Sexuality

Question 1

In what species does scramble competition (intrasexual competition) occur?

Answer 1

Species with multi-male mating systems (e.g., chimpanzees, bonobos)

Question 2

What are adaptations the result from sperm competition

Answer 2

1) Bigger testes relative to body size
2) Faster swimming speeds of sperm

Question 3

What makes the mouse lemur special in terms of its testes?

Answer 3

Its testes swell during reproductive periods; large size is not permanently maintained

Question 4

Which species have a single-male mating system?

Answer 4

Gorillas and hamadryas baboons

Question 5

Which species has a multi-male mating system?

Answer 5

Chimpanzees, bonobos, macaques, olive baboons

Question 6

How do primatologists measure testicle size relative to body size?

Answer 6

Drawing of line of best fist and measurement of residuals (average distance from the line)

Question 7

What is the midpiece of a sperm?

Answer 7

The midpiece is a portion below the neck of the sperm which contains the mitochondria

Question 8

What does the size of the midpiece indicate?

Answer 8

1) Larger midpiece indicates faster sperm and testes size (positive correlation to testes size)
2) Larger midpiece indicates multi-male mating systems

Question 9

In what species is shorter durations of copulations found?

Answer 9

In primates with multi-male mating systems

Question 10

In what species is longer durations of copulations found?

Answer 10

In primates with single-male mating systems such as gorillas and orangutans

Question 11

What are 3 characteristics of the penis that vary between species?

Answer 11

1) Length
2) Baculum (bone)
3) Spinosity

Question 12

How does penis length compare between species of different mating systems?

Answer 12

The penis tends to be longer in species with multi-male mating systems than species with single-male mating systems

Question 13

What is the advantage of having a longer penis?

Answer 13

Allows for deposition of sperm closer to the egg

Question 14

How does baculum compare between species in different mating systems?

Answer 14

The baculum tends to be longer in species where copulations have longer duration

Question 15

What is the benefit of having a baculum?

Answer 15

Long copulations may require mate-guarding

Question 16

What is the benefit of having spines?

Answer 16

1) Lock the penis into the vagina
2) Expel sperm plug
3) Provide biofeedback to males

Question 17

What are secondary sexual characteristics?

Answer 17

Traits that function in reproduction but are not necessary for reproduction

Question 18

What is the handicap principle?

Answer 18

Female selection for secondary characteristics are those that indicate good health and vigor (an honest signal)
Which may also signal ability to withstand parasites

Question 19

What are measures of female attractiveness?

Answer 19

1) Male copulatory approaches
2) Male party size (bigger party size = more attraction)
3) Copulation rate with high-ranking vs low-ranking males
4) Rates of male-male competition

Question 20

Why do humans consider youth to be attractive?

Answer 20

Because humans 1) maintain long-term pair bonds therefore future reproductive potential is important, and 2) have menopause which limits women’s future fertility

Question 21

How can we predict when males are more attracted to older females?

Answer 21

In species lacking long-term pair bonds and menopause, there is no value in young mates

Question 22

Do chimpanzees prefer older or younger females?

Answer 22

Older females

Question 23

What type of beard growth is considered most attractive amongst humans?

Answer 23

Heavy/light stubble