Sexual Selection

Question 1

Define anisogamy

Answer 1

Gametes of different sizes

- usually mean males invert less per offspring than females

Question 2

Costs of sexual reproduction

Answer 2

1. Meiosis = production of gametes by meiosis breaks up parental genome
   
   • splits gene combinations that were successful in parents
   • dilutes personal contribution to next generation
2. Finding mate = searching time; investment in courtship
3. Useless males = in polygamous spp. few males are needed to fertilise
   
   • chances of producing successful males MUCH LESS than successful female

Question 3

Benefits of sexual reproduction

Answer 3

1. Recombination = increases chances of finding right combination of genes to favour offspring
2. Avoid Mullers ratchet = accumulation of bad genes
3. Allows a massive increase in biodiversity

Question 4

Consequences of anisogamy

Answer 4

1. Females invest more per gamete
2. Lifetime reproductive success of each sex determined differently
   
   • females limited by production of young
   • males limited by access to females
3. Variance
   
   • most females breed, so variance low

Question 5

Main forms of sexual selection

Answer 5

• intrasexual = males fight each other, females stuck with winner
• intersexual = males display, females choose

Question 6

Consequences of intrasexual selection

Answer 6

• alternative reproductive strategies
• first male advantage
• most fertile male advantage
• infanticide

Question 7

Main forms of intersexual selection

Answer 7

Material = nuptial gifts (food and territory)

Displays of quality = sexual dimorphism in colour, shape and size