Kin selection

Question 1

Give 2 examples of cooperation between animals.

Answer 1

1. Slime moulds: in times of starvation will differentiate into cells in a fruiting body and disperse to new areas
2. Honey pot ants: eat lots and store it in abdomen, regurgitate for others in times of starvation

Question 2

Give 2 examples of animals that display eusociality.

Answer 2

1. Order hymenoptera

2. Naked mole rats

Question 3

Define eusociality.

Answer 3

Organisms form colonies in which there is a division of labour and cooperative brood care.

Question 4

Define cooperation.

Answer 4

Both the actor and recipient of the behaviour benefit.

Question 5

Defection from a cooperative strategy is often advantageous for the defector. True or false?

Answer 5

True.

Question 6

How did cooperation evolve?

Answer 6

Repeated interaction leads to reciprocity. Individuals are more likely to cooperate if they know they will gain a direct selfish benefit.

Question 7

Define altruism.

Answer 7

An entirely selfless act that harms the actor.

Question 8

Altruism is observed in eusocial insects. Why is altruism thought to have evolved?

Answer 8

Because of kin selection.

Question 9

Define inclusive fitness.

Answer 9

Fitness is seen as the transmission of genes.

Question 10

What is a) direct and b) indirect inclusive fitness?

Answer 10

a) Direct: transmission of genes via offspring

b) Indirect: if an organism helps to raise the offspring of another with the same genotype, e.g. their sibs.

Question 11

In a monogamous population, what is the proportion of relatedness an organism shares with a) its siblings or b) its offspring?

Answer 11

They are both the same, 1/2 related.

Question 12

Thus what can be said about monogamous populations in terms of genes?

Answer 12

There is ‘equality of genetic worth’.

Question 13

Altruism generally arises in monogamous or ancestrally monogamous populations. Why?

Answer 13

Because the actor still has inclusive fitness by helping to pass on some of its genes.

Question 14

Give Hamilton’s rule and explain it.

Answer 14

rb > c

Says that relatedness x benefit is greater than cost, i.e. the actor may not benefit directly but the relatives will from its actions.

Question 15

Under Hamilton’s rule, who are the interactions between if a) r = 0, b) r = 1/2 and c) r = 1.

Answer 15

a) random individuals
b) full sibs
c) clones

Question 16

The more closely related individuals are, the more beneficial it is to be altruistic. True or false?

Answer 16

True - this was shown in an experiment with slime moulds. Newly evolved cells would migrate to the fruiting body and ‘sacrifice’ the cells in the stalk because they were less related.

Question 17

Dispersal is a costly behaviour. Why is it seen in nature?

Answer 17

It reduces kin competition.

Question 18

When the benefit is large there is a higher rate of dispersal. True or false?

Answer 18

True.

Question 19

Define spite.

Answer 19

The actor sabotages the recipient to reduce competition, although there are often costs for them too.

Question 20

The effect of spite is increased in large populations. True or false?

Answer 20

False - the effect of spite is diluted in large populations.

Question 21

Spite requires genetic recognition cues. Why?

Answer 21

So the actor does not sabotage a relative.

Question 22

What are genetic recognition cues likely to be?

Answer 22

Pheromones.

Question 23

Genetic recognition cues are often referred to as what?

Answer 23

‘Green beard’ or ‘selfish’ genes.

Question 24

Briefly outline the study on South African fire ants which is an example of a selfish gene.

Answer 24

1. 2 social forms of ant that differ in a single locus
2. One form is monogynous (1 queen), both queens and workers are homozygous dominant.
3. Second form is polygynous (many queens), both queens and workers are either homozygous dominant, heterozygous but homozygous recessive is lethal.
4. Heterozygotes of the polygynous colonies will murder monoygnous queens. It is thought it is because they possess a recessive allele which has been identified as the selfish gene.

Question 25

At which locus do the 2 social forms of South African fire ants vary?

Answer 25

Gp9 marker locus.

Question 26

Upon further study of the Gp9 locus it was found that it is not a single gene, but a large inverted sequence that cannot recombine. This has been termed as what?

Answer 26

A social chromosome.