KA 2: evolution: drift and selection Flashcards

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1
Q

what is evolution?

A

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

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2
Q

during evolution, when do changes in allele frequency occur?

A

-non-random processes of natural selection and sexual selection

-random process of genetic drift

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3
Q

what does natural selection act on in populations?

A

genetic variation

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4
Q

variation in traits arises as a result of…

A

mutation

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5
Q

what is mutation?

A

the original source of new sequences of DNA

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6
Q

what can the new sequences from a mutation be?

A

novel alleles

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7
Q

what are most mutations?

A

harmful or neutral

in rare cases they may be beneficial to the fitness of an individual

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8
Q

populations produce…

A

more offspring than the environment can support

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9
Q

what happens to individuals with variations that are better suited to their environment?

A

they tend to survive longer and produce more offspring, breeding to pass on those alleles that conferred an advantage to the next generation

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10
Q

what does the selection result in?

A

the non-random increase in the frequency of advantages alleles and the non-random decrease in the frequency of deleterious alleles

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11
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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12
Q

what does sexual selection lead to?

A

dimorphism

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13
Q

what can sexual selection be due to?

A
  • male-male rivalry
  • female choice
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14
Q

what is male-male rivalry?

A

large size or weaponry increases access to females through conflict

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15
Q

what is female choice?

A

involves females assessing the fitness of males

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16
Q

when does genetic drift occur?

A

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

17
Q

why is genetic drift more important in small populations?

A

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

18
Q

when do population bottlenecks occur?

A

when a population size is reduced for at least one generation

19
Q

when does the founder effect occur?

A

through the isolation of few members of a population from a larger population

the gene pool of the new population is not representative of that in the original gene pool

20
Q

why is a gene pool altered by genetic drift?

A

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

21
Q

where selection pressures are strong…

A

the rate of evolution can be rapid

22
Q

what are selection pressures?

A

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

23
Q

selection pressures can be: (give examples)

A

-biotic (competition, predation, disease, parasitism)

-abiotic (changes in temp, light, humidity, pH, salinity)

24
Q

State The Hardy-Weinberg (HW) principle

A

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

25
Q

what are the conditions for maintaining the HW equilibrium?

A

-no natural selection
-random mating
-no mutation
-large population size
-no gene flow (through migration, in or out)

26
Q

what can the HW principle be used to determine?

A

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

27
Q

what is the HW formula?

A

p2 + 2pq + q2 = 1

28
Q

what does each letter in the Hardy-Weinberg (HW) formula mean?

A

p=frequency of dominant allele
q=frequency of recessive allele
p^2=frequency of homoxygous dominant genotype
2pq= frequency of heterozygous genotype
q^2=frequency of homozygous recessive genotype

29
Q

changes suggest…

A

evolution is occuring