Lecture 8

Question 1

Who termed and described sexual selection

Answer 1

Charles Darwin

Question 2

Sexual selection

Answer 2

Selection that depends on the advantage which certain individuals have over others of the same sex
and species solely in rescpect of reproduction (characteristics/behaviours that increase ability to reproduce)

Question 3

Source of fitness differences

Answer 3

• Survival (viability selection)
• Gamete production (fecundity)
• Mating ability (gamete exchange)
• Fertilizing ability (gamete fusion)

Question 4

Darwins´ view of natural selection

Answer 4

• Operates via phenotypic differences in survival and gamete production (higher survival and increased reproductive capacity)
• Darwin introduced sexual selection for phenotypic selection

Question 5

What was darwins introduction for phenotypic selection of sexual selection based on

Answer 5

Differences in mating and fertilizing ability.

Question 6

Secondary sexual characteristics

Answer 6

Characteristics of males and females not directly involved in the process of reproduction

Question 7

What is sexual selection used to explain

Answer 7

The existence of secondary sexual characteristics and sexual dimorphism

Question 8

Examples of secondary sexual characteristics

Answer 8

• Horns
• Antlers
• Colourful feathers

Question 9

Intrasexual selection

Answer 9

When individuals of one sex compete among themselves for mate or fertilize gametes

Question 10

Intersexual selection

Answer 10

When individuals choose mates of the opposite sex on the basis of some particular trait

Question 11

Sexual dimorphism

Answer 11

Males and females from the same species look different

Question 12

Examples of intrasexual

Answer 12

Combat / fighting

Question 13

Examples of intersexual selection

Answer 13

• Plumages
• Showy displays
• Songs
• Nest building

Question 14

Why might individuals make choices based on intersexual selection characterstics (e.g. plumages, songs, etc)

Answer 14

Honest signals of good genes, the traits are honest signals of best qualities

Question 15

What is reproductive investment?

Answer 15

The time and resources expended on each offspring

Question 16

How is female reproductive investment?

Answer 16

Female produce larger gametes, higher reproductive investment than males

Question 17

Which sex typically shows more variation in reproductive success?

Answer 17

The low-investment sex (usually males) shows more variation in reproductive success because it is limited by mating opportunities rather than resources

Question 18

Why does the high-investment sex (usually females) have lower variability in reproductive success?

Answer 18

Because it is primarily limited by resource availability for producing gametes or offspring, rather than the number of mates

Question 19

What is the main factor limiting reproductive success for the low-investment sex?

Answer 19

Mating opportunities – the number of mates determines reproductive output

Question 20

What is the main factor limiting reproductive success for the high-investment sex?

Answer 20

Resource availability – the ability to produce and care for offspring determines reproductive success

Question 21

If females are the high-investment sex, should they prioritize quantity or quality in mate choice?

Answer 21

Quality – Females invest heavily in reproduction, so they benefit from choosing a high-quality mate to produce high-quality offspring

Question 22

Why do females prioritize mate quality over quantity?

Answer 22

Because their reproductive success is limited by resources, not mating opportunities. Investing in a high-quality mate maximizes offspring survival and fitness

Question 23

What is the expected female strategy in mate selection?

Answer 23

Be selective – Choose mates based on traits that indicate good genes, resources, or parental care

Question 24

What type of sexual selection is most important for high-investment females?

Answer 24

Intersexual selection (mate choice) – Females choose mates based on traits that indicate good genes, resources, or parental care

Question 25

What is the reproductive strategy of low-investment males?

Answer 25

Indiscriminate mating – Males maximize reproductive success by increasing the quantity of mating opportunities

Question 26

What type of sexual selection is going to be particularly important for low investment males?

Answer 26

INTRAsexual selection To gain access to mates there is competition between males

Question 27

2 first Bateman's Principles

Answer 27

1. Reduced investment in gametes and parental care by males increases their potential rate of reproduction, biasing the relative numbers of sexually active males to receptive females at any one time. 2. This leads to increased intensity of intrasexual competition, greater variance in breeding success and stronger selection for traits affecting competitive ability in males than in females

Question 28

2 last Bateman's principles

Answer 28

3. This leads to greater selectivity in choice of mating partners by females 4. Which generates selection pressure in males (selection pressure in males) for traits that display their quality as breeding partners. i.e. secondary sexual characteristics

Question 29

Exceptions

Answer 29

- Females can be promiscuous: genetic compatibility, reduced risk of inbreeding and protection against infacticide - Males can be choosey: sperm is not always cheap, copulation can be demanding, sex-role reversal

Question 30

Male barn swallows (birds) have longer tails than females do. This situation is an example of: a. sexual selection b. sexual dimorphism c. directional selection d. All of the above are correct

Answer 30

d. All of the above are correct

Question 31

In the painted greater snipe (a bird), females are larger and more colourful than males. This suggests that: a. Intersexual selection has occurred b. Intrasexual selection has occurred in females c. Intrasexual selection has occurred in males d. A and B e. All of the above

Answer 31

d. A and B

Question 32

If the roaring sounds of male elk, or the croaking of bullfrogs, are sexually selected, honest signals of male quality, you would expect that: a. Larger males could produce lower pitch (frequency) sounds b. Females would select mates on the basis of their sounds c. Males with sounds preferred by females would father more offspring d. B & C e. All of the above!

Answer 32

d. B & C

Question 33

Inter-sexual selection typically involves: a. competition among females for access to males b. competition among males for access to females c. competition between males and females for access to resources such as food d. selection by males as to whether to fight with other males or not e. choice of mates by females

Answer 33

e. choice of mates by females