Conflict within families 2

Question 1

Parental-offspring conflict model

Answer 1

• Trivers 1974
• parental investment against benefit or cost
• benefit plateuxs (can only do so much)
• costs accelerates (as costly)
• cost curve for child is half that of parents
• max diff between benefit and cost = parental max inclusive fitness FOR PARENTS & OFFSPRING (use diff cost curves)
• They’re different
• offspring wants more investment
• • can use it to look at siblings

Question 2

sibling rivalry:

Answer 2

• conflict over limited resources
• spade foot toad: at high density and limited food tadpoles will develop canabilism and eat siblings

SIBLICIDE

Question 3

sibling rivalry hyenas

Answer 3

Frank et al 1991

• twin pups fight in burrows and one often dies (sharp canines)
• rivalry more intense with same sex twins, as they’re future reproductive competitors

Question 4

sibling rivalry: black eagles

Answer 4

• 2 eggs hatch 3 days apart
• 1 always dies, older chick attacks younger chick as soon as it hatches
  (cainism)
• OBLIGATE

Question 5

sibling rivalry: Blue-footed boobies

Answer 5

• 2 chicks, 1 hatches earlier than other
• if food becomes scarce, larger kills younger
• FACULTATIVE

Question 6

Characteristics of siblicide:

Answer 6

1) Resource competition
2) monopolisable (control) resources
3) spatial confinement
4) weaponry (but not essential)
5) competitive disparities (normally under parental control)

Question 7

why does siblicide occur?

Answer 7

1) insurance –> second offspring is. only enough resources for one. e.g. black eagles
2) parental optimism: produce large clutch, in gd conditions all will survive, if bad siblicide will occur

Question 8

Parental-offspring conflict: American Coot

Answer 8

LYON ET AL 1994

• parental care is essential (50% of any brood starve to death)
• parens control who gets food and who doesn’t
• changed ornamentation on head to see if this had a bias:
• • more brightly coloured, fed more. orange grew, fed and survived more

Question 9

Parental-offspring conflict: humans

Answer 9

• HAIG 1993
• foetal and mother
• foetal genes select for max transfer of nutrients
• mother selects to not exceed maternal optimum
• foetus on implantation modifies endometrial arteries to low resistance, non-constricting vessels
• –foetus gains direct access to maternal blood,
• –blood flow not under local control
• –placenta release hormones directly into mothers blood
• LEADS TO DISEASES IN MUM
• • gestational diabetes
• • pre-eclampsia