BSC 385 Lecture Notes - Lecture 13: Natural Selection, Outcrossing, Disruptive Selection

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graysardine594

22 Mar 2016

School

University of Alabama

Department

Biological Sciences

Course

BSC 385

Professor

Jonathan Benstead

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Document Summary

Both reproductive modes occur, but sex is much more common. In some species, there is both sexual and asexual reproduction. Asexual reproduction is not the same as self-fertilization. Two fold cost of sex: it takes twice as many parents to produce the same number of offspring (cid:1) The persistence of sex is a paradox, because a simple model shows that asexual females should rapidly take over any population (cid:1) (cid:1) lived (cid:1) Asexual lineages tend to die out quickly but some are occasionally long. Two main theories to explain how offspring of asexual mothers have reduced fitness (cid:1) (cid:1) (cid:1) (cid:1) (cid:1) (cid:1) All of those mutants will only have mutant offspring. In sexual population, 2 mutant parents can produce non-mutant offspring. Genetic load does not ratchet up (cid:1) (cid:1) (cid:1) (cid:1) Selection in a constantly changing environment favors sex. Sex increases the variability of the offspring. Sex facilitates evolutionary arms race : both sides adapting to each other.

Related Questions

Need help with evolution questions:

1.) A haplotype is best defined as the ________________.

	haploid genotypes of all the gametes produced by a diploid individual

ABO blood type conferred by an individual gamete

genotype of either the paternal or maternal chromosomal complement

multilocus genotype of a chromosome or gamete

2.) Which of the following statements regarding linkage disequilibrium is true?

Exists when D is less than zero, but not when it is greater than zero.

Is reduced by sexual reproduction.

Is increased by crossing-over during meiosis.

Is increased by any random sampling error that happens to create or destroy certain chromosome genotypes but not others.

Is reduced by selection that favors certain combinations of genotypes.

3.) Selection on multilocus genotypes in random-mating populations leads to linkage disequilibrium when _______________.

it reduces mutation rates

it eliminates all haplotypes from the population

it prevents crossing-over during meiosis

some allele combinations confer greater fitness than do others

4.) When two loci are in linkage equilibrium, the allele carried on a chromosome at one locus is independent of the allele carried on the chromosome at another locus. When this is the case, _________________.

allele frequencies will not change over time

the two loci (or, more specifically, their protein products) do not interact

the frequency of each haplotype can be calculated by multiplying the frequency of its two alleles

all possible haplotypes occur at equal frequency

5.) Which of the following accurately characterize(s) Muller's ratchet model for the selective advantage of sexual reproduction?

Drift establishes linkage disequilibrium because multilocus genotypes with few mutations are eliminated by chance events.

In populations without sexual reproduction, deleterious mutations accumulate, eventually imposing such a burden that the population goes extinct.

Sex is favored selectively because it recreates the zero-mutation genotypes lost due to drift.

All of the above correctly characterize Muller's ratchet model for the evolution of sexual reproduction.

6.) The genetic signature of recent positive selection on a locus is _______________.

high frequency and low linkage disequilibrium

low frequency and low linkage disequilibrium

low frequency and high linkage disequilibrium

high frequency and high linkage disequilibrium

7.) Sexual reproduction is advantageous both in changing environments and in constant environments, compared to asexual reproduction.

True

False

8.) Sexual reproduction causes genetic recombination via crossing-over, which combines genotypes from different parents.

True

False

9.) One reason sex may be maintained in natural populations is proposed by the "Red Queen Hypothesis", which states that.....

genotypes created by sex are created by natural selection over and over

recombination creating novel genotypes that can resist infection by parasites

mutation load is reduced by novel adaptive mutations

the ability of sex to fix multiple

BSC 385 Lecture Notes - Lecture 13: Natural Selection, Outcrossing, Disruptive Selection

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