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evolution > envs lecture 11 > Flashcards

envs lecture 11 Flashcards

1
Q

what are life history traits

A

traits that affect survival and reproduction across various stages of life

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2
Q

what is variation in life history tied to

A

variation in history

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3
Q

what do life history trait do

A

evolve

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4
Q

what are life history strategies

A

the series of events that take place across the life of a given organism

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5
Q

what is the first life history variable that comes to mind when we think about variables tied to fitness

A

lifespan

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5
Q

if an organism lives long what does it have the potential to do

A

reproduce a lot

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5
Q

do all species have same lifespan

A

nope; species vary greatly

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5
Q

what two things can evolve by natural selection

A

fecundity and lifespans

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5
Q

what kind of tradeoffs are involved

A

self-maintenance (survival) and growth & reproduction

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6
Q

is fecundity the same among living things

A

no, it varies

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6
Q

who reproduces more slowly, long-lived organisms or short-lived organisms

A

long-lived organisms reproduce more slowly

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6
Q

what is fecundity

A

number of offspring

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6
Q

what did some biologists used to think

A

some species produced huge numbers of eggs to compensate for high mortality to ensure the survival of the species

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6
Q

what do we need to know in order to understand how fecundity and lifespan

A

age at which reproduction begins and ends, fecundity at each age, avg survival to each possible age

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7
Q

what did biologists used to think was the reason why species produced huge numbers of eggs

A

to compensate for high mortality to ensure survival of species

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8
Q

what else did biologists think in terms of why animals died of old age

A

to make room for the new generation

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9
Q

what are both of these statements

A

group selectionist statements

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10
Q

why is group selection wrong

A

future presistence or extinction of a species cannot affect the course of natural selection acting among individuals

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11
Q

what is group selection

A

a proposed mechanism of evolution in which natural selection acts at the level of the group, instead of at the level of the individual or gene

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12
Q

what is a component of fitness that operates on diff life history traits

A

natural selection

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13
Q

what does natural selection perate w/

A

diff intensity during various parts of life cycle, bC of tradeoffs among life history functions: self maintenance (survival), growth, and reproduction

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13
Q

what needs to be allocated to diff life cycle events

A

energy and nutrients

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13
Q

why does selection operate w/ diff intensity during various parts of life cycle

A

b/c of tradeoffs among life history functions –> self-maintenance (survival), growth, and reproduction

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14
Q

what can the fitness benefits of one function may be

A

a fitness cost for another

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15
Q

how does fitness vary

A

varies among life stages and times

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16
Q

is variance in fitness more pronounced in some stages or the same throughout

A

more pronounced in some stages; must be partitioned between life stages, or between times functionally significant for reproductive success

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17
Q

what is strongly correlated w/ measures of fitness

A

body size

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18
Q

describe how body size is correlated w/ measures of fitness

A

mores strongly correlated at some life history stages than others

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19
Q

what else has positive correlation (but not as steep a slope)

A

fertility of males and offspring survivorship

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20
Q

what is the cost of reproduction

A

trade-off between reproduction and all other functions

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21
Q

what does brown anole experiment demonstrate

A

high cost of reproduction on growth and survival of these lizards

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22
Q

what did individuals w/ ovaries removed have

A

much higher survival than controls

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23
Q

what does allocation to reproduction do

A

reduced both females’ growth and survival

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24
Q

semelparous life history

A

simple case where individuals produce once than die (pacific salmon)

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25
Q

iteroparous life history

A

individuals reproduce more than once in their lives

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26
Q

what do we need to do for iteroparous life history

A

need to add up reproduction over all ages to calculate lifetime reproductive success

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27
Q

is it harder to determine fitness for iteroparous or semelparous organisms

A

iteroparous

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28
Q

how do we determine fitness for iteroparous organisms

A

a life table to predict average expected lifetime reproductive success

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29
Q

in species w/ separate sexes, describe life tables of males and females

A

different life tables

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30
Q

what is lifetime reproductive success related to

A

intrinsic rate of increase (r)

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31
Q

what happens if R is much diff from 1

A

then age at when children are born needs to be taken into account

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32
Q

what do we use life tables for

A

to determine fitness and predict avg expected lifetime reproductive success (R)

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33
Q

what is lifetime reproductive success (R) a sum of

A

all the products of probability of survival and the average fecundity across all ages in a given population of organisms

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34
Q

what is expected lifetime reproductive success (R) related to

A

intrinsic rate of increase (r)

