Chapter 20 bio 1108

what is statistical variance?

-a measure of how far a set of numbers is spread out -when zero, all values are the same -gives a measure of how the data are distributed around the mean

what are the conditions/assumptions of hardy-weinberg?

1. no differential survival; or reproductive success of individuals 2. no migration 3. no mutation 4. no small population 5. no mate choice

what happens if observed allele frequency is not equal to 1?

1. you have no accounted for all the alleles 2. you have not measured the frequency correctly 3. both 4. HW equilibrium is not met

intrasexual selection

A direct competition among individuals of one sex (usually the males in vertebrates) for mates of the opposite sex.

2pq

Aa (heterozygous)

what is variation?

Any difference between individuals of the same species

what is molecular evolution?

a change in DNA or amino acid sequences over time

fitness

a measure of the extent to which the individual's genotype is represented in the next generation

the modern synthesis

a synthesis between Darwin's theory of natural selection and Mendelian genetics

a man who carries an allele of an X-linked gene will pass it on to...

all of his daughters

phenotype

an organism's physical appearance, or visible traits.

how can patterns of genetic variation be described by allele frequencies?

because genetic variation within a population is measured according to the number of different alleles of all genes and frequencies with which they appear. variation is high when there are many different allelic forms of all genes and when there are many different combination of those alleles

examples of artificial selection

corn (type of grass), types of tomatoes, domestic dogs,

what are the three things a mutation can be?

deleterious, neutral, and advantageous

what does genetic variation refer to?

differences in DNA sequences

what do stimulations lead to due to genetic drift in small populations?

either the fixation or extinction of the allele in relatively few generations

If a population is not in Hardy-Weinberg equilibrium, we can conclude that:

evolution has occurred because one of the assumptions of the Hardy-Weinberg equilibrium has been violated.

why do characteristics that decrease survival, or are metabolically very expensive, persist in any population?

exist because these characteristics are what call for mating, although these organisms will not live long, they take a chance to get mating done and for DNA/genotypes to be passed down for generations

what does variable mean?

factor or quantity whose value may vary in contrast to a constant whose value is fixed. may be expressed in symbols whose value may change depending on the values of the other variable

T or F. stimulations lead to fixation or extinction in large populations

false

an individual with a novel adaptation has evolved that adaption. this statement is...

false

directional selection is ALWAYS adaptive

false

q frequency

frequency of a recessive allele (a)- q^2 for aa

p frequency

frequency of dominant allele (A)- p^2 for AA

how are fruit flies different from humans in genetic make-up?

fruit flies are more variable in genetic make-up than humans (10x more)

how do we measure evolutionary changes in frequency?

hardy-weinberg equilibrium model

Bb

heterozygous

PP

homozygous for the dominant allele

aa

homozygous for the recessive allele

does genetic variation impact DNA?

in the vast majority of DNA that has no function, has no impact. genetic variation can be positive, providing an advantage in changing environments

how are individuals of the same species different?

individuals of the same species share similar characteristics, but are never identical, this difference is variation. they are different because of random assortment that happens during meiosis I

what are other factors that cause changes in allele frequencies?

migration, mutation, genetic drift

what is the original source variation?

mutation (somatic and germ-line)

What are the nonadaptive mechanisms of evolution?

mutation, migration, genetic drift, non-random mating

where else does variation come from?

mutations (creates entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (reshuffles alleles within an organism's offspring)

how do we measure change in evolution?

observable physical traits, relative size of genes: gel electrophoresis, specific genetic code: DNA sequencing

non-random mating

occurs when the probability that two individuals in a population will mate is not the same for all possible pairs of individuals (more likely for those individuals to mate)

What is HW allele frequency equation?

p + q= 1, p + q for that gene in that population will always equal 1 (or 100%)

what is the HW genotype frequency equation?

p^2 + 2pq + q^2=1, always equal to 1, the sum of all possible genotypes for that gene in that population

genotype

pairing of alleles, made of 2 different alleles, "condition"

how are penguins different from humans in genetic make-up?

penguins are more variable in genetic make-up than humans (5x more)

after a mutation has occurred, what happens to the chromosomes in the offspring?

recombination gives new combinations not present in the parent population

artificial selection

selection by a breeder rather than by natural selection

directional selection

selects against one of the two extremes phenotypes, shifts the population mean

stabilizing selection

selects against the extreme phenotypes, small and high values are up for high mortality rates

disruptive selection

selects against the mean

what is the difference between genetic drift in small populations and large populations?

small populations is more dramatic and large populations is less dramatic

gene loci (locus)

specific or fixed position on a chromosome where a particular gene or genetic marker is located

Hardy-Weingberg Equilibrium

states that genetic variation will remain constant from one generation to the next in the absence of disturbing factors (no evolution will occur, if disturbed evolution occurs)

What is natural selection?

survival of the fittest, leads to adaptations, which enhance the fit between an organism and its environment. it is a cornerstone of modern evolutionary theory

what is the heterozygote advantage with artificial selection?

the advantage describes the case in which the heterozygous genotypes have a higher relative fitness than either the homozygous dominant or recessive genotypes, due to a single locus known as over dominance

natural selection

the change in an allele's frequency over time based on that particular allele's impact on survival and reproduction

what is evolution?

the change in the frequency of alleles or genotypes in a population over time

sampling error

the error caused by the selection of a sample instead of conducting a census of the population, reduced by selecting large samples

what is the frequency of an allele?

the number of that particular allele present in a population divided by the total number of alleles

inbreeding depression

the reduced biological fitness in a given population as a result of inbreeding, or breeding of related individuals, results from population bottleneck

how is variation measured?

to measure genetic variation, you must know the rates of occurrence of the alleles in the population. allele frequency = # of copies of an allele/ total # of alleles in population

sexual selection favors...

traits that increase an individual's access to reproductive opportunities

T or F. allele frequencies are subject to genetic drift, caused by sampling error from generation to generation

true

what is made possible if the HW conditions are met?

we are able to compute the frequencies of the three possible genotypes AA (p^2), Aa (2pq), and aa (q^2)

When does natural selection occur?

when individuals with certain heritable traits produce more offspring than do individuals without those traits. they become more common in the population and leads to evolution

are evolutionary changes significant?

yes, they reflect the adaption of organisms to their changing environments and can result in altered genes, novel traits, and new species, depend on genetic variability and allele frequencies over time