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AP Biology > AP biology: 23 The evolution of populations > Flashcards

AP biology: 23 The evolution of populations Flashcards

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1
Q

Natural selection acts on……..

A

individuals but populations evolve

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2
Q

generic variations in populations….

A

contribute to evolution

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3
Q

Microevolution

A

Is change in the genetic makeup of a population from generation to generation

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4
Q

Population genetics

A

Study of changes within gene pool/ allele distribution over time
Reconciled Darwin’s and Mendel’s ideas

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5
Q

A population

A

Is a localized group of individuals that are capable of interbreeding and producing fertile offspring

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6
Q

The gene pool

A

Is the total of genes in a population at any one time ( all alleles for that trait)
Consists of all gene loci in all individuals of the population

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7
Q

The Hardy-Weinberg theorem

A

Describes a population that is not evolving
Frequencies of alleles and genotypes in a population’s gene pool stay the same over time.
Assumes that segregation and recombination of alleles are at work

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8
Q

Mendelian inheritance

A

Preserves genetic variation in a population

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9
Q

Hardy-Weinberg equilibrium

A

Describes a population where allele frequencies do not change

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10
Q

The Hardy-Weinberg theorem

A

Describes a hypothetical population

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11
Q

In real populations

A

Allele and genotype frequencies do change over time

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12
Q

If p and q represent the relative frequencies of the only two possible alleles in a population at a particular locus, then

A

p2 + 2pq + q2 = 1
And p2 and q2 represent the frequencies of the homozygous genotypes and 2pq represents the frequency of the heterozygous genotype

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13
Q

The five conditions for non-evolving populations

A 
are rarely met in nature
Extremely large population size
No gene flow
No mutations
Random mating
No natural selection
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14
Q

We can use the Hardy-Weinberg equation

A

To estimate the percentage of the human population carrying the allele for an inherited disease

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15
Q

Mutation and sexual recombination

A

produce the variation that makes evolution possible

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16
Q

Two processes

A

mutation and sexual recombination

Produce the variation in gene pools that contributes to differences among individuals

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17
Q

A point mutation

A

Is a change in one base in a gene
Can have a significant impact on phenotype
Is usually harmless, but may have an adaptive impact

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18
Q

Chromosomal mutations that affect many loci

A

Are almost certain to be harmful

May be neutral and even beneficial

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19
Q

Mutation rates

A

Tend to be low in animals and plants
Average about one mutation in every 100,000 genes per generation
Are more rapid in microorganisms

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20
Q

In sexually reproducing populations

A

sexual recombination

Is far more important than mutation in producing the genetic differences that make adaptation possible

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21
Q

Three major factors alter allele frequencies and bring about most evolutionary change

A

Natural selection
Genetic drift
Gene flow

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22
Q

Differential success in reproduction

A

Results in certain alleles being passed to the next generation in greater proportions

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23
Q

Genetic Drift

A

Due to random changes
Statistically, the smaller a sample
The greater the chance of deviation from a predicted result

24
Q

Genetic drift Describes

A

how allele frequencies can fluctuate unpredictably from one generation to the next
Tends to reduce genetic variation

25
Q

In the bottleneck effect

A

A sudden change in the environment may drastically reduce the size of a population
The gene pool may no longer be reflective of the original population’s gene pool

26
Q

Understanding the bottleneck effect

A

Can increase understanding of how human activity affects other species

27
Q

The founder effect

A

Occurs when a few individuals become isolated from a larger population
Can affect allele frequencies in a population
Hemophilia is a result of this ( son of Czar Nicholas)

28
Q

Gene flow

A

Causes a population to gain or lose alleles
Results from the movement of fertile individuals or gametes ( Migration)
Tends to reduce differences between populations over time

29
Q

Natural selection

A

Accumulates and maintains favorable genotypes in a population

30
Q

Genetic variation

A

Occurs in individuals in populations of all species

Is not always heritable

31
Q

Phenotypic polymorphism

A

Two or more distinct forms for a character are present in high enough frequencies to be readily noticeable

32
Q

Genetic polymorphisms

A

Are the heritable components of characters that occur along a continuum in a population

33
Q

Population geneticists

A

Measure the number of polymorphisms in a population by determining the amount of heterozygosity at the gene level and the molecular level

34
Q

Average heterozygosity

A

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

35
Q

Most species exhibit

A

geographic variation

Differences between gene pools of separate populations or population subgroups

36
Q

Some examples of geographic variation occur as a

A

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

37
Q

Natural selection increases the

A

frequencies of certain genotypes, fitting organisms to their environment over generations
Fitness= baby making potential
Depends on genetic makeup

38
Q

The phrases “struggle for existence” and “survival of the fittest”

A

Are commonly used to describe natural selection

Can be misleading

39
Q

Reproductive success

A

Is generally more subtle and depends on many factors

40
Q

Selection

A 
Favors certain genotypes by acting on the phenotypes of certain organisms
Three modes of selection are
Directional
Disruptive
Stabilizing
41
Q

Directional selection

A

Favors individuals at one end of the phenotypic range

42
Q

Disruptive selection

A

Favors individuals at both extremes of the phenotypic range

43
Q

Stabilizing selection

A

Favors intermediate variants and acts against extreme phenotypes

44
Q

Various mechanisms help to preserve

A

genetic variation in a population

45
Q

Diploidy

A

Maintains genetic variation in the form of hidden recessive alleles

46
Q

Balancing selection

A

Occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population
Leads to a state called balanced polymorphism

47
Q

Heterozygote Advantage

A

Some individuals who are heterozygous at a particular locus

Have greater fitness than homozygotes

48
Q

The sickle-cell allele

A

Causes mutations in hemoglobin but also confers malaria resistance
Exemplifies the heterozygote advantage

49
Q

In frequency-dependent selection

A

The fitness of any morph declines if it becomes too common in the population

50
Q

Sexual selection

A

Is natural selection for mating success

Can result in sexual dimorphism, marked differences between the sexes in secondary sexual characteristics

51
Q

Intrasexual selection

A

Is a direct competition among individuals of one sex for mates of the opposite sex

52
Q

Intersexual selection

Occurs

A

when individuals of one sex (usually females) are choosy in selecting their mates from individuals of the other sex
May depend on the showiness of the male’s appearance

53
Q

Sexual reproduction

Produces

A

fewer reproductive offspring than asexual reproduction, a so-called reproductive handicap

54
Q

If sexual reproduction is a handicap, why has it persisted?

A

It produces genetic variation that may aid in disease resistance

55
Q

Why Natural Selection Cannot Fashion Perfect Organisms

A

Evolution is limited by historical constraints

Adaptations are often compromises

AP Biology (11 decks)

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