Sex Allocation

Question 1

primary sex ratio

Answer 1

sex at conception

Question 2

secondary sex ratio

Answer 2

sex at birth

Question 3

tertiary sex ratio

Answer 3

sex at sexual maturity/adulthood

Question 4

sex allocation

Answer 4

investment in male vs. female.
dependent on environment and mating system

Question 5

Fishers 1:1 sex ratio rule

Answer 5

the only stable strategy is to produce males and females in equal numbers. ESS to invest equally in both sexes.

Question 6

evolutionary game theory

Answer 6

analysis of consequences of adopting new strategies in the context of how this decision is affected by the decisions of others in the population.
a strategy is an evolutionarily stable strategy if the individuals who play it cannot be invaded by an alternative strategy. it cannot be beat.

Question 7

departures from equal sex ratios

Answer 7

local mate competition
local resource competition
maternal condition
sex ratio distorters

Question 8

local mate competition (sex ratio departure)

Answer 8

competition among relatives can affect selection. sex ratio is biased towards sex experiencing least amount of kin selection. ex. fig wasp males.
1:1 is ESS only if there is random mating in population.

Question 9

local resource competition (sex ratio departure)

Answer 9

local competition with a certain sex reduces their value. Ex. if sons disperse but daughters stay, daughters are less valuable. male bias would be observed.

Question 10

maternal condition is also called

Answer 10

travers-willard hypothesis

Question 11

maternal condition hypothesis

Answer 11

if maternal condition influences the reproductive success of her offspring, then a better strategy than 1:1 is to produce the more stable sex (ie a daughter) when condition is poor, and a more competitive sex if condition is good (ie a son)

Question 12

3 assumptions of maternal condition/trivers-willard hypothesis

Answer 12

1.parental condition influences offspring condition
2. differences in offspring condition persist to adulthood
3. good condition influences the mating success of one sex more than the other

Question 13

sex ratio distorters

Answer 13

1. MSR: maternal sex ratio, a maternally transmitted factor that causes females to fertilize eggs, which produces 100% daughters
   2: SK: son killer, infectious bacterium that kills fertilized eggs that would have been sons
   3: PSR: paternal sex ratio chromosomes, “paternally” transmitted, to convert fertilized female eggs into males with PSR chromosome
   4: wolbachia: inherited bacteria present in eggs that feminized males, produces sperm incompatibility

Question 14

haploiddiploidy

Answer 14

fertilized eggs have 2 sets of chromosomes and are female, unfertilized eggs with one set of chromosomes are male. happens in many social insects.

Question 15

chromosomal departures from 1:1 sex ratios

Answer 15

1. maternal testosterone hypothesis: testosterone in females influence offspring sex ratio
2. good condition hypothesis: maternal glucose levels and dietary fat influence offspring sex ratio

Question 16

seychelles warbler

Answer 16

have “nest helpers” to raise chicks. its the females who help, but these helpers are beneficial in good conditions (help for offspring is good), and a detriment in poor conditions (another mouth to feed)
more sons produces in low quality territories, and more daughters produced in high quality territories.