey, which would result in a lower return of energy for energy invested. Animals that do so have a higher chance of survival as they have more energy.
Mechanism: It feeds selectively because its visual and tactile senses are most responsive to large and active prey, and possibly it is unable to handle smaller prey.
What causes a behaviour can also be linked into motivation. Understanding the causation of behaviour requires knowledge of how external and internal factors affect the nervous system. For example collared doves that are put together do not mate immediately. They need stimulus. This stimulus is the courtship displays of the male that induces the female to follow the male and help build a nest, leading to mating and laying. However a female can be induced into the same behaviour just by using a projected image of a male courtship display, rather than a real male. This causes hormonal changes in the female required for egg laying. Alternatively these hormones can be injected into the female for the same response.
Development: Antechinus sp. feeds selectively either because it learned the behaviour from a young age or because it has an innate choice of particular prey items.
Evolution: Antechinus sp. feeds selectively because ancestors that were less discriminating were less likely to survive and reproduce.
"Nothing in biology makes sense except in the light of evolution" - Theodosius Dobzhansky, 1973
(full text of essay here) (I will comment on this after finishing the lecture).
This statement is particularly true of animals behaviour.
What is evolution and how does it work?
Evolution means change. Biological evolution: change in the properties of populations of organisms or groups of such populations, over the course of generations. Or the process of biological and organic change in organisms by which descendants come to differ from their ancestors.
Descent with modification (and diversification)
It can be slight or substantial and happen over short or long periods of time.
It is not changes in a single individual - only the differences between parents and their children, but also the continuation of heritable traits over generations. Organisms do not necessarily evolve into more complex forms.
Textbook definition;
"All the changes that have transformed life on Earth from its earliest beginnings to the diversity that characterises it today."
Evolution is the basic principle of modern biology (including behaviour). It is a framework for understanding features of all living things including;
Speciation/phylogeny
ecology
behaviour
biogeography
physiology
molecular biology
biochemistry
and has implications for anthropology, sociology and philosophy (and thus how we view ourselves).
Natural Selection. At the core of evolutionary theory is Charles Darwin and the publication of The Origin of Species (1859).
"If I were to give an award for the single best idea anyone has ever had, I'd give it to Darwin, ahead of Newton and Einstein and everyone else. In a single stroke, the idea of evolution by natural selection unifies the realm of life, meaning, purpose, with the realm of space and time, and cause and effect, mechanism and physical law." - Daniel Dennett (1995).
What is Natural Selection?
Natural Selection is the means by which evolution occurs. It is sometimes called "survival of the fittest" although this term is an over-simplification. Essentially the characteristics of each offspring vary from those of their parents (compare yourself to your parents and your siblings for example. Are you completely identical? I have an identical twin and we're not completely identical...) This variation results in variation in their chances of survival and reproduction. Particular environmental factors will make some traits more likely to survive and reproduce than others. Thus the favoured characteristics will accumulate in the population. Natural selection is not due to chance, but obviously there is randomness in the differences of each generation. Can be selective of alleles, genotypes, populations and species.
Not all gene combinations are equally suited to a particular environment, and individuals differ in their biological fitness.
Fitness
What is meant by fitness?
Fitness: an "individual's" reproductive success is its fitness.
Fitness is measured as number of descendants per individual counted as newly produced offspring (fertilised eggs or newborns) after 1 generation. Or sometimes after multiple generations (grand kids etc.). Basically it is the number of descendants with your genes that you leave behind.
Natural selection is differential reproduction by individuals of different genotypes.
1. Individuals are not the same.
2. They have heritable genetic differences.
3. They are in competition (and there are winners and losers).
4. Different individuals have different numbers of progeny.
5. The form of the trait that leads to the most progeny becomes more common over generations = evolution.
For natural selection to occur, there must be variability in phenotypes and phenotypes must differ in some measure of fitness.
Selection pressure
What is selection pressure?
Selection pressure is the strength of environmental effects on the fitness of different individuals. Or; How strongly does the environment differentially affect different-looking individuals? The change in the population from one generation to another is the response to selection. Without selection pressure there can be no evolution through natural selection.
Studying Evolution; How do you do it?
Adaptations are often complex. For example behavioural changes usually involve changes in physiology, biochemical processes, hormones and morphology. Costs and benefits need to be taken into account. For example a big tail might help get girls but get caught in undergrowth, be energetically expensive and make it hard to fly. The benefit needs to outweigh the cost.
Constraints on evolution; All species do not behave in the same way - Why not? Constraints can be phylogenetic, physiological, or behavioural.
Behavioural Constraints
Behaviours evolve under selective pressure. Foraging strategies need to both get the best food but avoid predators. Display behaviours to attract mates might also attract predators. Displays also take energy, they need to be able to acquire that from somewhere.
Physiological constraints
Principal constraints are trade-offs in the allocation of energy. There is only so much energy to go around and if it's used for one function it can't be used for another. There can be numerous reasons for limits on intake of energy. Physics is also important. I.e. leg length vs leg strength (longer legs will be weaker unless more energy is invested in more strength etc.)
Phylogenetic constraints
History of species limits variation in characters that evolution can act on.
Feathers in birds (not sure what this limits)
Ectothermy/endothermy leads to thermal dependence of behaviour
Exoskeletons in arthropods limits size.
Behaviour in the context of evolution
Why does the behaviour persist/evolve? - There must be some evolutionary fitness gain.
Leads to more questions;
What is the evolutionary fitness gain?
How does it increase either survival or reproductive output of the individual?
How is the change achieved?
What limits it? Does the behaviour incur a cost?
If it incurs a cost, is it outweighed by its benefit at some time and place during the individuals life cycle?
The basics of studying behaviour.
Because behaviour is so diverse, a range of different techniques are needed to study it. Behaviour can range from the twitch of muscles to sophisticated social interactions.
Repeatability and functionality.
A behaviour is consistent and allows repeated observation. This means it can be measured reliably and used to test hypotheses. It can be broken down into recognisable and measurable units (patterns). Individuals perform the same way each time (for example; scratching or nest building). It should be recognisable and convey a meaning (functionality). Behaviour must have a function or purpose. This should be conveyed by behavioural ecologists in their description of the behaviour.
How could you quantify "laughter?" What kind of hypotheses could you set up? It can be seen in many species, not just humans. Alternatively so can grief and sadness.
Purpose is a difficult concept in studying animal behaviour. All behaviours can be assigned a purpose and meaning and it could be said that animals have a sense of what needs to be achieved but that does not imply that they wake up in the morning and think "what do I need to achieve today?" It is important not to assign human emotions and motivations to animals (anthropomorphism). However all behaviours do have a purpose in terms of survival and ultimately reproductive output (i.e. fitness). This leads to the question of what is the purpose of a behaviour and why does the animal do it?
The Dutch zoologist and ethologist Nikolass Tinbergen (who won a Nobel prize in 1973 for physiology for discoveries in the organisation and elicitation of individual and social behaviour patterns in animals, and also taught Richard Dawkins) proposed that there are 4 questions we should ask about any animal behaviour.
The first two are proximate mechanisms - they relate to the specific behaviour being observed.
1. Causation (mechanism): What are the stimuli that elicit the observed response and how has it been modified through learning? How does the behaviour function on a molecular, physiological, neuro-ethological, cognitive and social level and what are the relationships between each level?
2. Development (Ontogeny): How does the behaviour change as the animal ages? What early experiences are necessary for the behaviour to be shown? Which developmental steps and environmental factors play a role in the behaviour and how?
The second pair are ultimate mechanism - looking at the behaviour as a whole and how it came about.
3. Evolution (phylogeny): How does the behaviour compare to similar behaviour in related species? How might it have arisen through the process of phylogeny? Why did it evolve in this manner and not another manner?
4. Function (Adaptation): How does the behaviour impact on the animals chances of survival and reproduction?
For example Antechinus sp. exhibits the behaviour of selectively feeding towards the most energetically rewarding food. We can apply these four questions to this behaviour.
Function; Antechinus sp. feeds selectively so as to only take the most nutritious prey to maximise foraging efficiency. It can save energy by not eating and digesting less nutritious prey, which would result in a lower return of energy for energy invested. Animals that do so have a higher chance of survival as they have more energy.
Mechanism: It feeds selectively because its visual and tactile senses are most responsive to large and active prey, and possibly it is unable to handle smaller prey.
What causes a behaviour can also be linked into motivation. Understanding the causation of behaviour requires knowledge of how external and internal factors affect the nervous system. For example collared doves that are put together do not mate immediately. They need stimulus. This stimulus is the courtship displays of the male that induces the female to follow the male and help build a nest, leading to mating and laying. However a female can be induced into the same behaviour just by using a projected image of a male courtship display, rather than a real male. This causes hormonal changes in the female required for egg laying. Alternatively these hormones can be injected into the female for the same response.
Development: Antechinus sp. feeds selectively either because it learned the behaviour from a young age or because it has an innate choice of particular prey items.
Evolution: Antechinus sp. feeds selectively because ancestors that were less discriminating were less likely to survive and reproduce.
"Nothing in biology makes sense except in the light of evolution" - Theodosius Dobzhansky, 1973
(full text of essay here) (I will comment on this after finishing the lecture).
This statement is particularly true of animals behaviour.
What is evolution and how does it work?
Evolution means change. Biological evolution: change in the properties of populations of organisms or groups of such populations, over the course of generations. Or the process of biological and organic change in organisms by which descendants come to differ from their ancestors.
Descent with modification (and diversification)
It can be slight or substantial and happen over short or long periods of time.
It is not changes in a single individual - only the differences between parents and their children, but also the continuation of heritable traits over generations. Organisms do not necessarily evolve into more complex forms.
Textbook definition;
"All the changes that have transformed life on Earth from its earliest beginnings to the diversity that characterises it today."
Evolution is the basic principle of modern biology (including behaviour). It is a framework for understanding features of all living things including;
Speciation/phylogeny
ecology
behaviour
biogeography
physiology
molecular biology
biochemistry
and has implications for anthropology, sociology and philosophy (and thus how we view ourselves).
Natural Selection. At the core of evolutionary theory is Charles Darwin and the publication of The Origin of Species (1859).
"If I were to give an award for the single best idea anyone has ever had, I'd give it to Darwin, ahead of Newton and Einstein and everyone else. In a single stroke, the idea of evolution by natural selection unifies the realm of life, meaning, purpose, with the realm of space and time, and cause and effect, mechanism and physical law." - Daniel Dennett (1995).
What is Natural Selection?
Natural Selection is the means by which evolution occurs. It is sometimes called "survival of the fittest" although this term is an over-simplification. Essentially the characteristics of each offspring vary from those of their parents (compare yourself to your parents and your siblings for example. Are you completely identical? I have an identical twin and we're not completely identical...) This variation results in variation in their chances of survival and reproduction. Particular environmental factors will make some traits more likely to survive and reproduce than others. Thus the favoured characteristics will accumulate in the population. Natural selection is not due to chance, but obviously there is randomness in the differences of each generation. Can be selective of alleles, genotypes, populations and species.
Not all gene combinations are equally suited to a particular environment, and individuals differ in their biological fitness.
Fitness
What is meant by fitness?
Fitness: an "individual's" reproductive success is its fitness.
Fitness is measured as number of descendants per individual counted as newly produced offspring (fertilised eggs or newborns) after 1 generation. Or sometimes after multiple generations (grand kids etc.). Basically it is the number of descendants with your genes that you leave behind.
Natural selection is differential reproduction by individuals of different genotypes.
1. Individuals are not the same.
2. They have heritable genetic differences.
3. They are in competition (and there are winners and losers).
4. Different individuals have different numbers of progeny.
5. The form of the trait that leads to the most progeny becomes more common over generations = evolution.
For natural selection to occur, there must be variability in phenotypes and phenotypes must differ in some measure of fitness.
Selection pressure
What is selection pressure?
Selection pressure is the strength of environmental effects on the fitness of different individuals. Or; How strongly does the environment differentially affect different-looking individuals? The change in the population from one generation to another is the response to selection. Without selection pressure there can be no evolution through natural selection.
Studying Evolution; How do you do it?
Adaptations are often complex. For example behavioural changes usually involve changes in physiology, biochemical processes, hormones and morphology. Costs and benefits need to be taken into account. For example a big tail might help get girls but get caught in undergrowth, be energetically expensive and make it hard to fly. The benefit needs to outweigh the cost.
Constraints on evolution; All species do not behave in the same way - Why not? Constraints can be phylogenetic, physiological, or behavioural.
Behavioural Constraints
Behaviours evolve under selective pressure. Foraging strategies need to both get the best food but avoid predators. Display behaviours to attract mates might also attract predators. Displays also take energy, they need to be able to acquire that from somewhere.
Physiological constraints
Principal constraints are trade-offs in the allocation of energy. There is only so much energy to go around and if it's used for one function it can't be used for another. There can be numerous reasons for limits on intake of energy. Physics is also important. I.e. leg length vs leg strength (longer legs will be weaker unless more energy is invested in more strength etc.)
Phylogenetic constraints
History of species limits variation in characters that evolution can act on.
Feathers in birds (not sure what this limits
)Ectothermy/endothermy leads to thermal dependence of behaviour
Exoskeletons in arthropods limits size.
Behaviour in the context of evolution
Why does the behaviour persist/evolve? - There must be some evolutionary fitness gain.
Leads to more questions;
What is the evolutionary fitness gain?
How does it increase either survival or reproductive output of the individual?
How is the change achieved?
What limits it? Does the behaviour incur a cost?
If it incurs a cost, is it outweighed by its benefit at some time and place during the individuals life cycle?
Nothing in Biology Makes Sense Except in the Light of Evolution - Theodosius Dobzhansky
Interesting essay and good procrastination. Not much information that I hadn't heard before apart from some of the awesome specific examples, like the larva of the fly Drosophila carciniphila live only in the nephric grooves beneath the flaps of the third maxilliped of the land crab Geocarcinus ruricola which is found on certain islands in the Caribbean. Also Dobzhansky makes the rather obvious mistake of failing to apply his same essay title to humans, and argues that God created the world 14.7 billion years ago and it has evolved since then (obviously religion is another animal behaviour, and a great deal of research has gone into explaining using Tinbergen's 4 questions etc.
