Chapter 11 Part 1 Flashcards
What is the key to explaining diversity in parental behavior across species?
cost-benefit approach
time and energy invested in offspring
parental investment
reproductive value
a measure of the potential of an individual to leave surviving descendants in the future
Depends on ecological or social circumstances an individual is born into, a value which influences amount of care provided by parents
Variations in offspring care may be due to:
behavior (advertising need or quality), behavior of parents, and parent-offspring conflict
signal of need hypothesis
signals that advertise an offspring’s level of need in order to maximize their chance of being fed by their parents
signal of quality hypothesis
signals that advertise an offspring’s quality or merit in order to maximize their chance of being fed by their parents
Ex. the bright red mouths of songbirds; obtained through carotenoids in the diet and an indication of immune functioning and health
Barn swallow research
offers support for the signal of quality hypothesis
offspring with artificially enhanced red mouths given preferential treatment; offspring made ill given less parental care
Whether a species uses a signal of need or signal of quality to determine allocations of parental care depends on:
the different ecological conditions experienced by parents while raising young
In instances with food and resource abundance, parents will preferentially feed the (neediest/highest quality) offspring; in instances with food and resource shortages, parents will preferentially feed the (neediest/highest quality) offspring
- neediest
2. highest quality
Altricial
referring to young that reside in the nest for an extended period of time
ex. swallows
precocial
referring to young that are mobile soon after hatching
ex. coots; exceptionally needy chicks are refused resources and pecked to death by their parents
Red mason bee parental favoritism
when females are young and robust will give more food to offspring and produce daughters (fertilized, bigger); when females begin to deteriorate they provide less and produce males (unfertilized, smaller)
Ronald Fisher & Fisherian ratio of males to females among a population
1:1
over time the population would equilibrate; assumes males and females are equally costly to make
local competition hypothesis
when related individuals compete for resources or mates, then one sex is more costly to produce; sex ratio would be skewed in favor of a single sex (if one sex of potential offspring will compete with a parent for resources –> beneficial to have offspring that will disperse)
local enhancement hypothesis
when one sex provides resources or enhances the mating success of its relatives, then that sex is cheaper to produce (if one sex of potential offspring will help a parent –> more of that sex)
Seychelles warbler
if food was scarce would produce more sons that disperse; if food was plentiful would produce more daughters that stayed and helped
Trivers-Willard hypothesis
mothers can adjust offspring sex ratio according to their own body condition (itself related to territory quality and resource availability)
Parental Favoritism in humans
the potential to be polygamous gives sons a higher reproductive value than daughters in certain conditions; they will also have higher reproductive value if they are developmentally advantaged and can compete with rival males
Examples of parental favoritism in humans
Rwanda - high-ranking mothers have more sons than do low-ranking mothers
Inheritance rules in relation to polygamy; sons more likely to receive greater portion of inheritance than daughters
Mukogodo tribe of Kenya - participate in livestock pastoralism but arrived at that type of livelihood far after their neighbors and thus are considered ‘poor’ and sons are unable to obtain many wives because they are unable to provide the dowry necessary; women however have greater reproductive success because they are all likely to marry - as infants mothers are more likely to nurse daughters longer and take then to get medical care sooner than sons
sibling conflict
evolutionary conflict resulting from divergent interests among current and/or future siblings
ex. great egrets
siblicidal behavior
behavior that results in an individual killing a sibling or siblings
parent-offspring conflict
evolutionary conflict arising from differences in optimal parental investment in an offspring from the standpoint of the parent versus that of the offspring
ex. blue footed boobies that resist siblicidal behaviors
obligate siblicide
behavior that always results in an individual killing a sibling or siblings
facultative siblicide
behavior that occasionally results in an individual killing a sibling or siblings
reproductive insurance hypothesis
mothers in siblicidal species lay a second egg as insurance against hatching failure
facultative siblicide hypothesis
parents permit siblicidal behavior only when resource availability is low
Ghalambor and Martin predict this regarding costs of parental care:
two key factors:
1) nature of the predator 2) annual mortality rate for breeding adults
(if a parent is likely to survive to produce more, will provide less parental care/risk; if a parent is likely to die, will invest a great amount of care/risk)
