Sexuality Flashcards
In what species does scramble competition (intrasexual competition) occur?
Species with multi-male mating systems (e.g., chimpanzees, bonobos)
What are adaptations the result from sperm competition
1) Bigger testes relative to body size
2) Faster swimming speeds of sperm
What makes the mouse lemur special in terms of its testes?
Its testes swell during reproductive periods; large size is not permanently maintained
Which species have a single-male mating system?
Gorillas and hamadryas baboons
Which species has a multi-male mating system?
Chimpanzees, bonobos, macaques, olive baboons
How do primatologists measure testicle size relative to body size?
Drawing of line of best fist and measurement of residuals (average distance from the line)
What is the midpiece of a sperm?
The midpiece is a portion below the neck of the sperm which contains the mitochondria
What does the size of the midpiece indicate?
1) Larger midpiece indicates faster sperm and testes size (positive correlation to testes size)
2) Larger midpiece indicates multi-male mating systems
In what species is shorter durations of copulations found?
In primates with multi-male mating systems
In what species is longer durations of copulations found?
In primates with single-male mating systems such as gorillas and orangutans
What are 3 characteristics of the penis that vary between species?
1) Length
2) Baculum (bone)
3) Spinosity
How does penis length compare between species of different mating systems?
The penis tends to be longer in species with multi-male mating systems than species with single-male mating systems
What is the advantage of having a longer penis?
Allows for deposition of sperm closer to the egg
How does baculum compare between species in different mating systems?
The baculum tends to be longer in species where copulations have longer duration
What is the benefit of having a baculum?
Long copulations may require mate-guarding
What is the benefit of having spines?
1) Lock the penis into the vagina
2) Expel sperm plug
3) Provide biofeedback to males
What are secondary sexual characteristics?
Traits that function in reproduction but are not necessary for reproduction
What is the handicap principle?
Female selection for secondary characteristics are those that indicate good health and vigor (an honest signal)
Which may also signal ability to withstand parasites
What are measures of female attractiveness?
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
Why do humans consider youth to be attractive?
Because humans 1) maintain long-term pair bonds therefore future reproductive potential is important, and 2) have menopause which limits women’s future fertility
How can we predict when males are more attracted to older females?
In species lacking long-term pair bonds and menopause, there is no value in young mates
Do chimpanzees prefer older or younger females?
Older females
What type of beard growth is considered most attractive amongst humans?
Heavy/light stubble
