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Evolution > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

What is genetic drift?

A

Genetic drift is a random evolutionary force that produces a distinct pattern.

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2
Q

Name 3 long-term consequences of genetic drift on populations.

A

Populations become genetically different, eventually one allele is fixed, heterozygosity declines over time

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3
Q

What is the single parameter that determines the rate of genetic drift in nature?

A

The initial population size

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4
Q

What determines probability of fixation?

A

The starting frequency in the population

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5
Q

How fast is heterozygosity lost?

A

How fast the allele fixes

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6
Q
  1. Why aren’t all populations completely devoid of genetic variation, even though they must have a finite number of individuals?
A

neutrality

Mutation+drift ?

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7
Q
  1. Define non-random mating, and give an example for each of the three different broad categories of non-random mating.
A 
Non-random mating is where individuals with similar phenotypes/genotypes mate more often than less similar individuals. 
Categories: 
	Inbreeding 
	Assortative mating 
	Dis-assortative mating
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8
Q

What affects does each type of non-random mating have on genotype frequencies?

A

Inbreeding= selfing, loss of heterozygotes/ symmetric gain of homozygotes
Assortative mating= loss of heterozygotes
Dis-assortative mating= more heterozygotes

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9
Q

How does each type of non-random mating affect population allele frequencies?

A

Inbreeding= no effect on allele frequencies
Assortative mating= no effect on allele frequencies
Dis-assortative mating= no effect on allele frequencies

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10
Q

How does non-random mating affect Hardy Weinberg rules?

A

Nonrandom mating changes genotype frequencies. Genotype frequencies are not predictable from allele frequencies

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11
Q

Is non-random mating an evolutionary force?

A

No

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12
Q

What are the evolutionary forces?

A

Mutation, Genetic drift, Migration, Selection

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13
Q

What are the types of selection?

A

natural, artificial, sexual, kin

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14
Q

What are the 4 postulates of natural selection?

A

Variation, competition, non-random fitness differences, heritability

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15
Q
  1. What were the effects of small population size on the evolutionary forces affecting of greater prairie chickens?
A

Small population lead to inbreeding, and then loss of heterozygotes

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16
Q

How did inbreeding arise in prairie chickens, and what were the consequences for the size of the population?

A

Loss of habitat leading to small sub-groups, then inbreeding Consequences= loss of heterozygotes

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17
Q

Why did migration alter the fitness of the declining populations?

A

Introduction of new genes, more possibilities of heterozygotes.

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18
Q
  1. Name three types of natural selection, based upon the shape of the fitness function. For each of these types of natural selection, how do they influence the average phenotype and phenotypic variation in a population?
A

Directional Selection
Changes the mean value of a trait
Positive is increasing the mean and negative is decreasing the mean
Stabilizing Selection
Reduces phenotypic variance
Disruptive Selection
Increases phenotypic variance by eliminating intermediate forms

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19
Q

Name an example of stabilizing selection in humans.

A

Human birth weight

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20
Q
  1. What is a selection gradient?
A

Measures the strength of selection

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21
Q

What is a selection differential?

A

The difference in a mean trait value

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22
Q

Of selection gradient and selection differential which one of these is a slope?

A

Selection gradient

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23
Q

Of selection gradient and selection differential which of these measures is the ‘S’ in the Breeder’s equation?

A

Selection differential

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24
Q
  1. What is the breeder’s equation?
A

R=h2S

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25
Q

What does the breeders equation predict?

A

Predicts the mean in the next population

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26
Q

Why is it useful for studying the outcome of both natural and artificial selection?

A

You can see the similarities between parent and offspring and assess the amount that the trait is controlled by genes vs. the environment.

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27
Q
  1. In simple words, what causes there to be additive genetic variance in a population (VA)?
A

The replacing of one allele for another in an individual.

VA equals the covariance between offspring and parents
Covariance is the association between variation at two traits

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28
Q

Why is additive genetic variance (VA) necessary for a trait to evolve in response to natural selection?

A

Because you are adding an allele for another causing variation allowing NS to either favor or not favor the allele working on the gene.

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29
Q
  1. Why is the heritability of head number undefined in humans?
A

There is no variation in human head number

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30
Q
  1. You are studying a population of warblers. You find that the average body mass in this population is 13 ounces. Following a massive period of mortality, the remaining warblers pair off and reproduce; these warblers have an average body mass of 11 ounces.
    Is there positive or negative directional selection operating in this population?
A

Negative directional selection

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31
Q
  1. You are studying a population of warblers. You find that the average body mass in this population is 13 ounces. Following a massive period of mortality, the remaining warblers pair off and reproduce; these warblers have an average body mass of 11 ounces.

If the heritability of body mass is 0.37, what is the expected body mass in the next generation?

