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ENVS 212 > Lecture 6: Phenotypic Evolution (Part 2) > Flashcards

Lecture 6: Phenotypic Evolution (Part 2) Flashcards

1
Q

Genotypic variation encoded in DNA is an example of what type of variation? Why?

A

Discrete, only four possible nucleotides

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2
Q

Quantitative (phenotypic) traits such as height are which type of variation?

A

Continuous

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3
Q

What two factors smooth out the phenotypic distributions?

A

More loci and more environmental variance

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4
Q

What is the shape of the phenotypic variation curve?

A

Bell-shaped, normal distribution

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5
Q

Are quantitative traits affected by few or many genes?

A

Many

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6
Q

What do fitness functions describe/quantify?

A

How selection acts on quantitative traits

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7
Q

What is correlational selection?

A

Selection that favors combinations of traits

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8
Q

What is an example of a species that displays correlational selection?

A

Northwestern garter snake

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9
Q

What are two traits in northwestern garter snakes that can be acted on by correlational selection?

A

Coloration (striped vs spotted)

Escape behavior (tendency to reverse course when escaping vs escaping in straight line)

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10
Q

How many alleles does each locus have?

A

2

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11
Q

What is the frequency of each allele of a locus?

A

1/2

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12
Q

What is selection differential?

A

The difference between the mean of a trait in the existing population and the next generation

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13
Q

What can selection differential be used to predict?

A

The amount of evolutionary change given directional selection

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14
Q

What is the breeder’s equation? What do the variables mean?

A

deltaZ = h^2 x S

deltaZ: amount of evolutionary change in a trait

h^2: heritability of the trait

S: selection differential

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15
Q

If h^2 = 0 …

A

Parents and offspring do not resemble each other

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16
Q

If h^2 = 1 …

A

Parents and offspring are identical

17
Q

What is the role of h^2 in the graph of the breeder’s equation?

A

the slope of a regression line of the mean value of a trait from two parents and the value of the trait in their offspring

18
Q

The more positive h^2 is …

A

the more heritable the trait is between parents and offspring

19
Q

What is the equation for phenotypic variance? What do the variables represent?

A

Vp = Vg + Ve

Vp: overall phenotypic variance
Vg: genetic variance (phenotypic variation caused by genetic variation)
Ve: environmental variance components

20
Q

What can Vg depend on?

A

Age, tissue type, interactions among gene loci, and direct environmental influence

21
Q

What is the formula for genetic variance? What do the variables stand for?

A

Vg = Va + Vd + Vi

Vg: genetic variance
Va: additive genetic variance
Vd: Dominance variance
Vi: epistatic variance

22
Q

What is Va (additive genetic variance)?

A

The average effect of substituting one allele for another

23
Q

What is Vd (dominance variance)?

A

Variance due to dominance of alleles at the same locus

24
Q

What is Ve (epistatic variance)? What is epistasis?

A

Variance due to epistatic interactions of alleles at different loci

Epistasis is where the effect of one allele depends on another allele

25
Q

Which component of genetic variance contributes directly to evolutionary change?

A

Va

26
Q

When is a locus overdominant?

A

A heterozygote exhibits a phenotype different from either homozygote

27
Q

For most traits, which type of genetic variance is largest?

A

Va

28
Q

Do traits with high genetic variance have high or low heritability? What are some examples of such traits (2)?

A

High

Height, length

29
Q

Do traits that require lots of resources have high or low heritability? Why? Examples (3)?

A

Low

These traits are sensitive to environmental variation of those resources

Body weight, litter size, puberty age

30
Q

True or false: A fluctuating environment can maintain variation and heritability.

A

True

31
Q

How is Isla Daphne an example of how fluctuating environmental variance maintain variation and heritability?

A

During low rainfall years, the food supply is low and most seeds are large/hard to crack, so body and bill sizes are large. After El Nino, there were lots of small, soft seeds available, so body and bill size dropped.

32
Q

What protein does the MC1r gene produce?

A

Melanocortin Receptor 1 (MC1r)

33
Q

What does the melanocortin receptor 1 regulate?

A

Melanin production in hair, feathers, and scales

34
Q

How is the MC1r gene an example of parallel phenotypic evolution?

A

Changes occur in different parts of the gene in different organisms but cause melanization in all of them

35
Q

Why do lesser snow geese exhibit a wide array of phenotypes rather than simply three?

A

There may be multiple copies of the MC1r gene

36
Q

Why do parasitic jaegers only have three phenotypes rather than a wide array?

A

There is only one copy of the MC1r gene

ENVS 212 (10 decks)

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