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Day 7
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Lecture 7:Kin selection:
The evolution of cooperation is not easy to understand:
- Competition between individuals (but also between other units, organelles within cells)
usually disfavours cooperation
- Tragedy of the commons usually prevents the evolution of cooperative strategies that are
best for the group.
- Examples
o Plant growth
o Sex ratio
- Nevertheless: extreme examples of cooperation exist.
For example:
- If you have a group with 9 females and 9 males you can get 9 offspring
o Fitness is ( ) = 9
- If you have a group with 5 females and 5 males, you can get 5 offspring
o If there is also a hierarchy then the one male mates with the 5 females and the other
4 males do not mate.
o The average fitness of the male (5 (offspring) / 5 (males) = 1
- Because the fitness of the male is high, if there is a mutation in which you get more males
there will be selecte for and you get more males.
Major transitions in evolution (maynard smith en Szathmáry, 1995)
- Previously independent units unite to a new entity (unit of selection)
o Genes chromosomes
o Prokaryotes eukaryotes
, o …..
Social interactions between individuals of a single species:
Spite: Behaviour were an individual see recording
Examples of mutually beneficial interactions (++)
- Herd behaviour:
o By being member of a herd, a flock or a swarm, an individual has an advantage, but
also provides benefits to other members of the group (Hamilton: the selfish herd)
- Some bacteria excrete siderophores, for iron uptake. This is in their own interest, but also in
others interest.
Altruism (-+)
- Behaviour that benefits a recipient, but causes some reduction in donor fitness
- Large graduation, from subtle to eusocial
o Bee’s, ants, but also the naked mole rat
o A few reproductive members and a workers who don’t reproduce.
Not every behaviour that is called altruism is altruism
- Some seemingly altruistic hehaviour in fact
, You do something for an individual but you expect something in return (reciprocal altruism)
The evolution of altruism is a central paradox in evolutionary biology:
- How can natural selection favour a trait that results in behaviour benefiting other individuals
at the expends of the individual with that trait?
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