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BIO106 - Evolutionary Biology > Lesson 8: Natural Selection > Flashcards

Lesson 8: Natural Selection Flashcards

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1
Q

What are the four evolutionary mechanisms

A
  1. genetic drift
  2. migration
  3. mutation
  4. natural selection
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2
Q

types of mechanisms

A
  1. non-adaptive mechanism
  2. adaptive mechanism
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3
Q

what are the non-adaptive mechanisms

A
  1. genetic drift
  2. migration
  3. mutation
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4
Q

what are the adaptive mechanisms

A

natural selection

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5
Q

According to Darwin, evolution acts through changes in what?

A

allelic frequency at each generation

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6
Q

According to Darwin, how does evolution happen

A

via natural selection

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7
Q

where does natural selection act upon

A

genetic or epigenetic variation in population

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8
Q

generates genetic variation

A

mutation

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9
Q

changes expression of genes

A

epigenetic modification

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10
Q

can reduce genetic variation

A

genetic drift

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11
Q

Darwin’s contribution: Population speciation as result of natural selection

A
  1. too many offpsring produced
  2. limited resources and competition
  3. variation in population
  4. better adapted individuals survive
  5. survivors leave more offspring
  6. average character of population is altered
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12
Q

natural selection is not random, but __

A

deterministic

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13
Q

Selection imposed by transmittion rate on virulence of HIV

A
  1. high transmission rate: high virulence
  2. low transmission rate: low virulence
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14
Q

can grow fast and jump to the next host; ok if host dies; genetic strain that grows faster will win

A

high transmission rate: high virulence

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15
Q

more virulent strains would die with the host and get selected out; less virulent strain will win

A

low transmission rate: low virulence

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16
Q

mutant allele of the receptor CCR5

A

CCR5-Δ32

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17
Q

traits that are usually coded by one or a few genes (loci)

A

discrete traits

18
Q

trait coded by many loci

A

quantitative traits

19
Q

Different modes of selection

A
  1. Directional selection
  2. Stabilizing selection
  3. Disruptive selection
20
Q

selection changes frequency of allelese in one direction

A

directional selection

21
Q
  • selection acts against the extremes (favors intermediate trait)
  • purifying selection
  • average trait value stays the same
  • genetic diversity is reduced
A

stabilizing selection

22
Q
  • selection favors the extremes
  • genetic diversity is increased (help maintain genetic variation; knowck our alleles that code for intermediate traits)
  • can lead to formation of new species
A

disruptive selection

23
Q

disruptive selection can lead to what?

A

formation of new species

24
Q

example of disruptive selection

A

sexual selection for different traits (blue birds mate with blue, red birds mate with red)

25
Q

generic term to refer to any type of selection that acts to maintain genetic variation in a population

A

balancing selection

26
Q

Examples of balancing selection

A
  1. selection for heterozygotes
  2. selection for different traits in different environments
  3. selection for different traits at different times
27
Q

selection for different traits at different times

A

fluctuating selection

28
Q

Selection:
With malaria

A

balancing selection for heterozygote

29
Q

lead to amino acid change

A

nonsynonymous mutation/missense mutation (position 1 and 2)

29
Q

Selection:
Without malaria

A

directional selection for homozygous wild type (HAHA)

30
Q

does not lead to amino acid change

A

synonymous mutation/silent mutation (position 3)

31
Q

test for selection

A

Ka/Ks test

32
Q

Ka

A

nonsynonymous substitution rate

33
Q

Ks

A

synonymous substitution rate

34
Q

absence of selection

A

Ka/Ks = 1

35
Q

positive selection

A

Ka/Ks > 1

36
Q

negative selection / purifying selection

A

Ka/Ks < 1

37
Q

out of all possible number of mutations, how many fixed

A

substitution rate

38
Q

selection occurs through __ __ which is not random

A

differential reproduction

39
Q

Selection favoring the heterozygote

A

Overdominance

BIO106 - Evolutionary Biology (20 decks)

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