Sex

Question 1

Sexual dimorphism

Answer 1

difference between phenotypes of females v males

Question 1

Charles Darwin “sexual selection” quote description:

Answer 1

• males/females have differences in appearance; though similar lifestyles
• variations driven by competition for mating (males attract mates)
• advantageous traits passed on to male offspring –> leading to evolution of distinct characteristics between sexes

Question 2

Natural selection vs Sexual selection

Answer 2

NS - survival/reproduction between individuals w/ diff phenotypes and external conditions; fitness

SS - struggle between same sex, males, w/ diff phenotypes; mating success - result is few or no offspring

Question 3

Bateman’s Principle

Answer 3

females typically invest more energy in producing offspring due to the larger size of eggs compared to sperm (limiting factor)

• greater variance in male repro. success than females bc males produce many cheap sperm, allowing them to potentially mate with multiple females and significantly increase their reproductive output if successful

Question 4

Bateman’s gradient (graph)

Answer 4

relationship between mating opportunities and reproductive output

• male repro. success increases with more mates (steep positive slope)
• female: little change with additional mates (flat, weak pos slope); number of pregnancies limits female success

Question 5

Sometimes males invest more than females in mating…example provided

Answer 5

Broad-nosed pipefish: eggs fertilized, male carries eggs in pouch —females have less time/energy to produce eggs; males now have to carry and brood eggs longer (Bateman’s gradient reversed)

Question 6

INTRAsexual selection

Answer 6

male-male competition

Question 7

Male-male competition: Alternative male mating strategies

Answer 7

some males have direction competition tactics, some have deceptive methods for access to females (orange/blue/yellow lizards)

Question 8

Male-male competition: Infanticide

Answer 8

male animal killing offspring of another male within same species; driven by desire to inc own reproductive success –> females more attracted

Question 9

INTERsexual selection

Answer 9

Female choice sexual selection - females choose mates

Question 10

INTERsexual selection examples

Answer 10

Frigate birds - male red throat punch

Widowbird - males with better conditions have longer tails (attract females); cost - long tail spend less time defending territory

Grey Treefrog - females prefer long calls vs short calls

Question 11

3 explanations why females care about these characteristics (long tail, longer call)

Answer 11

1. good genes
2. direct benefits
3. sensory bias
4. chase-away sexual selection

Question 12

Indirect genetic benefits to female fitness

Answer 12

offspring of males have good indicator traits = inc survival or reproductive success

Ex: Grey tree frogs; have greater survival/reproduction

Question 13

direct benefits

Answer 13

females prefer males with resources that help them now
- females provided with male resources should have higher fitness

Ex: females choose males with evidence of fewer parasites

Question 14

What is the term for taking advantage of the female sensory system?

Answer 14

Sensory bias

Ex: Tungara frog males call with a whine and chuck. Females more naturally sensitive to the chuck (prefer it)

Question 15

Battle of Sexes (just understand this bigger picture)

Answer 15

males evolve mechanisms to INC reproductive success; females evolve counter adaptations (what’s good for males is not always good for females); males then evolve in response to females = continuous selection and evolution