Sexual selection Flashcards
Evolution: Darwin:
Evolution favours development of some features attractive to opposite sex.
What is natural selection?
Organisms better adapted to environment tend to survive and produce more offspring (survival of the fittest).
What is sexual selection?
Natural selection of characteristics increasing reproductive success (survival of the hottest).
What is sexual dysmorphism?
Differences in size and shape between males and females of same species.
Singh (2002): Waist to hip ratio:
Males find waist to hip ratio of 0.7 attractive. Is ‘honest signal’ the woman is fertile.
What is anisogamy?
Difference between male and female sex cells (gametes).
Consequence of anisogamy?
No shortage of fertile males, but fertile females limited.
Male gametes:
Small and highly mobile. Created continuously in vast number from puberty to old age.
Female gametes:
Large and static. Produces at intervals for limited number of fertile years. Lots of effort to produce.
Intra-sexual selection (male):
Competition of males to be able to mate with female, winner of competition reproduces and gets to pass on characteristics which contributed to the victory onto offspring.
Inter-sexual selection (female):
Ova require greater energy to produce. Female need to select partner who can provide resources and is genetically fit, so have to be choosy so don’t face consequences of making wrong choice.
Fisher (1930): Sexy son hypothesis:
Women mate with males who have desirable characteristics and their ‘sexy trait’ inherited to their son. Increases chance females procreate with her son and pass on mother’s genes.
Strength: RS inter-sexual selection:
Research support for inter-sexual selection. Uni campus asked the opposite sex if they would go to bed with them tonight - no females agreed, 75% of males agreed.
Strength: RS intra-sexual selection:
Research support for intra-sexual selection. Males from 37 different cultures all prefer young, physically attractive women.
Limitation: Social and cultural differences.
Ignore social and cultural differences. Compared partner preferences in China over 25 years - found some preferences had changed, whereas some had stayed the same.
