Lecture 22 - Adaptation and its Limits

Question 1

The 3 requirements of natural selection

Answer 1

1. There is variation amongst individuals (almost every single population has infinite variation)
2. Some of the variation is heritable (e.g. height as a trait that shows continuous variation. Distribution of height is almost bell shaped, some height variation gets passed on from parents)
3. Variation effects survival and reproduction (Antler size, mating calls, beak depth, speed)

Any trait that exhibits these features can adapt by natural selection

Question 2

What is an adaptation

Answer 2

a trait currently favoured by natural selection, and previously shaped by natural selection

adaptation is a trait not a process

Question 3

What is the meaning of “adaptive” and “maladaptive”

Answer 3

Adaptive - a trait that enhances fitness

Maladaptive - a trait that reduces fitness

Question 4

What other force can affect evolution of traits?

Can this force lead to adaptation

Answer 4

Genetic drift, allele frequencies change on the basis of chance alone. These changes may have an affect on a trait. The size of changes are likely to be larger in small populations)

genetic drift - random change in allele frequency
natural selection - drives change based on fitness advantages

NO - only natural selection leads to adaptation

Question 5

What does slope of a graph have to be for a trait to be heritable?

Answer 5

Positive slope - heritability
Zero slope - no heritability
Negative slope - ?

Question 6

Is natural selection random?

Answer 6

natural selection is not random (generation of genetic variation may be random, but the election process is not)