Microevolution 2

Question 1

Do most species exist as many populations which are isolated from each other to some extent?

Answer 1

No. Populations occasionally exchange members

Question 2

How are most population structured?

Answer 2

Spatially. Individuals tend to cluster in areas of suitable habitat

Question 3

Local aggregations that regularly exchange members are called

Answer 3

Subpopulations

Question 4

an evolutionary force that results from migration of individuals or the dispersal of seeds, spores, etc.

Answer 4

Allele Flow

Question 5

Allele flow can potentially cause evolutionary change, provided that:

Answer 5

The species has multiple subpopulations

There are differences in allele frequency among populations or among subpopulations within populations

Question 6

Can small amounts of allele flow negate genetic drift?

Answer 6

Yes

Question 7

If sufficiently strong allele flow occurs, what can it cause allele frequencies in different populations to do?

Answer 7

Converge on a single, population wide mean

Question 8

In the allele flow equation, this variable = the proportion of migrants exchanged per generation

Answer 8

m

Question 9

In the allele flow equation, the number of individuals in each population

Answer 9

N

Question 10

Allele flow will negate the effects of genetic drift if…

Answer 10

If m>(1/2N)

Question 11

How many migrants every other generation is sufficient to prevent genetic drift from causing evolutionary differences among populations of species or subpopulations within a populations of a species

Answer 11

One migrant every other generation or .5 migrants every generation

Question 12

Can allele flow oppose selection?

Answer 12

Yes

Question 13

Allele flow from a large, central population adapted to a different environment might swamp the effects of natural selection,

Answer 13

by causing an influx of less fit alleles every generation to counterbalance the unfit alleles lost to selection.

Question 14

Two important patterns of nonrandom mating that affect evolution

Answer 14

1. Inbreeding (includes selfing)

2. Assortive mating

Question 15

is common in many species, was formerly common in humans, before the advent of increasingly sophisticated forms of transportation.

Answer 15

Inbreeding

Question 16

High levels of inbreeding lead to the loss of the ___________, although allele frequencies are not necessarily changed

Answer 16

heterozygous genotype

Question 17

Inbreeding exposes recessive alleles to selection, since they are more likely to be present in the homozygous state if the population is inbred.

Answer 17

!

Question 18

How can inbreeding cause a dramatic decline in the fitness of a population, possibly extinction,

Answer 18

Deleterious alleles that are hidden from selection are more likely to be expressed

Question 19

Are all species affected by inbreeding?

Give an example

Answer 19

No.

Parasitic Hymenopetera

Question 20

This occurs when individuals choose their mates based on their resemblance to each other at a certain locus or a certain phenotype.

Answer 20

Assortative Mating

Question 21

This type of assortative mating occurs when like genotypes or phenotypes mate more often than would be expected by chance.

Answer 21

Positive assortative mating

Question 22

This type of assortative mating occurs when similar genotypes or phenotypes mate less often than would be expected by chance.

Answer 22

Negative Assortative Mating

Question 23

This group of ppl have a very high positive assortative mating, individuals with achronoplastic dwarfism pair up much more often than would be expected by chance

Answer 23

Dwarfs

Question 24

IQ
Height
Redheads

Answer 24

IQ: Slight positive assortative mating
Height: Slight positive assortative mating
Redheads: negative assortative mating

Question 25

This is the differential survival and reproduction of individuals with certain traits.

Answer 25

Natural Selection

Question 26

What does natural selection act on?

Answer 26

Phenotypes

Question 27

Does natural selection act on genotypes, and therefore cause change in the frequency of alleles through time?

Answer 27

Yes because phenotypes are in part determined by genotypes at one or several loci

Question 28

Any allele that affects the ability of an organism to survive and reproduce will be subject to natural selection.

Answer 28

!

Question 29

In populations, natural selection operates whenever individuals in the population vary in their ability to survive and reproduce.

Answer 29

Natural selection causes evolutionary change whenever there is genetic variation for traits that affect fitness.

Question 30

2 things that must occur for natural selection to operate

Answer 30

1) The must be variation | 2) Some of the variation must affect survival and reproduction of individuals

Question 31

What must occur for natural selection to cause evolutionary change?

Answer 31

There must also be allelic variation for characteristics that affect fitness

Question 32

The ability of an individual to survive and make copies of its alleles that are represented in the next generation

Answer 32

Fitness

Question 33

The fitness of an individual organisms is essentially the same as its...

Answer 33

Lifetime reproductive success

Question 34

The fitness of a genotype is the average fitness of all the individuals in the population that have that genotype.

Answer 34

!

Question 35

Is fitness physical performance?

