Lecture 10 T

Question 1

What is sexual selection ?

Answer 1

Natural selection arising through preference by one sex for certain characteristics in individuals of the other sex

Question 2

What is male-male competition?

Answer 2

The struggle between individuals of the same sex, generally males in order to drive away or kill their rivals, the female remaining passive

Question 3

What is female choice?

Answer 3

The struggle between individuals of the same sex, generally the females, which no longer remain passive, but select the more agreeable partners

Question 4

Give examples of traits that improve a males success in combat

Answer 4

Males with the greatest size/ or smallest

Largest weapons

Question 5

Give an example of female mate choice

Answer 5

Long-tailed widow bird- males have long tails

• costly for males
• longer tailed males mate more

Barn swallows

• males have elongated tails
• less effective at foraging
• impacts future reproductive success

Pheasants
-elaborate colouration

Question 6

Why are females choosy?

Answer 6

1. Resources “direct benefits”
   - territories
   - Food
   - defences
   - paternal care
2. Genetic benefits “indirect benefits”

Question 7

Do females gain attractive sons from being choosy?

Answer 7

1. females preferred males with e.g long tails
   - could fly better
   - were more detectable
   - females had sensory bias
2. Genes for long tails passed onto sons
3. Genes that cause females to prefer longer tails passed onto daughters

Question 8

Give an example of fishers hypothesis

Answer 8

Stalk-eyed flies

• females prefer males with longer stalks in the field and in the lab
• female preference changes when selected for short stalks in lab

Question 9

Which traits become exaggerated?

Answer 9

Seems to be arbitrary (personal choice)

Suggests that females have a ‘sense of the beautiful’ akin to the aesthetics sense in humans

Question 10

Do females gain ‘good genes’?

Answer 10

Females prefer long tails because they are an handicap so reveal a males general (genetic) quality

-these ‘good genes’ will be passed onto their sons

Question 11

What is the paradox of the lek?

Answer 11

If only males with the best genes are selected, then all males should eventually have these ‘good genes’

Question 12

What are the solutions to the paradox of the lek?

Answer 12

1. Males are constantly subject to deleterious mutations
2. Traits may be related to ‘condition’ which is affected by a large number of genes
3. Females may prefer different males in different years, or different females may have different preferences
4. Females are selecting males that are genetically equipped to cope with current diseases
5. Females may be selecting genetically compatible mates

Question 13

What is genetic compatibility?

Answer 13

Refers to how well the genes of the two parents function together in their offspring

-the choosing sex must know their own genotype as well as the genotype of potential mates

Question 14

Can females have ‘ornaments’?

Answer 14

Yes!

• some bird species
• baboons