Unit 2 Lecture 11

Question 1

What are the definitions of the two sexes?

Answer 1

females: produce larger gametes

males: produce small gametes

Question 2

What does anisogamy mean?

Answer 2

Gametes of unequal size (one big one small)

Question 3

Explain the animal kingdom?

Answer 3

Male birds typically have the colorful feathers and females are usually just brown or neutral colors
- All of these are used to attract females

Question 4

What’s the definition of natural selection and sexual selection?

Answer 4

Natural Selection: occurs when fitness, i.e. number of gene copies contributed to next generation, is correlated with traits that individuals have

Sexual Selection: occurs when variation in the number of eggs fertilized is correlated with a trait
- When you have a trait that allows you to make many offspring, that will be selected for

Question 5

Explain some of the limitations on reproductive success difference for the the sexes

Answer 5

• Anisogamy is an important driver of behavior because it constitutes a difference between the sexes in their relative investment in offspring
• Females are limited by fecundity
• Males are limited by the number of mates they can obtain

Question 6

What does fecundity mean?

Answer 6

Reproductive capacity of an individual e.g. how many eggs a female can produce and provision

Question 7

Explain why male parental care is rare

Answer 7

Uncertain Paternity:
- Females know that the eggs they lay are their offspring, but males do not

Question 8

What does operational sex ratio mean?

Answer 8

Ratio of males to females capable of reproducing at a given time (not 50/50)
- Males do not get pregnant and therefore keep mating, creating a ‘surplus’ of males and a shortage of females

Question 9

Do males experience stronger sexual selection? why?

Answer 9

Yes; because they typically exhibit greater variance in reproductive success

Question 10

Bigger difference in number of eggs fertilized (# offspring) among males equally what 2 things?

Answer 10

1. Greater payoff for competition over mates in males
2. Greater potential for sexual selection (also called “opportunity for sexual selection”)

Question 11

The sex with more variance in reproductive success experiences stronger _______ ________

Answer 11

Sexual selection

Question 12

Name three traits that make it possible to win contests over mates

Answer 12

1. Large body size
2. Weapons
3. Aggressiveness

Question 13

What is the difference between intrasexual selection and intersexual selection?

Answer 13

Intrasexual: Male-male competition
- Males compete/fight for access to females, resources and territories
- Females mate with whichever male wins

Intersexual: female choice
- Traits that attract potential mates

Question 14

What does sexual dimorphism mean?

Answer 14

in traits under sexual selection
- if bigger males get more mates, males bigger than female
- If flashy ornaments/displays attract mates… males are flashier than females

Question 15

Male-male competition can also occur at what level?

Answer 15

Sperm (who’s sperm fertilizes the females egg?)
- Called Sperm Competition

Question 16

What are some traits under sperm competition?

Answer 16

• Increased sperm production
• Traits to prevent other male’s sperm from reaching egg
• Traits to make sperm swim faster

Ex: Penis of damselfly designed to scrape out previous male’s sperm

Question 17

Under what conditions will sperm competition be likely to occur?

Answer 17

1. Female mates with multiple males
2. Females has the ability to retain sperm for a while

Question 18

Explain the female choice?

Answer 18

Males advertise their ‘quality’ with ornaments, colors, songs, or dances, and females pick the one they like

Question 19

What’s the difference between direct benefits and indirect benefits?

Answer 19

Direct Benefits: Females get something from mating with certain males

Indirect Benefits: Females benefit because offspring of certain fathers do better

Question 20

Name some examples of direct benefits

Answer 20

• Protection
• Good territories
• Food
• Help raising young
• Reduced risk of disease