Lecture 5: Evolution & Intro to Plasticity

Question 1

Evolution definitions

Answer 1

• descent w/ modification & often diversification (macro)
• change in allele frequency in population (micro)
• change in the inherited traits of a population of organisms through successive generations

Question 2

Forces that change allele frequencies in populations

Answer 2

• mutation - random (ultimate source of genetic variation)
• selection - adaptive
• genetic drift - random
• gene flow - emigration/immigration

Question 3

Evolution by natural selection

Answer 3

Acts on phenotypes –> changes allele frequencies
Ingredients:
* Variability in phenotypic trait
* Differential fitness
* Heritability

Question 4

Selection differential

Answer 4

traint mean of original population vs. surviving parents

Question 5

Types of phenotypic shifts

Answer 5

• Directional
• Stabilizing (extreme @ adv/disadv)
• Disruptive (not intermediate)

Question 6

Genetic drift

Answer 6

• smaller # of offspring –> greater possible change in gene frequencies
• lower allele frequency in parents –> greater chance of loss

Drift randomly reduces genetic variability –> more prominent in small pop

Question 7

Inbreeding depressions (small populations)

Answer 7

Reduced fitness (result of mating –> expression of deletrious recessive alleles)

Question 8

Gene flow

Answer 8

Reinforces/opposes changes that occur via natural selection/drift
* net movement of particular alleles to/from population
* if movement not random –> gene flow occurs

Question 9

Adaptive evolution relies on…

Answer 9

Chance events (mutations & recombination) & non-random process of selection

Question 10

Constraints on adaptation

Answer 10

• requires standing genetic variation
• fitness is relative
• adaptive traits may trade-off w/ each other
• selection pressure is variable
• can take a long time, even if environments constantly change

Question 11

Phenotypic plasticity

Answer 11

ability of the same genotype to produce different phenotypes in response to variation in the environment

Question 12

Reaction norm

Answer 12

shows relationship between phenotype & environmental conditions for given genotype when phenotype is continous