Evolution of Populations : Biology

Question 1

Microevolution

Answer 1

Change in allele frequencies in a population over generational time.
- ONLY population evolves, not individuals
- smallest unit of evolution
- small scale DOESNT equal new species

Question 2

Gene

Answer 2

Made up of two alleles.

Question 3

Gene Pool

Answer 3

The make up of a population.

Question 4

Allele

Answer 4

Shift of frequencies that occurs over time within a population.

Question 5

Fixed Locus

Answer 5

All individuals in a population are homozygous for the allele.
- NO variation for trait

Question 6

Unfixed Locus

Answer 6

2+ alleles exist for a locus.
- individuals can be homo or heterozygous
- evolution can only occur if unfixed

Question 7

Locus

Answer 7

Location of a gene on the chromosome.

Question 8

Variation

Answer 8

Inheritable traits, prerequisite for evolution.

Question 9

Homozygous

Answer 9

Same alleles.
- Homo Dominant or Homo Recessive
- AA aa

Question 10

Heterozygous

Answer 10

Different alleles.
- one dominant one recessive
- Aa

Question 11

Population

Answer 11

A localized group of individuals capable of interbreeding and producing fertile offspring.
- Individuals within pops are more closely related compared to other pops

Question 12

Why do populations evolve and not individuals?

Answer 12

Population evolve as gene frequencies change, individual organisms cannot.

Question 13

What are the 4 sources of genetic variation?

Answer 13

1. Mutation
2. Chromosomal Changes
3. Rapid Reproduction
4. Sexual Reproduction

Question 14

Explanation of the 4 sources of genetic variation

Answer 14

1. Mutation :
   - one of the 5 mechanisms of evolution
   - original source of new alleles, neutral
2. Chromosomal changes : usually harmful
3. Rapid Reproduction : mutation occur quickly
4. Sexual Reproduction : shuffles existing genetic variation

Question 15

Explain why mutation is the only original source of genetic variation and how this makes it a fundamental mechanism of evolution.

Answer 15

In the absence of such variation, no subsequent change can be achieved. Genetic variation is ultimately all generated by mutation.

Question 17

Why is genetic variation a prerequisite of evolution?

Answer 17

Genetic variation is essential. For natural selection to occur, a population must have a wide variety of individuals with different traits.

Question 18

Microevolution

Answer 18

As species change, they become better adapted to their environment.
- more likely to occur

Question 19

Macroevolution

Answer 19

If species change enough, new species may arise.

Question 20

What are the modes of Natural Selection?

Answer 20

• Directional Selection
• Disruptive Selection
• Stabilizing Selection

Question 21

Directional Selection

Answer 21

One extreme phenotype favored, and the distribution curve shifts in that direction.
- Common when environment changes, peppered moths example, finch beaks

Question 22

Disruptive Selection

Answer 22

Two or more extreme phenotypes are favored over an intermediate phenotype.

Question 23

Stabilizing Selection

Answer 23

An intermediate phenotype (out of a continuous variation of phenotypes) is favored.
- Reduces variation and favors status quo

Question 24

Peter and Rosemary Grant finch study.

Answer 24

• Drought occurs, finches with tougher beaks withstood.
• Deep beaked finches had higher survival and reproduction rates.
• Beak size did not change, population evolved to all have deeper beaks.

Question 25

What are the Mechanisms of microevolution? (Chart)

Answer 25

• Natural Selection
• Genetic Drift
• Gene Flow
• Sexual Selection
• Mutation

Question 26

Natural Selection

Answer 26

Favorable alleles are passed on to the next generation in proportions that differ from present generation. (Differential reproduction success)
- Can adapt to changes in environment
- Decreases or Stabilizes
- Beneficial alleles

Modes:
Disruptive selection: Two or more extreme phenotypes are favored over an intermediate phenotype.
Stabilizing selection: intermediate phenotype, reduce variation.

Question 27

Genetic Drift

Answer 27

Unpredictable allele frequency, one generation to another.
- All frequencies change due to chance
- Decreases genetic variation (inbreeding)
- Can cause beneficial or harmful alleles

Modes:
Founder effect: occurs when a few individuals become isolated from larger pop. (large pop goes to new area and becomes bigger)
Bottleneck effect: Drastic reduction in pop size due to sudden environmental change. (most die)

Question 28

Gene Flow

Answer 28

Movement of alleles (individual) between populations. (via fertile individuals or gametes)
- Due to chance
- Increases in genetic variation
- Neutral
- No modes

Question 29

Sexual Selection

Answer 29

Natural selection for mating success. May result in sexual dimorphism. (size difference)
- Showy, not due to chance
- Decreases or stabilizes
- Beneficial

Modes:
Intrasexual and Intersexual

Question 30

Intrasexual Selection (Males)

Answer 30

• Individuals of opposite sex compete for mates
• males father many offspring
• direct and indirect competition

Question 31

Intersexual Selection (Females)

Answer 31

• females are choosy when it comes to choosing a mate
• females produces limited number of offspring

Question 32

Mutation

Answer 32

Original source of new alleles.
- due to chance
- Increases in genetic variation
- Neutral

Modes:
Germline mutations: occur in gametes.
Somatic mutations: occur in other cells of the body.