7b slides Flashcards

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1
Q

what is evolution at its finest level

A

change in allele frequencies in a population over generations

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2
Q

what are the three main mechanisms that cause allele frequency change

A

-natural selection
-genetic drift
-gene flow

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3
Q

what is the only thing that causes adaptive evolution

A

adaptive evolution

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4
Q

adaptive evolution is

A

a process in which traits that enhance survival or reproduction tend to increase in frequency over time, resulting in a better match between organisms and their environment

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5
Q

gene pool

A

all the alleles in a population

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6
Q

what is a population a mix of

A

homozygous and heterozygous individuals

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7
Q

genetic drift

A

chance events cause unpredictable fluctuations in allele frequencies from one generation to the next

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8
Q

random genetic drift

A

more beneficial or less beneficial trait may increase

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9
Q

what type of population are effects of genetic drift most obvious

A

small populations

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10
Q

what are the mehcnaisms of genetc drift

A

-founder effect
-bottleneck effect

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11
Q

when does genetic drift founder effect occur

A

when a few individuals become isolated from a larger population and form a new population

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12
Q

is the founder gene pool reflective of the original population

A

no

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13
Q

bottleneck effect

A

genetic drift that occurs when the size of a population is reduced randomly

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14
Q

How is natural selection more “predictable” than genetic drift?

A

Natural selection is more “predictable” in that it alters allele frequencies in a nonrandom way: It tends to increase the frequency of alleles that increase the organism’s reproductive success in its environment and decrease the frequency of alleles that decrease the organism’s reproductive success. Alleles subject to genetic drift increase or decrease in frequency by chance alone, whether or not they are advantageous.

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15
Q

gene flow

A

The transfer of alleles from one population to another due to movement of fertile individuals or their gametes

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16
Q

gene flow tends to _______ variation ________ populations and _______ variation _______ a population

A

reduce/between

increase/within

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17
Q

what does natural selection result in

A

alleles being passed to the next generation in proportions that differ from those in the present generation in a nonrandom way

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18
Q

Why is natural selection the only mechanism that consistently leads to adaptive evolution in a population?

A

Although both gene flow and genetic drift can increase the frequency of advantageous alleles in a population, they can also decrease the frequency of advantageous alleles or increase the frequency of harmful alleles. Only natural selection consistently results in an increase in the frequency of alleles that enhance survival or reproduction. Thus, natural selection is the only mechanism that consistently leads to adaptive evolution.

19
Q

what are the three general modes of natural selection that affect quantitative trait/character

A

-directional selection
-disruptive selection
-stabilizing selection

20
Q

who does directional selection favor

A

individuals at one extreme end of the phenotypic range

21
Q

Quantitative trait/character

A

A heritable feature that varies continuously over a range rather than in an either-or fashion

22
Q

who does disruptive selection favor

A

individuals at both extremes of the phenotypic range

23
Q

who does stabilizing selection favor

A

intermediate variants and acts against extreme phenotypes

24
Q

what does stabilizing selection reduce

A

variation, acts against extreme phenotypes

25
Q

sexual dimorphism

A

marked the differences between the sexes in secondary sexual characteristics

26
Q

example of organisms that exhibits sexual dimorphism

A

elephant seal

27
Q

secondary sexual charcateristics

A

characteristics not directly involved in reproduction

28
Q

which is usually the showier sex

A

males

29
Q

intrasexual selection

A

competition among individuals of one sex (usually males) for mates of the opposite sex

30
Q

intersexual selection (aka mate choice)

A

individuals of one sex (usually female) are choosy in selection of mates

31
Q

intra

A

within

32
Q

inter

A

between

33
Q

what does the good genes hypothesis suggest

A

suggests that if a phenotype is correlated with “good genes” (e.g., larval survival), both the male trait and female preference for that trait should increase in frequency

34
Q

is their a benefit to females under the good genes hypothesis

A

no direct benefit to the female for her choice under this hypothesis, only her offspring

35
Q

when does balancing selection occur

A

when natural selection maintains stable frequencies of two or more phenotypic forms in a population

36
Q

what do balancing selection mechanisms include

A

-frequency dependent selection
-heterozygote advantage

37
Q

what does the fitness of a phenotype depend on for frequency dependent selection

A

on how common it is in the population

38
Q

when does heterozygote advantage occur

A

when heterozygotes have a higher fitness than both homozygotes

39
Q

4 reasons why natural selection cannot fashion perfect organisms

A
  1. Selection can act only on existing variations
  2. Evolution is limited by historical constraints
  3. Adaptations are often compromises
    intersexual selection/mate choice
  4. Chance, natural selection, and the environment interact
40
Q

what can hardy Weinberg equation be used to test

A

whether a population is evolving

41
Q

Hardy-Weinberg equilibrium serves as

A

a baseline for comparison to data collected from a population

42
Q

what does it mean when there is no difference with Hardy-Weinberg equilibrium

A

population is not evolving

43
Q

what does it mean when there is a difference with Hardy-Weinberg equilibrium

A

population is evolving