AO1

• What is sexual selection?


  An evolutionary explanation of partner preference. Attributes or behaviours that increase reproductive success are passed on and may become a exaggerated over succeeding generations of offspring
• What is anisogamy?


  The difference in size and structure between male and female gametes.
• What is a consequence of anisogamy?


  No shortage of fertile males but a fertile female is a much rarer ‘resource’.
• Anisogamy is important in partner preference because it gives rise to two types of sexual selection
• Anisogamy is important in partner preference because it gives rise to two types of sexual selection
• What are the 2 types of sexual selection?


  Inter sexual selection and intra sexual selection
• What is inter-sexual selection?


  Strategies that males use to select females and vice versa
• Which sex prefers inter-sexual selection?


  Females
• Who pointed out that the female makes a greater investment of time, commitment and other resources before, during and after the brith of her offspring?

  Trivers
• Why might females make a greater investment of time and commitment?


  Consequences of making a wrong partner choice are more serious for the female, so it pays for her to be especially selective
• What is a female’s optimum matin strategy?


  Select a genetically fit partner who is able to provide resources
• The female preference is what determines which feature are passed on to the offspring.


  For example, a desirable trait in males like height, will increase in the male population over successive generations because in each generation, females will select the tallest males and thus the characteristic gradually becomes exaggerated (a runaway process).
• Who proposed the sexy sons hypothesis?

  Fisher
• What is the sexy sons hypothesis?


  Evolutionary theory suggesting that females prefer mates who possess traits that will increase the reproductive success of their sons.
• What is intra-sexual selection?


  Strategies used within each sex
• Which sex prefers to use intra-sexual selection?


  Males (quantity over quality as there is a plenty supply of sperm)
• How does intra-sexual selection work?


  There is competition between males to be selected to mate with a female. The winner of the competition reproduces and therefore the characteristic that contributed to his victory may be passed on to his offspring
• What has intra-sexual selection led to?


  Dimorphism
• What is dimorphism?


  Means ‘two forms’. Males and females end up looking very different because of intra-sexual selection
• Example of dimorphism


  In any physical competition between males, size matters. Larger males have an advantage and are therefore more likely to be reproductively successful. On the other hand, females do not compete for reproductive rights, so there is no evolutionary drive towards favouring larger females. However, in females youthfulness is selected because males have a preference to mate with more fertile women
• Other than physical consequences, what else can intra-sexual selection lead to?


  Behavioural consequences
• Example of behavioural consequences


  Behaviours like deceitfulness, intelligence and aggression may have allowed a male to outcompete his rivals