Unit 2 Lecture 11 Flashcards
What are the definitions of the two sexes?
females: produce larger gametes
males: produce small gametes
What does anisogamy mean?
Gametes of unequal size (one big one small)
Explain the animal kingdom?
Male birds typically have the colorful feathers and females are usually just brown or neutral colors
- All of these are used to attract females
What’s the definition of natural selection and sexual selection?
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
Explain some of the limitations on reproductive success difference for the the sexes
- 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
What does fecundity mean?
Reproductive capacity of an individual e.g. how many eggs a female can produce and provision
Explain why male parental care is rare
Uncertain Paternity:
- Females know that the eggs they lay are their offspring, but males do not
What does operational sex ratio mean?
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
Do males experience stronger sexual selection? why?
Yes; because they typically exhibit greater variance in reproductive success
Bigger difference in number of eggs fertilized (# offspring) among males equally what 2 things?
- Greater payoff for competition over mates in males
- Greater potential for sexual selection (also called “opportunity for sexual selection”)
The sex with more variance in reproductive success experiences stronger _______ ________
Sexual selection
Name three traits that make it possible to win contests over mates
- Large body size
- Weapons
- Aggressiveness
What is the difference between intrasexual selection and intersexual selection?
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
What does sexual dimorphism mean?
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
Male-male competition can also occur at what level?
Sperm (who’s sperm fertilizes the females egg?)
- Called Sperm Competition
What are some traits under sperm competition?
- 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
Under what conditions will sperm competition be likely to occur?
- Female mates with multiple males
- Females has the ability to retain sperm for a while
Explain the female choice?
Males advertise their ‘quality’ with ornaments, colors, songs, or dances, and females pick the one they like
What’s the difference between direct benefits and indirect benefits?
Direct Benefits: Females get something from mating with certain males
Indirect Benefits: Females benefit because offspring of certain fathers do better
Name some examples of direct benefits
- Protection
- Good territories
- Food
- Help raising young
- Reduced risk of disease
