Phenotypic Evolution

Question 1

Phenotype

Answer 1

The sum total of multiple genes interacting with each other and the environment

Question 2

Quantitative traits

Answer 2

Polygenic traits
Vary continuously and are affected by many loci
Influenced by environment

Question 3

Phenotypic variance

Answer 3

Variation in quantitative trait

Question 4

Variance

Answer 4

The average squared deviation of an observation from the arithmetic mean

Question 5

Fitness function

Answer 5

Quantifies how selection acts in quantitative traits

Question 6

Directional selection

Answer 6

Favours either an increase or decrease in a traits mean
Changes mean of trait
May or may not change variation in the trait

Question 7

Stabilizing selection

Answer 7

Favors individuals who’s trait values are near the population mean
(Optimum phenotype)
Reduces variation in trait
Mean stays constant

Question 8

Disruptive selection

Answer 8

Favors phenotypes at both extremes
When environment divides population into 2 sub-populations that experience different selective pressures on a trait
-populations become differentials fixed for alleles
—> mating barrier and further divergence

Question 9

All modes of selection

Answer 9

Can cause speciation

Question 10

Selection gradient

Answer 10

Measures strength of directional selection on a quantitative trait
Analogous to selection coefficient for alleles at a single locus
If gradient positive = selection favors increased mean
If negative = selection favors decreased mean

Question 11

Phenotypic plasticity

Answer 11

Individuals phenotype changes in response to the environment
Can be reversible and irreversible
Visualized using reaction norm

Question 12

Reaction norm

Answer 12

A plot showing how environmental conditions affect expression of phenotype
In reaction norm, genetic variation is referred to as genotype-environment interaction