EXAM 3 Flashcards
(153 cards)
1
Q
2 examples of selection
A
Stabilizing and Disruptive
2
Q
Selects against less adapted individuals at both tails of the distribution
A
Stabilizing selection
3
Q
Before and after stabilizing selection
A
Before: broad range of variation in the population
After: for some generations later the distribution narrows but has about the same mean as before
4
Q
______ is often observed in nature due to trade offs
A
Stabilizing selection
5
Q
Ex of stabilizing selection (gall fly)
A
Gall size in gall fly
Large galls attract birds
Small size attracts parasitoids (Stronger agent of selection)
6
Q
Ex of stabilizing selection (human)
A
Human birth weight
Infants with birth weights <5 or >9, had lower chance of surviving in the first month of life
7
Q
What has influenced the selection of birth weights in humans
A
Medical intervention has decreased selection pressure by increasing survival rates of extreme birth weights
8
Q
Selection occurs against less adapted individuals at middle of distribution; result produces > or equal to 2 character states (morphes)
A
Disruptive selection
9
Q
Before and after disruptive selection:
A
Before: a broad range of variation exists in population
After: for generations later, individuals at both extremes of phenotypic ranges are favored over intermediate phenotypes
10
Q
Disruptive selection is
A
antagonistic
bimodal
11
Q
Ex of disruptive selection (seedcrackers)
A
Bill size in seedcrackers
black bellied seedcracker has 2 distinct beak sizes, large and small adapted to two different seed sizes
12
Q
Phenomenon of disruptive selection sometimes called:
A
multiple niche polymorphism
13
Q
Ex of disruptive selection (butterflies)
A
Mimicry complexes in butterflies
African mocker swallowtail butterfly avoids predators by mimicking poisonous ones
14
Q
Person responsible for researching bill size in seed crackers
A
Smith
15
Q
________ changes gene (allele) frequencies in populations
A
Natural selection
16
Q
Why do organisms never achieve “perfect fits” to their environments
A
Nat sel. acts on genotypes that are already present (best of the worst)
Envt is ever changing
Organisms constantly make tradeoffs
Any adaptation has structural/physiological limits
17
Q
Tracking allele frequencies through time
A
Evolution’s Null Model
18
Q
stable populations
A
Populations that show no phenotypic change over many generations
EX: horses, sharks
19
Q
Stability over time described mathematically by
A
Hardy-weinberg theory
20
Q
Hardy-weinberg explains
A
genetic equilibrium of a large sexually reproducing population
21
Q
H-W: ___________ frequencies of a population will __________ from one generation to the next, unless ________________________
A
Allele and genotype
remain constant
they are acted on by outside forces
22
Q
Conditions required for Hardy-Weinberg Equilibrium
A
Large population Random mating No migration (no gene flow) No selection pressure No mutation
23
Q
H-W equations
A
P2 + 2PQ + Q2 = 1
P + Q = 1
24
Q
Significance of H-W
A
HW denied Genophagy: dominant alleles must, over time, eliminate recessive alleles
25
Most famous case of evolution by natural selection
Industrial melanism in peppered moths
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Why did the allele freq. change in moths
Burning of coal produced soot that killed lichens blackening tree trunks, making typical moths more conspicuous
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How allele freq. changed in moths
frequency of moths with melanic allele ↑ as air pollution ↑, while moths with gray typical allele ↓
coal burning ↓ dramatically and trees slowly lost their coatings of soot
Frequency of melanic moths ↓ from about 100% to about 0%
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Agent of selection in peppered moths
Birds
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publication bias
Evidence for selection more often reported than no evidence for selection
30
many studies of loci in natural populations reveal
Strength of selection varies greatly, from low to very high
Selection on survival and reproduction traits can be very strong
Selection strength also depends on heritability (h²)
31
reproduction traits
fecundity, fertility, sexual selection
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natural selection is a _________ in evolution
powerful force
33
components of fitness of individual genotypes- the basis of natural selection
Life history traits
34
Life history traits:
Species vary greatly in life span
Species vary greatly in fecundity
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EX of variety in life span
Ex: Bristlecone pines are among the oldest known individual organisms
Asexually propagating corals may not age and persist for thousands of years
Some rotifers live for only a few weeks
36
EX of variety in fecundity
Spawning oysters release clouds of minuscule eggs and sperm
Coconut is single large seed, coconut palms produce only a few at a time
X-ray of kiwi bird shows its single large egg (can only have one egg at a time)
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Trade offs in life history traits
Genetic correlations occur between survival (or growth) and fecundity (reproduction)
38
Evidence of the cost of reproduction
female Anolis lizards
OVX lizards grew larger and lived longer than ovary producing lizards
39
_______ prevent organisms from evolving indefinitely long life spans and infinite fecundity
Trade offs
40
ESS
Evolution Stable Strategy
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Creator of ESS
JM Smith
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a strategy which, if adopted by a population in a given environment, becomes fixed
ESS
natural selection alone is sufficient to prevent an alternative (mutant) strategy
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ESS refined from:
Nash equilibrium
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EX of Evolution stable strategy
ritualized aggression in E. African oryx
Subordinate male responds to dominant male by lowering his head
If dominant male increases threat by rotating horns forward, subordinate lays back horns, leaving him defenseless against attack.