Interesting essay and good procrastination
. Not much information that I hadn't heard before apart from some of the awesome specific examples, like the larva of the fly Drosophila carciniphila live only in the nephric grooves beneath the flaps of the third maxilliped of the land crab Geocarcinus ruricola which is found on certain islands in the Caribbean. Also Dobzhansky makes the rather obvious mistake of failing to apply his same essay title to humans, and argues that God created the world 14.7 billion years ago and it has evolved since then (obviously religion is another animal behaviour, and a great deal of research has gone into explaining using Tinbergen's 4 questions etc.Evolutionary Principles, Sexual Selection and Life History Theory (EW).
This presentation is a combination of the last lecture with some new slides. I will skip over things that have already been covered.
Natural selection; phenotypic vs genotypic variablity - do you need both for selection to take place. That is, the observable physical nature and behaviour of the animal vs it's genetic make up. Selection acts on the phenotype by it will change genotype if the phenotypes differ in genotype. That is to say that the selection will occur in the actual physical nature and actions of the organism, and if there is a genetic relationship to the variation in behaviour or physiology of the organism then the genotype will change - but possibly their could be a change in behaviour without a change in genetics. The environmental effects on phenotypes is call phenotypic plasticity.
Example - compare the evolution of height in giraffes with the changes in height of humans. i.e. Giraffes evolved to be taller because taller giraffes have access to more food, meaning they have more energy and are evolutionary fitter. On the other hand, humans are taller today than in the past because of changes to nutrition rather than any selective pressure. This is phenotypic plasticity, not genetic. ie. Phenotypes have changed by genes have not.
Sexual selection.
Sexual selection is the fact that different members of the same species produce different numbers of children due to variation in their ability to get mates. It is selection for characters that enhance mating success and is a form of natural selection. It affects number of offspring. Male reproductive success is based on sexual selection. Female reproductive success is based on number of offspring (fecundity selection - ie. more fecund females will pass on more genes than less fecund females) and offspring success (sexual selection).
Sexual selection arises because males and females have different sexual strategies. Females have few large gametes while males have many small gametes. Males therefore have a strategy of trying to mate with as many females as possible, although because all males have the same strategy complexities arise. Females eggs are fertilised by one male, so there is strong selection on females to choose the best partner. Females make a much larger investment in mating than males, so are more selective. This leads to sexual selection and sexual conflict, and is why males often are very colourful with interesting features etc.
Sexual selection was Darwin's solution to the problem of why conspicuous traits such as bright colours, horns and displays of males of many species have evolved. Darwin proposed two types of sexual selection.
1. Contests between males for access to females (intrasexual).
2. Female choice (or "preference") of some male phenotypes over others (intersexual).
"Sexual selection depends not on the struggle for existence, but a struggle between males for the passions of females, the result of which is not death of an unsuccessful, but few or no offspring." Darwin (1871).
Elephant seal reproductive success.
Male elephant seals fight for access to females. Only a small portion of males succeed in mating, and then guard many females, most of which reproduce with the strongest males. For example a study by Gould and Gould (1997) found that of 140 males and females, 1 male produced 93 weaned offspring, the next best 82, then 41, the next five produced a total of 42 and the other 132 produced none. On the other hand almost 60% of females produced offspring.
Mechanisms of sexual selection and favoured characters
Mechanism; Same sex contests.
Characters favoured; large size, strength, weapons, threat signals
Mechanism; mate preference by females
Characters favoured; attractive and stimulatory features, food offerings, resources
Mechanism; scramble
Characters favoured; early and rapid location of mates, well developed sensory organs.
mechanism; endurance rivalry
characters favoured; ability to stay reproductively active
mechanism; sperm competition
characters favoured; ability to displace rival sperm, production of abundant sperm, mate guarding behaviour, sperm plugs.
Contests between males
Males engage in contests directly for females and/or resources. They use a range of contests such as physical fights or displays. Displays can vary such as displays about size, use of ornaments, threat displays or vocalisations. In vertebrates male size is approximately equal to success but experience is also very important and using alternative tactics.
In elephant seals size determines male success. In deer it is the size of their weapons (antlers) that determines contest success.
Often there are relationships between non sexual natural selection and sexual selection.
Female mate selection
Many traits used by males in male-male contests are also used by females to select mates. Traits included in female selection include body size, male ornamentation, male vocalisation, display behaviours, variety of diverse traits such as nest building skills, bowers, food gifts etc.
"They charm the female by vocal or instrumental music of the most varied kinds. They are ornamented by all sorts of combs, wattles, protuberances, horns, air distended sacs, top-knots, naked shafts, plumes and lengthened feathers gracefully spring from all parts of the body. The beak and the naked skin about the head, and the feathers are often gorgeously coloured. The males sometimes pay court by dancing, or by fantastic antics performed either on the ground or in the air...
I see no reason to doubt that females, by selecting, during thousands of generations, the most melodious or beautiful males, according to their standard of beauty, might produce a marked effect...
We may conclude that the pairings of these birds is not left to chance; but that those males which are best able by their various charms to please or excite the female are ...accepted" - Darwin (1871)
edit; This is only half the lecture but I have to go to a study group. Will finish it off when I get back
This presentation is a combination of the last lecture with some new slides. I will skip over things that have already been covered.
Natural selection; phenotypic vs genotypic variablity - do you need both for selection to take place. That is, the observable physical nature and behaviour of the animal vs it's genetic make up. Selection acts on the phenotype by it will change genotype if the phenotypes differ in genotype. That is to say that the selection will occur in the actual physical nature and actions of the organism, and if there is a genetic relationship to the variation in behaviour or physiology of the organism then the genotype will change - but possibly their could be a change in behaviour without a change in genetics. The environmental effects on phenotypes is call phenotypic plasticity.
Example - compare the evolution of height in giraffes with the changes in height of humans. i.e. Giraffes evolved to be taller because taller giraffes have access to more food, meaning they have more energy and are evolutionary fitter. On the other hand, humans are taller today than in the past because of changes to nutrition rather than any selective pressure. This is phenotypic plasticity, not genetic. ie. Phenotypes have changed by genes have not.
Sexual selection.
Sexual selection is the fact that different members of the same species produce different numbers of children due to variation in their ability to get mates. It is selection for characters that enhance mating success and is a form of natural selection. It affects number of offspring. Male reproductive success is based on sexual selection. Female reproductive success is based on number of offspring (fecundity selection - ie. more fecund females will pass on more genes than less fecund females) and offspring success (sexual selection).
Sexual selection arises because males and females have different sexual strategies. Females have few large gametes while males have many small gametes. Males therefore have a strategy of trying to mate with as many females as possible, although because all males have the same strategy complexities arise. Females eggs are fertilised by one male, so there is strong selection on females to choose the best partner. Females make a much larger investment in mating than males, so are more selective. This leads to sexual selection and sexual conflict, and is why males often are very colourful with interesting features etc.
Sexual selection was Darwin's solution to the problem of why conspicuous traits such as bright colours, horns and displays of males of many species have evolved. Darwin proposed two types of sexual selection.
1. Contests between males for access to females (intrasexual).
2. Female choice (or "preference") of some male phenotypes over others (intersexual).
"Sexual selection depends not on the struggle for existence, but a struggle between males for the passions of females, the result of which is not death of an unsuccessful, but few or no offspring." Darwin (1871).
Elephant seal reproductive success.
Male elephant seals fight for access to females. Only a small portion of males succeed in mating, and then guard many females, most of which reproduce with the strongest males. For example a study by Gould and Gould (1997) found that of 140 males and females, 1 male produced 93 weaned offspring, the next best 82, then 41, the next five produced a total of 42 and the other 132 produced none. On the other hand almost 60% of females produced offspring.
Mechanisms of sexual selection and favoured characters
Mechanism; Same sex contests.
Characters favoured; large size, strength, weapons, threat signals
Mechanism; mate preference by females
Characters favoured; attractive and stimulatory features, food offerings, resources
Mechanism; scramble
Characters favoured; early and rapid location of mates, well developed sensory organs.
mechanism; endurance rivalry
characters favoured; ability to stay reproductively active
mechanism; sperm competition
characters favoured; ability to displace rival sperm, production of abundant sperm, mate guarding behaviour, sperm plugs.
Contests between males
Males engage in contests directly for females and/or resources. They use a range of contests such as physical fights or displays. Displays can vary such as displays about size, use of ornaments, threat displays or vocalisations. In vertebrates male size is approximately equal to success but experience is also very important and using alternative tactics.
In elephant seals size determines male success. In deer it is the size of their weapons (antlers) that determines contest success.
Often there are relationships between non sexual natural selection and sexual selection.
Female mate selection
Many traits used by males in male-male contests are also used by females to select mates. Traits included in female selection include body size, male ornamentation, male vocalisation, display behaviours, variety of diverse traits such as nest building skills, bowers, food gifts etc.
"They charm the female by vocal or instrumental music of the most varied kinds. They are ornamented by all sorts of combs, wattles, protuberances, horns, air distended sacs, top-knots, naked shafts, plumes and lengthened feathers gracefully spring from all parts of the body. The beak and the naked skin about the head, and the feathers are often gorgeously coloured. The males sometimes pay court by dancing, or by fantastic antics performed either on the ground or in the air...
I see no reason to doubt that females, by selecting, during thousands of generations, the most melodious or beautiful males, according to their standard of beauty, might produce a marked effect...
We may conclude that the pairings of these birds is not left to chance; but that those males which are best able by their various charms to please or excite the female are ...accepted" - Darwin (1871)
edit; This is only half the lecture but I have to go to a study group. Will finish it off when I get back
Evolutionary Principles, Sexual Selection and Life History pt2 (EW)
Sexual selection can also be seen very clearly in humans. Fashion, make up, demonstrations of wealth and power, sport, dancing etc.
(there was a lot of stuff from the previous lecture here).
An example of a physiological constraint is the tracheal system in insects limits their oxygen and stops them from being able to grow larger. For them to grow larger they would need massive changes to their oxygen dispersal which would be backwards survival steps before they could get to a stage where the changes would allow them to grow larger. Evolution only occurs in relation to the present - not with a future direction in mind.
Life history theory and Evolution
Definition: An individual's pattern of allocation, throughout life of time and energy to various fundamental activities such as growth, repair of cell and tissue damage and reproduction.
Phenotypes can be described as a series of traits. Reproductive traits include age and size at maturity, longevity/lifespan, reproductive frequency, number and size of offspring. The study of life history of evolution attempts to explain why these traits vary between species and within species. A collection of traits represent the fitness of an individual. For example a tortoise matures at 30 years, live for 120 and reproduce around every 5 years. Fruit flies mature at 12 days, live for months and reproduce repeatedly.
Ideally an organism would live forever and produce an infinite number of offspring each generation. However this is not possible so organisms evolve with the best compromise between different longevity and fertility patterns open to it, given the trade-offs imposed by external (and internal) constraints. Because life histories are about trade-offs between traits, traits are inter-linked. It is difficult to look at traits in isolation, so when you look at one you should consider the consequences this trait has on other traits. Life history strategies evolve to maximise individual fitness (number of offspring in next generation). TRV stands for the total reproductive value. At any stage of lifespan TRV will be the sum of Current Reproductive Value and Residual Reproductive Value. TRV = CRV + RRV. The things an organism uses for reproduction now will detract from what it can use later for reproduction and survival. Another trade off; reproductive intensity versus reproductive frequency.
Reproduction
4 main variables to consider;
1. When to start reproducing (ie. at what age they reach reproductive maturity).
2. How often to reproduce in a lifetime.
3. How much energy to put into each reproductive effort.
4 How many offspring produced at each reproductive event?
For example different birds might produce a different number of eggs; Ring-neck pheasant's produce around 20 while a kiwi only produces 1.
Decisions at the individual level
How many eggs? Maximum or optimum?
David Lack predicted that birds should lay the number of eggs that maximise the number of you reaching maturity, not the maximum number that can lay. This is known as the "Lack Clutch." However this can easily be tested by adding or removing eggs from a nest and it's been found that birds lay less eggs than the Lack clutch.
(My guess would be that if birds lay less than the optimum but then there is a change in environment that leads to less than usual resources they'll still have a better chance of having their offspring survive, while if they have too many offspring and the drop in resources mean that the food is spread equally across more offspring than can be supported they will all die. Because of the high variability of climate from one year to the next, it's fairly probably that there will be occasions when there is less than ideal food supply).
Plants and seeds
Plants essentially have 2 strategies. They can have a few large seeds with a lot of reproductive energy invested in a small number or they can have a lot of small seeds with not so much reproductive energy invested per seed. For example Eucalyptus regnans has a life span of 400+ years, it grows up to 100m tall, it has leaves 10-20cm long and fruit that are less than 20g. Coconut palm, on the other hand, has a lifespan of 100 years, grows to 30m, has leaves 4 to 6m long and fruit that weigh 1-2kg. Eucalyptus regnans produces many more seeds than coconut palms, but both are successful in their environments.
Life history strategies are best studied within a single animal group. Phylogenetic constraints may restrict what is possible.
The advantages of a large seed/egg size are that you can out compete your neighbours, grow faster, produce more seed when mature, flower or mature first and escape predators better.
The advantages of small seed/egg are that there are more of them, they may disperse more significantly over larger areas, smaller body size and less competition with parents.
Age at first reproduction.
If there were no trade-offs with reproduction then obviously the best thing to do is start reproducing at birth so as to maximise the number of offspring over the whole time. Mortality rates play a big role in determining the optimal time to start reproducing = survivorship curves. Low early mortality means that the organism can afford to delay the start of reproduction. A high early reproduction means that the organism has to reach maturity earlier.
How many times to reproduce?
There are two extremes. You can reproduce once, but a lot, in your entire life. This is called Semelparity - examples are things like salmon and mayflies. Or you could reproduce many times continually throughout your life. This is called Iteroparity. It is better to demonstrate semelparity when you live in an unpredictable climate - such as desert plants. When you do get the right conditions you should invest everything in making sure that reproductive event is successful because the right conditions may not come around again in your life time. On the other hand if you have a predictable climate then regular reproduction is better as you can reproduce many times without as much investment and have more chances of passing on genes.
These two strategies are divided in r- selection and k-selection. r selection is in an unstable environment and is density independent. r Selection tends to be small organisms, many offspring are produced, early maturity, short life expectancy, individuals produce once (semelparity). Type III survivorship pattern in which most of the individuals die within a short time but a few live much longer.
