Chapter 23 Flashcards

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1
Q

Population

A

a group of individuals of the same species that live in the same area and interbreed, producing fertile offspring

the smallest unit that can evolve

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2
Q

microevolution

A

change in allele frequencies in a population over generations

evolution on its smallest scale

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3
Q

difference between characters that vary discretely and continuously (quantitatively)

A

discrete characters are an either/or thing and are determined by a single gene locus

quantitative characters vary along a contiuum within a population and results from the influence of 2 or more genes on a single phenotypic character

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4
Q

Hardy-Weinberg Principle

why is it useful in describing the genetic structure of a nonevolving population?

A

fundamental theorem of population genetics

allele frequency will NOT change if…

1) no mutation
2) no natural selection or sexual selection
3) no migration
4) population is very large
5) no gene flow

with it, we can find the frequencies of alleles and genotypes and describe the gene pool of a nonevolving population

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5
Q

Geographic variation

A

results when two or more populations are separated by geography and develop different genetic compositions

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6
Q

Cline

A

a graded change in a character along a geographic axis

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7
Q

Gene pool

A

a count of all alleles present in a population

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8
Q

What does it mean to say an allele is fixed in a population?

A

an allele is considered fixed whenever there can be no variation to it because only one allele exists for a particular locus in a population

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9
Q

What 3 evolutionary mechanisms cause allele frequencies within a gene pool to change?

A

1) genetic drift (bottleneck effect, founder effect)
2) gene flow
3) natural/sexual selection

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10
Q

What is the only mechanism that consistently causes adaptive evolution?

A

natural selection

requires 2 things:

1) genetic variability - from mutation and sexual recombination, random
2) differential success of genotypes (=relative fitness) - variability reduced as certain genes are selected against, weeded out, non-random

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11
Q

Genetic drift

A

chance events that cause allele frequencies to fluctuate unpredictably from one generation to the next (especially in small populations)

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12
Q

Relative fitness

A

the contribution an individual makes to the gene pool of the next generation relative to the contribution of other individuals

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13
Q

Three “modes” of natural selection

A

1) directional selection - moving mean
2) disruptive selection - selecting for two extremes
3) stabilizing selection - selecting for intermediate

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14
Q

Sexual selection

A

when individuals with certain inherited characteristics are more likely to find mates

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15
Q

sexual dimorphism

A

the difference between the two sexes in secondary sexual characteristics

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16
Q

limits to natural selection

A

it can’t create perfect organisms because:

1) selection can only act on existing variations
2) evolution is limited by historical constraints
3) adaptations are often compromises
4) chance, natural selection, and the enviroment interact

17
Q

sources of genetic variation

A

1) mutations
2) independent assortment of chromosomes in meiosis
3) crossing-over in meiosis
4) sexual reproduction

18
Q

a group of individuals of the same species that live in the same area and interbreed, producing fertile offspring

the smallest unit that can evolve

A

Population

19
Q

change in allele frequencies in a population over generations

evolution on its smallest scale

A

microevolution

20
Q

discrete characters are an either/or thing and are determined by a single gene locus

quantitative characters vary along a contiuum within a population and results from the influence of 2 or more genes on a single phenotypic character

A

difference between characters that vary discretely and continuously (quantitatively)

21
Q

fundamental theorem of population genetics

allele frequency will NOT change if…

1) no mutation
2) no natural selection or sexual selection
3) no migration
4) population is very large
5) no gene flow

with it, we can find the frequencies of alleles and genotypes and describe the gene pool of a nonevolving population

A

Hardy-Weinberg Principle

why is it useful in describing the genetic structure of a nonevolving population?

22
Q

results when two or more populations are separated by geography and develop different genetic compositions

A

Geographic variation

23
Q

a graded change in a character along a geographic axis

A

Cline

24
Q

a count of all alleles present in a population

A

Gene pool

25
Q

an allele is considered fixed whenever there can be no variation to it because only one allele exists for a particular locus in a population

A

What does it mean to say an allele is fixed in a population?

26
Q

1) genetic drift (bottleneck effect, founder effect)
2) gene flow
3) natural/sexual selection

A

What 3 evolutionary mechanisms cause allele frequencies within a gene pool to change?

27
Q

natural selection

requires 2 things:

1) genetic variability - from mutation and sexual recombination, random
2) differential success of genotypes (=relative fitness) - variability reduced as certain genes are selected against, weeded out, non-random

A

What is the only mechanism that consistently causes adaptive evolution?

28
Q

chance events that cause allele frequencies to fluctuate unpredictably from one generation to the next (especially in small populations)

A

Genetic drift

29
Q

the contribution an individual makes to the gene pool of the next generation relative to the contribution of other individuals

A

Relative fitness

30
Q

1) directional selection - moving mean
2) disruptive selection - selecting for two extremes
3) stabilizing selection - selecting for intermediate

A

Three “modes” of natural selection

31
Q

when individuals with certain inherited characteristics are more likely to find mates

A

Sexual selection

32
Q

the difference between the two sexes in secondary sexual characteristics

A

sexual dimorphism

33
Q

it can’t create perfect organisms because:

1) selection can only act on existing variations
2) evolution is limited by historical constraints
3) adaptations are often compromises
4) chance, natural selection, and the enviroment interact

A

limits to natural selection

34
Q

1) mutations
2) independent assortment of chromosomes in meiosis
3) crossing-over in meiosis
4) sexual reproduction

A

sources of genetic variation