Evolutionary explanations for partner preferences

Question 1

Sexual selection

Answer 1

selection of the characteristics that aid successful reproduction

• Females who select males with such characteristics are more likely to produce robust offspring

Question 2

Anisogamy

Answer 2

Differences between male and female sex cells (gametes)

Male gametes - small, produced in large numbers, does not require much energy

Female gametes - large, relatively rare, require lots of energy - gives rise to 2 mating strategies

One consequence of anisogamy is there is no shortage of fertile males, but fertile women are more rare

Anisogamy important in partner preference because gives rise to 2 types of sexual selection: Inter/Inra

Question 3

Inter-Sexual Selection

Answer 3

Strategy one sex uses to select partner of opposite sex

• Preferred female strategy - select quality on quantity (ova are rarer than sperm)

Trivers - females invest in time, commitment and other resources before, during and after birth of offspring

Both sexes are choosy - as choices determine features passed on

But females especially selective so they select genetically fit partner who is able to provide resources

Fisher - sexy sons hypothesis - genes we see today are those that enhanced reproductive success.

Question 4

Intra-sexual selection

Answer 4

Members of same sex compete for members of opposite sex

Preferred male strategy, seeks quantity over quality (plentiful sperm supply)

Competition - winner reproduces - characteristics that contributed towards victory passed to offspring

Leads to dimorphism - the obvious physical differences between males and females

EG - Physically larger males would be more likely to defeat rival males, whereas there is no need for females to be physically large.
Female youthfulness is selected as males have preference to mate with more fertile female

Question 5

Intra sexual selection behavioural consequences

Answer 5

Compete for fertile females - to pass on victorious genes allow male to outcompete rivals

Includes deceitfulness & aggression, leading to selection of aggression in males

Question 6

(A03) Research Support for Inter-sexual selection

Answer 6

Clark & Hatfield - 75% males agreed to sexual request from opposite sex student, 0% females
Supports females more selective, & males have evolved different strategy to ensure reproductive success

Question 7

(A03) Research Support for Intra-sexual selection

Answer 7

Buss - survey consisting 10,000 adults in 33 countries, aking about partner preference
Found: Males seek signs of reproductive capacity, Females want resources
Supports consistent sex differences in partner preferences & support predictions from sexual selection theory

Question 8

(A03) Can’t explain homosexuality

Answer 8

cannot explain partner preferences of gay men and lesbian women
Lawson - looked at personal ads placed by gay and straight men & women - describing what they’re looking for and what they are offering in a partner, found homosexual strategies differ like men/women differ