45
Deceptive signals in ESS
claw signaling behavior in male fiddler crabs
Large regenerated claw is an effective bluff, but has less muscle and is weaker than original claw
deters opponents and is effective at mating
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In most organisms, reproduction occurs multiple times over their lifetimes
Iteroparity
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In other organisms, reproduction occurs once, after many years and then death
Semelparity (or masting)
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Delayed onset of reproduction most likely evolved in
species with high rates of adult survivorship
Ex: In some snakes and lizards, the lower the annual mortality rate of adults, the later they reach reproductive maturity
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EX of semelparity: ______ engage in highly synchronous reproduction and then die
Bamboos
50
Advantageous if reproduction is so stressful (or risky) that an individual is unlikely to reproduce more than once
Big bang reproduction seen in Coho salmon
51
___________________ are extremely variable among different animals
Parental Care and Mating systems
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In most animals, one or both sexes may mate with multiple partners
promiscuous mating
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In many ____ and _____, females provide care, but males do not and may mate with multiple partners
birds
mammals
polygyny
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In some _____, ____, and ______, females may mate and lay eggs with different males
fish
frogs
new birds
polyandry
EX: males guard eggs and care for offspring
EX: male seahorses give birth
55
In many ____, some _____ and ____, males and females form pair bond and contribute biparental care of offspring
birds
mammals
insects
monogamy
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Females may also increase their reproductive success by laying eggs in nests of unwitting foster parents
brood parasites
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mochokid catfish
mouth brooder
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Cuckoos and cowbirds
Brood parasites
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At old age, selection for reproduction and survival is weak, but the timing of reproduction and death can evolve
Senescence
60
Two evolutionary theories of senescence
Antagonistic pleiotropy
| Mutation accumulation
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alleles that increase allocation in reproduction early in life will decrease function later in life
Antagonistic pleiotropy:
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random mutations accumulate later in life and cannot be selected against
Mutation accumulation:
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Drosophila populations selected for higher fecundity later in life show their egg production is lower, as predicted
Ex of Antagonistic pleiotropy
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In Drosophila, genetic variance for reproductive success increases for older than younger age classes, as predicted
In birds and mammals, mating between relatives results in increase in inbreeding depression at later than earlier ages
Ex of Mutation accumulation
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In ______________________, sex determines solely by _______
humans, other mammals and insects
genetics
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Sex determination in humans, other mammals and insects
```
Females = XX
Males = XY
```
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In ______ and lepidoptera (_______), sex chromosomes are ________
birds
moths and butterflies
reversed
```
Females = WZ
Males = ZZ
```
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In other groups, sex determined partly by ______ or ___________
physical
social environment
Ex: in reptiles
cool temps = males
Warm temps = females
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Still other animal exhibit _________
hermaphroditism
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All hymenoptera (_____________) exhibit ________
ants, bees, wasps, scale insects, and many mites
| haplodiploidy
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Accumulation of _______ is faster in sexual than asexual populations
beneficial mutations
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For sexual species strength of ______ on new mutations is markedly _____ due to _______
natural selection
↑
recombination effects
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Ex of hermaphrodism
leopard slug
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All start as males but then switch to female
