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Biology > Ch. 21 - Evolution Of Populations > Flashcards

Ch. 21 - Evolution Of Populations Flashcards

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1
Q

Microevolution

A

Change in allele frequency of a population over time

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2
Q

do individuals evolve?

A

no, populations evolve over time

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3
Q

what is the main thing that makes evolution possible?

A

genetic variation

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4
Q

what two ways does phenotype occur?

A

either/or or variation of multiple alleles

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5
Q

gene variability is…

A

the average percentage of loci that are heterozygous

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6
Q

nucleotide variability is…

A

genetic variation at the molecular level

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7
Q

phenotypic variation is..

A

can be changed but not effect alleles

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8
Q

what are the sources of genetic variation?

A

mutation, duplication, deletion

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9
Q

relevant mutations occur in what cells?

A

gamete cells, the only mutated cells that can be passed to the next generation

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10
Q

what must exist for evolution to occur?

A

genetic variation

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11
Q

what is allele frequency?

A

how common that allele is in a population

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12
Q

hardy-weinberd equilibrium

A

frequencies of alleles and genotypes can remain constant from generation to generation

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13
Q

what conditions must exist for equilibrium to be met?

A

no mutations, random mating, no natural selection, extremely large population size, no gene flow

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14
Q

genetic drift

A

change events cause allele frequencies to change randomly and fluctuate unpredictably

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15
Q

the founder effect

A

when few individuals are isolated from the population and establish a new population

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16
Q

bottleneck effect

A

sudden change drastically changes the size of a population

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17
Q

is genetic drift more important in larger or small populations?

A

smaller populations have a greater risk of over or underrepresentation of alleles in the next generation

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18
Q

gene flow

A

the transfer of alleles due to fertile individuals leaving or entering the population

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19
Q

relative fitness

A

the contribution an individual makes to the gene pool of the next generation

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20
Q

directional selection

A

conditions favor one end of the phenotypic range

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21
Q

disruptive selection

A

favors both ends of the phenotypic range, but not the middle

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22
Q

stabilizing selection

A

selects for the middle, against the extremes

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23
Q

what is the only evolutionary mechanism that always leads to adaptive evolution?

A

natural selection

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24
Q

intrasexual selection

A

a member of one sex competing for mates with another member of the sex

25
Q

intersexual selection

A

one sex picks the mate

26
Q

neutral variation

A

difference in alleles are neither good or bad

27
Q

diploidy

A

recessive alleles are less favorable and don’t pop up very often

28
Q

balancing selection

A

natural selection maintains two or more forms in a population

29
Q

In the context of populations, how do we define evolution?

A

Evolution is a change in a population’s allele frequencies over generations.

30
Q

Which of the following mechanisms can alter allele frequencies?

A

Natural selection, gene flow, and genetic drift can all cause microevolution

31
Q

Which of the following can form entirely new alleles?

A

mutation

32
Q

Sexual recombination includes the shuffling of chromosomes in _____ and fertilization

A

meiosis

33
Q

Which type of mutation plays the most important role in increasing the number of genes in the gene pool?

A

duplication

34
Q

In a large population of randomly breeding organisms, the frequency of a recessive allele is initially 0.3. There is no migration and no selection. Humans enter this ecosystem and selectively hunt individuals showing the dominant trait. When the gene frequency is reexamined at the end of the year, _____.

A

the frequency of the homozygous dominants will go down, the frequency of the heterozygous genotype will go down, and the frequency of the homozygous recessives will go up

35
Q

In a large population of bonobos, the frequency of the recessive allele is initially 0.1. There is no migration and no selection. What is the frequency of the dominant allele? Assume that there are two alleles of this gene.

A

90%

36
Q

Approximately 1 out of every 2,500 Caucasians in the United States is born with the recessive disease cystic fibrosis. According to the Hardy-Weinberg equilibrium equation, approximately what percentage of people are carriers?