K selection is in a stable environment with density dependent interactions. Usually large organisms with few offspring produced, late maturity, long life expectancy, individuals produce many times in their lifetime (iteroparity). Type I or II survivorship patter where most individuals live to near the maximum life span.
These are extremes of the strategies, most organisms fall between the two.
The terms r-selected and K-selected come from descriptions of their population growth. In an r-selected, environmental instability means that the population is reduced before it reaches carrying capacity. On the other hand in K-selected, population size is near to the carrying capacity due to density dependent factors.
Sexual selection can also be seen very clearly in humans. Fashion, make up, demonstrations of wealth and power, sport, dancing etc.
(there was a lot of stuff from the previous lecture here).
An example of a physiological constraint is the tracheal system in insects limits their oxygen and stops them from being able to grow larger. For them to grow larger they would need massive changes to their oxygen dispersal which would be backwards survival steps before they could get to a stage where the changes would allow them to grow larger. Evolution only occurs in relation to the present - not with a future direction in mind.
Life history theory and Evolution
Definition: An individual's pattern of allocation, throughout life of time and energy to various fundamental activities such as growth, repair of cell and tissue damage and reproduction.
Phenotypes can be described as a series of traits. Reproductive traits include age and size at maturity, longevity/lifespan, reproductive frequency, number and size of offspring. The study of life history of evolution attempts to explain why these traits vary between species and within species. A collection of traits represent the fitness of an individual. For example a tortoise matures at 30 years, live for 120 and reproduce around every 5 years. Fruit flies mature at 12 days, live for months and reproduce repeatedly.
Ideally an organism would live forever and produce an infinite number of offspring each generation. However this is not possible so organisms evolve with the best compromise between different longevity and fertility patterns open to it, given the trade-offs imposed by external (and internal) constraints. Because life histories are about trade-offs between traits, traits are inter-linked. It is difficult to look at traits in isolation, so when you look at one you should consider the consequences this trait has on other traits. Life history strategies evolve to maximise individual fitness (number of offspring in next generation). TRV stands for the total reproductive value. At any stage of lifespan TRV will be the sum of Current Reproductive Value and Residual Reproductive Value. TRV = CRV + RRV. The things an organism uses for reproduction now will detract from what it can use later for reproduction and survival. Another trade off; reproductive intensity versus reproductive frequency.
Reproduction
4 main variables to consider;
1. When to start reproducing (ie. at what age they reach reproductive maturity).
2. How often to reproduce in a lifetime.
3. How much energy to put into each reproductive effort.
4 How many offspring produced at each reproductive event?
For example different birds might produce a different number of eggs; Ring-neck pheasant's produce around 20 while a kiwi only produces 1.
Decisions at the individual level
How many eggs? Maximum or optimum?
David Lack predicted that birds should lay the number of eggs that maximise the number of you reaching maturity, not the maximum number that can lay. This is known as the "Lack Clutch." However this can easily be tested by adding or removing eggs from a nest and it's been found that birds lay less eggs than the Lack clutch.
(My guess would be that if birds lay less than the optimum but then there is a change in environment that leads to less than usual resources they'll still have a better chance of having their offspring survive, while if they have too many offspring and the drop in resources mean that the food is spread equally across more offspring than can be supported they will all die. Because of the high variability of climate from one year to the next, it's fairly probably that there will be occasions when there is less than ideal food supply).
Plants and seeds
Plants essentially have 2 strategies. They can have a few large seeds with a lot of reproductive energy invested in a small number or they can have a lot of small seeds with not so much reproductive energy invested per seed. For example Eucalyptus regnans has a life span of 400+ years, it grows up to 100m tall, it has leaves 10-20cm long and fruit that are less than 20g. Coconut palm, on the other hand, has a lifespan of 100 years, grows to 30m, has leaves 4 to 6m long and fruit that weigh 1-2kg. Eucalyptus regnans produces many more seeds than coconut palms, but both are successful in their environments.
Life history strategies are best studied within a single animal group. Phylogenetic constraints may restrict what is possible.
The advantages of a large seed/egg size are that you can out compete your neighbours, grow faster, produce more seed when mature, flower or mature first and escape predators better.
The advantages of small seed/egg are that there are more of them, they may disperse more significantly over larger areas, smaller body size and less competition with parents.
Age at first reproduction.
If there were no trade-offs with reproduction then obviously the best thing to do is start reproducing at birth so as to maximise the number of offspring over the whole time. Mortality rates play a big role in determining the optimal time to start reproducing = survivorship curves. Low early mortality means that the organism can afford to delay the start of reproduction. A high early reproduction means that the organism has to reach maturity earlier.
How many times to reproduce?
There are two extremes. You can reproduce once, but a lot, in your entire life. This is called Semelparity - examples are things like salmon and mayflies. Or you could reproduce many times continually throughout your life. This is called Iteroparity. It is better to demonstrate semelparity when you live in an unpredictable climate - such as desert plants. When you do get the right conditions you should invest everything in making sure that reproductive event is successful because the right conditions may not come around again in your life time. On the other hand if you have a predictable climate then regular reproduction is better as you can reproduce many times without as much investment and have more chances of passing on genes.
These two strategies are divided in r- selection and k-selection. r selection is in an unstable environment and is density independent. r Selection tends to be small organisms, many offspring are produced, early maturity, short life expectancy, individuals produce once (semelparity). Type III survivorship pattern in which most of the individuals die within a short time but a few live much longer.
K selection is in a stable environment with density dependent interactions. Usually large organisms with few offspring produced, late maturity, long life expectancy, individuals produce many times in their lifetime (iteroparity). Type I or II survivorship patter where most individuals live to near the maximum life span.
These are extremes of the strategies, most organisms fall between the two.
The terms r-selected and K-selected come from descriptions of their population growth. In an r-selected, environmental instability means that the population is reduced before it reaches carrying capacity. On the other hand in K-selected, population size is near to the carrying capacity due to density dependent factors.
Lecture 5 Individual vs Group selection (EW)
Behaviours (or traits) can evolve by selective pressures derived from the environment, other species, competition, own species (such as mate selection and reproduction), and evolution proceeds when there are benefits to the individual in terms of fitness (i.e. steps that increase its reproductive output). However very often individual animals can behave in a manner that confers no direct or obvious benefit to itself. This is often called "altruistic behaviour."
Altruism; "any behaviour that is detrimental in some way to the immediate well-being of the animal doing it, but beneficial to another organism."
There are many examples of this such as cooperative breeding in elephants, birds and bees. Warning calls in meerkats.
Early behavioural ecologists interpreted these behaviours in terms of "group selection." There may be no benefit to the individual, but overall the group benefits, and so the behaviour can evolve and become fixed in the population. Vero C. Wynne-Edwards (1962) proposed that animals behave for the good of the group. He suggested a population would become extinct if it over-exploited its food resources. On the surface this appears to make sense.
However natural selection would favour selfish individuals that received the benefits of altruism without giving anything back, and their genes would be passed on and become dominate in a population.
The "new synthesis" and the problems with group selection.
Essentially, group selection arguments don't work because "a cheater" stands to gain by exploiting his/her friends. W.D Hamilton and other behavioural ecologists realised that selection therefore could not operate on groups, but only on individuals. This builds on the knowledge that an individual is concerned with passing on its genes to the next generation. It highlights the importance of the gene and individuals as the carrier of the gene.
Considering the case of meerkats
How do we explain altruistic and group type behaviour?
How did these altruistic behaviours evolve? What is the evolutionary pay-off for an individual that wastes resources or risks its life without continuing its genetic line?
In every case there is a pay-off. Individuals involved in altruistic behaviour (e.g. cooperative breeding) only do so when helping relatives. Those relatives carry at least some of their genes. By helping them you are helping your genes survive. The degree of relatedness affects the degree of altruistic behaviour. This is known as "Inclusive Fitness" (WD Hamilton).
Selfish Genes
Building on Hamilton's concept of inclusive fitness, Richard Dawkins (1976) proposed that genes are the fundamental unit of selection, and therefore that self-interest is not the species or the group, and indeed, not strictly the individual, but the gene. This term is a little confusing as it does not mean selfish in a human sense, but rather that genes survive because they promote the continuation of their own survival. They can use many techniques to do so, including promoting altruism within a species, but genes that did not help with the continued reproduction of copies of themselves would not continue to survive.
Co-Evolution
Animal behaviour cannot be understood in isolation. Many behaviours evolve in response to other species. The evolution of species involve in a "contest" is referred to as a co-evolution arms race. For example predator/prey or host/parasite relationships. Co-evolution requires a specific evolutionary response by both species involved in the contest. Specific new defences against specific new responses. An example of co-evolution is cheetahs getting faster and faster to catch gazelles, that in turn get faster and faster to escape.
Brood Parasitism is another example of co-evolution.
Many bird species have evolved a 'parasitic' behaviour of despositing eggs in other species' nests. Not all birds do it, so there are costs and benefits. The benefits are that all the incubation and feeding costs are met by the host which frees more time for the mother, possibly allowing them to lay more eggs. The cost is if the egg or chick is recognised it will be rejected or neglected.
Why is it accepted?
Since it has evolved many times, presumably there are costs and benefits to the host as well. The answer might be in the origin of the behaviour. Initially it may have started as active take over of nests within species? Parasitism evolves in order to avoid costs of fighting and total loss of eggs? Intra-specific brood parasitism led to facultative parasitism let to inter-specific hosts. Cost to host - rarely fledge young and exhaustion of host parent. However you don't want to reject your own eggs/young.
If you were a cuckoo what would you do to maximise chances of success? Small eggs with short incubation times. Egg mimicry, chick mimicry. Egg ejection by nestlings. Be big and tough so you can beat up hosts. If you were a host what would you do to minimise costs? Do not leave nest unattended. Egg and chick recognition. Nest desertion/nest burial. Learn to count. Tolerate when advantageous.
"Brood parasitism as an alternative female breeding tactic is particularly common in ducks, where hosts often receive eggs laid by parasitic females of the same species and raise their offspring."
Co-evolution is not only between animal species - it can be between animals and plants, or even plants and plants (and other kingdoms of course).
Recap;
Evolutionary principles in studying behaviour
Natural selection, fitness and selective pressure
Trade-offs and constraints
Life History Theory
Individual versus group fitness
Inclusive fitness and the selfish gene
Co-evolution
Behaviours (or traits) can evolve by selective pressures derived from the environment, other species, competition, own species (such as mate selection and reproduction), and evolution proceeds when there are benefits to the individual in terms of fitness (i.e. steps that increase its reproductive output). However very often individual animals can behave in a manner that confers no direct or obvious benefit to itself. This is often called "altruistic behaviour."
Altruism; "any behaviour that is detrimental in some way to the immediate well-being of the animal doing it, but beneficial to another organism."
There are many examples of this such as cooperative breeding in elephants, birds and bees. Warning calls in meerkats.
Early behavioural ecologists interpreted these behaviours in terms of "group selection." There may be no benefit to the individual, but overall the group benefits, and so the behaviour can evolve and become fixed in the population. Vero C. Wynne-Edwards (1962) proposed that animals behave for the good of the group. He suggested a population would become extinct if it over-exploited its food resources. On the surface this appears to make sense.
However natural selection would favour selfish individuals that received the benefits of altruism without giving anything back, and their genes would be passed on and become dominate in a population.
The "new synthesis" and the problems with group selection.
Essentially, group selection arguments don't work because "a cheater" stands to gain by exploiting his/her friends. W.D Hamilton and other behavioural ecologists realised that selection therefore could not operate on groups, but only on individuals. This builds on the knowledge that an individual is concerned with passing on its genes to the next generation. It highlights the importance of the gene and individuals as the carrier of the gene.
Considering the case of meerkats
How do we explain altruistic and group type behaviour?
How did these altruistic behaviours evolve? What is the evolutionary pay-off for an individual that wastes resources or risks its life without continuing its genetic line?
In every case there is a pay-off. Individuals involved in altruistic behaviour (e.g. cooperative breeding) only do so when helping relatives. Those relatives carry at least some of their genes. By helping them you are helping your genes survive. The degree of relatedness affects the degree of altruistic behaviour. This is known as "Inclusive Fitness" (WD Hamilton).
Selfish Genes
Building on Hamilton's concept of inclusive fitness, Richard Dawkins (1976) proposed that genes are the fundamental unit of selection, and therefore that self-interest is not the species or the group, and indeed, not strictly the individual, but the gene. This term is a little confusing as it does not mean selfish in a human sense, but rather that genes survive because they promote the continuation of their own survival. They can use many techniques to do so, including promoting altruism within a species, but genes that did not help with the continued reproduction of copies of themselves would not continue to survive.
Co-Evolution
Animal behaviour cannot be understood in isolation. Many behaviours evolve in response to other species. The evolution of species involve in a "contest" is referred to as a co-evolution arms race. For example predator/prey or host/parasite relationships. Co-evolution requires a specific evolutionary response by both species involved in the contest. Specific new defences against specific new responses. An example of co-evolution is cheetahs getting faster and faster to catch gazelles, that in turn get faster and faster to escape.
Brood Parasitism is another example of co-evolution.
Many bird species have evolved a 'parasitic' behaviour of despositing eggs in other species' nests. Not all birds do it, so there are costs and benefits. The benefits are that all the incubation and feeding costs are met by the host which frees more time for the mother, possibly allowing them to lay more eggs. The cost is if the egg or chick is recognised it will be rejected or neglected.
Why is it accepted?
Since it has evolved many times, presumably there are costs and benefits to the host as well. The answer might be in the origin of the behaviour. Initially it may have started as active take over of nests within species? Parasitism evolves in order to avoid costs of fighting and total loss of eggs? Intra-specific brood parasitism led to facultative parasitism let to inter-specific hosts. Cost to host - rarely fledge young and exhaustion of host parent. However you don't want to reject your own eggs/young.
If you were a cuckoo what would you do to maximise chances of success? Small eggs with short incubation times. Egg mimicry, chick mimicry. Egg ejection by nestlings. Be big and tough so you can beat up hosts. If you were a host what would you do to minimise costs? Do not leave nest unattended. Egg and chick recognition. Nest desertion/nest burial. Learn to count. Tolerate when advantageous.