Answer 35

No. Differences in fitness may be due to differences in survivorship, differences in fecundity, or both.

Question 36

The total number of surviving offspring that an individual produces during its lifetime (its lifetime reproductive success).

Answer 36

Absolute Fitness

Question 37

An organisms chance of living to a certain age

Answer 37

Age specific survivorship

Question 38

The number of offspring an organism produces in a certain time interval

Answer 38

Age specific fecundity

Question 39

Fecundity and survivorship are.....

Answer 39

components of fitness

Question 40

Absolute fitness is standardized to get

Answer 40

relative fitness

Question 41

The genotype with the highest absolute fitness has a relative fitness of...

Answer 41

1.0

Question 42

For every other genotype, their relative fitness is....

Answer 42

absolute fitness of genotype/absolute fitness of fittest genotype

Question 43

The variable for fitness

Answer 43

w

Question 44

Is survivorship a component of fitness?

Answer 44

Yes, it is necessary to assume fecundity is identical in the three morphs to calculate relative fitness.

Question 45

the selection coefficient, is the difference in the fitness of a genotype between its own value, and the ideal of 1.0.

Answer 45

s So, for a deleterious, recessive allele. w (AA)=1.0, w (Aa)=1.0, and w(aa)=1-s

Question 46

Occurs when the most extreme phenotype is the most fit. When applied to a single locus, that means one allele becomes more common until it reaches fixation (I.e., frequency 1.0)

Answer 46

Directional Selection

Question 47

What does directional selection tend to eliminate over time?

Answer 47

Genetic Variation

Question 48

If directional selection is to proceed for a long time, new mutations must replace lost genetic variation

Answer 48

In laboratory experiments, directional selection causes rapid change in phenotypes, followed by a plateau, caused by the loss of genetic variation.

Question 49

The peppered moth, Biston bettularia is an example of

Answer 49

Directional Selection

Question 50

What characteristic in the peppered moth exhibits directional selection?

Answer 50

Industrial melanism

Question 51

It has two forms: dark (melanic) and light. Controlled by a single locus with two alleles. Melanic is dominant, so that MM and Mm are dark, mm is light the moth rests on trees during the day, and uses crypsis as protection from predation by birds.

Answer 51

Kettlewell (1955) showed that the two forms differ in their suceptibility to bird predation.

Question 52

The melanic form was rare in 1848. When it was first reported outside Manchester, it was visible against the lichen-covered trees and often eaten by birds.

Answer 52

Museum collections indicate that by 1898, the melanic form had increased from 98% of the population

Question 53

What happened?

Answer 53

Soot had darkened the trees, making the light form most visible. In rural areas with no soot, the melanic form was still rare. (Since the passage of clean air laws in Britain, the trend has reversed, and the light form is more common once again.)

Question 54

By imposing directional selection on this species, researchers have documented changes in body size, sternopleural bristle number, and life history characteristics such as age at reproduction.

Answer 54

Drosophilia Melanogaster

Question 55

Selection in laboratory populations often produces dramatic change quickly, followed by ______ as genetic variation is exhausted

Answer 55

Plateaus

Question 56

What type of phenotypes are the most fit?

Answer 56

Intermediate

Question 57

When applied to a single locus, stabilizing selection implies that the heterozygous genotype is most fit, and is called

Answer 57

balancing selection

Question 58

Generally, stabilizing selection maintains the mean value for the trait, and decreases the variation for the trait (thus, it usually decreases genetic variation). What about in the sepecial case of balancing for a single locus?

Answer 58

Genetic variation is preserved since both alleles are maintained

Question 59

It is well known that early mortality is highest for extreme birth weights. Both very small and very large infants suffer high mortality.

Answer 59

Example of stabilizing selection

Question 60

Females that lay intermediate numbers of eggs have the highest reproductive success. Too many, and the offspring all starve. Too few, and the mother could have laid more. This phenomenen is called _____ and applies to many birds and also parasitoids

Answer 60

Lack optimum

Question 61

caused by an allele that causes hemoglobin to deform under low oxygen conditions, causing the red blood cell to “sickle”.

Answer 61

Sickle cell anemia

Question 62

Homozygotes for normal hemoglobin Hb+ Hb+ have no illness. Homozygotes for the sickle allele HbSHBShave a very serious genetic disease. Heterozygotes HbS Hb+ appear normal, but occasionally their blood cells sickle under stress. This is not particularly debilitating.

Answer 62

Sickle Cell anemia

Question 63

(In countries without malaria)) There is strong selection against homozygotes for the sickle cell disease, w(HbSHBS)=0, because, they rarely survive long enough to have many offspring.

