Lecture 1 - introduction Flashcards
describe the adaptationist approach
Any trait seen in an organism is an adaptation of selection – however we can interpret that adaptation in many different ways
describe the process of natural selection
natural selection is the process by which individuals of different genotypes make a differential contribution to offspring to the next generation
why does natural selection occur?
because genetically different individuals tend to leave different numbers of offspring in future generations so the genetic composition of a population changes
what are the units of natural selection?
genes or interacting groups of genes (=individuals)
what must the units of natural selection have the ability to do?
have the ability to survive, reproduce and make accurate copies of itself
what is the general expectation of behaviour?
that it should be selfish rather than cooperative
describe the social organisation of weavers
varies in many ways e.g. grey capped lives in loose colonies, black headed has much larger colonies, sociable weaver – extreme example of sociality
who tackled the question of varied sociality of weavers?
John crook (1964)
what 2 questions did john crook ask about the sociality of weavers?
- Why are some solitary and others colonial?
- Why are some dimorphic and others monomorphic?
what did john crook find to have an effect on the sociality of weavers?
he found that the food type had an effect on the social organisation of the weavers – predation had an effect too, but food was the main driver
what are the 3 main ways of studying/interpreting adaptation?
1) hypothesis testing (theoretical approaches)
2) comparative analysis (considers interspecific variation)
3) intraspecific studies which investigate individual trait variation (lab or field studies, observation or experiment)
describe comparative analysis and what is it also important to take into account
look at how a trait differs across species in relation to another trait (eg. How Food type effects social organisation in birds and monkeys) – IMPORTANT to take into account phylogeny when trying to understand how traits have evolved -Now have very powerful ways to understand phylogeny (Jetz et al 2012)
what are 2 questions often asked when considering comparative analysis?
1) Why do individuals vary in morphology or behaviour? E.g. ruffs in lekking – dark, light ruff, female mimic – individual variation
2) What are the causes and fitness consequences of this variation?
describe the use of individual variation to study adaptations
study of individuals– unusual behaviour strategies can often be explained by individual variation e.g. infanticide, male pregnancy (way for males to ensure paternity – male seahorses have the smallest testes as they don’t have the issue of competition), sexual cannibalism
The study of individuals can be made by observations in field/lab: what is the good and bad of long term studies?
Long term studies of marked individuals are particularly valuable but have drawbacks – long-time scales require lots of funding and some animals have long lifetimes (elephant)
what is an alternative to observational studies and an example?
experimental studies in the field or the lab:
- e.g. long tailed widowbird – stuck long tails onto birds – looked at reproductive success testing sexual selection – mates gained increased with increasing tail length)
why do we expect conflict to be rife in the natural world?
because genes/individuals are selected to to maxmise their fitness at the expense of others
what are the key timings of the development of evolutionary theory?
C Darwin 1850s – 1870s RA Fisher 1930s – 1940s WD Hamilton 1960s – 1990s J Maynard Smith 1960s – 1990s (hawk dove game theory) RL Trivers 1970s….. \+ R Dawkins 1976 ‘The Selfish Gene’
what is the adaptationist approach founded by?
by evolutionary theory which allows us to understand patterns or animal behaviour – happens under context which is provided by the ecology of the organism
- Weigh up the costs and benefits of a behaviour to determine its adaptive significance
- What is the evolutionary value (function) of a particular trait?
i. e. Why has it evolved?
what do selfish genes and individuals =?
conflict
describe the levels of selection?
Natural selection acts on either genes or individuals - individuals die, survive and reproduce, but consequence is that gene frequencies in population change
what is the general rule of group selection?
doesnt work…it is vulnerable to selfish behaviour by individuals
give examples of conflict that occurs in potentially cooperative contexts (e.g. sexual reproduction)?
1) parents are in conflict over their respective investments in offspring
2) offspring are in conflict over their share of that investment
3) parents and offspring are in conflict over how that investment is distributed within and between broods
define cooperative behaviour
behaviour that benefits another individual and that has been selected for because of its beneficial effects on the recipient
cooperation is seen everywhere, why is it an evolutionary puzzle to biologists?
how does cooperative behaviour evolve and persist in a world of selfish individuals - the problem is encapsulated by the tragedy of the commons
describe the public goods game
- Cooperative investment in public goods = benefits shares and costs are borne individually - However, Free riders don’t pay the cost of contribution and still get the benefits
what is the social dilemma or the public goods game?
groups of cooperators out-compete non-cooperators
- non-cooperators do better than cooperators within groups - benefits are shared but costs are borne individually – whenever there is cooperation there is always a temptation to defect( e.g. not cooperate)
describe the tragedy of the commons
- When there are shared benefits or a ‘public good’ that individuals contribute to, there will be a temptation to cheat or free-load
give an example of the tragedy of the commons
e.g. sociable weavers – overall structure of nest needs to be maintained – can last for decades – easy to freeload and just look after their own nest chamber but when observed they all spend a lot of times looking after the whole nest – must be mechanism in pace to maintain this
the main overarching question is why is cooperative behaviour so ubiquitous despite ‘the tragedy of the commons’- what are the 5 things discussed as potential solutions to this social dilemma?
1) group selection
2) kin selection
3) reciprocity
4) mutualism
5) manipulation