"Brood parasitism as an alternative female breeding tactic is particularly common in ducks, where hosts often receive eggs laid by parasitic females of the same species and raise their offspring."
Co-evolution is not only between animal species - it can be between animals and plants, or even plants and plants (and other kingdoms of course).
Recap;
Evolutionary principles in studying behaviour
Natural selection, fitness and selective pressure
Trade-offs and constraints
Life History Theory
Individual versus group fitness
Inclusive fitness and the selfish gene
Co-evolution
Animal Behaviour
Ways of studying behaviour (EW)
1. Observations
2. Experiments
3. Look at inheritance of behaviour (and do experiments)
4. Comparisons between species or environment
5. Theoretical models (devise a mathematical model)
So how do we study (the evolution of) behaviour? Behaviour in the context of evolution. Why has the behaviour evolved? What is its function? How has it evolved? Behaviours don't leave fossils.
1. Observation
Observe present day behaviours and infer what selective pressures led to them. Common in field based studies. There are many classic experiments based on initial observation of interesting behaviour. Establishes working hypotheses. Basis of subsequent carefully controlled experiments. Can be viewed as experiments in retrospect - record all variables and control for them. Problems faced though in that observer could affect behaviour and it is very hard to standardise the setting.
2. Experiments
From observations or literature comes a series of hypotheses. Competing hypotheses - reduce number of explanations. Manipulate variable of interest, control those not of interest. Outcome should allow experimenter to eliminate hypotheses. Need to be systematic, carefully controlled and grounded in natural history where possible. Experiments usually lead to further experiments.
Example; Widowbirds. Common bird in African grasslands. Have been intensively observed and studied. Two observations. Males have unusual red patches on shoulders and extremely long tails. Why? How do you test ideas?
Experiment a - what are the red patches for? Experimental design - change the size of red patch by using paint of some kind. Observe the changes in male success - territory size. Male to male interactions. Number of females. Conclusion - males with smaller patches had their territory invaded more. This was costly in energy expended and territory size. Therefore there must be positive selection on males with bigger patches.
Experiment b - what is the long tail for? Experimental design - change the length of the tail - shorten or tape on extra tail feathers. Observe changes in male success - territory size, male to male interactions, number of females. Conclusion - Males with shorter tails attracted less females. Males with longer tails attracted more females. Control - no change. Therefore there must be positive selection on tail length.
Example - Sand lizards. Common across Europe. Long term field based study in Sweden (1984-2004). Series of observations and experiments. Population of approximately 100 males and 100 females. Emerge from hibernation around May 1. Active daily when weather is suitable. Short season but long days.
Field observations;
Females are longer than males
Males have bigger shoulders and heads than females
Females are brown/grey while males are bright green
males have many more parasites than females
males stay with females after mating for days
^ why?
Experiments. (results of experiments found)
Females are longer than males because longer females have more eggs. The more eggs you have the more offspring survive (fitness). Female offspring are longer than male offspring. Also determined by female body condition.
Males are "chunkier" than females because they fight each other for females. Positive relationship between head size and fights won, territory size, access to females and offspring fathered. More offspring = greater fitness.
Males are green, females are not. Greeness is used to assess size and fighting ability. Thus males with more green fight less and have larger territory, more females and more offspring - ie. greater fitness. However big badges have a positive relationship with high testosterone. Testosterone suppresses immune system. Therefore there is a positive relationship between badge size and the number of ticks. This means that only really big strong males can cope with having big green badges. Smaller weaker males need to have smaller badges and less testosterone.
Males stay with females for days after mating because both males and females mate multiple times. Males want to prevent access to "their" females from other males. They also have to wait for their sperm to replenish, so gain no advantage by immediately looking for new females.
Behaviour and genetics
It's easy to understand that your hair coulour is inherited from your parents (or wrinkly skin in peas) and easy to describe mathematically (single genes), however all behaviour is dependent, at least to some extent, on genetics (that's why it evolves). We are talking both about structures and true behaviour. There is no such thing as a single "behaviour gene." Genes affecting behaviour are promoted through differences in the success of individuals, thus providing the heritability of behaviour. For behaviours to evolve, the variation in behaviour must be attributable, in part, to genetic variation. However not all behaviours are genetically coded (such as learnt ones - however the ability to learn is presumably genetic).
In some cases the same gene can be code for different phenotypic traits. Drosophila sp. yellow mutant (single gene) males vibrate and lick less; therefore, less likely to stimulate female. However most behaviours are the result of a complex interaction of many different genes (e.g. the many aspects that are involved in a courtship dance). Alternatively a single gene can affect many different behaviours. For example a gene that had an effect on testosterone level could affect mating behaviour, stature, musculature, aggression, sexual ornaments and metabolism.
Although behavioural traits can have a complex genetic basis, we do not need to identify all the genes involved to demonstrate that the trait is heritable. There are two ways to do this.
1. Look at inheritance of the behaviour between generations - ie. do males with high display rates give rise to sons with high display rates? However there are problems with this; Complex behaviours are hard to measure. Behaviour can be learned from others, including parents. Often there is not a significant amount of variation in behaviour. Can take a long time and often large sample sizes are needed.
2. Selection experiments - breeding experiments with artificial high selection. Basically experimenter breeds animals and deliberately select that ones that perform best or worst with a particular behaviour. Usually restricted to simple systems in controlled environments. Organisms such as Drosophila and lab rats are useful because large numbers of generations can be produces in a relatively short time frame. For example rats can be selectively bred for fast or slow learning of a maze and induced to follow trajectories over relatively few generations. With Blackcaps (Sylvia atricapilla) 75% of the population usually migrate while 25% of the population "stay." Selective breeding can induce populations of 100% migrators in 3 generations and 100% home stayers in 6 generations. Breeds of dog, and human domestication of animals is another example of selection experiments.
Comparative experiments
A powerful way of understanding behaviour is to compare performance/behaviour across different species and environments. Based on the assumption that different selective pressures in different environments have moulded behaviours in predictable ways - therefore infer why it occurs. Comparative method applied across species is a major tool in evolutionary explanations. Particularly useful for more complex behaviours from organisms that cannot be reared in the lab. Molecular techniques identifying the relatedness of taxa have improved this approach. However it's important not to interpret culturally transmitted or learned behaviours as evolved. It's also important to examine behaviours as structures - what is their origin - is it homologous or analogous? Homologous means it has evolved from the same origin although may now serve a different function. Analogous means it has come from a different origin - ie. convergent evolution. This is covered again later but examples are like wings on birds, insects and bats - or eyes in chordates and cephalopods. I.e. the same trait has evolved separately in different organisms.
Phylogeny and behavioural change
Darwin's Finches and adaptive radiation. How to assess evolution of behavioural changes in feeding? Understanding number of origins of features (including behaviour) requires knowledge of phylogeny. Modern molecular techniques establish the degree of species relatedness - "trees" can be constructed. Behaviours within each species can be examined. Reconstruct how a behaviour might have changed over evolutionary time. Parsimony - attribute differences to least number of evolutionary steps.
Mathematical and theoretical models
Sometimes it's not possible or desirable to collect data empirically. Instead we can derive models to describe outcomes (changes in fitness) of hypothetical or real situations. We can then use models to predict what might happen in any given situation and test empirically.
Game theory and the evolution of Evolutionary Stable Strategies (John Maynard Smith).
Two species co-exist through co-evolutionary strategies - how does species A react to species B? How does species B react to changes in species A etc. could go on forever so modelling is more powerful.
Summary;
Animals behaviour changes in response to selection pressures. Identifying these is one of the goals of studying behaviour - environment, intraspecific (other sex, competition, offspring), interspecific (co-evolution). Variety of approaches to understanding behaviour: Observation, experiments (within and between species/environments), artificial selection on traits, theoretical and mathematical modelling.
Responses to selection, selection on traits (to maximise fitness) is a long process that occurs over multi-generations and occurs by small steps (usually).
Ways of studying behaviour (EW)
1. Observations
2. Experiments
3. Look at inheritance of behaviour (and do experiments)
4. Comparisons between species or environment
5. Theoretical models (devise a mathematical model)
So how do we study (the evolution of) behaviour? Behaviour in the context of evolution. Why has the behaviour evolved? What is its function? How has it evolved? Behaviours don't leave fossils.
1. Observation
Observe present day behaviours and infer what selective pressures led to them. Common in field based studies. There are many classic experiments based on initial observation of interesting behaviour. Establishes working hypotheses. Basis of subsequent carefully controlled experiments. Can be viewed as experiments in retrospect - record all variables and control for them. Problems faced though in that observer could affect behaviour and it is very hard to standardise the setting.
2. Experiments
From observations or literature comes a series of hypotheses. Competing hypotheses - reduce number of explanations. Manipulate variable of interest, control those not of interest. Outcome should allow experimenter to eliminate hypotheses. Need to be systematic, carefully controlled and grounded in natural history where possible. Experiments usually lead to further experiments.
Example; Widowbirds. Common bird in African grasslands. Have been intensively observed and studied. Two observations. Males have unusual red patches on shoulders and extremely long tails. Why? How do you test ideas?
Experiment a - what are the red patches for? Experimental design - change the size of red patch by using paint of some kind. Observe the changes in male success - territory size. Male to male interactions. Number of females. Conclusion - males with smaller patches had their territory invaded more. This was costly in energy expended and territory size. Therefore there must be positive selection on males with bigger patches.
Experiment b - what is the long tail for? Experimental design - change the length of the tail - shorten or tape on extra tail feathers. Observe changes in male success - territory size, male to male interactions, number of females. Conclusion - Males with shorter tails attracted less females. Males with longer tails attracted more females. Control - no change. Therefore there must be positive selection on tail length.
Example - Sand lizards. Common across Europe. Long term field based study in Sweden (1984-2004). Series of observations and experiments. Population of approximately 100 males and 100 females. Emerge from hibernation around May 1. Active daily when weather is suitable. Short season but long days.
Field observations;
Females are longer than males
Males have bigger shoulders and heads than females
Females are brown/grey while males are bright green
males have many more parasites than females
males stay with females after mating for days
^ why?
Experiments. (results of experiments found)
Females are longer than males because longer females have more eggs. The more eggs you have the more offspring survive (fitness). Female offspring are longer than male offspring. Also determined by female body condition.
Males are "chunkier" than females because they fight each other for females. Positive relationship between head size and fights won, territory size, access to females and offspring fathered. More offspring = greater fitness.
Males are green, females are not. Greeness is used to assess size and fighting ability. Thus males with more green fight less and have larger territory, more females and more offspring - ie. greater fitness. However big badges have a positive relationship with high testosterone. Testosterone suppresses immune system. Therefore there is a positive relationship between badge size and the number of ticks. This means that only really big strong males can cope with having big green badges. Smaller weaker males need to have smaller badges and less testosterone.
Males stay with females for days after mating because both males and females mate multiple times. Males want to prevent access to "their" females from other males. They also have to wait for their sperm to replenish, so gain no advantage by immediately looking for new females.
Behaviour and genetics
It's easy to understand that your hair coulour is inherited from your parents (or wrinkly skin in peas) and easy to describe mathematically (single genes), however all behaviour is dependent, at least to some extent, on genetics (that's why it evolves). We are talking both about structures and true behaviour. There is no such thing as a single "behaviour gene." Genes affecting behaviour are promoted through differences in the success of individuals, thus providing the heritability of behaviour. For behaviours to evolve, the variation in behaviour must be attributable, in part, to genetic variation. However not all behaviours are genetically coded (such as learnt ones - however the ability to learn is presumably genetic).
In some cases the same gene can be code for different phenotypic traits. Drosophila sp. yellow mutant (single gene) males vibrate and lick less; therefore, less likely to stimulate female. However most behaviours are the result of a complex interaction of many different genes (e.g. the many aspects that are involved in a courtship dance). Alternatively a single gene can affect many different behaviours. For example a gene that had an effect on testosterone level could affect mating behaviour, stature, musculature, aggression, sexual ornaments and metabolism.
Although behavioural traits can have a complex genetic basis, we do not need to identify all the genes involved to demonstrate that the trait is heritable. There are two ways to do this.
1. Look at inheritance of the behaviour between generations - ie. do males with high display rates give rise to sons with high display rates? However there are problems with this; Complex behaviours are hard to measure. Behaviour can be learned from others, including parents. Often there is not a significant amount of variation in behaviour. Can take a long time and often large sample sizes are needed.
2. Selection experiments - breeding experiments with artificial high selection. Basically experimenter breeds animals and deliberately select that ones that perform best or worst with a particular behaviour. Usually restricted to simple systems in controlled environments. Organisms such as Drosophila and lab rats are useful because large numbers of generations can be produces in a relatively short time frame. For example rats can be selectively bred for fast or slow learning of a maze and induced to follow trajectories over relatively few generations. With Blackcaps (Sylvia atricapilla) 75% of the population usually migrate while 25% of the population "stay." Selective breeding can induce populations of 100% migrators in 3 generations and 100% home stayers in 6 generations. Breeds of dog, and human domestication of animals is another example of selection experiments.
Comparative experiments
A powerful way of understanding behaviour is to compare performance/behaviour across different species and environments. Based on the assumption that different selective pressures in different environments have moulded behaviours in predictable ways - therefore infer why it occurs. Comparative method applied across species is a major tool in evolutionary explanations. Particularly useful for more complex behaviours from organisms that cannot be reared in the lab. Molecular techniques identifying the relatedness of taxa have improved this approach. However it's important not to interpret culturally transmitted or learned behaviours as evolved. It's also important to examine behaviours as structures - what is their origin - is it homologous or analogous? Homologous means it has evolved from the same origin although may now serve a different function. Analogous means it has come from a different origin - ie. convergent evolution. This is covered again later but examples are like wings on birds, insects and bats - or eyes in chordates and cephalopods. I.e. the same trait has evolved separately in different organisms.
Phylogeny and behavioural change
Darwin's Finches and adaptive radiation. How to assess evolution of behavioural changes in feeding? Understanding number of origins of features (including behaviour) requires knowledge of phylogeny. Modern molecular techniques establish the degree of species relatedness - "trees" can be constructed. Behaviours within each species can be examined. Reconstruct how a behaviour might have changed over evolutionary time. Parsimony - attribute differences to least number of evolutionary steps.