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35
Q

describe R and r in a population with stable size

A

R=1, r = 0

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36
Q

what is R=1

A

accurate measure of fitness; if R not 1 then a correction is needed

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37
Q

what does natural selection favor

A

early reproduction

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38
Q

what happens if we have 2 asexual lizards with R=2

A

1st lives 2years, produces 2 offspring and dies. 2nd matures after one year, produces two offspring then dies (reproduces at an earlier age). after 2 years first lizard has 2 descendants and second lizard has 4. genes of second lizard are spreading more quickly in population –> natural selection favors early reproduction

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39
Q

why doesn’t natural selection act to prolong survival beyond the last age of reproduction

A

increasing survival and fecundity at earlier age has larger effect on fitness than increasing it at a later age.

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40
Q

senescence

A

organisms aging

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41
Q

does nat selection act to prolong survival beyond age of last reproduction

A

nope, unless there is post-reproductive parental care

42
Q

what 2 major factors explain idea that increasing survival and fecundity at earlier ages has a larger effect on fitness than at later ages

A

mutation accumulation and antagonistic pleiotropy

43
Q

what two factors affect senescence and lifespan

A

mutation accumulation and antagonistic pleiotropy

44
Q

who identified mutation accumulation

A

peter medwar

45
Q

what is mutation accumulation

A

mutations that compromise important biological functions will reduce fitness less the later in life they exert these effects

46
Q

describe selection against these mutations

A

weaker

47
Q

what happens as a result of selection against these mutations being weaker

A

persist at higher frequencies than if they affected younger reproductive individuals

48
Q

what does mutation accumulation cause

A

greater genetic variance in reproductive success for older rather than younger age classes of individuals

49
Q

who came up w/ antagonistic plieotropy

A

george williams

50
Q

what is pleiotropy

A

when a single gene can have multiple phenotypic effects

51
Q

what is antagonistic pleiotropy

A

because of allocation tradeoffs, alleles that increase reproduction early in life are likely to have pleiotropic effects on reproduction and survival later in life

52
Q

why do alleles that increase reproduction early in life have pleiotropic effects on reproduction and survival later in life

A

because allocation of resources to reproduction comes at a cost, so alleles that increase the allocation to reproduction early in life will reduce function later in life

53
Q

what does the greater the fitness impact on early reproduction cause

A

advantage of reproducing when young to outweigh the pleiotropic disadvantages when older

54
Q

describe the relationship b/w early reproduction and longevity & later reproduction

A

negative relationship

55
Q

what happens to reproduction with age

A

dwindles

56
Q

what happens to production early in life

A

reduce allocation to maintenance later in life

57
Q

what two things play a role in senescence

A

mutation accumulation and antagonistic pleiotropy

58
Q

what happens if mutation accumulation is an important factor in senescence

A

genetic variance for reproductive success increase w/ age

59
Q

describe the tradeoff in allocation

A

population that has been selected for older reproduction cannot allocate as much to reproduction at an early age

60
Q

what are values of survival and fecundity in populations affected by

A

population growht rates

61
Q

what “should” happen as mutations that increase R (lifetime reproductive success) spread thru a population

A

“should” cause a high rate of population growth

62
Q

but what actually happens as populations grow large

A

pop growth limited by resources, predation, or disease

63
Q

what do these factors cause population growth to be

A

density-dependent

64
Q

what does density dependent mean

A

growth rate r is constrained by population size

65
Q

what does reduction in population size cause

A

causes population size to reach a stable equilibrium called carrying capacity (K)

66
Q

what are values of survival and fecundity affected by

A

population growth rates

67
Q

what happens when populations of these flies are near or at carrying capacity

A

nat selection favors alelles that affect characteristics that increase K (carrying capacity)

68
Q

what happens as population density approaches equilibrium

A

a more competitive genotype may sustain positive population growth, this more competitive genotype is likely to achieve a higher EQ density (K)

69
Q

what does the densities of these two populations increasing over 70 generations imply

A

implies adaptation to high densities and improved conversion of food into flies

70
Q

what would happen w/o evolutionary change

A

potential rate of increase of this species is so great that w.o evolutionary change, population would reach carrying capacity in less than 10 weeks and would remain constant in size

71
Q

what does this imply

A

nat selection can act on the evolution of rates of increase in population density

