2: Sexual selection

Question 1

define sexual dimorphism

Answer 1

Different morphological forms of a species in the same pop., based on sex

Question 2

describe monogamy + examples

Answer 2

1 male + 1 female
Little sexual selection, no sexual dimorphism
E.g Albatross
Extra-pair paternity e.g Dunnocks = appear as monogamy but actually polyandry

Question 3

Define polygamy

Answer 3

male and female have multiple partners

Question 4

Define polyandry

Answer 4

female has multiple partners

Question 5

Define polygyny

Answer 5

male has multiple partners

Question 6

Intrasexual competition: describe male-male competition

Answer 6

(fighting), winner mates with female

Question 7

Intrasexual competition: describe mate guarding

Answer 7

male has ‘won’ female and attempts to stop other from mating with her

Question 8

Intrasexual competition: describe sperm competition

Answer 8

in polyandry different males sperm must compete with one another

Question 9

Intrasexual competition: describe lek competition

Answer 9

gathering of males display and females observe
- Females choose the ‘best mate’
- Lekking is costly for males

Question 10

Describe intersexual selection

Answer 10

Females choice, what do they gain?
Access to resource → allo/courtship feeding
Access to good genes, e.g resistance to parasites - utilitarian
Access to good genes - attractiveness

Question 11

Describe Runaway sexual selection (Anderson, 1982)

Answer 11

Experimentally altered tail length of male Widowbirds
Reduced tail → lower mating success
Increased tail → more mating success
→ female preference drives positive feedback, trait continues to be selected for and becomes more extreme (potentially at the cost of survival for the males)

Question 12

What determines the trade off between natural/sexual selection?

Answer 12

Depends on which has most pressure in diff conditions
e.g if no predator present sexual selection favored