A

about 4%

37
Q

In a certain group of African people, 4% are born with sickle-cell disease (homozygous recessive). If this group is in Hardy-Weinberg equilibrium, what percentage of the group has the selective advantage of being more resistant to malaria (heterozygous) than those individuals who are homozygous for normal hemoglobin or for sickle-cell disease?

A

32%

38
Q

Assume a population in Hardy-Weinberg equilibrium for a character trait with these genotypic frequencies: AA = 0.25, Aa = 0.50, and aa = 0.25. If you remove all the homozygous dominants and allow the remaining population to reproduce (again under Hardy-Weinberg conditions), what will be the frequency of homozygous dominants in the next generation?

A

0.11

39
Q

Which of the following sets of conditions is required for Hardy-Weinberg equilibrium?

A

random mating, no natural selection, and a large population

40
Q

_____ and _____ generate variation, whereas _____ results in an adaptation to the environment.

A

mutation … sexual recombination … natural selection

41
Q

A population of 15 birds inhabits a fairly new island. Ten of the birds are dark brown and five of them are light brown. By chance, two of the dark brown birds and three of the light brown birds die before producing any offspring. All of the birds in the next generation are dark brown. This change in phenotypic frequency can be attributed to…

A

genetic drift

42
Q

An earthquake hits a small island. All but a small group of closely related lizards are eliminated, and the survivors spread out over the island. This is an instance of…

A

bottleneck effect

43
Q

Which of the following scenarios would most likely result in the microevolution of a population of humans?

A

A colony of humans on the moon is isolated from Earth.

44
Q

Which of the following is the best example of gene flow?

A

Wind blows pollen from one population of plants to another and cross-fertilization occurs.

45
Q

Which of the following most accurately measures an organism’s fitness?

A

how many fertile offspring it produces

46
Q

Antibiotic resistance in bacteria is an example of which of the following?

A

directional selection

47
Q

For several years, scientists have warned doctors of the danger of overprescribing antibiotics such as penicillin. Scientists are concerned because…

A

strains of microorganisms that are resistant to these drugs will be selected for

48
Q

A population of squirrels is preyed on by small hawks. The smaller squirrels can escape into burrows. The larger squirrels can fight off the hawks. After several generations, the squirrels in the area tend to be very small or very large. What process is responsible for this outcome?

A

disruptive selection

49
Q

stabilizing selection..

A

favors intermediate variants in a population

50
Q

Birds with average-size wings survived a severe storm more successfully than other birds in the same population with longer or shorter wings. If severe storms occur regularly, then over time, one should expect these storms to bring about…

A

stabilizing selection

51
Q

Tay-Sachs disease, which is lethal, results from having the homozygous recessive condition of the responsible gene. Which of the following statements is true?

A

Heterozygous individuals will survive and may pass the recessive allele on to their offspring.

52
Q

Which type of selection maintains stable frequencies of two or more phenotypic forms in a population?

A

balancing selection

53
Q

Which of the following would seem to be an example of neutral variation?

A

human fingerprints

54
Q

What is the importance of neutral variation in evolution?

A

Neutral variation increases genetic variation, allowing a population to carry more alleles that may help it respond to environmental change.

55
Q

Selection that acts over evolutionary time to preserve traits that increase an individual’s ability to mate is known as…

A

sexual selection

56
Q

Which statement below is true about sexual selection?

A

Sexual selection can result in sexual dimorphism—marked differences between the sexes in secondary sexual characteristics that are not associated directly with reproduction.

57
Q

How does natural selection fashion organisms?

A

Chance and the environment interact with natural selection, so that the best available traits are selected for.

58
Q

A number of mosquito populations today are resistant to insecticides that were once quite effective. Biologists think that insecticide resistance evolved in mosquitoes because…

A

a few mosquitoes were probably resistant to the insecticide before it was ever used, and these individuals were more likely to survive and reproduce

Biology (8 decks)

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