Social Behaviour: Module 4

Question 1

what are some possible explanations as to why species may tend to come together in groups?

Answer 1

-the habitat that is right for them, may have limiting resource needs, so individuals may tend to benefit from cluster living
-there could be fitness benefits to group living (ex. better protected, larger groups has more eyes, more sensory organs, detect predators, defend against predators)

Question 2

what is fitness the product of?

Answer 2

survival and reproductive success

Question 3

who is the actor in a group? who is the recipient in a group?

Answer 3

-actor: the individual that initiates the behaviour
-Recipient: the individual that the behaviour is directed at

Question 4

define co-operation.

Answer 4

-when initiating a behaviour that both the actor and recipient benefit
- strongly favoured by natural selection (increases individual fitness)

Question 5

what is selfish behaviour?

Answer 5

-actor benefits, recipient is harmed in terms of reduced fitness
-favoured by natural selection

Question 6

what type of behaviour is it when an individual bird were to aggressively displace another bird from a patch of food?

Answer 6

selfish behaviour

Question 7

what is altruistic behaviour?

Answer 7

-actor reduces its own fitness, but benefits the fitness of the recipient
-think of “selfless behaviour”
-can be understood by slightly redefining fitness

Question 8

what is spiteful behaviour?

Answer 8

-actor and recipient suffer reduced fitness
-very difficult to evolve
-selected against: doesn’t help them, but raises the relative fitness of all of the other individuals in the population

Question 9

what is a behaviour that is frequency dependent?

Answer 9

-depend upon frequency of individuals exhibiting that and other behaviours
-can be understood through game theory

Question 10

what is game theory? define the aggressive vs submissive domination tactic. what is the hawk? what is the dove? explain

Answer 10

-game theory: investigates the outcomes of multi-individual interactions
-agressive: hawk strategy
-submissive: dove strategy
-resource competing for: V
-Cost of fighting over a resource: C (in terms of reduced fitness cost)
-hawk vs dove: hawk beats the dove, hawk gets all of the resources, dove nothing, hawk (wins V fitness units) dove gets zero fitness pay off
-dove vs dove: share the resource (V/2)
-hawk vs hawk: one gets the resource, one suffers the cost of fighting (average pay off: (V-C)/2)
-fitness depends on the frequency of hawks and doves in the population
-since the hawk strategy always results in higher fitness, there should only be hawks in the population, but the cost of fighting for the resource is slightly higher than the value of resource (so there should be less hawks so less cost)
-when hawk become more common, the fitness of doves is higher than of hawks
-but for doves to exist, the cost of fighting must be higher than the value of the resource
-social behaviour natural selection will sometimes depend upon the frequencies of individuals exhibiting contrasting behavioura

Question 11

why would a parent sacrificing for their offspring maximize the fitness of the parent?

Answer 11

because it would maximize the repersentation of their genes in the population

Question 12

what does hamilton’s rule explain?

Answer 12

altruistic behaviour could evolve through an extension of natural selection called kin selection

Question 13

how can individual fitness be estimated?

Answer 13

number of survivng offspring an individual leaves to future generations, but individuals also have a genetic share in the offspring of their relativese

Question 14

what is inclusive fitness?

Answer 14

-the total fitness of an individual is related to its individual fitness as well as the fitness of its relative
-the total effect an individual has of carrying on its genes by reproducing and providing aid that enables other close offspring, who share many of the same genes, to produce offspring

Question 15

how would a gene that causes altruistic behaviour spread?

Answer 15

if it increased the fitness of related individuals that also carry the same gene

Question 16

walk through hamilton’s equation for altruistic behaviour.

Answer 16

• B: fitness benefit to the recipient of the behaviour
• C: cost to the actor
• r: the relatedness of the recipient to the actor
• Br-C > 0 –> this is where the altriusm should evolve, when greater than zero
• if a recipient is unrelated to the actor, then r=0, and the behaviour should not evolve

Question 17

how do we calculate r for hamiltons equation (degree of relatedness)?

Answer 17

• half siblings: r=1/4
• parent: r=1/2
• full siblings: r=1/2
• cousins: r=1/8

Question 18

what is a eusocial society?

Answer 18

when one female, known as the queen, does all of the reproducing while the other females act as workers, and never reproduce themselves (bees)

Question 19

how can kin selection explain the supposed altruistic act of Bees and Ants?

Answer 19

• males develop from unfertilized eggs: they are haplodid
• females: develop from fetilized eggs, and are diploid
• when doing hamilton rule calculations, a worker is more related to her sister, than she would ever be to her offspring
• therefote, a worker who does not reproduce is favoured by kin selection

Question 20

define game theory

Answer 20

evaluates alternative strategies in situations where the outcome depends on the strategues of all individuals invovled