lecture 22

Question 1

Reciprocal altruism

Answer 1

altruistic acts are beneficial if they are reciprocated; however, it may maximize the receiver’s fitness by not reciprocating

Question 2

Prisoner’s dilemna

Answer 2

Each of two criminals has 2 possible strategies: cooperate with other criminal and refuse to implicate him or defect and implicate the other criminal for a reward; the player gains more by defection only if the other play cooperates, if both defect then both receive a punishment; if both cooperate, both receive a reward- which is less than that given to player if he was only one to defect

Question 3

Tit for tat strategy

Answer 3

always cooperate first, defect only after other player defected, be forgiving

Question 4

Requirements for reciprocity to be evolutionarily stable

Answer 4

repeated interactions with no knowledge of final interaction (if you knew it was final interaction, would be advantageous to cheat) and ability to detect and punish cheaters

Question 5

Olive baboons-example of reciprocity

Answer 5

juvenile males form coalitions; one juvenile will distract alpha male while other mates with the females, and then they switch roles

Question 6

Blood sharing in vampire bats

Answer 6

bats will starve after 60 bloodless hours; blood is donated from bats with plenty to those in critical need of blood; recipients gain more than donors lose by percent; donors will regurgitate blood and give it to donor; donors are able to recognize and expel cheaters; past associations help predict likelihood of regurgitation

Question 7

Cooperation vs. reciprocal altruism

Answer 7

both have the same ultimate results, except in cooperation- altruistic acts take place at the same time and in reciprocal altruism, they take place sequentially

Question 8

Eastern tent caterpillers

Answer 8

They hunt collectively, have coordinated foraging along pheromone based trails

Question 9

Cooperative breeding

Answer 9

form of group living where adults provide care to young that are not their own genetic offspring; care often is provided by helpers at the nest or offspring that delay dispersal to help their parents raise more offspring

Question 10

Questions associated with cooperative breeding

Answer 10

1. Why delay dispersal instead of breeding independently?
   - Ecological constraints
2. Why do helpers help?

Question 11

Acorn woodpeckers study

Answer 11

Used to answer question, “why delay dispersal?”
as the proportion of vacant territories increases, percent yearlings that delay dispersal increases; also, % yearlings that delay dispersal increases when have higher quality natal territory-because you are getting better resources

Question 12

3 hypotheses for “Why do helpers help?”

Answer 12

1. Increased probability of becoming breeders in future, due to territory expansion or inheritance
2. Improved parental ability because of helping experience
3. Increased inclusive fitness by helping to rear close genetic relatives

Question 13

Evolution of helping as a 2 step process

Answer 13

Step 1: Whether or not to attempt independent breeding- depends on the presence of ecological factors that constrain breeding
Step 2: Whether or not to become a helper- become helper when fitness gains from helping exceed those of not helping

Question 14

3 requirements of Eusociality

Answer 14

1. Cooperative care of young
2. Overlap of generations
3. Reproductive division of labor- worker vs. reproductive castes

Question 15

Worker-queen conflict

Answer 15

Sisters are related to other sisters by 75% and to brothers by only 25%; Workers (females) should prefer to raise sisters: brothers in 3:1 ratio, while queens prefer a 1:1 ratio; even though queen may have control over sex ratio while laying eggs, workers preferentially care for the female brood, leading to a 3:1 weight ratio of females weighing 3x more than males

Question 16

Subsocial path to eusociality

Answer 16

ancestral solitary insects evolve to nest guarding by the females and then evolves to young staying at home to help out at the nest, and then to young permanently staying at home and never breeding

Question 17

Semisocial path to eusociality

Answer 17

several reproductive females build nests close together and then evolve to cooperate in nest building and defense, with each female reproducing–> domination by one female and other females lose ability to reproduce–> overlap of generations and young females become workers

Question 18

Naked mole rats- eusociality without high relatedness

Answer 18

in each colony, have 1 queen and a few kings; queen is much larger than other females and produces pheromone that suppresses ovaries of other females; you have 3 castes: breeders, workers, and soldiers

Question 19

Examples of group living for enemy defense

Answer 19

snapping shrimp, naked mole-rats- defend against snakes

Question 20

Examples of group living to defend a fortress

Answer 20

termites, ambrosia beetles, gall thrips

Question 21

Reproductive skew

Answer 21

term that describes the distribution of direct reproduction among cooperating individuals; in a high skew condition- the alpha is getting a much higher proportion of matings than beta, and a low skew has the beta still getting less than the alpha, but more even