Compare the benefits and costs of living in social groups vs living alone.
Group living benefits: reduced predation risk, cooperative defense/care of young, increase foraging, social learning.
Costs of group living: competition for food/mates, increased disease transmission, higher visibility, risk of exploitation
Living alone: less competition, full control of resources but higher predation risk, no cooperative care and lower mating opportunities.
Give an example of mutualism in a social group.
Oxpeckers and large mammals: birds remove parasites while gaining food.
Male long-tailed manakins participate in a courtship ritual where only one male ever gets to mate. How is this adaptive?
Subordinate males gain future mating opportunities. They learn courtship, and inherit display sites. This is delayed direct fitness.
Is the behavior of meerkats “taking turns” at being a sentinel instead of foraging an example of reciprocity? Why or why not?
No it is not a true example. They guard because the behavior is low cost and directly beneficial in that moment. It’s better explained as byproduct mutualism.
Explain how vampire bats engage in reciprocity.
They endgame in true reciprocity by sharing food. Bats that were fed will regurgitate blood to roost mates that were unsuccessful. Bats share with those who have shared with them in the past because they remember.
Altruism used to be explained by “the good of the species”. What is a better way of explaining why altruism has evolved?
Altruism evolves because it increases the transmission of shared genes, not because it benefits the whole species.
What is the coefficient of relatedness? What would the coefficient of relatedness be to yourself? Your parents? You siblings? Your niece and nephews?
Myself = 1.0 (all genes)
Parents = 0.5 (half genes from each parent)
Siblings = 0.5 (half genes shared)
Niece/nephew = 0.25 (half from siblings who shares half with me)
What is the difference between indirect and direct fitness? What is inclusive fitness?
Direct fitness is where fitness is gained by producing your own offspring. Indirect fitness is gained by helping relatives produce.
Inclusive fitness = Direct fitness + indirect fitness.
Explain how the alarm call of the Beldings ground squirrel is an example of indirect selection.
It is an example of indirect selection because the individual giving the call increases the survival of its relatives even through its putting itself in danger. The callers indirect fitness increase because relatives that survive are more likely to reproduce.
How do pied kingfishers increase their inclusive fitness by staying behind and helping their parents?
They increase their inclusive fitness by staying to help their parents raise additional offspring instead of breeding on their own. By helping protect and feed their younger siblings they increase the survival of close relatives that share their genes.
Seychelle’s warbler females can decide to stay or nest. What conditions make them stay and what make them go off and find a mate to start a brood?
Warbler females stay as helpers when high quality territories are already occupied and resources are limited. They leave to find a mate and start their own brood when those territories are vacant and high quality, and food is abundant.
Explain how eusocial obligate altruists have evolved in the Hymenoptera.
Beldings ground squirrels have alarm calls to arm relatives of predators. Pied Kingfishers increase inclusive fitness by helping parents raise siblings. Seychelles warbler females stay when good territories are unavailable. Hymenoptera eusociality evolved through kin selection and haploidiploidy where helping close relatives increase inclusive fitness more than reproducing independently.
Why do you think there is more care by mothers than fathers? Explain using the cost/benefit strategies
Mother usually care more because their costs of not caring are higher while the benefits of care directly increase offspring survival. While father caring has higher opportunity costs.
In fish, many times it’s the male that guards nests and protects the young while females only lay eggs. Why has this evolved?
Males guard nests because their cost of care is lower after fertilization while females gain more benefit by producing additional eggs.
Male water bugs provide uniparental care. How/why has this evolved.
They evolved uniparental care because males carry eggs on their backs which increases offspring survival. The benefits of care outweigh the costs.
Why have some bird species evolved unique baby bird calls, while other species all seem to sound the same?
Unique baby bird calls evolve when parents need to recognize and preferentially feed their own chicks, especially in crowded colonies where mix-ups are costly.
Seagulls have evolved a readiness to feed any chick in their nest. Why is this considered adaptive?
This is adaptive because the cost of mistakenly rejecting their own chick is higher than the cost of occasionally feeding a non-related chick.
Explain how a brood parasite like a cuckoo likely evolved.
Brood parasitism likely evolved because laying eggs in other birds nests reduces the cost of parental care while still gaining the benefit of offspring survival.
Give examples of brood parasitism in waterfowl.
Examples include redhead ducks which lay their eggs in the nests of other duck species like canvasbacks.
What are some costs of not accepting a parasite egg?
Costs include accidentally rejecting their own egg or wasting energy inspecting and defending the nest which can reduce reproductive success.
Explain how the Horfield’s bronze-cuckoo and the superb fairy wren are in an evolutionary arms race of brood parasitism.
The bronze-cuckoo lays eggs that mimic the superb fairy wrens eggs, while the wren evolved better egg recognition and rejection. Each adaptation by one species selects a counter adaptation in the other, creating an evolutionary arms race.
Why do some bird parents seem to allow or even encourage siblicide?
It reduces competition among offspring, and ensures the strongest chick survives when resources are limited, maximizing parental fitness.
What are some ways bird parents evaluate the reproductive value of offspring?
Bird parents evaluate offspring by size, begging intensity, and health cues, helping them decide which chicks to feed or invest in to.
What is the male assistance hypothesis? Give and describe an example of a species behavior that supports this hypothesis.
Suggests that females stay or help because male help increases offspring survival, boosting the females fitness. In Pied Kingfishers, females remain as helpers when males assist in feeding chicks.
