Lecture 4: Selection Flashcards Preview

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Flashcards in Lecture 4: Selection Deck (16):
1

What would the heritability of a trait with no genetic variation be?

0.

2

Define 'selection differential' (S).

The selection differential is the difference of the base population mean and the mean of the selected parents.

3

Define 'response to selection' (R).

How much gain you make when mating the selected parents.

4

Related response to selection and selection differential.

R = h(squared) x S.

5

Define 'phenotypic evolution'.

Change in the mean or variance of a trait across generation due to changes in allele frequencies.

6

Define 'fitness'.

Relative transmission of alleles to the next generation.

7

How can you measure directional selection?

Linear regression.

8

Define 'standardisation' (z-scores).

Standardisation of phenotypic traits allows to interpret selection as a number of standard deviation from the mean.

9

How do you calculate a z-score?

The score minus the mean score, divided by the standard deviation.

10

How can you measure non-linear selection?

Quadratics.

11

Does a positive quadratic represent destructive or stabilising non-linear selection?

Destructive. (sad face)

12

Does a negative quadratic represent destructive or stabilising non-linear selection?

Stabilising. (smiley face)

13

Define 'direct selection'.

Causal relationship between a 
phenotypic trait and fitness.

14

Define 'indirect selection'.

Covariance between a trait and fitness 
caused by a phenotypic correlation between that trait 
and another trait under direct selection.

15

What is stabilising selection?

Favours intermediate phenotype. There are no changes in the mean but a reduction in variance. It is expected to reduce genetic variation.

16

What is disruptive selection?

Favours both phenotypic extremes. There are no changes in the mean but a reduction in variance. it is expected to increase genetic variation.