2: Selfish Genes

Question 1

What was found about alarm calls in Beldin’s ground squirrels?

Answer 1

• Alarm call when predator is near = altruistic
• Sherman & colleagues studied evolution of alarm calls in groups
• Likelihood of an individual giving an alarm call related to whether the group contains relatives or not

Question 2

Describe the altruism found in Florida Scrub Jays

Answer 2

In most birds fledglings leave the nest when able to fly
In Scrub Jays, the chicks stay and help raise siblings = sacrificing own reproduction

Question 3

Describe how altruism is an evolutionary conundrum

Answer 3

Altruism potentially challenges the idea of selfish genes
Selection favours the spread of genes if they code for traits that increase fitness
A gene that codes for altruistic behaviour will help other genes?

Question 4

Describe how natural selection is gene selection

Answer 4

Selection occurs when genotypes differ in their ability to pass genes onto the next gen
If a genotype is successful, its genes will increase in frequency & vise versa
Kin selection tell us it doesn’t actually matter which individual possesses the gene

Question 5

Describe kin selection theory

Answer 5

→ explanation for altruistic behaviour
→ An altruistic action will be favoured if it benefits kin
Altruism increases the fitness of other individuals (kin) and increases the rate of gene spread
This will evolve if: r x b > c
r = relatedness of target individual
b = benefit to target
c = cost to giver

Question 6

What is relatedness?

Answer 6

proportion of genes shared because of common ancestry

Question 7

What is the relatedness of an offspring & parent?

Answer 7

0.5

Question 8

What is the relatedness of a sibling & sibling?

Answer 8

0.5

Question 9

What is the relatedness of a grandparent & grandchild?

Answer 9

0.25

Question 10

What is the relatedness of a cousin & cousin

Answer 10

0.125

Question 11

Describe the green beard model

Answer 11

Altruistic gene linked to an obvious phenotype will spread if possessors are altruistic towards each other
Does not require relatedness (kin selection)
Few examples .. so kin selection is more common
False beards can easily cheat
Cheating: possess green beard but do not reciprocate altruism
Probably evolutionarily unstable

Question 12

Give an example of the green beard model

Answer 12

All egg laying queens are Bb
bb queens die naturally
BB queens are killed by workers
Use odours to distinguish BB from Bb
Genotype linked to behaviour = green beard effect

Question 13

Describe the selfish genetic elements.
Give an example

Answer 13

Gene-selection can be more important than individual selection
Gene level selection affects evolution of genetic material with gene competition
E.g: Meiotic drive (Drosphila)