C&C Ch.7 and 8

Question 1

Why do humans still age despite evolution?

Answer 1

ageing evolves because of the greater selective value of variants with favourable effects on survival or fertility early in life, compared with variants that act late.

Question 2

How can selection cause ageing?

Answer 2

• by keeping early acting mutations rare in populations, while allowing ones with effects late in life to become common
• variants that have beneficial effects early in life will be more likely to spread through the population than those whose good effects come only in old age

Question 3

describe the various factors affecting rate of ageing

Answer 3

• species with low externally caused death rates should evolve low rates of ageing and longer lifespans
• smaller species of animals tend to age much faster and reproduce earlier (reflecting greater vulnerability of small animals to accidents and predation)
• flying features are notable for longevity (flying is a good defence against predators)

Question 4

define sterility as a problem for evolutionary theory

Answer 4

the existence of sterile individuals in a number of types of social animals; I social wasps, bees, and ants, some of the females in a nest are workers and do not reproduce.

How can individuals evolve to forgo reproduction? How can the extreme adaptations of sterile workers evolve if they do not reproduce and so cannot be subjected to natural selection?

Question 5

how can sterility in social animals be justified?

Answer 5

• the members of a social group are generally close relatives, sharing same mum and dad
• a genetic variant that causes its carriers to forgo their own reproductive success to help raise its relatives may help the relatives’ genes pass to the next generation, and the relatives’ genes are often (because of relatedness) the same as the helper individual’s own genes.
• if the sacrifice by sterile individuals results in a sufficient increase in the numbers of surviving and reproductively successful relatives, the increase in number of copies of the worker gene can outweigh the decrease due to their own lost reproductive success

Question 6

state two other largely unsolved problems in evolution

Answer 6

the origin of the basic features of living cells and the origin of human consciousness
- we cannot use comparisons among living species to make firm inferences about how they may have occurred

Question 7

what have been the major advances since Darwin and Wallace ?

Answer 7

• much richer body of data demonstrating the action of natural selection at every level of biological organisation
• we now understand the mechanism of inheritance.