Lecture 3 - The Function & Evolution of Animal Behaviour Flashcards
What does it mean to have a function?
To have a function implies some sort of “design’ and this implies that a “designer” is involved.
What is the definition of selection?
Acts to sift variants of behaviour, favouring those that provide their bearer with greater representation in the next generation.
What is selection for survival?
Natural selection
Why is there a need for selection?
Environment is not static but dynamic and changes so animals must evolve to keep up with these changes
How does natural selection work in practice?
- Huge numbers of individuals are produced.
- Insufficient resources for all, so many die before reproducing.
- Individuals vary in attributes.
- Individuals with attributes better suited to environment are less likely to die.
- These individuals will be over represented in next generation.
What are phenotypes?
An expression of your genotypes. It is what you can see.
What is sexual dimorphism?
different behaviours by sexes to mate. overall population advantage .e.g male spotted by predators as visible but gets lots of mates
Behaviours are a result off…
A trade off between selective forces
How to stick insects find partners?
Not true hermaphrodites - one stick insect just needs to find another to reproduce
Behaviours function to maximise…
- Likelihood of long-term survival
- Lifetime reproductive output
What behaviours maximise survival?
- Hiding from predators
- Escaping from predators
- Increasing amounts of food eaten
- Reducing energetic costs
What behaviours aid reproduction?
- Increasing attractiveness
- Increasing access to mates
- Increasing fecundity
- Increasing survival of young
Example of how ostriches aid reproduction
Female is brown and male is black. They split the devision of labour equally. Females sit on eggs during day time and males at night time due to their colour
Example of prairie dog’s dysfunctional behaviour
Stand on their back legs and yell loudly to warn everyone that there is a predator and they need to go underground to a burrow. The caller will stand there until the predator is really close and everyone has gone underground
Example of common buzzards dysfunctional behaviour
mobbing - a group of prey species gather together to drive off predator. By clubbing together they are more successful and driving them out of their territory
Who does dysfunctional behaviours directly benefit?
individual
Who does dysfunctional behaviours indirectly benefit?
Kin and offspring
How have behaviours evolved?
Have more offspring and/ or enable species to continue for as long as possible
What is behaviour a compromise of?
Animal and the situation (despite the strength of selection pressures)
How to behaviours develop?
Refine previous behaviours exhibited by the species or its relatives
Do behaviours make an individual less fit that it previously was?
No
Why is the understanding of early relatives’ behaviours important?
We can better understand the behaviours we see today
What is epistasis?
a phenomenon whereby the expression of one gene depends upon the presence of the others around it. A gene can be expressed or repressed by the other genes around it
What is divergent evolution?
Evolution of different features from a common ancestor; resulting in differences between species.
What is an example of divergent evolution?
Darwin studied large ground finch. Some on the Galapagos island had wide beaks, some thin, some used tools. They have diverged onto different forms on the different islands depending on what was required - called adaptive radiation
What is convergent evolution?
Evolution of similar features in unrelated species due to similar environmental pressures.
What is an example of convergent evolution?
sharks and dolphins - look the same as they both live in the sea and hunt the same
When did behaviour arise?
Parsimony
- The process that requires the least number of changes. (being tight - doing it with the least amount of effort)
Example of parsimony
Peacock - three species from different countries - all have feathers on their heads and are blue and green - a small tweak gets you three types of animals
Why does behaviour arise?
- Pre-existing behaviour. - something the animal already does is co-optive for a new purpose
- Pre-existing bias. - maybe some males like it but females don’t. This is a colour used for this signal but at different times of year I use it for this signal
- Adaptive co-evolution. - at the same time something else evolves alongside it
What are complicating factors to evolution?
- Missing species.
- Changed environment.
- Changed selection pressures
Why are missing species a complicating factor?
Where does behaviour come from if the fossil record is incomplete?
Why is a changed environment a complicating factor?
Behaviour can develop in response to localised climatic change, which will increase the fitness of the individual in the long-term.
Why is a changed selection pressure a complicating factor?
Behaviours themselves can change the selective pressures on future generations.
How can we study past behaviour?
Evolution tells us what happens through showing us fossils
Fossil example
Usual dinosaur bones, patterns / indents in limestone show feathers - evolved changes to hair and skin. Clue as to something that could be used for particular behaviour.
