ch 21: Natural Selection Flashcards

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1
Q

Microevolution

A

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

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2
Q

Sources of new alleles (allows evolution to occur)

A
  1. Mutations
    - point and chromosomal
  2. Sexual Recombination
    - Crossing over, ind assorting, and fertilization
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3
Q

Population Genetics

A

Study of how population genetics change over time

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4
Q

Population

A

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

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5
Q

Gene Pool

A

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

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6
Q

Allele Frequency

A

the frequency at which an allele exists in a population

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7
Q

Fixed Allele

A

when all members are homozygous for the same allele

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8
Q

The Hardy-Weinberg Theorem

A

explains how allele frequencies (genotypes) change over time

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9
Q

Hardy-Weinberg Equilibrium

A

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

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10
Q

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

A
  • Extremely large population size
  • No gene flow
  • No mutations
  • Random mating
  • No natural selection
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11
Q

Events that alter a population’s genetic composition

A

Natural Selection
Genetic Drift
Gene Flow

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12
Q

Natural Selection

A

differential selection

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13
Q

Genetic Drift

A

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

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14
Q

2 types of genetic drift

A

population bottleneck

The Founder Effect

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15
Q

population bottleneck

A

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

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16
Q

The Founder Effect

A

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

17
Q

Gene Flow

A

introductions of new variations through immigration and emigration

18
Q

Natural Selection as a Mechanism of Evolution

A

relative fitness

Acts on Phenotype

19
Q

relative fitness

A

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

20
Q

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

A
  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
21
Q

The Preservation of Genetic Variation(5)

A
Diploidy
Balancing Selection
Heterozygote advantage
Frequency-Dependent Selection
Neutral Variation
22
Q

Diploidy

A

recessives are hidden (heterozygosity)

23
Q

Balancing Selection

A

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

24
Q

Heterozygote advantage

A

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

25
Q

Frequency-Dependent Selection

A

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

26
Q

Neutral Variation

A

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

27
Q

3 types of selection(3)

A
  1. sexual dimophism
  2. Intrasexual selection
  3. Intersexual selection
28
Q

Sexual dimorphism

A

phenotypic differences in secondary sex characteristics between the sexes.

29
Q

Intrasexual selection

A

mating selection/competition within the same sex

30
Q

Intersexual selection

A

mate choice. Female selecting male

31
Q

Why natural selection cannot produce perfect organisms

A
  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.