Mathematical and theoretical models
Sometimes it's not possible or desirable to collect data empirically. Instead we can derive models to describe outcomes (changes in fitness) of hypothetical or real situations. We can then use models to predict what might happen in any given situation and test empirically.
Game theory and the evolution of Evolutionary Stable Strategies (John Maynard Smith).
Two species co-exist through co-evolutionary strategies - how does species A react to species B? How does species B react to changes in species A etc. could go on forever so modelling is more powerful.
Summary;
Animals behaviour changes in response to selection pressures. Identifying these is one of the goals of studying behaviour - environment, intraspecific (other sex, competition, offspring), interspecific (co-evolution). Variety of approaches to understanding behaviour: Observation, experiments (within and between species/environments), artificial selection on traits, theoretical and mathematical modelling.
Responses to selection, selection on traits (to maximise fitness) is a long process that occurs over multi-generations and occurs by small steps (usually).
Lecture 7 (EW)
Ethology and Behavioural Ecology
Animal behaviour cannot be understood in isolation. Instead you need to understand what behaviour is, evolutionary principles, ways of studying behaviour, history and "School of thought", development and learning of behaviour and the senses involved in behaviour. This lecture looks at the history and "schools of thought" in behavioural ecology.
How did we get where we are today?
Although it is such an important aspect of biology, "animal behaviour" is very young. However understanding behaviour was used outside of biology for hunting and domestication and the earliest philosophers pondered aspects of animal behaviour (and can demonstrate quite well why philosophy is a waste of time, and science can give you real answers). Aristotle noticed that swallows disappeared in winter, and having seen them gather in reed beds, speculated that they hibernate in mud at the bottom of ponds. He also speculated that warblers turn into robins in winter to account for their disappearance.
Charles Darwin was one of the first modern scientists to appreciate the importance of behaviour, and included an entire chapter on instinct in "The Origin of Species." However it was another 50 years before other scientists started looking seriously at behaviour. "Animal behaviour" did not become a common term until the early 1900s. Prior to this, animals were assigned 'emotions', 'habits', 'manners', 'customs' and 'instincts.' These had a strong emphasis on human feelings, and they were viewed in a very anthropomorphised manner. They were also used largely to understand humans.
The Ethologists
In the 1930s an Australian, Konrad Lorenz, started to observe and record animal behaviour in a systematic and scientific way. His initial interest was in the behaviour he called "imprinting" - the way new born animals form an attachment to their parents. He found that new born chick does not immediately recognise its mother, but will follow, learn from, and "imprint" any large moving object that it is exposed to in the first hours after hatching. Of course usually this is its mother, but it can also be a fake bird, a toy, a human or even an aeroplane. This is used to assist in the migration of some endangered birds.
Niko Tinbergen (4 questions of behaviour - causation, development (proximate), evolution and function (ultimate)) also did many behavioural studies (the slide says we'll look at these later).
Another early ethologist was Karl von Frisch who described the dance of honey bees.
These three people were awarded the Nobel Prize for medicine/physiology in 1973 (1972 according the lecture slide, but I'm pretty sure this is wrong). They established the discipline of 'ethology.'
Ethology was defined by Tinbergen as the "biological study of behaviour" (1963). By Wilson (I presume E. O.) as "the study of whole patterns of animal behaviour in natural environments, stressing the analysis of adaptation and the evolution of patterns" (1975). In my textbook as "the study of animal behaviour in natural conditions." Many different disciplines were interested in behaviour, but ethologists are essentially biologists, which gives them a different perspective to philosophers or human psychologists etc. Ethologists interpret behaviour in natural situations. The early ethologists were convinced that painstaking observations and recording of behaviour was an essential prelude to understanding behaviour.
Ethograms
An important step in the study of behaviour of a particular animal species was the development of what behavioural scientists call an ethogram. An ethogram is a comprehensive listing and description of all naturally occurring behaviours. Ethograms are based on the results of "naturalistic observations" - observations of the species in its natural environment. Although they're not used so much, they are still done today and are an important way of identifying particular behaviours - such as headbobbing and arm waving in lizards or whale displays.
For example a study of jacky dragons (lizard) found that they carry out a regular sequence of motions in a particular order; Tail flick>backward arm wave>forward arm wave>push up>body rock. Many agamids (lizard family) also have particular colours to supplement their behaviour. These behaviours are expressions of aggression and submission and to test opponents.
Through the use of ethograms, early ethologists realised that different species tend to have an array of stereotyped behavioural patterns, some of which are shared with different species and some of which are unique. This was a fundamental breakthrough in understanding animal behaviour.
Another good example is Tinbergen's (causation, development - proximate, evolution, function - ultimate - sorry I keep writing these out when I mention his name because it's almost certainly going to be on the exam in some description) studies of sticklebacks (fish). They are a common fish in freshwater streams in Europe and have been studies extensively because they tend to behaviour in the same manner in captivity as in nature. Males breed in spring when daylight and water temperature increases. Their physical appearance at this time changes and they become bright red on the underside and iridescent blue on the face. They also change behaviour and gather weed to make a nest on the bottom of the river. Tinbergen found that they use their markings to woo females and encourage them to lay their eggs in the nest. His ethogram identified a number of behavioural patters that are common in all male three-spined sticklebacks; gluing (nest building), zig-zag dance, creeping through, fanning, head down posture. Identification of these behaviours allowed their function to be identified. The head down posture is in response to competition from other males. It can be induced by any object with a red underside, or even by red postal trucks driving past a fish tank.
The early ethologists advanced very general theories based on these careful observations. They then used hypothesis driven experimental investigation and Tinbergen's 4 whys (causation, development, evolution, function). This is the approach still taken in field-based biology today. Today the term "ethologist" is not used very much, although there is still a current journal.
The comparative psychologists
While Lorenz et al. were developing their idea in Europe, there was another school of behavioural thought emerging in the USA - the American school of comparative psychology. Although both groups were interested in the behaviour of animals, they approached their studies in very different ways. While the ethologists were mainly zoologists and were interested in the evolution and behaviour of a wide variety of species and the difference between the species, the comparative psychologists only studied a very small number of species - mainly rats and pigeons - mainly in the laboratory.
A leading figure in early comparative psychology was J.B. Watson who believed that the mind was a blank slate on which subsequent experience was written. Comparative psychologists were not interested in the difference between species but the similarities and were trying to construct general laws of behaviour. They wanted to be able to apply their laws to all species including humans. They carried out rigorously controlled lab experiments on a few species. They assumed that if you could understand the behaviour of rats or pigeons you could apply this to all species - in contrast to the "adaptive" field based approach in ethology. Both groups were interested in the development of behaviour and it became a debate of nature vs nurture, which lead to heated discussion in the 1960s.
Ivan Pavlov was another comparative psychologist famous for the "Pavlov's Dogs" experiment demonstrating classical conditioning (dogs were conditioned to salivate when a bell was rung using an unconditioned stimulus - meat, illiciting the unconditioned response, salivation, while using a conditioned stimulus - ringing a bell. When the unconditioned stimulus was removed but the conditioned stimulus remained the dog would still salivate).
Another leading figure was B. F. Skinner. Famous for the "Skinner box" for rats and pigeons. He believed that most behaviour was learned and used his box to demonstrate operant conditioning - reinforcing or punishing a behaviour makes it more or less common).
Modern approaches
While ethologists and comparative psychologists have largely resolved their differences, both approaches are seen to be too restrictive on their own. The study of animal behaviour now largely focuses on the ultimate causes of Tinbergen's 4 questions - evolution and function. I.e. What is the purpose of the behaviour and why did it evolve the way it did. Studies on animal behaviour today are even more exciting that in the past as they encompass new disciplines such as behavioural ecology and socio-biology. (I'm guessing this statement is an effort to convince students to keep studying this kind of stuff - I do find it interesting though).
Behavioural Ecology
Behavioural ecology is a fusion of ethology, ecology and evolutionary biology. It is the study of the relationships between an organism's behaviour and the environment in which that behaviour has evolved or is expressed. Behavioural ecologists study both the function of behaviour (why animals and plants behave the way the do), and the role of behaviour in determining population dynamics and community patterns. It is a predictive science and has had some "stunning successes." It has also been criticised for looking too much at function at the expense of underlying mechanisms and a balanced view of the 4 whys. A variety of tools and approaches are used in modern behavioural ecology and the best studies are now multi-disciplinary.
Behavioural Ecology and Sociobiology
The application of behavioural ecology to social behaviour. This is the study of behaviour of social animals, including humans. Sociobiology developed from studies in population biology and genetics. Edward Osborne Wilson is a very important figure in this field (also a fucking hero, my favourite scientist). In his 1975 book Sociobiology he attempted to find the evolutionary pressures which led to the evolution of social behaviour in a diverse group of animals. This has been very controversial when directed towards human behaviours such as crime, mate choice, marriage and promiscuity. (When you read his work in full, and then comments directed at it by both the political left and right, it demonstrates so perfectly why ideology is wrong, and why we should form opinions based solely on evidence. Dismissing scientific fact as wrong because you don't like the implications morally, ethically or it doesn't agree with your personal opinions is completely illogical and irrational. The world is not how we'd like it to be, it is how it is, and the sooner we can realise that and start making decisions based on how it actually is, the sooner we can fix it. In the time it's taken you to read this post, 1 organism has gone extinct in the world due to human irrationality - not greed or selfishness, because preserving the environment is clearly in our best interests. Just short sightedness and an inability to think rationally, and clearly).
Ethology and Behavioural Ecology
Animal behaviour cannot be understood in isolation. Instead you need to understand what behaviour is, evolutionary principles, ways of studying behaviour, history and "School of thought", development and learning of behaviour and the senses involved in behaviour. This lecture looks at the history and "schools of thought" in behavioural ecology.
How did we get where we are today?
Although it is such an important aspect of biology, "animal behaviour" is very young. However understanding behaviour was used outside of biology for hunting and domestication and the earliest philosophers pondered aspects of animal behaviour (and can demonstrate quite well why philosophy is a waste of time, and science can give you real answers). Aristotle noticed that swallows disappeared in winter, and having seen them gather in reed beds, speculated that they hibernate in mud at the bottom of ponds. He also speculated that warblers turn into robins in winter to account for their disappearance.
Charles Darwin was one of the first modern scientists to appreciate the importance of behaviour, and included an entire chapter on instinct in "The Origin of Species." However it was another 50 years before other scientists started looking seriously at behaviour. "Animal behaviour" did not become a common term until the early 1900s. Prior to this, animals were assigned 'emotions', 'habits', 'manners', 'customs' and 'instincts.' These had a strong emphasis on human feelings, and they were viewed in a very anthropomorphised manner. They were also used largely to understand humans.
The Ethologists
In the 1930s an Australian, Konrad Lorenz, started to observe and record animal behaviour in a systematic and scientific way. His initial interest was in the behaviour he called "imprinting" - the way new born animals form an attachment to their parents. He found that new born chick does not immediately recognise its mother, but will follow, learn from, and "imprint" any large moving object that it is exposed to in the first hours after hatching. Of course usually this is its mother, but it can also be a fake bird, a toy, a human or even an aeroplane. This is used to assist in the migration of some endangered birds.
Niko Tinbergen (4 questions of behaviour - causation, development (proximate), evolution and function (ultimate)) also did many behavioural studies (the slide says we'll look at these later).
Another early ethologist was Karl von Frisch who described the dance of honey bees.
These three people were awarded the Nobel Prize for medicine/physiology in 1973 (1972 according the lecture slide, but I'm pretty sure this is wrong). They established the discipline of 'ethology.'
Ethology was defined by Tinbergen as the "biological study of behaviour" (1963). By Wilson (I presume E. O.) as "the study of whole patterns of animal behaviour in natural environments, stressing the analysis of adaptation and the evolution of patterns" (1975). In my textbook as "the study of animal behaviour in natural conditions." Many different disciplines were interested in behaviour, but ethologists are essentially biologists, which gives them a different perspective to philosophers or human psychologists etc. Ethologists interpret behaviour in natural situations. The early ethologists were convinced that painstaking observations and recording of behaviour was an essential prelude to understanding behaviour.
Ethograms
An important step in the study of behaviour of a particular animal species was the development of what behavioural scientists call an ethogram. An ethogram is a comprehensive listing and description of all naturally occurring behaviours. Ethograms are based on the results of "naturalistic observations" - observations of the species in its natural environment. Although they're not used so much, they are still done today and are an important way of identifying particular behaviours - such as headbobbing and arm waving in lizards or whale displays.
For example a study of jacky dragons (lizard) found that they carry out a regular sequence of motions in a particular order; Tail flick>backward arm wave>forward arm wave>push up>body rock. Many agamids (lizard family) also have particular colours to supplement their behaviour. These behaviours are expressions of aggression and submission and to test opponents.
Through the use of ethograms, early ethologists realised that different species tend to have an array of stereotyped behavioural patterns, some of which are shared with different species and some of which are unique. This was a fundamental breakthrough in understanding animal behaviour.
Another good example is Tinbergen's (causation, development - proximate, evolution, function - ultimate - sorry I keep writing these out when I mention his name because it's almost certainly going to be on the exam in some description) studies of sticklebacks (fish). They are a common fish in freshwater streams in Europe and have been studies extensively because they tend to behaviour in the same manner in captivity as in nature. Males breed in spring when daylight and water temperature increases. Their physical appearance at this time changes and they become bright red on the underside and iridescent blue on the face. They also change behaviour and gather weed to make a nest on the bottom of the river. Tinbergen found that they use their markings to woo females and encourage them to lay their eggs in the nest. His ethogram identified a number of behavioural patters that are common in all male three-spined sticklebacks; gluing (nest building), zig-zag dance, creeping through, fanning, head down posture. Identification of these behaviours allowed their function to be identified. The head down posture is in response to competition from other males. It can be induced by any object with a red underside, or even by red postal trucks driving past a fish tank.
The early ethologists advanced very general theories based on these careful observations. They then used hypothesis driven experimental investigation and Tinbergen's 4 whys (causation, development, evolution, function). This is the approach still taken in field-based biology today. Today the term "ethologist" is not used very much, although there is still a current journal.
