9/ selfish genes Flashcards
1
Q
examples of seemingly altruistic behaviour
A
- ground squirrels giving alarm calls
- florida scrub jay - some chicks stay in nest to help their parents raise offspring, sacrificing their own reproduction
2
Q
explanation for altruistic behaviour
A
- increases survival and reproduction of other individuals
- other individuals are kin, so share same genes
- altruistic genes increase rate of spread of themselves via relatives
2
Q
relatedness between: offspring-parent, sibling-sibling, grandparent-grandchild, cousin-cousin
A
- 0.5
- 0.5
- 0.25
- 0.125
- can draw pedigree tree to work it out
2
Q
when does kin selection/altruistic behaviour occur - equation
A
- r x b > c
- relatedness of target individual/prob that a member of kin contains gene for altruistic act
- benefit too target/number of extra copies of the gene that act yields
- cost to giver/lost number of copies of the gene that individual produces
2
Q
relatedness definition
A
proportion of genes shared bc of common ancestry
3
Q
main principle behind this lecture
A
genes contained within individuals, who are actually reproducing and dying. but its the genes themselves that are being selected for
3
Q
green beard effects in red fire ants
A
- all egg laying queens are Bb
- bb queens die naturally
- BB queens killed by Bb workers who use odours to distinguish between them
- allows fatal recessive allele to persist in pop
- genotype linked to behaviour hence green beard effect
3
Q
green beard genes thought experiment
A
- idea: an altruism gene that is linked (v close on same chromosome) to an obvious phenotype will spread if possessors are altruistic to each other
- does not require relatedness (obvious phenotype and altruism gene could be further apart/unlinked)
- kin selection is thought of as more likely since there are few green beard examples
3
Q
green beard effects in lizards
A
- unrelated male lizards with blue throats form partnerships to protect territories
- under some circumstances male doesn’t produce any offspring - true altruism
- genes for throat colour and cooperation are linked
4
Q
what does evolution act on
A
- replicators
- individual units that replicate themselves
- those that leave most copies are most successful
- species and sexually reproducing individuals are not replicators - only pass on half of genome to offspring
4
Q
why do we see few green beard examples
A
- false beards can cheat - benefit from altruism without being altruistic themselves
- probably evolutionarily unstable
- nevertheless represents an important principle of gene level selection
4
Q
selfish genes in meiosis
A
- competition between genes to place themselves in gametes
- segregation distortion/meiotic drive
- eg segregation disorder in drosophila
- ultimate selfishness - good for gene but reduces individuals fitness