clownfishes
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Some _____ have flowers that do not open
cacti
| Reproduce almost entirely by self fertilization
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Use conjugation and other mechanisms to exchange genetic material
Bacteria like E. coli
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Many animals include ____________ to attract and court mates
sex pheromones
Commonly released by females; detected by males through antennae
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male orchid bees of tropical america
Collect a scent from certain flowers and use it as their sex pheromone
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Exploitation of pheromones in Agriculture
Pheromone traps are used in apple orchards to manage codling moths
For orchards >5 acres, a minimum of 5 traps is recommended
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Condition where 2 sexes exhibit different traits beyond differences in their sexual organs
Sexual dimorphism
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EX of Sexual dimorphism
anglerfishes
When a male finds a female, he bites and attaches himself to her permanently
His body fuses with hers and his organs degenerate except for testes
More than one male can attach
82
When one individuals behavior benefits another it is _______
cooperative
Mutualism, altruism
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If both individuals are harmed behavior is
Spiteful
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If only recipient is harmed and actor is benefited behavior is
Selfish
85
If both individuals are benefited behavior is
Mutualistic
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If recipient is benefited and actor is harmed behavior is
Altruistic
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The ______ and ______ each individual gets from _______ is measured as ______ (i.e., contribution of genes to future generations)
advantage
disadvantage
cooperation
fitness
88
Inclusive fitness:
direct fitness + indirect fitness
89
direct fitness
effect on fitness of individual beating it
90
indirect fitness
fitness of other individuals that carry same alleles
91
Fitness
contribution of genes to future generations
92
Biological differences between species prevent successful breeding, leading to ____________
isolation mechanisms
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Ex of isolation mechanisms
Almost all reproductive isolation in monkeyflowers caused by elevational separation & pollination isolation
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2 types of barriers
pre zygotic and post zygotic
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Pre zygotic barriers
traits that impede gamete transfer to other species
96
Factors influencing prezygotic barriers
Habitat isolation
Temporal isolation
Behavioral isolation
Post mating barriers
97
Habitat isolation:
spatially separated species
98
Temporal isolation
populations breed at different seasons or times of day
99
Behavioral isolation
species-specific calls, rituals, postures
100
EX of behavioral isolation in Lace WIngs
Lacewings that all belong to the same genus, but different species, have different sound waves of their songs. So they each only attract specific males
101
Postmating barriers
mating occurs, but gametes don’t transfer, and zygotes don’t form.
102
Factors influencing post mating barriers
Mechanical isolation
| Gamete isolation
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Mechanical isolation
Failure of mechanical fit of reproductive structures
104
Gamete isolation
Failure of proper transfer of gametes or fertilization
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EX of mechanical isolation
genital arch in male Drosophila involved in transferring sperm to females
106
EX of Gamete isolation in abalones
among abalones, sperm only enters if protein lysin (from sperm) can dissolve egg membrane
107
Postzygotic barriers
Lower survival or reproductive rates of hybrid zygotes
108
Hybrid sterility often limited to heterogametic
Haldanes rule
109
EX of post zygotic barriers
chromosomes of zebra and donkey parents differ in number and structure
both male ligers and tigrons are sterile, but female of both species can successfully breed with tigers and lions
110
Genetic distances among species measured by
degree of difference (D) in allozyme allele
111
summarized 60 years of experiments on Drosophila
Coyne and Orr
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Findings of Coyne and Orr:
_______ of prezygotic and postzygotic isolation were ___________ with time since populations were separated
Strength
| increased gradually
113
Reinforcement
When there is stronger prezygotic isolation due to selection against low fitness
