Evolutionary explanation:

• Sexual selection:

  Anisogamy: differences between male and female sex cells (gametes).

  Male gametes:

  • small
  • produced throughout life
  • less energy required

  Female gametes:

  • relatively large
  • produced for a limited amount of time
  • required significant energy
• Inter-sexual selection:

  FEMALE VIEW:

  Choosing the wrong partner had more sever consequences for females, so it leads to a female to be more picky as we have a limited time for fertility and takes a long time using up a significant amount of energy.

  Therefore we look for genetically fit partner who is able to provide resources for the offspring to survive.

  Quality> quantity.
• Inter-sexual selection

  FEMALE VIEW

  Trivers 1972

  • It's the female’s preference which determines which features are passed onto the offspring
  • Whatever the characteristic is seen as desirable for the offspring, it will be selected in mating and hence the characteristic increases overtime
  • In the next generation females would choose to mate with that individual and thus that characteristic gradually becomes exaggerated as it grows. known as a runaway process
• Inter-sexual selection:

  Fisher 1930

  • Sexy sons hypothesis - the genes we see today are those that enhanced reproductive success.
  • A female mates with a father (males) who have a certain trait which is seen to be ‘sexy’. This would mean her sons are also more likely to be selected b successive generations of females who will mate with her offspring. Therefore the preference for this ‘sexy’ trait is perpetuated.
• Intra-sexual selection:

  MALES VIEW:

  There is competition between the males for a female. The stronger one survives. This winner will be seen as more attractive in the women's eye as they will provide the strongest gene.

  The need for males to show the female that they are fit and strong has led to ‘dismorphisum’ , males are brightly coloured compared to females in peacocks.
• Intra-sexual selection

  Preferred strategy for males is quantity> quality of partners as this ensures that their genes are being passed on in the event of female not successful to reproduce. This is because they have many sperm to have babies with compared to women who only have a certain number of years till their fertility ends.

  In female youthful is selected because males have a preference to mate with a younger, more fertile women
• Intra-sexual selection:

  Intra-sexual selectional has behavioural consequences, although there are controversial, the characteristics that are favoured and passed on are those that allow a ale to outcompete with his rivals, including intelligence and aggression.