Altruism (Siva-Jothy)

Question 1

Altruistic Behaviour

Answer 1

Altruistic behaviour: Behaviour that benefits other individuals at a cost to the altruistic individual.
There is a reduction of fitness to the altruistic individual.

Question 2

Examples of altruistic behaviour

Answer 2

Honeybees

• Guard bees sit at the entrance to the hive, if you approach it will come out and sting you, therefore killing itself.
• It is giving up reproduction to benefit all other bees in the population.
• All bees give up reproduction except for the queen bee, instead helping her to reproduce.

Vampire bats
-If they have a blood meal and others haven’t, they will regurgitate part of their meal to feed others.

Question 3

How could altruistic behaviour evolve?

Answer 3

1. The behaviour is not really altruistic?
2. Altruism is reciprocated at a later time?
3. Adaptations have evolved for “the good of the species”?
4. Adaptations have evolved for the good of the gene.

Question 4

The behaviour is not really altruistic?

Answer 4

Monkeys
One doesn’t feed and looks for predators, then screams if there are predators spotted, to warn the other monkeys feeding, therefore thought it was altruism.
- Might not be altruism and could be because by screaming and many monkeys running, it reduces the risk of one monkey getting attacked and eaten.
-However, the monkey still goes without feeding properly, so it is altruistic behaviour.

Question 5

Altruism is reciprocated at a later time?

Answer 5

The altruistic behaviours balance out.
-E.g. vampire bats regurgitating food for another when it gets hungry, but the role is reversed when the first altruistic bat goes hungry.

Question 6

Adaptations have evolved for the “good of the species”?

Answer 6

-Sterile worker castes
-Alarm calls
-Ritualised fighting
-Senescence
Such adaptations could not have evolved by individual selection. Nothing evolves for the good of the species

Question 7

Group selection (problems) (“good of the species”)

Answer 7

If selection worked in a group, mutations would quickly affect the whole group.
-The turnover rate of a group is always faster than that of the individual, so there would be an invasion of non-altruistic mutation.

Question 8

Adaptations have evolved for the good of the gene?

Answer 8

Altruistic behaviour occurs at the level of the individual. Behaviour is selfish at the level of the gene.
It enhances the fitness of individual genes
-It increases the frequency of a gene in the population, due to Kin selection

Question 9

Kin selection

Answer 9

• Altruism will evolve when rb > c (Hamilton’s Rule)
• c = cost of altruism
• b = benefit to recipient
• r = coefficient of relatedness (% of genes shares)

Question 10

% of genes shares (coefficient of relatedness)

Answer 10

Parent - child = 50%

Grandparent - child = 25%

Full siblings = 50%

Half-siblings = 25%

Cousins = 12.5%

Question 11

With an altruistic act..

Answer 11

rb > c

• If c increased, less genes are passed to own offspring
• If rb increases, more genes are passed through kin’s offspring

Question 12

Helper’s at the nest (kin selection)

Answer 12

Seychelles warbler
Male brings food to female and offspring. There is sometimes another male helper who brings food as well.
-He is altruistic, as he is not reproducing with the female.
-The helpers are often sons of the parents chicks, they don’t have the ability to reproduce, but are increasing the success of reproduction of the mother and father.

rb > c

• c = number of chicks helper would have if it bred
• b = extra chicks the pair raises
• r = relatedness to pair (calculated by DNA fingerprinting).