The comparative psychologists
While Lorenz et al. were developing their idea in Europe, there was another school of behavioural thought emerging in the USA - the American school of comparative psychology. Although both groups were interested in the behaviour of animals, they approached their studies in very different ways. While the ethologists were mainly zoologists and were interested in the evolution and behaviour of a wide variety of species and the difference between the species, the comparative psychologists only studied a very small number of species - mainly rats and pigeons - mainly in the laboratory.
A leading figure in early comparative psychology was J.B. Watson who believed that the mind was a blank slate on which subsequent experience was written. Comparative psychologists were not interested in the difference between species but the similarities and were trying to construct general laws of behaviour. They wanted to be able to apply their laws to all species including humans. They carried out rigorously controlled lab experiments on a few species. They assumed that if you could understand the behaviour of rats or pigeons you could apply this to all species - in contrast to the "adaptive" field based approach in ethology. Both groups were interested in the development of behaviour and it became a debate of nature vs nurture, which lead to heated discussion in the 1960s.
Ivan Pavlov was another comparative psychologist famous for the "Pavlov's Dogs" experiment demonstrating classical conditioning (dogs were conditioned to salivate when a bell was rung using an unconditioned stimulus - meat, illiciting the unconditioned response, salivation, while using a conditioned stimulus - ringing a bell. When the unconditioned stimulus was removed but the conditioned stimulus remained the dog would still salivate).
Another leading figure was B. F. Skinner. Famous for the "Skinner box" for rats and pigeons. He believed that most behaviour was learned and used his box to demonstrate operant conditioning - reinforcing or punishing a behaviour makes it more or less common).
Modern approaches
While ethologists and comparative psychologists have largely resolved their differences, both approaches are seen to be too restrictive on their own. The study of animal behaviour now largely focuses on the ultimate causes of Tinbergen's 4 questions - evolution and function. I.e. What is the purpose of the behaviour and why did it evolve the way it did. Studies on animal behaviour today are even more exciting that in the past as they encompass new disciplines such as behavioural ecology and socio-biology. (I'm guessing this statement is an effort to convince students to keep studying this kind of stuff
- I do find it interesting though).Behavioural Ecology
Behavioural ecology is a fusion of ethology, ecology and evolutionary biology. It is the study of the relationships between an organism's behaviour and the environment in which that behaviour has evolved or is expressed. Behavioural ecologists study both the function of behaviour (why animals and plants behave the way the do), and the role of behaviour in determining population dynamics and community patterns. It is a predictive science and has had some "stunning successes." It has also been criticised for looking too much at function at the expense of underlying mechanisms and a balanced view of the 4 whys. A variety of tools and approaches are used in modern behavioural ecology and the best studies are now multi-disciplinary.
Behavioural Ecology and Sociobiology
The application of behavioural ecology to social behaviour. This is the study of behaviour of social animals, including humans. Sociobiology developed from studies in population biology and genetics. Edward Osborne Wilson is a very important figure in this field (also a fucking hero, my favourite scientist). In his 1975 book Sociobiology he attempted to find the evolutionary pressures which led to the evolution of social behaviour in a diverse group of animals. This has been very controversial when directed towards human behaviours such as crime, mate choice, marriage and promiscuity. (When you read his work in full, and then comments directed at it by both the political left and right, it demonstrates so perfectly why ideology is wrong, and why we should form opinions based solely on evidence. Dismissing scientific fact as wrong because you don't like the implications morally, ethically or it doesn't agree with your personal opinions is completely illogical and irrational. The world is not how we'd like it to be, it is how it is, and the sooner we can realise that and start making decisions based on how it actually is, the sooner we can fix it. In the time it's taken you to read this post, 1 organism has gone extinct in the world due to human irrationality - not greed or selfishness, because preserving the environment is clearly in our best interests. Just short sightedness and an inability to think rationally, and clearly).
Lecture 8 (EW)
Development of behaviour; instinct and nature vs nurture
In the previous lecture we discussed the views of ethologists and comparative psychologists, and before that we talked about the evolutionary basis of behaviour. The evolutionary basis of behaviour suggests that behaviour is determined by genes and inheritance. Comparative psychology argues that it comes through learning.
The debate wasn't just from different fields, but it was also very regional. The ethologists were European while the comparative psychologists were American. Their debate is essentially the nature (ethology) vs nurture (comparative psychology).
[recap of Pavlov's dogs - classical conditioning]
J B Watson carried out the famous little Albert experiment where he used classical conditioning to make a baby afraid of white lab rats, and possibly all white things. (However my psychology lecturers last semester were unable to explain why Albert reacted strongly to the conditioned stimulus - a loud noise behind him - if behaviour is learned, or could even understand my question "but what would people who did believe in nurture over nature say?"). Humans also appear to be naturally pre-disposed to fearing many things that pose no real danger - such as spiders. Why, and how could that evolve?
[Skinner box and operant conditioning - ie. behaviour that is rewarded becomes more common, punished behaviour becomes less common]
However ethologists developed experiments where animals were kept in isolation and not given the opportunity to learn and looked for changes in behaviour. They found that many behaviours were expressed without being learned.
Example;
In one experiment duckings from tree nesting species and ground nesting species were put on a table with gap and glass over the gap. Tree nesting duckings were not afraid of the height and tried to leap over the gap. Ground nesting ducklings attempted to avoid it.
However some behaviours in animals are drastically altered if they are reared in isolation, and this demonstrates that both nature and nurture are important in the development of animals. Most likely nurture is more important in K- selection species while nature is more important in r- selection species - and a mix is important for almost all species (certainly nature is always important, but nurture cannot possibly be a factor in many r- selection species as they never get a chance to learn).
Problems with isolation studies
There are obviously ethical issues (boo). Also it's difficult to know what the animal has been deprived of. It might not express the behaviour because there are not the environmental triggers, rather than a lack of learning. There is the problem of viewing behaviour as either nature or nurture - could be a combination. Natural selection has only determined how development should take place in the normal environment of the species. Psychologists have found that different species have different capacities to learn - so there has obviously been natural selection on learning ability and learning ability is genetic (nature).
Genetics and Environment
Song development in birds.
Song development in birds is a classic example of genetic and environmental influences on development. Song birds have complex songs that can be species specific or even population specific. Songs in males is important for territory and attracting girls. Males reared in isolation produce very different songs. However their songs are still about the same length, correct frequency range, contain the right number of notes but lack the detailed structure and were not split into the right phases. With a social influence birds played exactly the songs they were taught. They can learn the song in the first weeks of life but don't start singing it until 8 months later - they store a memory of the sound and match it to their output when they mature. They are constrained in what they can learn and only their correct song or closely related songs. Some species cannot learn from recordings and need a live tutor. Some species can produce normal songs while being deaf, while others cannot. Some can be trained to learn a huge range of songs and sounds. The timing of learning also varies significantly between species. Testosterone plays an important role in this.
Recognising predators and prey.
Recognising predators and food is just as important as being able to find mates, but threats and food come in many forms.
For example coastal garter snakes eat slugs for food, while inland snakes do not, but instead eat frogs and fish. Why?
Recognition of potential prey types can be inbuilt (genetic) or learned. Learned allows them to adapt to new prey types.
Poisoning rats.
When rats encounter a new prey type they take a small nibble and then wait to see what happens. If they get ill they reject the the prey type. This means that the initial poison needs to be very strong. Rats can also learn food preferences from their mothers milk and from copying or even just smelling other older rats.
Predator recognition.
Harbour seals in British Columbia have learnt to tell the difference between predatory seal eating killer whales and resident killer whales that specialise on fish. When they hear familiar whale calls they are unconcerned but when they hear the calls of transient whales they take action.
Learning from own mistakes can be fatal, it is better to learn from the experience of others. Social context is very important to young animals. This is especially the case in animals that form social groups. Once one individual learns a particular skill or acquires a piece of information it can spread throughout the whole group. This is called cultural transmission. Sometimes this can be controversial as it is hard to understand why the behaviour is copied. It's not always restricted to juveniles.
Social influences on learning can take many forms. Continuum from full imitation to "facilitated learning" - Great tits and the great cream robbery.
Great tits (Parus majori) started stealing cream from milk bottles in the 1930s in the UK. The birds are naturally attracted to bright objects, such as the aluminium caps of milk bottles). They also naturally gain access to sources of food (such as nuts) by hammering at them with their beaks. Some individuals learned to hammer at a milk cap and get access to energy rich milk. The behaviour quickly spread throughout the UK so that soon no milk bottle was safe. At first seen as cultural inheritance. However mapping of the habit showed it spread out from specific focal points and experiments suggested it could not have spread through imitation. It was found that birds only learnt the behaviour if they found bottles that already had holes in them and learnt to regard the bottle as a source of cream. They then figured out how to get it by themselves (so no direct species to species learning occurred).
Tools
Thinkers as diverse as Freud and Carlyle have long pointed to tool use as one of the defining behaviours of man. Freud wrote that tool use was among mankind's first acts of civilisation. However tool use is found in many animals, especially social animals - this is usually learned through cultural transmission.
When behaviours are learned, either independently or from others in a social environment, the behaviour is obviously not genetic. However these behaviours occur from one generation to the next. On what trait might selection act and therefore lead to these behaviours occurring from generation to generation? (obviously ability to learn). (Note that "memes" are the term for the learned skills and information being transmitted in these situations.)
Conclusion
Animals need to know many things to survive, some are inherited and some are learned. The development of behaviour is complex and can occur in many different ways. Some behaviours are flexible and are successful in a wide range of circumstances. Others do not work in a range of situations and must be adaptable. There are many genetic constraints on learning, just as there are many environmental modifications to inherited behaviours. Genes and environment both affect behaviour and interact to produce adaptive outcomes.
Development of behaviour; instinct and nature vs nurture
In the previous lecture we discussed the views of ethologists and comparative psychologists, and before that we talked about the evolutionary basis of behaviour. The evolutionary basis of behaviour suggests that behaviour is determined by genes and inheritance. Comparative psychology argues that it comes through learning.
The debate wasn't just from different fields, but it was also very regional. The ethologists were European while the comparative psychologists were American. Their debate is essentially the nature (ethology) vs nurture (comparative psychology).
[recap of Pavlov's dogs - classical conditioning]
J B Watson carried out the famous little Albert experiment where he used classical conditioning to make a baby afraid of white lab rats, and possibly all white things. (However my psychology lecturers last semester were unable to explain why Albert reacted strongly to the conditioned stimulus - a loud noise behind him - if behaviour is learned, or could even understand my question "but what would people who did believe in nurture over nature say?"). Humans also appear to be naturally pre-disposed to fearing many things that pose no real danger - such as spiders. Why, and how could that evolve?
[Skinner box and operant conditioning - ie. behaviour that is rewarded becomes more common, punished behaviour becomes less common]
However ethologists developed experiments where animals were kept in isolation and not given the opportunity to learn and looked for changes in behaviour. They found that many behaviours were expressed without being learned.
Example;
In one experiment duckings from tree nesting species and ground nesting species were put on a table with gap and glass over the gap. Tree nesting duckings were not afraid of the height and tried to leap over the gap. Ground nesting ducklings attempted to avoid it.
However some behaviours in animals are drastically altered if they are reared in isolation, and this demonstrates that both nature and nurture are important in the development of animals. Most likely nurture is more important in K- selection species while nature is more important in r- selection species - and a mix is important for almost all species (certainly nature is always important, but nurture cannot possibly be a factor in many r- selection species as they never get a chance to learn).
Problems with isolation studies
There are obviously ethical issues (boo). Also it's difficult to know what the animal has been deprived of. It might not express the behaviour because there are not the environmental triggers, rather than a lack of learning. There is the problem of viewing behaviour as either nature or nurture - could be a combination. Natural selection has only determined how development should take place in the normal environment of the species. Psychologists have found that different species have different capacities to learn - so there has obviously been natural selection on learning ability and learning ability is genetic (nature).
Genetics and Environment
Song development in birds.
Song development in birds is a classic example of genetic and environmental influences on development. Song birds have complex songs that can be species specific or even population specific. Songs in males is important for territory and attracting girls. Males reared in isolation produce very different songs. However their songs are still about the same length, correct frequency range, contain the right number of notes but lack the detailed structure and were not split into the right phases. With a social influence birds played exactly the songs they were taught. They can learn the song in the first weeks of life but don't start singing it until 8 months later - they store a memory of the sound and match it to their output when they mature. They are constrained in what they can learn and only their correct song or closely related songs. Some species cannot learn from recordings and need a live tutor. Some species can produce normal songs while being deaf, while others cannot. Some can be trained to learn a huge range of songs and sounds. The timing of learning also varies significantly between species. Testosterone plays an important role in this.
Recognising predators and prey.
Recognising predators and food is just as important as being able to find mates, but threats and food come in many forms.
For example coastal garter snakes eat slugs for food, while inland snakes do not, but instead eat frogs and fish. Why?
Recognition of potential prey types can be inbuilt (genetic) or learned. Learned allows them to adapt to new prey types.
Poisoning rats.
When rats encounter a new prey type they take a small nibble and then wait to see what happens. If they get ill they reject the the prey type. This means that the initial poison needs to be very strong. Rats can also learn food preferences from their mothers milk and from copying or even just smelling other older rats.
Predator recognition.
Harbour seals in British Columbia have learnt to tell the difference between predatory seal eating killer whales and resident killer whales that specialise on fish. When they hear familiar whale calls they are unconcerned but when they hear the calls of transient whales they take action.
Learning from own mistakes can be fatal, it is better to learn from the experience of others. Social context is very important to young animals. This is especially the case in animals that form social groups. Once one individual learns a particular skill or acquires a piece of information it can spread throughout the whole group. This is called cultural transmission. Sometimes this can be controversial as it is hard to understand why the behaviour is copied. It's not always restricted to juveniles.
Social influences on learning can take many forms. Continuum from full imitation to "facilitated learning" - Great tits and the great cream robbery.
Great tits (Parus majori) started stealing cream from milk bottles in the 1930s in the UK. The birds are naturally attracted to bright objects, such as the aluminium caps of milk bottles). They also naturally gain access to sources of food (such as nuts) by hammering at them with their beaks. Some individuals learned to hammer at a milk cap and get access to energy rich milk. The behaviour quickly spread throughout the UK so that soon no milk bottle was safe. At first seen as cultural inheritance. However mapping of the habit showed it spread out from specific focal points and experiments suggested it could not have spread through imitation. It was found that birds only learnt the behaviour if they found bottles that already had holes in them and learnt to regard the bottle as a source of cream. They then figured out how to get it by themselves (so no direct species to species learning occurred).
