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AP Biology Semester 1 > Chapter 23 > Flashcards

Chapter 23 Flashcards

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1
Q

micro evolution

A

the change in allele frequencies in a population over generations

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2
Q

what are three things that cause allele frequency change?

A
  • natural selection
  • genetic drift
  • gene flow
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3
Q

what causes adaptive evolution?

A

natural selection

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4
Q

what is essential to have in a population in order for evolution to occur

A

variation in heritable traits

  • you get variation from different genes
  • you need a gene to make a certain protein which causes a phenotype
  • if you don’t have the gene to a trait then you can’t have the trait
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5
Q

Both ____ and _____ characters contribute to variation within a population

A
  • discrete

- quantitative

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6
Q

true or false:

discrete characters can be classified on an either - or basis

A

true

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7
Q

true or false:

quantitative characters vary along a continuum within a population

A

true

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8
Q

average heterozygosity

A

measures the average percent of loci that are heterozygous in a population

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9
Q

how is nucleotide variability measured?

A

measured by comparing the DNA sequences of pairs of individuals

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10
Q

geographic variation

A

most species exhibit this.

-differences between gene pools of separate populations

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11
Q

cline

A

which is a graded change in a trait along a geographic axis

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12
Q

how can new genes and alleles arise?

A

by mutation or gene duplication

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13
Q

what is a mutation?

A

a change in nucleotide sequence of DNA

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14
Q

only mutations in cells that produce _____ can be passed to offspring

A

gametes

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15
Q

what is a point mutation

A

a change in one base in a gene

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16
Q

what are the possible effects of point mutations?

A
  • can be harmless
  • mutations in a genes can be neutral because of redundancy in the genetic code
  • result in a change in protein production are often harmful
  • result in a change in protein production that can sometimes be beneficial
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17
Q

what type of chromosomal mutations are typically harmful?

A

mutations that delete, disrupt, or rearrange many loci

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18
Q

what type of chromosomal mutations are less harmful?

A

duplication of small pieces of DNA increases genome size and is usually less harmful

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19
Q

what can shuffle existing alleles into new combinations?

A

sexual reproduction

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20
Q

population

A

a localized group of individuals capable of interbreeding and producing fertile offspring

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21
Q

gene pool

A

consists of all the alleles for all loci in a population

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22
Q

how is a locus fixed?

A

if all individuals in a population are homozygous for the same allele

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23
Q

how can frequency of an allele in a population be calculated for diploid organisms

A

p + q = 1

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24
Q

what is the hardy-weinberg principle

A
  • describes a population that is not evolving

- frequencies of alleles and genotypes in a population remain constant from generation to generation

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25
Q

if a hardy weinberg equation is not in equilibrium what does this mean?

A

-if a population does not meet the criteria of the Hardy-Weinberg principle, it can be concluded that the population is evolving

26
Q

what equation is used to find the genotypic ratio of alleles?

A

p^2 + 2pq + q^2 =1

  • p is dominant
  • 2pq is heterozygous
  • q is recessive
27
Q

what does the hardy weinberg theorem describe?

A

a hypothetical population that is not evolving

FYI in real populations, allele and genotype frequencies do change over time

28
Q

what five conditions have to occur for nonevolving populations?

A
  1. No mutations
  2. random mating
  3. no natural selection
  4. extremely large population size
  5. no gene flow
29
Q

true or false:

natural populations can evolve at some loci, while being in Hardy-weinberg equilibrium at other loci

A

TRUE

30
Q

what three major factors alter allele frequencies and bring about most evolutionary change:

A
  • natural selection
  • genetic drift
  • gene flow
31
Q

genetic drift

A

describes how allele frequencies fluctuate unpredictably from one generation to the next

32
Q

what does genetic tends to reduce what?

A

genetic variation through losses of alleles

33
Q

the smaller a sample of population, the greater the chance of____

A

deviation from a predicted result

34
Q

founder effect

A

occurs when a few individuals become isolated from a larger population
-allele frequencies in the small founder population can be different from those in the larger parent population

35
Q

bottleneck effect

A

a sudden reduction in population size due to a change in the environment
-the resulting gene pool may no longer be reflective of the original population’s gene pool

36
Q

if the population remains small, it may be further affected by ______

A

genetic drift

37
Q

what are 4 things to know about genetic drift?

A
  1. significant in small populations
  2. causes allele frequencies to change at random
  3. can lead to a loss of genetic variation within populations
  4. can cause harmful alleles to show up
38
Q

gene flow

A

consists of movement of alleles among populations

-alleles can be transferred through the movement of fertile individuals or gametes

39
Q

gene flow tends to reduce ______

A

variation among populations over time

40
Q

gene flow can decrease _____

A

the fitness of a population

41
Q

gene flow can increase____

A

the fitness of a population

42
Q

evolution by natural selection involves both _____ and ______

A
  • change

- sorting

43
Q

new genetic variations arise by _____

A

chance

44
Q

beneficial alleles are sorted and favored by

A

natural selection

45
Q

how does natural selection bring about adaptive evolution

A

acting on an organism’s phenotype

46
Q

what does survival of the fittest really mean?

A

reproductive success

47
Q

relative fitness

A

the contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals
-selection favors certain genotypes by acting on the phoenotypes of certain organisms

48
Q

directional selection

A

favors individuals at one end of the phenotypic range

49
Q

disruptive seleciton

A

favors individuals at both extremes of the phenotypic range

50
Q

stabilizing seleciton

A

favors intermediate variants and acts against extreme phenotypes

51
Q

natural selection increases _____

A

frequencies of alleles that enhance survival and reproduction

52
Q

sexual selection

A

natural selection for mating success

53
Q

sexual dimorphism

A

marked differences between the sexes in secondary sexual characteristics

54
Q

intrasexual selection

A

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

55
Q

intersexual selection

A

often called mate choice, occurs when individuals of one sex are choosy in selecting their mates (usually females)

56
Q

neutral variation

A

genetic variation that does not confer a selective advantage or disadvantage

57
Q

how does diploidy maintain genetic variation?

A

in the form of hidden recessive alleles through heterozygotes

58
Q

balancing selection

A

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

59
Q

what does balancing selection include?

A
  • heterozygote advantage

- frequency-dependent selection

60
Q

heterozygote advantage

A

occurs when heterozygotes have a higher fitness than do both homozygotes
-natural selection will tend to maintain two or more alleles at that locus

61
Q

frequency dependent selection

A

the fitness of a phenotype declines if it becomes too common in the population
-selection can favor whichever phenotype is less common in a population

62
Q

why can natural selection not fashion perfect organisms? (4)

A
  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 environment interact

AP Biology Semester 1 (21 decks)

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