Social Evolution

Question 1

What is altruism?

Answer 1

behavior of an animal that benefits another at its own expense

“Mongoose gives off alarm call when it sees a hawk overhead”

Darwin: suggested selection would favor altruistic behaviors if they if they benefited close relatives

Question 2

Inclusive Fitness = Direct fitness + indirect fitness

Answer 2

Direct fitness = Personal reproduction

Indirect fitness = The additional reproduction by relatives that is made possible by an individual’s actions

Question 3

Kin selection

Answer 3

Natural selection favoring the spread of alleles that increase indirect fitness

Ex: black-tailed prairie dog —> with kin, more likely give alarm calls during pager attacks

Question 4

Another kin example - ground squirrels

Answer 4

Squirrels whistle for hawks, trill for mammals

Whistling for hawks – selfish bc those who whistle are less likely to get caught; exposes others, tho they are just trying to help

trilling is altrustic - looking out for others

Question 5

Another kin example - Nest helping; White-fronted bee-eaters

Answer 5

Non-breeding adults help with nesting efforts (called helpers)

• Helpers are more likely to help breeding pairs that are genetically close relatives

Question 6

Red squirrels adoption & Hamilton’s Rule
(organisms are more likely to help close relatives than non-relatives because it benefits their genes more)

Answer 6

many squirrels orphaned, most die, genetic relative could adopt - at cost of own offspring

Question 7

Evolution of Eusociality

Answer 7

Social systems with overlapping generations between parents and offspring, cooperative brood care, specialized casts of non-reproductive individuals {Distinct groups within the colony have specialized roles, like a queen (primary reproductive), drones (reproductive males), and workers (non-reproductive individuals performing various tasks)}

ex - bees, wasps, ants (Hymenoptera) and naked mole rats

Question 8

Hymenoptera is haplodiploid

Answer 8

males are haploid and develop from unfertilized eggs

females are diploid and develop from fertilized eggs

Question 9

Females maximize their inclusive fitness if _____

Answer 9

they raise sisters

Sister to sister: r = (1/2) + (1/2 x 1/2) = 3/4
Mother to own offspring: r = 1/2
Sister to brother: r = (1/2 x 1/2) = 1/4

Question 10

Reciprocal Altruism

Answer 10

Cooperation among non-kin occurs in nature

Individuals can be selected to dispense altruistic acts if equally valuable favors are later returned

Ex: Blood sharing in vampire bats; many bats fail to eat every night– bats more likely to regurgitate blood for individuals that have shared with them in the past, come across regularly, or are related to

Question 11

When does reciprocal altruism most likely to evolve?

Answer 11

1. Groups stable & individuals repeatedly interact
2. Many opportunities for altruism
3. Individuals have good memories
4. Potential altruists interact in symmetrical situations