Evolutionary Biology 14 Flashcards
what social interactions do group living lead to
1) Cooperative -> actor +recipient benefit
2) Altruistic -> Actor is
harmed + recipient benefits
3) Selfish -> Actor benefits + recipient is harmed
4) Spiteful Actor + recipient are harmed
group selection vs individual selection
Based on a simple argument: Individual organisms are more numerous, and turn over more quickly, than the populations they are in. The potential for replacement of less fit by more fit individuals is much greater than that for populations. Individual (lower level) selection should prevail over group selection.
Kin selection
evolutionary strategy that favours the reproductive success of an organism’s relatives, even at a cost to the organism’s own survival and reproduction.
- incorporates idea of “inclusive fitness”
Inclusive fitness
the ability of an individual organism to pass on its genes to the next generation, taking into account the shared genes passed on by the organism’s close relatives.
Inclusive fitness = direct fitness (personal fitness gains) + indirect fitness (additional fitness gained from relatives made possible by individuals actions)
what is indirect fitness and what affects the strength/amount of it
additional fitness gained from relatives made possible by individuals actions
Amount of indirect fitness depends on how related individuals are to each other
Hamiltons rule
rB - C > 0
B= benefit to recipient C= cost to the actor for an altruistic behaviour r= degree of relatedness (how many identicla genes by descent you chare)
- if C increases then an individuals direct fitness decreases, increases in both r + B can increase an individuals direct fitness.
Eusociality
the highest level of organisation of animal sociality, is defined by the following characteristics: cooperative brood care (including care of offspring from other individuals), overlapping generations within a colony of adults, and a division of labour into reproductive and non-reproductive groups.
E.g. termites, naked mole rats etc.
describe haplodiploidy and eusociality in Hymenoptera
- males are haploid, (develop from unfertilised eggs) females are diploid - sisters on average share 1/2 genes through mother and all of their genes through father (1/2+1)/2 = 3/4 - females therefore more closely related to one another (3/4) than they are to own off spring (1/2)
*could haplodiploidy be the explanantion of eusociality in hymeroptera
list 4 reasons why haplodiploidy is not the explanation for eusociality in hymeroptera
1) the previous analysis assumes only 1 male fertilises a queen (not the case)
2) in some species, colonies may be founded by > 1 queen
3) many eusocial non-hymeroptera are diploid (termites)
4) many hymeroptera are not eusocial
what could reasons for the evolution of eusociality be
may have independent origins associated with nest building and the need for help in rearing young
Eusociality occurs in species with
1) complex nests
2) extensive larval care
- females are unlikely to be successful if they breed on their own,(ecological not genetic reason)
an example of kin-selection discrimination
E.G. Cannibalistic spadefoot toad tadpoles
- Tadpoles either develop into typical morphs (that eat decaying plant matter) or into carnivores that eat other tadpoles.
- cannibal morphs are more likely to eat non-siblings then sibs when given a choice between one of each kind
What is sperm altruism
- in some species males produce distinct versions of sperm , one morph is fertile (eusperm) and one is infertile (parasperm)
- E.g. Drosophila pseudobscuras female tract contains spermicide
- parasperm protect brother eusperm from female spermicide.
How do organisms recognise “kin”
1) smell (mammals, insects)
2) song (some birds)
3) learned familiarity (raised together)
4) visual similarity (chimps , humans)
*note kin recognition is not nescecary for kin selection to operate ,
