R22 Adaptation and its limits

Question 1

What 3 things does natural selection require ?

Answer 1

1)there is variation amongst individuals
2) Some of that variation is heritable
3) Variation effects survival and reproduction

Question 2

What is adaptation ?

Answer 2

Adaptation: a trait currently favoured by natural selection, and previously shaped by natural selection
- Adaptive: a trait that enhances fitness
- Maladaptive: a trait that reduces fitness

Question 3

Is phenotypic and genotypic variation required for natural selection ?

Answer 3

Both genetic and phenotypic variation is both necessary for adaptation by natural selection
- Phenotypic is needed for natural selection to act, genetic is needed for variation to be heritable

Question 4

What are some methods for telling us if a trait is heritable ?

Answer 4

• Trait correlation between parents and offspring
• Comparing monozygotic and dizygotic twins
• Looking at associations between phenotypes and genotypes.

Question 5

What is adaptive story telling?

Answer 5

Adaptive story telling: providing a plausible story for the adaptive significance of a trait without demonstrating adaptation
- Why do we have noses – for glasses to sit

To avoid adaptive storytelling:
- Consider the alternatives

Question 6

What are the other reasons for adaptations to form ?

Answer 6

• Exaptation: a trait that performs a current function that is different than the function it originally evolved for
  o Feather evolution: feathers seem adapted to flight, but they originally evolved for the maintenance of body heat
• Not all traits can be explained by natural selection, may be due to the laws of chemistry or physics:
  o Why is blood red? Due to haemoglobin, not to alarm the animal of an injury
• Chance: some humans can roll their tongues
• Side-effect of other adaptation: sneezing allows the expelling of a foreign object but in turn allows the virus to spread
• Historical constraints: human back pain is from the arching of our ape ancestors

Question 7

How can we experiment the fitness of different genotypes ?

Answer 7

• Apply the same selection pressure to all the genotypes and observe the offspring produced of each.

Unethical

Question 8

Why do male mammals have nipples ?

Answer 8

a side-effect of females evolving nipples to feed their young