Lecture 11 - Reproductive behaviour

Question 1

Sex roles reproductive output

Answer 1

females = limited by number and viability of eggs
males = higher RO, 300 mil sperm each ejaculate

Question 2

Operational sex ratio

Answer 2

sexually active males : fertile females

Question 3

Parental investment

Answer 3

relative amount of investment by each sex
trade offs = finite amount resources, more investment for offspring x than y
test = sex role reversal
e.g. mormon cricket - produces spermatophore, nutrients for female

Question 4

Varying levels of male PI

Answer 4

females more = peacocks, male plumage more elaborate, males compete
equal = mute swan, similar appearance
males more = jacana, females bigger polyandrous

Question 5

Sperm competition

Answer 5

testes size increase with body size
zebra finch = small testes, low sperm comp
aqautic warbler = similar body size but bigger testes, high sperm comp

Question 6

Cryptic female choice

Answer 6

inside reproductive tract, influences paternity

Question 7

Residual testes size

Answer 7

how far above/below fitted line
above = relatively large, chimps - high female promiscuity
below = small, gorillas, faithful females

Question 8

Suicidal sex in marsupial insectivores

Answer 8

increasing stress hormones = immune system collapse = death after mating for males

• semelparous = single reproduction before death
• arrested sperm production, rely on stored sperm
• highly synchronised food peak