A

R=h2S
R=(0.37)(2) * remember that h2=heritability
R=0.74
X’=R+Xb= (.74)+(11)=11.74

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32
Q
  1. If all mutations in a codon are equally likely, is a mutation more likely to be non-synonymous or synonymous?
A

Non-Synonymous

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33
Q
  1. Revisit the neutral theory of molecular evolution. What two factors control the rate of nucleotide substitution?
A

(# of new mutations per generation) x (probability of fixation for each mutation)

34
Q
  1. What does the ratio of non-synonymous to synonymous substitutions (dN/dS) tell you about a gene?
A

dN/dS >1 means positive selection
dN/dS <1 means purifying selection
dN/dS =1 means neutral selection

35
Q

For genes evolving entirely a neutral fashion, what should this ratio be?

A

=1

36
Q

What ratio should be observed in the gene is under purifying selection?

A

<1

37
Q

What ratio should be observed for genes experiencing positive selection?

A

> 1

38
Q
  1. Why is adaptation by natural selection considered one of the triumphs of evolutionary biology?
A

Helps us to understand nature

39
Q

Define adaptation in words and graphically. Give 3 reasons why hypotheses about adaptation must be tested rigorously.

A

To make fit for the environment by modification. Must be tested rigorously because traits can be influenced by many things, and are around to serve different purposes, function may not always be the most visible. (Giraffe necks)

40
Q

What are 3 approaches to test adaptation? Be able to describe an example of each.

A

Observational test (watching the giraffes)
Experimental test (floral spur length, making the spur of the flower shorter and seeing if pollination could occur)
Comparisons across species (local adaption snail example, placed in different lakes)
Also talked about exquisite design here too, but said that this is misleading

41
Q
  1. Imagine the following scenario. Cutthroat trout in the mountain lakes in Idaho prey on small insects in high elevation mountain lakes, and small fish in low elevation lakes. You decide to test whether body size is adapted to prey size. Write a hypothesis about adaptation, make predictions, and design an observational study and an experimental study. Discuss with your study group, TAs, or professors.
A

Ho: There will not difference in body size of trout at different lake elevations
Ha: There will be a difference in body size of trout at different lake elevations because prey in each location differs in body size. Trout at high elevations prey on small fish and will be larger than trout at lower elevations that prey on small insects.
Use an experimental study in the lakes by transplanting eggs from each lake into different lakes and then measure body size.

42
Q
  1. Define local adaptation.
A

Individuals have the highest fitness in their home environment.

43
Q

What hypothesis is a reciprocal transplant experiment designed to test?

A

Local adaption

44
Q

Describe the experiment and data that shows that char were adapted to local lake conditions. That parasites were adapted to local hosts.

A

Fish had lower fitness when placed in a different environment and parasites were not able to infect foreign char like they infected the resident char.

45
Q
  1. Why are sex-limited extravagant traits difficult to explain by natural selection?
A

These traits are found in both species, but are only expressed in one. Through natural selection they should be the same.

46
Q

Why did Darwin think that these traits might be “fatal to my whole theory”?

A

If a structure of any species had been formed for the good of another species than it could not be explained by natural selection

47
Q
  1. Explain giraffe’s long necks using natural selection for foraging versus sexual selection for mate acquisition.
A

“Long necks allow the giraffe to eat at the tops of trees”- giraffes eat at shoulder height
“Necks are used for fighting other males”- correct

48
Q

In giraffes what evidence supports sexual selection? What evidence refutes natural selection?

A

Giraffe height/neck length is different between sexes

Same for natural selection

49
Q
  1. Define sexual selection.
A

A form of natural selection where selective advantages are measured as differences in mating success

50
Q

What is the difference in the way fitness is measured under natural selection versus sexual selection?

A

Fitness under sexual selection is: fitness=(survival)(offspring per mating)(# of matings)
Fitness under natural selection: fitness=(survival)(# of babies)

51
Q

How does fitness differ for males versus females, generally speaking?

A

Females are limited by number of eggs

Males limited by number of matings

52
Q
  1. Give at least 3 ways in which parental investment typically differs between males and females.
A

Females usually higher involvement
Females care for offspring at some point
High-energy cost of egg production
Females carry offspring

53
Q

Does selection favor extravagant traits in the sex with the highest or lowest parental investment? Why?

A

Usually extravigant traits are favored in sexes with lowest parental involvement because the one with the highest involvement is using energy to care for the offspring

54
Q
  1. What is Bateman’s Principle?
A

Fitness limited by number of mates in males (usually)

55
Q

Can you draw a graph showing Bateman’s Gradient when sexual selection acts more on males? On females?