114
Findings of Coyne and Orr:
Prezygotic isolation measured by observing
mating (vs failure to mate) between flies from different populations in lab
115
Findings of Coyne and Orr:
Postzygotic isolation: based on
survival and fertility of hybrid individuals in lab
116
_______ is a stronger barrier to gene exchange than __________
Prezygotic isolation
| postzygotic isolation
117
______ is stronger among _______ than among _______ pairs of taxa
Prezygotic isolation
sympatric
allopatric
118
Process by which new species form through reproductive isolation
Speciation
119
2 basic types of speciation
Splitting: two populations evolve differences until they eventually become separate species (first pic)
Budding: subpopulation “buds off” from main population and evolves; forms new species leaving most of larger population unchanged (2nd picture of arrows)
120
Two populations evolve differences until they eventually become separate species (first pic)
Splitting
121
subpopulation “buds off” from main population and evolves; forms new species leaving most of larger population unchanged (2nd picture of arrows)
Budding
122
__________ isolate species and prevent interbreeding
Geographical barriers
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EX of Geographical barriers
mountains, rivers, and oceans
124
in two antelope squirrel species live on opposite sides of the Grand Canyon
Separation is both ______ and______
geographical
| ecological
125
studied dusky salamanders from southern appalachian mountains in the Eastern US
Tilley
126
Dusky salmanders and fresh water fish experiments are evidence for
Allopatric speciation
127
Salamander experiment:
Brought males and females from different and same populations together and scored proportion of pairs that mated (mating experiments)
More geographically distant populations were more genetically different and were less likely to mate (picture of salamanders on graph)
128
studied 6 freshwater fish species from coastal plains of SE US
Avise
129
Avise's study on 6 spp of freshwater fish
Form 2 distinct clades in E and W Florida
Implies minimal gene flow between E and W
Genetic divergence occurred 3-4 MYA
130
Reproductive isolation occurs first within population
Sympatric speciation
131
Allopatric speciation is driven by
Geographic isolation
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some insect species programmed to lay eggs on host plants they were born on, leading to development of new species via _______
EX of sympatric speciation
Disruptive selection
133
“Host races” of apple maggot fly from hawthorn and apple hosts
Ex of Sympatric speciation
Hawthorns are ancestral host of fly
fly started to infest apple trees in same areas as normal host (now known as apple maggot)
Gene flow reduced to 2% between hosts
Three weeks separate emergence/mating time on apple and hawthorn (temporal isolation)
134
In sympatric speciation
Necessary conditions are more limited than in allopatric speciation
135
Sympatric speciation:
Many herbivorous insects mate on the plants they feed which ensures
mating will occur between individuals with same host preference
136
EX of sympatric speciation:
Sister spp. of palms on Lord Howe island
Island is small and remote, lying between Aus and NZ
Two palms are kentia palm and curly palm
Grow in close proximity and wind pollinated
Key driver is 6 wk difference in peak flowering times
reproductive isolation is based on separation by different flowering seasons
137
Sympatric Speciation caused by Chromosomal Abnormalities
Autopolyplpoidy
| Allopolyploidy
138
Auto and allopolyploidy
Become instant species through reproductive isolation form parent population
May also hybridize with closely related spp. with same chromosome number
139
Common cause for emergence of plant species
polyploidy
140
_____ of flowering plant spp may have originated as polyploids
~80%
141
BSI
Biological speciation interval
142
Biological speciation interval
mean time that has elapsed between 2 sequential forks in a phylogeny
143
How is BSI estimated:
from time between present number of species and common ancestor of clade
144
BSI for cichlid fishes
≤ 0.3 MY
145
BSI for horses
3 MY
146
BSI for bivalve mollusks
6-11 MY
147
TFS
Time for speciation
148
TFS determined using
Sequence divergence of mitochondrial DNA:
149
As a rule, TFS is ______ for ______ than speciation involving _______
shorter
polyploids
mutation or drift
150
Two studies agree that some NA songbirds diverged since ________ began
Pleistocene epoch
151
Frogs take ______, on average to complete speciation
1.5 MY
152
Models of sympatric speciation postulate the existence of
Disruptive selection based on resource usage
153
two antelope squirrel species live on opposite sides of the Grand Canyon ex of
Allopatric speciation via vicariance
