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BIO 1306 > Mechanisms Of Evolution > Flashcards

Mechanisms Of Evolution Flashcards

1
Q

What can break the Hardy-Weinberg equilibrium and cause evolution?

A

Mutations
Non-random mating
Natural selection
Genetic drift
Gene flow

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2
Q

What is significant about mutations?

A

They are completely random

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3
Q

What are mutations?

A

Changes in the DNA sequence of an organism (insertion, deletions, substitution at one or more sites)

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4
Q

Mutation contributes to…

A

Genetic variation

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5
Q

Mutation can…

A

Modify allele frequencies
Be good, bad or neutral

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6
Q

What is non-random mating?

A

It occurs when probability that two individuals in a population will mate is not the same for all possible pairs

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7
Q

What does non-random mating affect?

A

It affects the frequencies of homozygous and heterozygous genotypes

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8
Q

Natural selection is the only mechanism that…

A

Consistently leads to adaptive change

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9
Q

Natural selection is NOT…

A

Random
Predictive

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10
Q

Natural selection consistently…

A

Increases frequency of alleles that provide fitness benefits which leads to adaptive evolution

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11
Q

What are the types of natural selection.

A

Directional
Stabilizing
Disruptive
Balancing
Sexual selection

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12
Q

When does directional selection occur?

A

When conditions favor individuals with on extreme of a phenotypic range

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13
Q

How does directional selection shift?

A

Shifts the frequency curve in one direction (left or right)

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14
Q

Directional selection tends to…

A

Reduce genetic variation

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15
Q

Stability selection acts against…

A

Both extreme phenotypes and favors intermediate variants (mean trait value)

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16
Q

Stabilizing selection reduces…

A

Variation

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17
Q

Stabilizing selection maintains…

A

Status quo for a particular phenotypic trait

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18
Q

Stabilizing Selection there is no change in…

A

Average trait value over time

19
Q

Disruptive selection occurs…

A

When conditions favor individuals at both extreme of a phenotypic range over individuals with intermediate phenotypes

20
Q

Disruptive Selection tends to…

A

Increase genetic variation

21
Q

Disruptive Selection can lead to…

A

Speciation (two different species)

22
Q

How does stabilizing selection look on a graph?

A

Culls extreme variations
Narrows width of distribution

23
Q

How does directional selection look on a graph?

A

Favors one extreme
Shifts distribution left/right

24
Q

How does disruptive selection look on a graph?

A

Favors both extremes
Creates bio dual distribution

25
Q

What is balancing selection?

A

Selection may preserve variation at some loci, thus maintaining two or more phenotypic forms

26
Q

What are the two types of balancing selection?

A

Frequency dependent selection and heterozygote advantage

27
Q

What is frequency dependent selection?

A

Fitness of a phenotype depends on how common it is in the population

28
Q

What is a heterozygote advantage?

A

When individuals are heterozygous at a particular locus have greater fitness than both kinds of homozygotes , fitness is relative to others in the population and in the environment

29
Q

What is sexual selection?

A

Process where individuals with certain inherited characteristics are mo re likely than other individuals of the same sex to obtain mates

30
Q

What is sexual dimorphism?

A

Difference in the secondary sexual characteristics between males and females of same species

31
Q

What is intersexual selection?

A

Selection within the same sex

32
Q

What is intersexual selection?

A

Individuals of one sex are choosy when selecting mates from the other sex; also called mate choice

33
Q

Why doesn’t natural selection create perfect organisms?

A

Selection can only act on existing variation
Evolution is not forward looking
Limited by historical constraints
Adaptations often compromises
Interactions with other evolutionary processes and chance events

34
Q

What is genetic drift?

A

Chance events that cause allele frequencies to change unpredictability from one generation to the next, especially in small populations

35
Q

Genetic drift is significant in…

A

Small populations

36
Q

Genetic drift causes…

A

allele frequencies to change at random

37
Q

Genetic drift leads to…

A

A loss of genetic variation in a population

38
Q

Genetic drift can cause…

A

Harmful alleles to be fixed

39
Q

What are the two types of genetic drift?

A

Founder effect and bottleneck effect

40
Q

What is the founder affect?

A

When a few individuals become isolated from a larger population and go on to establish a new population whose gene pool differs from the source population

41
Q

What is the bottleneck effect?

A

A drastic reduction in the size of a population by chance alone that leads to certain alleles that are over represented/underrepresented among the survivors

42
Q

What is gene flow? Yeah

A

Aka migration, transfer of alleles in or out of a populations due to the movement of fertile individuals or their gametes

43
Q

Gene flow can help or hinder natural selection forces by…

A

Affecting how well populations are adapted to local environmental conditions

BIO 1306 (17 decks)

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