ch 21: Natural Selection

Question 1

Microevolution

Answer 1

Change in allele frequencies of a population over Generations (small scale)

Question 2

Sources of new alleles (allows evolution to occur)

Answer 2

1. Mutations
   - point and chromosomal
2. Sexual Recombination
   - Crossing over, ind assorting, and fertilization

Question 3

Population Genetics

Answer 3

Study of how population genetics change over time

Question 4

Population

Answer 4

A group of individuals of the same species that live in the same area an interbreed (offspring must be fertile)

Question 5

Gene Pool

Answer 5

all alleles for all genes for all members of a population (variation in the population)

Question 6

Allele Frequency

Answer 6

the frequency at which an allele exists in a population

Question 7

Fixed Allele

Answer 7

when all members are homozygous for the same allele

Question 8

The Hardy-Weinberg Theorem

Answer 8

explains how allele frequencies (genotypes) change over time

Question 9

Hardy-Weinberg Equilibrium

Answer 9

a tool to measure change, Hardy-Weinberg equilibrium describes the constant frequency of alleles in such a gene pool

Question 10

5 conditions for non-evolving populations are rarely met in nature

Answer 10

• Extremely large population size
• No gene flow
• No mutations
• Random mating
• No natural selection

Question 11

Events that alter a population’s genetic composition

Answer 11

Natural Selection
Genetic Drift
Gene Flow

Question 12

Natural Selection

Answer 12

differential selection

Question 13

Genetic Drift

Answer 13

(unpredictable fluctuations in allelic frequency from one generation to the next) Chance, random, nonadaptive, small pop = greater impact of allele change

Question 14

2 types of genetic drift

Answer 14

population bottleneck

The Founder Effect

Question 15

population bottleneck

Answer 15

the seals((big populations to little populations to big populations)

Question 16

The Founder Effect

Answer 16

splitter groups that separate from the larger, main group may or may not represent the larger group

Question 17

Gene Flow

Answer 17

introductions of new variations through immigration and emigration

Question 18

Natural Selection as a Mechanism of Evolution

Answer 18

relative fitness

Acts on Phenotype

Question 19

relative fitness

Answer 19

contribution an organism makes to the gene pool of next-generation relative to other members. Not size or strength, but only reproductive success

Question 20

Acts on Phenotype (indirectly on genotype) Changes heritable traits in 3 ways

Answer 20

1. Directional Selection- Favors individuals at one extreme of a
   phenotypic range
2. Disruptive Selection- Individuals on both extremes are favored
3. Stabilizing Selection- Acts against both extremes phenotypes
   individuals in the middle are favored

Question 21

The Preservation of Genetic Variation(5)

Answer 21

Diploidy
Balancing Selection
Heterozygote advantage
Frequency-Dependent Selection
Neutral Variation

Question 22

Diploidy

Answer 22

recessives are hidden (heterozygosity)

Question 23

Balancing Selection

Answer 23

natural selection maintains two stable frequencies of two or more phenotypes in a population

Question 24

Heterozygote advantage

Answer 24

those that are heterozygous at a particular gene locus have greater fitness than those that are not, specific disease

Question 25

Frequency-Dependent Selection

Answer 25

the fitness of anyone morph declines if it becomes too common in the population.

Question 26

Neutral Variation

Answer 26

when genetic variation has little or no impact on reproductive success, just a change

Question 27

3 types of selection(3)

Answer 27

1. sexual dimophism 2. Intrasexual selection 3. Intersexual selection

Question 28

Sexual dimorphism

Answer 28

phenotypic differences in secondary sex characteristics between the sexes.

Question 29

Intrasexual selection

Answer 29

mating selection/competition within the same sex

Question 30

Intersexual selection

Answer 30

mate choice. Female selecting male

Question 31

Why natural selection cannot produce perfect organisms

Answer 31

1. Selection can only edit existing variations. 2. Evolution is limited by historical constraints. 3. Adaptations are often compromised. 4. Chance, natural selection, and the environment interact.