2.2.1 evolution: drift and selection Flashcards

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1
Q

what is evolution

A

change over time in the proportion of individuals in a population differing in one or more inherited traits

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2
Q

what happens during evolution

A

changes in allele frequency occur through the non random processes of natural selection and sexual selection, and the random processes of genetic drift

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3
Q

what does natural selection act on

A

the genetic variation in populations

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4
Q

how does variation in traits arise

A

mutation

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5
Q

what is mutation

A

the original source of new sequences of DNA. they can be novel alleles. most mutations are harmful or neutral

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6
Q

can mutations be beneficial to the fitness of an individual

A

yes

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7
Q

how much offspring do populations produce

A

more than the environment can support

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8
Q

which individuals tend to survive longer and produce more offspring, breeding to pass on alleles that confer an advantage to the next generation

A

individuals with variations that are better suited to their environment

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9
Q

what does selection result in

A

the non random increase in the frequency of advantageous alleles and the non random decrease in the frequency of deleterious alleles

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10
Q

what is sexual selection

A

the non random process involving the selection of alleles that increase the individual’s chances of mating and producing offspring

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11
Q

what may sexual selection lead to

A

sexual dimorphism, which is when the different sexes of a species have distinct differences in size or appearance

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12
Q

what can cause sexual selection

A

male-male rivalry and female choice

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13
Q

what is male male rivalry

A

large size or weaponry which increases access to females through conflict

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14
Q

what does female choice involve

A

females assessing the fitness of males

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15
Q

when does genetic drift occur

A

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

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16
Q

why is genetic drift more important in small populations

A

as alleles are more likely to be lost from the gene pool

17
Q

when do population bottlenecks occur

A

when a population size is reduced for at least one generation

18
Q

what is the founder effect

A

this occurs through the isoltion of a few members of a population from a larger population. the gene pool of the new population is not as representative of that in the original gene pool

19
Q

what are gene pools altered by

A

genetic drift

20
Q

how are gene pools altered by genetic drift

A

because certain alleles may be under represented or over represented and allele frequencies changes

21
Q

when can the rate of evolution be rapid

A

when selection pressures are strong

22
Q

what are selection pressures

A

these are environmental factors that influence which individuals in a population pass on their alleles

23
Q

what are examples of biotic selection pressures

A

competition
predation
disease
parasitism

24
Q

what are examples of abiotic selection pressures

A

changes in temperature
light
humidity
pH
salinity

25
Q

what does the HW principle state

A

in the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over the generations

26
Q

what are the conditions for maintaining the HW equilibrium

A

no natural selection
random mating
no mutation
large population size
no gene flow

27
Q

what can the HW principle be used to determine

A

whether a change in allele frequency is occurring in a population over time

28
Q

what is the HW principle

A

p2 + 2pq + q2 = 1

29
Q

what does p mean in the HW principle

A

the frequency of the dominant allele

30
Q

what does q mean in the HW principle

A

the frequency of the recessive allele

31
Q

what does p2 mean in the HW principle

A

the frequency of the homozygous dominant genotype

32
Q

what does 2pq mean in the HW principle

A

the frequnecy of the heterozygous genotype

33
Q

what does q2 mean in the HW principle

A

the frequency of the homozygous recessive genotype

34
Q

what do changes in allele frequency in a population over time suggest

A

that evolution is occuring