Tools
Thinkers as diverse as Freud and Carlyle have long pointed to tool use as one of the defining behaviours of man. Freud wrote that tool use was among mankind's first acts of civilisation. However tool use is found in many animals, especially social animals - this is usually learned through cultural transmission.
When behaviours are learned, either independently or from others in a social environment, the behaviour is obviously not genetic. However these behaviours occur from one generation to the next. On what trait might selection act and therefore lead to these behaviours occurring from generation to generation? (obviously ability to learn). (Note that "memes" are the term for the learned skills and information being transmitted in these situations.)
Conclusion
Animals need to know many things to survive, some are inherited and some are learned. The development of behaviour is complex and can occur in many different ways. Some behaviours are flexible and are successful in a wide range of circumstances. Others do not work in a range of situations and must be adaptable. There are many genetic constraints on learning, just as there are many environmental modifications to inherited behaviours. Genes and environment both affect behaviour and interact to produce adaptive outcomes.
Senses and Signals (EW)
This lecture is 70 slides
Animals need to keep a constant check on their environment through the medium of their senses. Therefore we need to understand sensory processes and their relationship with behaviour to understand how behaviour is caused. It's not always simple! The environment is full of information that needs to be filtered to respond correctly. Nervous system registers a lot and then brain filters it down. We tend to misjudge the importance of senses other than sight and hearing because those are particularly well developed in humans. Understanding sensors requires some understanding of anatomy and/or physiology. Some species have better hearing and vision than us - such as owls. Bats and dolphins have hearing that is used for echolocation, and we are unable to hear many sounds that other animals can. Many animals can also see a greater range of wavelengths than we can.
An increasing number of birds have been shown to able to see within the UV range. They use colour to communicate a variety of information such as status, condition, sex, mate choice etc. Plants also use it to give cues to insects that can see UV. In 2004 it was also found that fish communicate and can see using UV. - Prey and predator detection, species recognition, schooling behaviour and intra-species communication are all influenced by UV colours. Some bats have also been found to see in UV (Nature 2003).
Snakes have special senses to allow them to sense vibrations, smell, and heat, as well as sight. I.e. snakes can see infrared light. Pigeons can detect magnetic fields and the platypus can detect electric fields.
How do males tell the difference between other males and females, and how do they know when to do which display?
Tinbergen (Causation, development, evolution, function) performed a classic series of experiments using models to explore this question. He was able to show that very few simple features have to be present to elicit the behaviours.
For example with Sticklebacks a red painted rock was enough to elicit an attack response while a slightly "swollen belly" shaped rock (with no red) was enough to elicit the zig-zag dance response. There is little cost to the dance and a good payback if she responds. Also almost any red resulted in the attack response. This is because the cost of letting one male get passed is very high.
So limited aspects of the stimulus may be enough to elicit a response. This is called "sign stimuli." Animals attend to a limited range of cues, rather than all the information, to make decisions easier and simpler. For sticklebacks this makes it easy to distinguish between males and females based on the red belly and easy to distinguish between ripe and unripe bellies based on the degree of swelling, and therefore act in the appropriate manner.
Evolution
Initially the stimuli provided a measure of a trait of interest and was used as a cue - males that could recognise a female with eggs were more likely to breed etc. Females are also helped by making it more obvious. Natural selection then exaggerates these signs and responses. Natural selection can also refine the signal to make it more effective. Sign stimuli that have arisen during evolution especially to function as signals from one animal to another are known as releasers. E.g. Butterfly wings, bird songs, bird markings, mammal scents.
Releasers are therefore an important part of communication. The early ethologists used a lock and key analogy. The sign stimulus was like a key that turned the lock somewhere in an animal. Technically this is referred to as the Innate Releasing Mechanism (IRM) which caused the animal to perform the appropriate act, referred to as Fixed Action Pattern (FAP). This is now regarded as a little too simplistic. It is better to explain in evolutionary terms - appropriate response to signal improves fitness and leads to selection on sign stimulus and response.
Stimulus filtering
An animal cannot response to all signals received, but it needs to always respond to some signals. So senses do more than passively receive input. Filtering of information occurs at two levels - within the sense organ and within the brain (processing).
The sensory world of frogs and toads
Have been intensively studied and provide some good examples. Visual information from the retina is sorted by different classes of ganglia according to sensitivity to size, contrast, motion, and colour. They are particularly sensitive to small objects (prey) and large moving objects (predators). Amphibian eyes are more complex than mammalian eyes. They have several layers of cells between the light receptors and the nerve fibres which travel to the brain. Each ganglion cell receives input from a large number of receptors. Some ganglion cells respond best to fairly specific objects. One class fires when a small rounded object passes into the field view, and keeps firing even if the object becomes stationary. These cells are called "bug detectors." The best stimulus is elicited to a thin dark line (ie. a worm). Therefore frog's eyes filter out a lot of irrelevant information before it is sent to the brain.
The problem with this kind of filtering is that it is very rigid - much potential food or predators will not be seen, especially if it is introduced (this is one of the reasons frogs are so vulnerable to introduced predators). These peripheral filters are therefore usually found in specialist animals with relatively simple requirements. In birds and mammals the eyes are much simpler but these means much more information is passed to the brain where the filtering occurs. In birds and mammals there are cells in the brain that fire in response to specific stimuli like sharps and edges, rather than in the eye.
Therefore birds and mammals are much better at recognising and respond to a wider range of stimuli. As a result they can recognise individual members of their species using a suite of subtle visual, auditory and olfactory cues. They can also detect small differences in potential predators and do not waste time and energy running from similar looking but harmless predators.
However our brain filtering and interpreting can lead to mistakes - ie. optical illusions etc.
[collection of standard optical illusions]
"The brain is a natural onboard virtual reality computer, construction images of the world according to rules honed by natural selection" - Richard Dawkins 1998.
Information is amplified, integrated, suppressed or synthesised to generate the best working hypothesis for functioning in the environment. Adaptive value is to allow the brain to rationalise the environment according to well-tried rules - saves time providing the errors are not too costly.
Perceptual rules of thumb predispose an animal to notice and respond to certain features within the environment. These sensory biases lead to evolutionary pathways and play an important role in the evolution of animal signalling systems. For example females choose big males (for a variety of reasons), males exploit this bias by evolving characters that make them appear larger (tails, fins, heads etc.) Similarly, many species judge size of individuals by the size of their eyes - leading to the evolution of artificial eye spots. Certain species have colour sensory bias (e.g blue because they forage on blue berries), so males exploit this by adopting that colour as their colour of choice. These are examples of sensory exploitation.
---
Having a break from study to go to touch football training.
This lecture is 70 slides
Animals need to keep a constant check on their environment through the medium of their senses. Therefore we need to understand sensory processes and their relationship with behaviour to understand how behaviour is caused. It's not always simple! The environment is full of information that needs to be filtered to respond correctly. Nervous system registers a lot and then brain filters it down. We tend to misjudge the importance of senses other than sight and hearing because those are particularly well developed in humans. Understanding sensors requires some understanding of anatomy and/or physiology. Some species have better hearing and vision than us - such as owls. Bats and dolphins have hearing that is used for echolocation, and we are unable to hear many sounds that other animals can. Many animals can also see a greater range of wavelengths than we can.
An increasing number of birds have been shown to able to see within the UV range. They use colour to communicate a variety of information such as status, condition, sex, mate choice etc. Plants also use it to give cues to insects that can see UV. In 2004 it was also found that fish communicate and can see using UV. - Prey and predator detection, species recognition, schooling behaviour and intra-species communication are all influenced by UV colours. Some bats have also been found to see in UV (Nature 2003).
Snakes have special senses to allow them to sense vibrations, smell, and heat, as well as sight. I.e. snakes can see infrared light. Pigeons can detect magnetic fields and the platypus can detect electric fields.
How do males tell the difference between other males and females, and how do they know when to do which display?
Tinbergen (Causation, development, evolution, function) performed a classic series of experiments using models to explore this question. He was able to show that very few simple features have to be present to elicit the behaviours.
For example with Sticklebacks a red painted rock was enough to elicit an attack response while a slightly "swollen belly" shaped rock (with no red) was enough to elicit the zig-zag dance response. There is little cost to the dance and a good payback if she responds. Also almost any red resulted in the attack response. This is because the cost of letting one male get passed is very high.
So limited aspects of the stimulus may be enough to elicit a response. This is called "sign stimuli." Animals attend to a limited range of cues, rather than all the information, to make decisions easier and simpler. For sticklebacks this makes it easy to distinguish between males and females based on the red belly and easy to distinguish between ripe and unripe bellies based on the degree of swelling, and therefore act in the appropriate manner.
Evolution
Initially the stimuli provided a measure of a trait of interest and was used as a cue - males that could recognise a female with eggs were more likely to breed etc. Females are also helped by making it more obvious. Natural selection then exaggerates these signs and responses. Natural selection can also refine the signal to make it more effective. Sign stimuli that have arisen during evolution especially to function as signals from one animal to another are known as releasers. E.g. Butterfly wings, bird songs, bird markings, mammal scents.
Releasers are therefore an important part of communication. The early ethologists used a lock and key analogy. The sign stimulus was like a key that turned the lock somewhere in an animal. Technically this is referred to as the Innate Releasing Mechanism (IRM) which caused the animal to perform the appropriate act, referred to as Fixed Action Pattern (FAP). This is now regarded as a little too simplistic. It is better to explain in evolutionary terms - appropriate response to signal improves fitness and leads to selection on sign stimulus and response.
Stimulus filtering
An animal cannot response to all signals received, but it needs to always respond to some signals. So senses do more than passively receive input. Filtering of information occurs at two levels - within the sense organ and within the brain (processing).
The sensory world of frogs and toads
Have been intensively studied and provide some good examples. Visual information from the retina is sorted by different classes of ganglia according to sensitivity to size, contrast, motion, and colour. They are particularly sensitive to small objects (prey) and large moving objects (predators). Amphibian eyes are more complex than mammalian eyes. They have several layers of cells between the light receptors and the nerve fibres which travel to the brain. Each ganglion cell receives input from a large number of receptors. Some ganglion cells respond best to fairly specific objects. One class fires when a small rounded object passes into the field view, and keeps firing even if the object becomes stationary. These cells are called "bug detectors." The best stimulus is elicited to a thin dark line (ie. a worm). Therefore frog's eyes filter out a lot of irrelevant information before it is sent to the brain.
The problem with this kind of filtering is that it is very rigid - much potential food or predators will not be seen, especially if it is introduced (this is one of the reasons frogs are so vulnerable to introduced predators). These peripheral filters are therefore usually found in specialist animals with relatively simple requirements. In birds and mammals the eyes are much simpler but these means much more information is passed to the brain where the filtering occurs. In birds and mammals there are cells in the brain that fire in response to specific stimuli like sharps and edges, rather than in the eye.
Therefore birds and mammals are much better at recognising and respond to a wider range of stimuli. As a result they can recognise individual members of their species using a suite of subtle visual, auditory and olfactory cues. They can also detect small differences in potential predators and do not waste time and energy running from similar looking but harmless predators.
However our brain filtering and interpreting can lead to mistakes - ie. optical illusions etc.
[collection of standard optical illusions]
"The brain is a natural onboard virtual reality computer, construction images of the world according to rules honed by natural selection" - Richard Dawkins 1998.
Information is amplified, integrated, suppressed or synthesised to generate the best working hypothesis for functioning in the environment. Adaptive value is to allow the brain to rationalise the environment according to well-tried rules - saves time providing the errors are not too costly.
Perceptual rules of thumb predispose an animal to notice and respond to certain features within the environment. These sensory biases lead to evolutionary pathways and play an important role in the evolution of animal signalling systems. For example females choose big males (for a variety of reasons), males exploit this bias by evolving characters that make them appear larger (tails, fins, heads etc.) Similarly, many species judge size of individuals by the size of their eyes - leading to the evolution of artificial eye spots. Certain species have colour sensory bias (e.g blue because they forage on blue berries), so males exploit this by adopting that colour as their colour of choice. These are examples of sensory exploitation.
---
Having a break from study to go to touch football training.
Sensory Exploitation
Males can adopt displays that match pre-existing preferences of females (sensory exploitation). For example water mites respond to vibrations produced by their prey. Courting males simulate these vibrations by trembling their legs and attracting females to them, exploiting their predisposition to the stimulus. Eye spots are another example of sensory exploitation (butterfly's wings etc.) They have two functions, to make them look bigger and to disorientate predators so that they attack the less vulnerable part of the animal. In swordtail fish, females prefer males with longer tails. However in similar related platys, which don't have swords, females prefer bigger males. One explanation is that swordtail males just make their tale larger rather than being larger themselves, and the females think that they're getting bigger mates when they're not.
Summary
Animals have many different senses, some nothing like ours. The senses can be fine tuned to particular stimulus. The information can be filtered by the sense organ itself or if the sense organ has a wide range of uses, central mechanisms are used to filter the information. Natural selection has led animals to be more sensitive to some stimuli than others, shaping evolutionary pathways and appropriate responses.
Communication
Whenever an animal responds to another (especially within a species), there must have been some form of communication. We've already covered many of the ways that animals can communicate and the different messages need to communicate. Further understanding of how animals communicate is an important further step in understanding and interpreting behaviour. To do that we need to be able to decipher their language. It's important to note that we're using "language" in the broadest possible sense. Any single that animals use to convey information we are calling language (very important, as usual, not to anthropomorphise).
Communication; The basics
The sender is the individual that transmits the signal.
The receiver is the individual whose probability of behaving in a particular way is altered by the signal.
The signal is the behaviour (posture, display, vocalisation) transmitted by the sender (can also be a "lack" of behaviour).
The channel is the medium through which the signal is transmitted (visual, vocal, or could be the environment ie. air, water).
The context is the setting or situation in which the signal is transmitted and received.
Noise is any background activity in the channel which is irrelevant to the signal being transmitted.
Variation in all of these drives diversity in signalling systems.
