Lecture 5- Fitness, Selection and Social Evolution

Question 1

what was Herbert Spencer’s beliefs

Answer 1

-social Darwinism
-survival of the fittest and struggle for survival imply conflict between individuals
-things are more complicated

Question 2

fitness

Answer 2

the relative probability of survival and reproduction of a given genotype (difficult to calculate precisely)

Question 3

what does fitness depend on

Answer 3

can vary depending on he number of copies of an allele

Question 4

sickle cell disease in terms of fitness

Answer 4

-homozygotes for the gene are unwell
-heterozygotes less likely to get malaria (though depends on the parasite)
-sickling variant is advantageous in malarial zones but heterozygotes are fitter

Question 5

why may genes be linked together

Answer 5

increased frequency of deleterious gene due to ‘hitchhiking’- physically close to a selected gene

Question 6

what is selected if species aren’t

Answer 6

individuals within the populations

Question 7

what does selection operate on

Answer 7

individuals who express phenotypes

Question 8

why do some traits reduce overall survival

Answer 8

traits may be disadvantageous e.g bright colours make an individual more noticeable to predators

Question 9

result of sexual selection

Answer 9

traits that may appear to be disadvantageous arise as a result of sexual selection
these traits may increase the organism’s chance of reproduction even if they reduce the chance of survival

Question 10

female choice

Answer 10

females play a key role in selecting mates and their preferences drive the evolution of such traits in males (e.g. the colourful plumage of male peacocks)

Question 11

runaway sexual selection

Answer 11

sexual selection can lead to the evolution of increasingly extreme traits as females continue to prefer males with more exaggerated characteristics (may have limits e.g if the trait becomes so extreme that it impacts survival)

Question 12

good gene hypothesis

Answer 12

traits favored by sexual selection often signal the male’s genetic quality
-they have direct benefits ( traits associated with the ability to provide resources or protection) or indirect benefits (traits reflecting good genes that confer survival advantage to offspring)

Question 13

peacock example and fitness

Answer 13

Male peacocks have large, colorful tails, which are costly to maintain and make them more visible to predators. The “handicap principle” suggests that surviving despite this handicap demonstrates the male’s genetic quality. Bright colors also signal the absence of parasites or good health.

Question 14

neuter insects

Answer 14

-Darwin
-a major problem for the theory of evolution by natural selection

Question 15

altruism

Answer 15

the behaviour of an animal that benefits another at its own expense

Question 16

Hamilton’s rule

Answer 16

natural selection of genes that lead to social actions via the sharing of these genes between performer and recipient

Question 17

what is the affect of being altruistic

Answer 17

has a cost to the performer