18 - Sexual Selection

Question 1

What is the difference between reproduction and sex?

Answer 1

reproduction - production of offspring
sex - combining genes

Question 2

What is the two fold cost of sex?

Answer 2

• In asexual reproduction the population will double in each generation
• in sexual reproduction this will not happen as men cannot directly reproduce
• the cost of males

Question 3

What is sexual selection?

Answer 3

A subset of selection which describes the evolutionary differences in males and females

Question 4

What is the limiting factor to females in reproduction?

Answer 4

amount of resources obtained

Question 5

What is the limiting factor to males in reproduction?

Answer 5

number of mates

Question 6

What does differential parental investment lead to?

Answer 6

• leads to sexual selection

Question 7

What does equal parental investment lead to?

Answer 7

no sexual selection

Question 8

What is intra-sexual selection?

Answer 8

competition between the same sex

Question 9

What is intersexual selection?

Answer 9

competition between the different sexes

Question 10

What are physical and physiological traits of intra-sexual selection?

Answer 10

• size
• weaponry
• sperm production

Question 11

What are pre-copularory mechanisms of pre-sexual selection?

Answer 11

• northern elephant - larger males have more females
• antlers on deer - more breeding success

Question 12

What are post-copulatory mechanisms of intra-sexual selection?

Answer 12

• sperm competition -> make more sperm than the other males, or spikes to remove sperm from previous male
• mate guarding -> physically guarding female, extended copulation, copulatory plugs
• mate manipulation -> proteins passed to females to change behaviours
• infanticide

Question 13

What are two traits of inter-sexual selection?

Answer 13

• behaviour
• ornamentation

Question 14

Why do females choose males?

Answer 14

• direct benefits -> food production, parental care, some males as food
• honest signalling -> phenotype signals direct benefits (genes ect)

Question 15

What is Fischers runaway selection?

Answer 15

Step 1: a mutation exaggerates male appearance and confers greater fitness

Step 2: the mutation or a second mutation causes females to prefer that trait

Step 3: Runaway selection - sexy sons and daughters that prefer that - no longer a direct fitness benefit

Question 16

What is sensory bias?

Answer 16

females will like a mutation of a male as they are already evolved to this

• ex - calls that only females can hear

Question 17

What is the spermatophore?

Answer 17

• contains sperm
• also nutrient rich

Question 18

What is frequency dependent selection?

Answer 18

• how the fitness is dependent on the frequency of different morphs