Communication may involve stylised signal or display resulting in obvious response by another. Signals in these cases are: distinctive, often exaggerated, noticeable, attention grabbing. However signals may also be subtle, which would mean that they're not obvious to a third party like us - such as responses of receiver to slight changes in posture (especially in social species), the signaller may not be present (ie. scent markings etc.). Response might be delayed (ie. impact of male odour on female reproduction).
Sometimes a signal bears no obvious relation to the meaning it conveys. For example a song bird may be singing to establish territory or to attract a mate, and it's not possible to immediately tell the difference between these two songs. In other cases the signal may convey information, such as pheromones to convey specific information on reproductive state, or the roar of a lion/deer indicates the size of the animal. The colour of a bird my reflect foraging capacity (ie. these signals give an analogue representation of the traits of the animal). Sometimes it is hard to find the link between the signal and the information, such as courtship dance of birds (how do females decide which is better?) or the colour of sand lizards (it turns represent immune capacity). Signals can also have different meanings to different individuals.
Information, manipulation and individual selection.
A lot of communication between individuals is about sharing information for the mutual benefit. That is both the signaller and receiver benefit in some way. However remember that natural selection works on individuals - so both the signaller and receiver must derive a fitness advantage from interpreting the message. Otherwise they would neither send the message or interpret it. Animals will produce signals that are to their benefit, regardless of the benefit to the receiver. So it may be better to regard animals as using signals to manipulate each other, rather than freely exchanging information. (such as sensory exploitation).
Most communication uses sight, sound or smell (sometimes touch or taste). Very rarely other forms are used, such as electrical discharges. Like everything else, the particular form of communication used and the associated use of particular senses has its advantages and disadvantages.
There are too many aspects to go through all of them, but here are some generalisations with examples.
Visual signals
Visual messages are usually conveyed through changes in posture or colour. Because day time predators tend to use vision as their most important sense there are risks involved in using vision as a signal. Vision also only works if the receiver can see the signaller (ORLY?) so it's not so good in dense forest or murky water etc. Visual cues therefore tend to be used in short-range communication between mates and rivals. Visual signallers minimise their risk by hiding when the signals are not needed.
Acoustic signals
Sound is not as private as sight since noise travels outwards in all directions and cannot easily be directed to a specific individual. However sound can travel around corners and so is good for general advertising. Sound also travels along way and works just as well in the dark or underwater. A lot of information can also be transmitted very quickly. Sound is an excellent form of communication, which is why humans use it as our principle mode of communication (language). Some sounds travel better in some mediums than others. Water is different to air and whale songs can be transmitted over 100kms if there are no boats. Whales also have finely tuned hearing, so their communication is very effective. However sounds can be distorted by objects (such as echo). Pure tones can travel without being distorted - so bird species in rainforests avoid rapid trills and use pure tones instead. Complexity of bird song (and visual signals) is related to their habitat.
Olfaction (smell)
Olfactory signals are called pheromones. Smells diffuse very slowly through the environment and their speed and direction of travel are highly wind dependent, but they can travel a long way. After one smell is released, time must elapse before another signal can be employed (unlike a song or display that can have a rapid change and frequency of information). Therefore only a small amount of information can be carried through smell. However under some circumstances pheromones are ideal. Small animals cannot and do not want to generate loud noises. Pheromones are usually also cheap to produce (can be by products of physiological processes) and can last a long time, even if the signaller is not there (such as territory markings). A moth cannot generate a noise that can be heard more than 100m away, but a male can smell a female several kilometres away. The female produces a chemical with very small molecules meaning it diffuses rapidly and the male can detect a very small number of molecules easily. Also obviously sharks and blood. Many animals take advantage of the fact that the signaller does not need to be present with the signal. That is why so many animals have scent glands - especially to mark territory.
When we see an animal that is brightly coloured, boldly patterned, or which is making a loud or obvious noise or smell we can be fairly sure that communication is taking place. The message must be important because it's bring attention to itself (risking predation, or competition).
For example tungara frogs in Panama use a very conspicuous call to attract mates. Fringe-lipped bats home in on those calls and are very successful at eating the frogs.
Animals try to reduce the costs of communication through crypsis or camouflage.
Prey can also use misleading signals to trick predators, such as birds that fake a broken wing to lure predators away from the nest, or the eyespots on butterflies. Predators also use misleading signals. For example the zone-tailed kite has a silhouette similar to the American vulture so as to trick prey into thinking it's not dangerous.
The bluegill sunfish of North America uses trick visual signals. Most males mature after 7 or 8 years and set up territories to attract females. Some males mature after only 2 or 3 years and look almost identical to the females. The larger males let them in to the territory and then they fertilise the females eggs before the larger male can. This is also a common strategy with some frogs.
In many contests for females, the size of the male is important. However sometimes it is cheaper to appear bigger than you actually are. Appearing bigger and using an aggressive display would reduce fights and allow you to deceive opponent without having to use the energy to actually be bigger. Many animals, such as Siamese fighting fish use this, and have elaborate ornaments that make them appear bigger than they are.
Males can adopt displays that match pre-existing preferences of females (sensory exploitation). For example water mites respond to vibrations produced by their prey. Courting males simulate these vibrations by trembling their legs and attracting females to them, exploiting their predisposition to the stimulus. Eye spots are another example of sensory exploitation (butterfly's wings etc.) They have two functions, to make them look bigger and to disorientate predators so that they attack the less vulnerable part of the animal. In swordtail fish, females prefer males with longer tails. However in similar related platys, which don't have swords, females prefer bigger males. One explanation is that swordtail males just make their tale larger rather than being larger themselves, and the females think that they're getting bigger mates when they're not.
Summary
Animals have many different senses, some nothing like ours. The senses can be fine tuned to particular stimulus. The information can be filtered by the sense organ itself or if the sense organ has a wide range of uses, central mechanisms are used to filter the information. Natural selection has led animals to be more sensitive to some stimuli than others, shaping evolutionary pathways and appropriate responses.
Communication
Whenever an animal responds to another (especially within a species), there must have been some form of communication. We've already covered many of the ways that animals can communicate and the different messages need to communicate. Further understanding of how animals communicate is an important further step in understanding and interpreting behaviour. To do that we need to be able to decipher their language. It's important to note that we're using "language" in the broadest possible sense. Any single that animals use to convey information we are calling language (very important, as usual, not to anthropomorphise).
Communication; The basics
The sender is the individual that transmits the signal.
The receiver is the individual whose probability of behaving in a particular way is altered by the signal.
The signal is the behaviour (posture, display, vocalisation) transmitted by the sender (can also be a "lack" of behaviour).
The channel is the medium through which the signal is transmitted (visual, vocal, or could be the environment ie. air, water).
The context is the setting or situation in which the signal is transmitted and received.
Noise is any background activity in the channel which is irrelevant to the signal being transmitted.
Variation in all of these drives diversity in signalling systems.
Communication may involve stylised signal or display resulting in obvious response by another. Signals in these cases are: distinctive, often exaggerated, noticeable, attention grabbing. However signals may also be subtle, which would mean that they're not obvious to a third party like us - such as responses of receiver to slight changes in posture (especially in social species), the signaller may not be present (ie. scent markings etc.). Response might be delayed (ie. impact of male odour on female reproduction).
Sometimes a signal bears no obvious relation to the meaning it conveys. For example a song bird may be singing to establish territory or to attract a mate, and it's not possible to immediately tell the difference between these two songs. In other cases the signal may convey information, such as pheromones to convey specific information on reproductive state, or the roar of a lion/deer indicates the size of the animal. The colour of a bird my reflect foraging capacity (ie. these signals give an analogue representation of the traits of the animal). Sometimes it is hard to find the link between the signal and the information, such as courtship dance of birds (how do females decide which is better?) or the colour of sand lizards (it turns represent immune capacity). Signals can also have different meanings to different individuals.
Information, manipulation and individual selection.
A lot of communication between individuals is about sharing information for the mutual benefit. That is both the signaller and receiver benefit in some way. However remember that natural selection works on individuals - so both the signaller and receiver must derive a fitness advantage from interpreting the message. Otherwise they would neither send the message or interpret it. Animals will produce signals that are to their benefit, regardless of the benefit to the receiver. So it may be better to regard animals as using signals to manipulate each other, rather than freely exchanging information. (such as sensory exploitation).
Most communication uses sight, sound or smell (sometimes touch or taste). Very rarely other forms are used, such as electrical discharges. Like everything else, the particular form of communication used and the associated use of particular senses has its advantages and disadvantages.
There are too many aspects to go through all of them, but here are some generalisations with examples.
Visual signals
Visual messages are usually conveyed through changes in posture or colour. Because day time predators tend to use vision as their most important sense there are risks involved in using vision as a signal. Vision also only works if the receiver can see the signaller (ORLY?) so it's not so good in dense forest or murky water etc. Visual cues therefore tend to be used in short-range communication between mates and rivals. Visual signallers minimise their risk by hiding when the signals are not needed.
Acoustic signals
Sound is not as private as sight since noise travels outwards in all directions and cannot easily be directed to a specific individual. However sound can travel around corners and so is good for general advertising. Sound also travels along way and works just as well in the dark or underwater. A lot of information can also be transmitted very quickly. Sound is an excellent form of communication, which is why humans use it as our principle mode of communication (language). Some sounds travel better in some mediums than others. Water is different to air and whale songs can be transmitted over 100kms if there are no boats. Whales also have finely tuned hearing, so their communication is very effective. However sounds can be distorted by objects (such as echo). Pure tones can travel without being distorted - so bird species in rainforests avoid rapid trills and use pure tones instead. Complexity of bird song (and visual signals) is related to their habitat.
Olfaction (smell)
Olfactory signals are called pheromones. Smells diffuse very slowly through the environment and their speed and direction of travel are highly wind dependent, but they can travel a long way. After one smell is released, time must elapse before another signal can be employed (unlike a song or display that can have a rapid change and frequency of information). Therefore only a small amount of information can be carried through smell. However under some circumstances pheromones are ideal. Small animals cannot and do not want to generate loud noises. Pheromones are usually also cheap to produce (can be by products of physiological processes) and can last a long time, even if the signaller is not there (such as territory markings). A moth cannot generate a noise that can be heard more than 100m away, but a male can smell a female several kilometres away. The female produces a chemical with very small molecules meaning it diffuses rapidly and the male can detect a very small number of molecules easily. Also obviously sharks and blood. Many animals take advantage of the fact that the signaller does not need to be present with the signal. That is why so many animals have scent glands - especially to mark territory.
When we see an animal that is brightly coloured, boldly patterned, or which is making a loud or obvious noise or smell we can be fairly sure that communication is taking place. The message must be important because it's bring attention to itself (risking predation, or competition).
For example tungara frogs in Panama use a very conspicuous call to attract mates. Fringe-lipped bats home in on those calls and are very successful at eating the frogs.
Animals try to reduce the costs of communication through crypsis or camouflage.
Prey can also use misleading signals to trick predators, such as birds that fake a broken wing to lure predators away from the nest, or the eyespots on butterflies. Predators also use misleading signals. For example the zone-tailed kite has a silhouette similar to the American vulture so as to trick prey into thinking it's not dangerous.
The bluegill sunfish of North America uses trick visual signals. Most males mature after 7 or 8 years and set up territories to attract females. Some males mature after only 2 or 3 years and look almost identical to the females. The larger males let them in to the territory and then they fertilise the females eggs before the larger male can. This is also a common strategy with some frogs.
In many contests for females, the size of the male is important. However sometimes it is cheaper to appear bigger than you actually are. Appearing bigger and using an aggressive display would reduce fights and allow you to deceive opponent without having to use the energy to actually be bigger. Many animals, such as Siamese fighting fish use this, and have elaborate ornaments that make them appear bigger than they are.
No worries. I'm glad somebody read it . I only managed to write out about 30% of the lectures, but it still helped a lot and I'm pretty sure I did well on the exam.
Evolutionary biology is really interesting, that's definitely the kind of area I'm looking at as well, although I haven't made my mind up about specifics yet.
. I only managed to write out about 30% of the lectures, but it still helped a lot and I'm pretty sure I did well on the exam. Evolutionary biology is really interesting, that's definitely the kind of area I'm looking at as well, although I haven't made my mind up about specifics yet.
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QuantumBalance
- 100-Watt Warlock
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Thanks Sam. I don't believe in supernatural concepts that have no physical evidence to support them such as Karma. In fact I read a recent article about Karma in Buddhism that basically said that Westerners grossly misunderstood the concept it really just meant that if you keep a positive view of the world you'll feel better than if you keep a negative view.
Anyway just a quick update to say I managed to pass Ecology with distinction, which just goes to show that going to class is for chumps.
Anyway just a quick update to say I managed to pass Ecology with distinction, which just goes to show that going to class is for chumps.
Jeremy thank you sincerely for this topic <---actually the main thing i posted to say
concerning karma - it seems reasonable that every thought and action you ever undertake creates a subtle imprint upon your psyche which has an effect on this mental attitude thing, which seems more infinitely complex and layered than 'positive' or 'negative' can do justice to
PS man i always really appreciated your presence on the forums
concerning karma - it seems reasonable that every thought and action you ever undertake creates a subtle imprint upon your psyche which has an effect on this mental attitude thing, which seems more infinitely complex and layered than 'positive' or 'negative' can do justice to
PS man i always really appreciated your presence on the forums
Cheers There were like 40 lectures in the course and I only covered like 7 in the subject so I didn't do a great job with this topic. I think I got pretty good marks though.
I think regarding what you've said about karma, it's important to consider how much control we actually have over our thoughts and emotions. Emotions especially are far more a reaction than a conscious choice. Susan Blackmore has written a lot of interesting stuff about this. She loves her meditation and Eastern philosophy, but she's also a scientists and a psychologist. She thinks that ultimately all our behaviour is just responses to our environment (and how we respond ultimately depends on our genetics and previous environments).
There were like 40 lectures in the course and I only covered like 7 in the subject so I didn't do a great job with this topic. I think I got pretty good marks though. I think regarding what you've said about karma, it's important to consider how much control we actually have over our thoughts and emotions. Emotions especially are far more a reaction than a conscious choice. Susan Blackmore has written a lot of interesting stuff about this. She loves her meditation and Eastern philosophy, but she's also a scientists and a psychologist. She thinks that ultimately all our behaviour is just responses to our environment (and how we respond ultimately depends on our genetics and previous environments).
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james_dean
- space cowboy
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