Topic 3

Question 1

natural selection

Answer 1

when there is variation within a population and organisms, and when that variation can be inherited, the variants best suited for growth and reproduction in a given environment will contribute disproportionately to the next generation

Question 2

environmental variation

Answer 2

variation among individuals due to differences in environment

Question 3

genetic variation

Answer 3

variation among individuals caused by differences in the genetic material that is transmitted from parent to offspring

Question 4

“descent with modification”

Answer 4

evolutionary changes that have accumulated over time since the two lineages split

Question 5

species

Answer 5

consists of individuals that can exchange genetic material through interbreeding

Question 6

gene pool

Answer 6

all the alleles present in all individuals in the species

Question 7

individuals represent different combinations of alleles drawn from:

Answer 7

the species’ gene pool

Question 8

population genetics

Answer 8

the study of genetic variation in natural populations

Question 9

population

Answer 9

interbreeding groups of organisms of the same species living in the same geographical area

Question 10

what are the two sources of genetic variation?

Answer 10

mutation and recombination (synapsis)-produces new alleles

Question 11

neutral mutations

Answer 11

having little or no effect-most common type of mutation because most of genome is noncoding DNA

Question 12

deleterious mutation

Answer 12

harmful effect-most common type of mutation in coding sections of genome

Question 13

advantageous mutation

Answer 13

improves carrier’s chance of survival or reproduction; least likely to occur

Question 14

which type of mutation allows for adaptation of a species (better able to survive and reproduce in that environment)?

Answer 14

advantageous mutation

Question 15

allele frequencies

Answer 15

rates of occurrence of alleles in population: number of allele x present in population divided by total number of alleles

Question 16

a population is FIXED for that allele

Answer 16

=population exhibits only one allele at a particular gene

Question 17

genotype frequency

Answer 17

the proportion in a population of each genotype at a particular gene or set of genes

Question 18

what are three ways to measure genotype and allele frequencies in populations?

Answer 18

observable traits, gel electrophoresis, and DNA sequencing

Question 19

observable traits require:

Answer 19

studies of traits/phenotypes that are encoded by a single gene

Question 20

gel electrophoresis was applied to:

Answer 20

proteins to focus on enzymes and thus detect genetic variation, but can ONLY study enzymes

Question 21

evolution is:

Answer 21

a change in allele OR genotype frequency over time (i.e. a change in the genetic makeup of a population over time)

Question 22

Hardy-Weinberg equilibrium

Answer 22

describes situations in which allele and genotype frequencies do not change, they change only when specific forces act on the population

Question 23

requirements to meet Hardy-Weinberg equilibrium:

Answer 23

1. There can be no differences in the survival and reproductive success of individuals
2. populations must not be added to or subtracted from migration
3. there can be no mutation
4. the population must be sufficiently large to prevent sampling errors
5. individuals must mate at random

Question 24

selection

Answer 24

the differential success of alleles

Question 25

genetic drift

Answer 25

a change in the frequency of an allele due to the random effects of limited population size

Question 26

non-random mating

Answer 26

individuals do not mate randomly, affects genotype frequencies from generation to generation but does not affect allele frequencies

Question 27

the Hardy-Weinberg relation predicts:

Answer 27

genotype frequencies from allele frequencies and vice versa

Question 28

what is the starting point for population genetic analysis?

Answer 28

the Hardy-Weinberg equilibrium-if population not in equilibrium, we can infer that evolution has occurred.

Question 29

fitness

Answer 29

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

Question 30

the Modern Synthesis combines:

Answer 30

Mendelian genetics and Darwinian evolution

Question 31

what is the result of natural selection?

Answer 31

increased frequency of advantageous mutations (alleles), decreased frequency of deleterious mutations

Question 32

positive selection

Answer 32

natural selection that increases the frequency of a favourable allele

Question 33

negative selection

Answer 33

natural selection that decreases the frequency of a deleterious allele

Question 34

how can deleterious alleles remain in the population?

Answer 34

the genetic disease may occur rarely only in homozygous genotypes, is not selected against when expressed as a heterozygote

Question 35

balancing selection

Answer 35

maintenance of an allele at some intermediate frequency between 0-100%, maintains two or more alleles in a population

Question 36

heterozygote advantage

Answer 36

an example of balancing selection in which the heterozygote's fitness is higher than either of the homozygotes, resulting in selection that ensures both alleles remain in the population at intermediate frequencies, ex. malaria

Question 37

stabilizing selection

Answer 37

maintains the status quo of phenotypes and acts against extremes; keeps a trait the same over time

Question 38

directional selection

Answer 38

leads to a change in trait over time

Question 39

artificial selection

Answer 39

a form of directional selection; analogous to natural selection but the competitive element is removed, instead, selection is done by breeder

Question 40

disruptive selection

Answer 40

operates in favour of extremes and against intermediate forms, can lead to formation of new species

Question 41

sexual selection increases:

Answer 41

an individual's reproductive success

Question 42

sexual selection

Answer 42

promotes traits that increase an individual's access to reproductive opportunities; phenotypes are generally a trade-off between conflicting demands of reproduction and survival

Question 43

intrasexual selection

Answer 43

focuses on interactions between individuals of one sex (ex. males compete with another for access to females)

Question 44

intersexual selection

Answer 44

focuses on interactions between females and males (males do not fight one another but compete for attention of female, females choose their mates)