Answer 63

The other two genotypes have a the same relative fitness w(Hb+ Hb+)=w(HbS Hb+ )=1, because carriers are essentially indistinguishable from those possessing normal hemoglobin

Question 64

Is there directional selection for or against the sickle cell allele in countries without malaria?

Answer 64

Against

Question 65

Heterozygotes for the sickle cell allele have some limited resistance to malaria, because the cells sickle and kill plasmodium within.

Answer 65

The heterozygote is most fit w(HbS Hb+ )=1, w(Hb+ Hb+)=.90, w(HbSHBS)=0.

Question 66

Selection acts to balance maintain both alleles because the heterozygote is favored, this is an example of balancing selection.

Answer 66

This explains why the original distribution of the sickle cell allele roughly matches the worldwide prevalence of malaria.

Question 67

Occurs when two or more phenotypes are most fit, but the intermediates have low fitness. Not particularly common in nature.

Answer 67

Disruptive or diversifying Selection

Question 68

In most cases, disruptive selection does what to the variance for a trait? How does it affect the mean?

Answer 68

Increases Variance Doesn't affect mean

Question 69

When disruptive selection combines with assortative mating, what type of population has the potential to perform?

Answer 69

Polymorphic population

Question 70

Selection can be frequency-dependent Frequency dependent selection where the most common type is the most fit Frequency dependent selection where the least common type is the most fit

Answer 70

+ frequency dependent selection - frequency dependent selection

Question 71

Elderflower orchids have two colors, yellow and purple. Populations typically have both color morphs, generally with the yellow morph being slightly more common. Bumblebees are the primary pollinator. Like many orchids, elderflower orchids are deceptive. They advertize to bees, but offer no nectar reward. What occurs?

Answer 71

Bumblebees learn to avoid the most common morph, giving an advantage to the least common morph

Question 72

Despite Darwin’s intuition, many documented examples of natural selection in the natural world show...

Answer 72

rapid evolution and dramatic response to natural selection

Question 73

The best know study of natural selection in the wild was the study of

Answer 73

Galapagos Finches

Question 74

What happened to the finch populations in response to drought?

Answer 74

Seed abundance goes down, beak size goes up to get at more difficult seeds. Population size went down because only specialized beaks could survivorship

Question 75

Alleles may have different fitnesses in different environments. An allele that is favored in one environment may have a disadvantage in another environment.

Answer 75

!

Question 76

For systems of ________, the genetic environment may affect the fitness of an allele

Answer 76

Epistasis

Question 77

The frequency of an allele may also affect

Answer 77

Fitness Ex: Sickle cell anemia, the Lap locus in mussels, color patterns in Heliconia butterflies, chromosomal inversions in Drosophila.

Question 78

Environmental change may do what to the effects of selection .

Answer 78

Reverse them. This is the rule rather than the exception

Question 79

There was no special driving force in evolution to produce human beings, or anything like us. This does not exactly make us an “accident:”, more precisely, it makes us one species among billions of potential evolutionary outcomes.

Answer 79

!! Selection does not act for the good of the species, nor for the good of the planet.

Question 80

Is selection weak or strong against rare recessive alleles?

Answer 80

Weak!

Question 81

Why is selection weak against rare recessive alleles?

Answer 81

Because heterozygotes are likely to exist in the heterozygous state

Question 82

How does selection act on a new mutation if the mutation is recessive?

Answer 82

It is very weak. Favorable recessive mutations can be lost by genetic drift before they have a chance to spread by selection

Question 83

In the mutation allele balance equation, what represents the mutation rate of allele A into disadvantageous allele a?

Answer 83

v

Question 84

v is usually on the order of what magnitude?

Answer 84

10^-8

Question 85

A mutation-selection balance will be reached where | If the relative fitnesses of genotypes AA and Aa are 1, and the relative fitness of the aa genotype is 1-s

Answer 85

!

Question 86

a selection coefficient that is a measure of how deleterious the recessive allele is. If it = 1, the allele is lethal, causes sterility, or zero fitness for another reason

Answer 86

s

Question 87

q*=equilibrium frequency of allele a =

Answer 87

(v/s)^1/2

Question 88

Sickle cell anemia, thallassemia, and cystic fibrosis are examples of

Answer 88

Balancing selection

Question 89

What was the likely agent of selection for sickle cell anemia and thallasemia? What about cystic fibrosis?

Answer 89

Malaria Typhus

Question 90

What other thing might have cause sickle cell anemia, thallasemia, Tay Sachs disease and cystic fibrosis to become more common?

Answer 90

Genetic Drift