A

Graph of males is positive linear, graph of females is positive linear until the # of eggs is exhausted and then plateaus

56
Q
  1. What evidence suggests that selection should act more strongly on male rough-skinned newts? Which trait has evolved by sexual selection in the newts?
A

Males with bigger crests get more matings, more matings gets more offspring. Sexual selection is stronger on bigger crests.

57
Q
  1. What is the difference between inter-sexual and intra-sexual selection?
A

Intersexual selection= display for mates

Intrasexual selection= competition for access to mates

58
Q

Under what circumstances is intersexual selection more important?

A

When males and females are not living in groups ??

59
Q

Sperm competition in bats is an example of intra- or inter-sexual selection?

A

Intra-sexual selection

60
Q
  1. What was the goal of the study of fruit bats and flying foxes?
A

Intra-sexual selection with sperm competition, used a comarative test between the bats and flying foxes

61
Q

Why was it important to consider the phylogeny of these bats?

A

Because the evolution of larger group size also evolved larger testes size

62
Q

What problem arises if comparative studies are done without information on phylogenetic relationships?

A

You can run the risk of comparing very different or very similar species against each other.

63
Q
  1. Define altruism,
A

Behaviors that appear to be detrimental to individual fitness

64
Q

define inclusive fitness,

A

Inclusive fitness= (direct fitness)+?(indirect fitness)
Direct fitness is individuals reproductive success
Indirect fitness is reproductive success of relatives

65
Q

define kin selection

A

Natural selection based on gains through indirect fitness

66
Q

Why did Darwin think that altruism might be “fatal to my whole theory”?

A

It does not increase, can decrease, and individuals fitness

67
Q

What was W.D. Hamilton’s insight about indirect fitness?

A

Added the indirect fitness aspect (2 brother, 4 cousins)

68
Q
  1. What criteria must be met for altruism to evolve under Hamilton’s Rule?
A

Costs must be less then the benefits

69
Q

Why would an individual risk their life for 2 siblings, 4 half-siblings, or 8 cousins?

A

Because those people on average carry the entirety of your genes and you can pass your genes and gain indirect fitness even if you were to die.

70
Q
  1. Hamilton’s Rule is used to determine whether an altruistic trait is favored by kin selection. (Example was from Turkeys). Why might group living favor the evolution of altruism?
A

Have higher inclusive fitness within the pair then what they would have on their own.

71
Q

In tadpoles of salamanders (text pages 453-455), altruist cannibals (discriminators) do not eat their kin. In the experiment, what was the cost to this behavior?

A

Decreased food source, compete for resources

72
Q

What was the benefit?

A

Higher inclusive firness

73
Q

Was altruism predicted to evolve under Hamilton’s rule?

A

?? Yes ?? parent higher fitness if they didn’t eat their kin.

74
Q
  1. Explain eusociality and how kin selection might favor its evolution according to the haplodiploidy hypothesis.
A

Eusociallity= specialized castes of non-reproductive individuals, cooperative brood care, overlapping in generations
Higher relatedness within haplodiploidy. Females are more related to each other than to males and stay in a eusocial environment

75
Q

Why might haplodiploidy help to explain “extraordinary” sex ratios in some insects?

A

Since the females are more related than to the males they want to favor a higher female sex ratio

76
Q

Consider normal bee colonies with one singly-mated queen: what sex ratio is expected? Explain your answer.

A

You would expect a 1:1 sex ration layed by the queen, however the female workers sabotage the males and give higher care to the females making the expected sex ratio of adults to be 3:1 females

77
Q
  1. What evidence would you cite to show that haplodiploidy is not necessary for the evolution of eusociality?
A

Benefits are higher than the costs. An example is the mole rats that are diploid organisms

78
Q

Which ecological factors that might favor the evolution of eusociality are shared by the eusocial mole rates, termites, shrimp and hymenoptera?

A

Clumped food resources, low reproductive success of solitary species, predation pressure, scarcity of nest sites

79
Q
  1. What basic crossing design is used to identify genes that influence variation in a quantitative trait (i.e. quantitative trait loci, or QTL)?
A

Take homozygotes and mate (F0)
Makes all identical heterozygotes (F1)
Cross heterozygotes to get F2 generation

80
Q
  1. What is a selective sweep?
A

Local loss of nucleotide variation within the genome

81
Q

Why does recent directional selection of a beneficial mutation reduce genetic variation in nearby chromosomal regions?

A

Physically closer and makes the recombination more likely, Strength of the selection determines the size of the region

82
Q
  1. Recall Hoekstra’s studies on the genetic basis of light-colored coat color in beach mice. Has this phenotype arisen a single time or multiple times?
A

Multiple times. Coat color mutations have been found by mice in different regions and have effects on fitness. The mutated genes are Yup, Agouti, Mc1r mutation

Evolution (2 decks)

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