Sexual selection Flashcards
What did Darwin say about sexual selection?
Different animals have different attractive features and the female chooses the most attractive male. These attractive features provide an advantage. For example, big antlers, long tails etc.
How can Darwins theory be generalised to humans?
Traits such as broad shoulders, big muscles, defined jawline can be seen as attractive features in males which leads to females choosing them.
Explain the basis of sexual selection.
Sexual selection explains why some characteristics that might appear disadvantageous actually are an advantage in human reproduction because the characteristics are attractive to potential mates or the characters provide competition over others for reproductive rights.
What is anisogamy?
the difference between male and female sex cells (gametes).
Explain anisogamy in human sex cells.
Sperm in human males are :
-small
-highly mobile
-created continuously in vast numbers from puberty to old age
-do not require a great expenditure of energy to produce
female gametes (eggs) are:
- relatively large
-static
-produced at intervals for a limited number of fertile years
- require a huge investment of energy.
Consequence of anisogamy in human sex cells.
There is no shortage of fertile males however a fertile woman is a ‘rare resource’.
What are the two types of sexual selection?
Intra-sexual selection
Inter-sexual selection
What is inter-sexual selection?
(Female)
Desirable qualities evolve due to preferences of chosen partners to mate with. The consequences of a female making a wrong choice are worse than for the male so it pays for her to be especially choosy. Therefore, the females mating strategy is to select a genetically fit partner who is able and willing to provide resources. This leaves males competing for this opportunity to mate with a fertile female.
What is the runaway process?
If height is an attractive feature, then over successive generations, height would increase in the male population as females would mate with taller males and produce sons who are taller in each generation. This would also produce daughters who have a preference for tall males.
What is intra-sexual selection?
(males)
There is competition between males and the winning male passes on their desirable traits to their offspring.
Give a strength of sexual selection (research support for anisogamy).
Buss carried out a survey of 10,000 adults in 33 countries. He asked questions relating to age and a variety of attributes that evolutionary theory predicts should be important in partner preference. He found that female respondents placed greater value on resource-related characterises, such as good financial prospects, ambition and industriousness, than males did. Males valued good looks and chasity and preferred younger mates.
These findings reflect sex differences in mate strategies due to anisogamy and supports predictions about partner preference derived from sexual selection theory.
Give a strength of sexual selection (research support for inter-sexual selection).
Clark and Hatfield showed that female choosiness is a reality in heterosexual relationships. Male and female psychology students were sent out across a university campus. They approached other students individually with the question ‘I have been noticing you around campus. I find you to be very attractive. Would you go to bed with me tonight? Not a single female student agreed to the request, whereas 75% of males did, immediately.
This supports evolutionary theories that females are choosier than males when it comes to selecting sexual partners.
Give a limitation of sexual selection. (ignores social and cultural influences).
Partner preferences over the past century have undoubtedly been influenced by rapidly changing social norms of sexual behaviour. These develop much faster than evolutionary timescales imply and instead have come about due to cultural factors.
Womens greater role in the workplace means that they are no longer dependent on men to provide for them and so it is argued that this social change has consequences for female mate preferences, which may no-longer be resource-orientated.
Mate preferences are therefore the outcome of a combination of evolutionary and cultural influences.
