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

AP biology: 23 The evolution of populations Flashcards

(55 cards)

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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

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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

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A

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

25
In the bottleneck effect
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
Understanding the bottleneck effect
Can increase understanding of how human activity affects other species
27
The founder effect
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
Gene flow
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
Natural selection
Accumulates and maintains favorable genotypes in a population
30
Genetic variation
Occurs in individuals in populations of all species | Is not always heritable
31
Phenotypic polymorphism
Two or more distinct forms for a character are present in high enough frequencies to be readily noticeable
32
Genetic polymorphisms
Are the heritable components of characters that occur along a continuum in a population
33
Population geneticists
Measure the number of polymorphisms in a population by determining the amount of heterozygosity at the gene level and the molecular level
34
Average heterozygosity
Measures the average percent of loci that are heterozygous in a population
35
Most species exhibit
geographic variation | Differences between gene pools of separate populations or population subgroups
36
Some examples of geographic variation occur as a
cline, which is a graded change in a trait along a geographic axis
37
Natural selection increases the
frequencies of certain genotypes, fitting organisms to their environment over generations Fitness= baby making potential Depends on genetic makeup
38
The phrases “struggle for existence” and “survival of the fittest”
Are commonly used to describe natural selection | Can be misleading
39
Reproductive success
Is generally more subtle and depends on many factors
40
Selection
``` Favors certain genotypes by acting on the phenotypes of certain organisms Three modes of selection are Directional Disruptive Stabilizing ```
41
Directional selection
Favors individuals at one end of the phenotypic range
42
Disruptive selection
Favors individuals at both extremes of the phenotypic range
43
Stabilizing selection
Favors intermediate variants and acts against extreme phenotypes
44
Various mechanisms help to preserve
genetic variation in a population
45
Diploidy
Maintains genetic variation in the form of hidden recessive alleles
46
Balancing selection
Occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population Leads to a state called balanced polymorphism
47
Heterozygote Advantage
Some individuals who are heterozygous at a particular locus | Have greater fitness than homozygotes
48
The sickle-cell allele
Causes mutations in hemoglobin but also confers malaria resistance Exemplifies the heterozygote advantage
49
In frequency-dependent selection
The fitness of any morph declines if it becomes too common in the population
50
Sexual selection
Is natural selection for mating success | Can result in sexual dimorphism, marked differences between the sexes in secondary sexual characteristics
51
Intrasexual selection
Is a direct competition among individuals of one sex for mates of the opposite sex
52
Intersexual selection | Occurs
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
Sexual reproduction | Produces
fewer reproductive offspring than asexual reproduction, a so-called reproductive handicap
54
If sexual reproduction is a handicap, why has it persisted?
It produces genetic variation that may aid in disease resistance
55
Why Natural Selection Cannot Fashion Perfect Organisms
Evolution is limited by historical constraints | Adaptations are often compromises

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