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2nd Year: Evolutionary Genetics > Multivariate evolution > Flashcards

Flashcards in Multivariate evolution Deck (21)
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1
Q

Define a univariate character.

A

Isolated traits with ‘one dimension’, e.g. number of bristles on a drosophila.

2
Q

Univariate characters follow a continuous distribution. True or false?

A

True.

3
Q

Univariate traits respond predictably to selection. True or false?

A

True.

N.B. if the phenotype is not genetically determined you will not see a response to selection.

4
Q

Define a multivariate trait.

A

Traits that have multiple dimensions.

5
Q

Give an example of a multivariate trait.

A

The condition-dependent trait of male eye stalk length in stalk-eyed flies.

6
Q

Multivariate characters are often linked. Why?

A

Because the same gene has more than one effect, thus the traits share genes.

7
Q

Give an example of linked multivariate characters.

A

Hair and eye colour.

8
Q

In univariate characters, the stronger the selection the greater the change in trait value. Give the equation that represents this.

A

Δz = σ2A x β

Δz = change in trait value
σ2A = additive genetic variance 
β = strength of selection
9
Q

With multivariate traits, there is interference between traits when there is covariance. True or false?

A

True.

10
Q

What is a ‘correlated response’ with regard to multivariate traits?

A

If one trait is selected for then they all change.

11
Q

What does it indicate about the covariance between traits if correlation is positive?

A

Covariance is also positive.

12
Q

What is an ‘accelerated response’?

A

When there a positive correlation and selection is also positive.

13
Q

What is an ‘adaptive conflict’?

A

When there is a positive correlation but selection is opposed.

14
Q

What role do multivariate traits have in sexual dimorphism?

A

The selection of one traits affects the selection of other traits, causing evolution of different forms.

15
Q

In males there is a linear pattern between the number of matings and the number of offspring. Is this true for females?

A

No - females can only fall pregnant a limited number of times per year. Thus more matings does not produce more offspring.

16
Q

What are the reproductive roles of a) males and b) females?

A

a) To acquire mating partners

b) To turn resources into offspring

17
Q

Males and females face opposing selection pressures. Give an example of this in drosophila.

A

Fast females are selected against, fast males are selected for. Fast females waste energy so can convert less energy into offspring. Fast males are more likely to find a mate if they move around a lot.

18
Q

Define sexual antagonism.

A

Where there is adaptive conflict between the sexes in that a new mutation is beneficial to one sex but deleterious to the other.

19
Q

If mutations are sexually antagonistic, when do they invade?

A

If the benefits outweigh the costs.

20
Q

Mutations that break down genetic correlation lead to sex-specific gene expression, meaning the sexes evolve apart. What is genetic correlation?

A

Genetic correlation is a measure of much genes are shared. Genes are shared between the sexes on the autosomes.

21
Q

Mutations that break down genetic correlation lead to sex-specific gene expression. Explain what happened with the X and Y chromosomes.

A

The Y underwent a series of inversions which now means it mostly cannot recombine with the X, thus genetic correlation has been broken.