Chapter 27.3 Microevolution

Question 1

Define microevolution

Answer 1

Evolution occurring at the population level

Question 2

Genetice changes occur within a ________

Answer 2

population

Question 3

________ do not evolve

Answer 3

individuals

Question 4

Define Evolution (within microevolution)

Answer 4

A change in gene frequencies within a population over time

Question 5

What happens when two populations diverge?

Answer 5

They can become separate species

Question 6

Define population (within population genetics)

Answer 6

all members of a species occupying a particular area at the same time

Question 7

Gene Population

Answer 7

the sum total of all alleles of all genes in a population

Question 8

Hardy-Weinberg Equilibrium

Answer 8

allele frequencies are stable

Question 9

What are the conditions that must be met in order to be at Hard-Weinberg equilibrium? (5)

Answer 9

1. No mutation
2. No genetic drift
3. No gene flow
4. Mating is random
5. No natural selection

Question 10

What is Hardy-Weinberg Equilibrium a null hypothesis?

Answer 10

1. Assumes evolutionary forces are absent

2. Deviations from equilibrium implies evolution

Question 11

What are the known evolutionary mechanisms? (5)

Answer 11

1. Mutation
2. Genetic drift
3. Gene flow
4. Nonrandom mating
5. Natural selection

Question 12

_____ is any change in DNA.

Answer 12

Mutation
The origin of genetic variation (new alleles)
Random in respect to needs of organism
Most mutations are harmful or neutral
Could be advantageous if conditions change
Mutation rates are low— 1:1,000,000 loci

Question 13

Mutation is the ____ of genetic variation

Answer 13

origin

Question 14

Genetic Drift

Answer 14

Random changes in allele frequencies

• Occurs without a selective force
• Trait doesn’t affect survival or reproduction
• Gene frequencies randomly fluctuate

Question 15

Population bottleneck

Answer 15

population reduced dramatically, surviving population has fewer alleles

Question 16

Founder Effect

Answer 16

small group colonizes new location, arriving population has fewer alleles

Question 17

Gene Flow

Answer 17

New alleles brought into population

Question 18

What causes a gene flow?

Answer 18

Results from the migration of individuals into population

Question 19

What is the effect of a gene flow?

Answer 19

new alleles arrive or gene frequency changed

Question 20

Nonrandom Mating

Answer 20

Individuals choose mates with particular phenotypes

-If a trait is preferred, that trait will leave more copies

Question 21

Sexual selection

Answer 21

Individuals with preferred traits have a higher reproductive success

• Acts on characters that determine reproductive success.
• If an individual survives but does not reproduce, it makes no contribution to the next generation.

Question 22

Dramatic differences between sexes are known as s_____ d_______.

Answer 22

sexual dimorphism

Question 23

Natural Selection

Answer 23

Only acts on phenotype – “Survival of the FIttest”

The best phenotype survives

Question 24

What is Fitness (within natural selection)?

Answer 24

the reproductive contribution of a phenotype to subsequent generations (# of offspring).
Changes in the relative

Question 25

Who leaves the most offspring?

Answer 25

Those with the most successful traits leave the most copies (offspring)

Question 26

Natural selection can act in 4 ways:

Answer 26

1. Stabilizing selection
2. Directional selection
3. Disruptive selection
4. Balancing selection

Question 27

Stabilizing selection

Answer 27

Preserves average phenotype.

• The mean value does not change 
- Natural selection is usually stabilizing
• human birth 7.5 lbs

Question 28

Directional Selection

Answer 28

Favors individuals that vary in one direction.

-A trait shifts over time toward the high or low extreme

Question 29

Disruptive Selection

Answer 29

Favors individuals that vary in opposite directions from the average.
-Individuals at either extreme are most successful

Question 30

Balancing Selection

Answer 30

Keeps two traits in a population

• Heterzygote advantage
• Surviving malaria