9 Selfish Genes Flashcards
What is altruistic behaviour?
One organism does something that benefits another member of the same species
Increases the survival and reproduction of other individuals (increases fitness)
What is an altruistic action in ground squirrels?
Alarm call given when predator approaches
- Likelihood of an alarm call being given related to whether group contains relatives or not
- May actually alert predator to their presence, making them a target - however may allow relative to survive and pass on genes
What are examples of altruistic behaviour?
Alarm calls
Helpers at nest - some chicks stay to help parents raise more broods, sacrificing their own reproduction
Why is altruistic behaviour odd?
It potentially challenges evolutionary ideas
A gene that codes for altruistic behaviour will surely help other genes
What is kin selection?
- An explanation for altruistic behaviour
- An altruistic action will be favoured if it benefits kin (relatives - possess same genes)
- Altruistic genes increase rate of spread of themselves via relatives
What is relatedness?
The proportion of genes shared because of common ancestry
e.g. A (parent) to B (offspring) r=0.5
B to C (siblings) r=0.5
A (grandparent) to D (grandchild) r=0.5x0.5=0.25
cousin - cousin = 0.125
What is r x b > c?
Kin selection will evolve if true
r - relatedness - probability that a member of kin contains a gene for an altruistic act
b - benefit to target - number of extra copies of the gene yielded by the act
c - cost to giver in terms of lost number of copies of the gene produced by that individual
What happens if r x b < c?
Individual is not related to the others so does not give out an alarm call
Predator eats the non relatives so the individual lives and can pass on its genes
When will a gene spread in a population?
Anything that a gene can do to favour its own spread at the expense of others will be favoured by selection - the genes are selfish
What is green beard selection?
An altruism gene that is linked to an obvious phenotype will spread if the possessors are altruistic towards each other
Individuals do not need to be related
What is an example of green beard selection?
Lizards
- Unrelated male lizards with blue throats form partnerships to protect territories
- One of these males may have no offspring
- Genes for throat colour and cooperation are linked
What are the issues with green beard effects?
Cheating - possess the green beard but do not reciprocate the altruism
Green beards probably evolutionarily unstable
Kin selection probably more common
What are replicators?
These are individual units that replicate themselves e.g. genes
- Selection acts on them
- Those that leave the most copies are the most successful
- Species and individuals are not replicators
