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evolution > envs lecture 6 (first 16 slides) > Flashcards

envs lecture 6 (first 16 slides) Flashcards

1
Q

what changed human civilization

A

selective breeding/domestication for agriculture

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2
Q

when did humans harness evolution

A

11,000 years ago

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3
Q

examples of selective breeding

A

bred wheat that provided more grain, cows that produced more milk

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4
Q

what did this selective breeding/domestication do

A

allowed ppl to abandon nomadic lifestyle and settle in communities

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5
Q

quantitative traits

A

traits that vary continuously and are therefore affected by anywhere from several to thousands of loci

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6
Q

example of quantitative traits

A

crop yield, milk production, body height

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7
Q

what are polygenic traits

A

quantitative traits; vary continuously, affected by several/thousands of loci [poly genic cuz multiple genes]

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8
Q

quantitative genetics

A

study of how quantitative traits are inherited and how they evolve

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9
Q

what effects quantitative traits

A

both genes and environment interact to affect it

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10
Q

example of domesticated plant

A

modern corn

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11
Q

where do phenotypic differences in branching pattern between modern corn and its ancestor come from

A

small number of genetic changes

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12
Q

examples of other differences

A

size of cob

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13
Q

where do differences in size of cob come from

A

changes at many loci

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14
Q

example of quantitative trait that varies continuously

A

human height

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15
Q

what is a normal distribution (varies continuously) curve look like

A

bell-shaped curve

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16
Q

genotypic variatoin

A

encoded in DNA: only 4 possible nucleotides, A, T, C, G

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17
Q

is genotypic variation discrete or continuous

A

discrete

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18
Q

is phenotypic variation discrete or continuous

A

continuous

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19
Q

what is another word for phenotypic traits

A

quantitative traits

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20
Q

what kinda distribution for quantitative/phenotypic traits

A

normal distribution

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21
Q

what kinda curve for quantitative traits

A

bell shaped curve

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22
Q

how do traits go from discrete genotype to continuous phenotype

A

many traits affected by many genes AND environmental influences on individual within its lifetime

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23
Q

are quantitative traits affected by many or only a few genes

A

many genes

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24
Q

example of quantitative traits

A

height

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25
Q

how many genes is height influenced by

A

thousands

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26
Q

how else are phenotypic traits influenced

A

by the environment over lifetime of individual

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27
Q

is this environmental influence genetic or non genetic

A

non-genetic

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28
Q

what does this variance in environment do to bell curve

A

smooths it out

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29
Q

can we see genotypes

A

no

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30
Q

is phenotype or genotype directly seen

A

phenotype

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31
Q

what is discrete vs continuous phenotype determined by

A

combo of genetic and environmental variation

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32
Q

what are blue bars

A

frequencies of phenotypes in population w/o influence of environmental variance

33
Q

green curves

A

frequencies of phenotypes for each of genotypes in given population w/ addition of environmental variance

34
Q

red curves

A

frequencies of phenotypes for entire population

35
Q

what does selection act on

A

phenotype; at level of individual

36
Q

how do phenotypic distributions become w/ more loci

A

smoother

37
Q

what happens w/ more loci

A

phenotypic distributions become normal

38
Q

what else can smooth out phenotypic distribution

A

more environmental variance

39
Q

what can occur from evolution of allele frequencies w/o addition of new mutations

A

large changes

40
Q

important component of evolution of quantitative traits

A

large changes in quantitative traits can occur by evolution of allele frequencies w/o addition of new mutations

41
Q

what is a key point for this polygenic quantitative trait

A

phenotypic distributions for allele frequencies p = 0.25 and p = 0.75 do not even overlap

42
Q

what can happen w/ multiple loci

A

can move outside initial range

43
Q

what do horns on head of horned lizard do

A

deters predation

44
Q

where is the natural variation in lizards

A

variation in length of these protective horns on head of lizard

45
Q

what does survival vary with for lizards

A

length of horn

46
Q

what does fitness function show

A

lizards w/ longer horns survive better

47
Q

what do fitness functions show

A

describe/quantifies how selection acts on quantitative traits

48
Q

3 basic modes of selection on quantitative traits

A

directional, stabilizing, disruptive

49
Q

what does directional selection do

A

favors change in the mean of a trait in one direction (either toward a greater or lesser value)

50
Q

what does stabilizing selection do

A

favors individuals near the population mean

51
Q

what does stabilizing selection reduce

A

phenotypic variance in trait –> gives narrower population phenotypic distribution

52
Q

what does disruptive do

A

favors largest and smallest

53
Q

what does disruptive do to variance

A

increases variance in the trait

54
Q

example of directional silection

A

drought led to changes in seed size; larger bills have higher survival ate –> mean beak size shifted and became larger

55
Q

example of stabilizing selection

A

human birth weight; infants w/ birth weight much smaller and much larger than average have lower probability of survival

56
Q

example of disruptive selection

A

black bellied seedcracker survival depends on lower mandible length; intermediate birds have lowest survival and become less common –> smallest and largest billed ones have highest fitness

57
Q

what does the type of selection acting on an organism depend on

A

both phenotypic distribution of organism and phenotypic distribution of food items

58
Q

when is directional selection at play

A

most individuals in a population fall within a region of the plot where the fitness function is increasing/decreasing [bill evolves toward a size that is optimal for feeding on hemlock]

59
Q

when is stabilizing selection at play

A

if population lies near a peak of the fitness function [tightens the mean around the bill size optimal for feeding on seeds from lodgepole pine cones]

60
Q

when is disruptive selection at play

A

if population lies at a low point in fitness function [causes bill size to evolve both larger and smaller towards the two diff sized but available food items]

61
Q

can selection act on more than one phenotypic trait at once

A

yeah

62
Q

correlational selection

A

selection favors combos of traits

63
Q

what do evolutionary biologists ask

A

how and why mean values of traits evolve (often caused by directional selection); important to quantify the strength of selection

64
Q

selection gradient

A

measures strength of directional selection on a quantitative trait

65
Q

relative fitness

A

individual fitness/mean fitness all individualsh

66
Q

how do you mesaure selection gradient

A

measure trait of interest and fitness for a set of individuals who vary in the trait of interest

67
Q

positive beta

A

indicates selection favors larger values of the trait

68
Q

negative beta

A

indicates selection favors smaller values of the trait

69
Q

beta is zero means

A

no directoinal selection

70
Q

female guppies

A

prefer males w/ more orange

71
Q

who has higher fitness among male guppies

A

males w/ more orange

72
Q

moderately strong directional selection

A

-0.5 and 0.5

73
Q

very strong directional selection

A

1

74
Q

is directional selection always strong

A

sometimes; other times it isn’t

75
Q

Stronger selection gradient (Beta produces

A

larger change in size

76
Q

Lower, but positive gradient (Beta) produces

A

smaller change in mean trait value

77
Q

negative selection gradient (-0.5 Beta)

A

produces a small reduction in size

78
Q

positive beta selection for

A

larger size

79
Q

negative beta selection for

A

smaller size

evolution (15 decks)

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