72
Q

what happens when populations are at or near carrying capacity

A

nat selection favors alleles that affect characters that can increase carrying capacity (K)

73
Q

example of nat selection favoring alleles that affect characters that can increase carrying capacity

A

alleles that increase an individual’s ability to compete w/ others for limited resources

74
Q

what two types of populations do we see

A

K-selected populations and r-selected populations

75
Q

what are K-selected populations

A

those that are adapted to crowded conditions, lower r (growth rates), and large bodied offspring

76
Q

what are r-selected populations

A

species where populations w/ higher r (growth rates) have higher fitness, high fecundity at young ages

77
Q

describe K-selected species

A

well-adapted to crowded conditions near carrying capacity, stable environment, low fecundity, long life expectancy, large bodied, parental care

78
Q

example of K selected species

A

rhino

79
Q

what kind of trade-offs do k-selected species have

A

pleiotropic trade-offs that decrease population’s max growth rate when far below carrying capacity

80
Q

what are r-selected species

A

well-adapted to rapid growth; unstable environment, high fecundity at young ages, short generation time, small bodied, dispersed offspring

81
Q

trade-offs for r-selected species

A

may be poor competitors

82
Q

what animals don’t fit this r or K model

A

long-lived, large, lots of eggs, no parental care

83
Q

what specific animals don’t fit this r-K model

A

swordfish; common life-history strategy for fish

84
Q

what plants don’t fit this model

A

cabbage palm, bamboo

85
Q

why don’t some plants fit this model

A

cuz some are semelparous –> reproduce once, after many years, then die

86
Q

what are species w/ high rates of adult survival more likely to have

A

delayed onset of reproduction

87
Q

describe the guppies

A

guppies from high predation environment reproduce earlier in life than LP.

88
Q

what happens if we move guppies from HP area to LP environment

A

evolve characteristics typical of LP populations

89
Q

what are LP fish adapted to

A

high density

90
Q

what does this workd emonstrate

A

life history differences b/w guppies from HP and LP environments are genetic

91
Q

what happens when reared in a controlled env.

A

populations founded w/ guppies from LP env. are less sensitive to effects of density than those from HP env.; LP fish adapted to high density

92
Q

what do coho salmon do

A

pre and post-breeding put all of their resources and E into a single big bang reproductive event

93
Q

what happens to coho salmon

A

their physiological and physical condition deteriorates as their E goes into reproductive activities; they die as semblances of their former selves

94
Q

why do they put all their E into reproduction

A

bc unlikely to mate more than once

95
Q

when is semelparous/big bang reproduction favored

A

if probability of survival increases w/ body mass, and if there is an exponential relationship b/w body mass and reproductive output

96
Q

describe annual reproductive effort

A

semelparous

97
Q

what is prennial reproductive ffort

A

iteroparous

98
Q

what is reproductive effort measured by

A

proportion of biomass allocated to flowers

99
Q

where is reproductive effort lower

A

iteroparous organisms

100
Q

why is reproductive effort lower in iteroparous species

A

b/c they put less effort into each individual reproductive effort

101
Q

where is reproductive effort greater

A

annual/semelparous species

102
Q

major advantage of iteroparity

A

increases the chances of successful reproduction in fluctuating environments, when reproduction or survival of offspring vary across reproductive seasons

103
Q

where do we see trade-offs in

A

clutch size (number of eggs laid in single nesting)

104
Q

what happens w/ clutch sive

A

parental survival is reduced by having to care for increased clutch sizes

105
Q

when is overall fitness optimized

A

intermediate sized clutch

106
Q

what is another factor that varies across species

A

seed size

107
Q

what is size/mass of seeds correlated w/

A

microhabitat (in which seedlings grow)

108
Q

what are larger seeds adapted for

A

species whose seedlings grow slowly due to dim light

109
Q

what are smaller seeds adapted to light gaps

A

germinate quickly

110
Q

how do we understand evolution of life history traits like reproductive rates and longevity

A

in terms of age-specific components of fitness

111
Q

when do diff selective forces act

A

at diff times in an organism’s life cycle

112
Q

how do organisms allocate resources for diff functions

A

allocate resources among diff functions at diff times

113
Q

what can selection favor depending on env. and life history

A

long life and low fecundity, long life and high fecundity, short life and high fecundity

114
Q

when is selection usually weakerr

A

advanced ages

115
Q

how does senescence occur

A

thru mutational accumulation and antagonistic pleiotropy

evolution (15 decks)

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