Chapter 22,23

Question 1

what is a species?

Answer 1

organisms that can interbreed in nature

Question 2

what is a gene pool?

Answer 2

all the alleles present in all individuals in the same species

Question 3

what is a population?

Answer 3

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

Question 4

what is evolution?

Answer 4

the change in allele/genotypic frequency in a population over time

Question 5

what is fitness?

Answer 5

the relative reproductive ability of an individual

Question 6

what is a monophyletic group?

Answer 6

a group of organisms that descended from the same common ancestor

Question 7

what is adaptation?

Answer 7

inherited traits that were shaped by natural selection and that promote survival and reproduction

Question 8

what can cause changes in allele/genotype frequencies?

Answer 8

factors such as mutations, gene flow, genetic drift, natural selection, and nonrandom mating

Question 9

What does genetic variation in a population depend on?

Answer 9

the rates of occurrence of the alleles in the population i.e allele frequency

Question 10

how do mutations cause changes in allele/genotype frequencies?

Answer 10

creates new alleles through random nucleotide changes and recombination of genetic info

Question 11

how does gene flow cause changes in allele/genotype frequencies?

Answer 11

• adds new alleles into populations they move into
• changes the frequencies of alleles already present in the population

Question 12

How has gene flow become an important agent of evolutionary change in human populations?

Answer 12

increase in human migration (i.e gene flow) has led to mating between dissimilar populations, causing the exchange of alleles and fewer genetic differences between those populations (amalgamation)

Question 13

how does natural selection cause changes in allele/genotype frequencies?

Answer 13

certain individuals have better fitness than others and these individuals with their genotypes produce more offspring, therefore leading to adaptation

Question 14

what does natural selection require for it to cause evolution?

Answer 14

a diverse population is needed for differential survival and reproduction to occur, a population of clones will have same fitness all around and will therefore be unable to adapt and evolve

Question 15

what is natural selection?

Answer 15

differential survival and reproductive success between individuals

Question 16

When can natural selection lead to evolution?

Answer 16

If genotypes differ in average fitness, then some genotypes that have better fitness relative to others will contribute more alleles to future generations

Question 17

what are the three patterns of natural selection?

Answer 17

• stabilizing
• directional
• disruptive

Question 18

what is stabilizing selection?

Answer 18

natural selection that selects against the extreme phenotypes/ selects for the mean

Question 19

what is directional selection?

Answer 19

natural selection that selects against one of the two extreme phenotypes

Question 20

what is disruptive selection?

Answer 20

natural selection that selects against the mean/ selects for the extremes

Question 21

Why does disruptive selection have the potential to create new species?

Answer 21

disruptive selection drives the extremes of a population apart, leading to speciation because of the divergence and isolation between the two extremes.

Question 22

what is artificial selection?

Answer 22

successful genotypes are selected by the breeders (usually humans), not by nature or by competition

Question 23

what form of selection is artificial selection?

Answer 23

Directional selection because artificial selection selects against one of the extremes and selects for the other

Question 24

what is sexual selection?

Answer 24

a form of natural selection in which individuals with certain characteristics are more likely to mate and reproduce than other individuals (more attractive)

Question 25

what is sexual dimorphism?

Answer 25

when males and females show distinctly different appearances

Question 26

How does sexual selection lead to sexual dimorphism?

Answer 26

the more attractive organisms are able to pass on their alleles to their offspring while the less attractive ones die off

Question 27

What form of selection can counteract sexual selection?

Answer 27

natural selection, more attractive organisms may have decreased fitness in order to be more attractive to opposite sex

Question 28

How does genetic drift cause changes in allele/genotype frequencies?

Answer 28

some individuals may by chance leave behind more descendants (and genes) than other individuals

Question 29

why are small populations more susceptible to genetic drift?

Answer 29

small populations have less individuals to randomly sample alleles from

Question 30

what are the two forms of genetic drift?

Answer 30

1. Founder Effect 2. Population Bottleneck

Question 31

what is the founder effect?

Answer 31

a small group leaves a large population and starts a new population, with random genes and alleles present in the new population that doesn't necessarily represent the allele/genotypic frequency of the large population

Question 32

what is population bottleneck?

Answer 32

a large population shrinks to a small number of individuals by chance (mass death, natural disaster) which reproduce to repopulate

Question 33

why can genetic drift lead to loss of genetic variation?

Answer 33

genetic drift causes allele frequencies to change at random, meaning some alleles can be lost no matter they have on fitness

Question 34

How does nonrandom mating cause changes in genotype frequencies?

Answer 34

nonrandom mating leads to nonrandom allele combinations, changing the population's genetic structure

Question 35

what are the types of nonrandom mating?

Answer 35

1. Assortative mating 2. Disassortative mating

Question 36

what is assortative mating?

Answer 36

mating between parents that are genetically or phenotypically similar, leading to offspring being genetically similar

Question 37

what is disassortative mating?

Answer 37

mating between parents that are genetically or phenotypically different, leading to offspring being genetically different

Question 38

How does nonrandom mating affect a population's genetic structure?

Answer 38

- assortative mating leads to excess homozygotes - disassortative mating leads to excess heterozygotes

Question 39

explain how diversity is impacted by mutations

Answer 39

increases diversity within populations

Question 40

explain how diversity is impacted by gene flow

Answer 40

increases diversity within populations decreases diversity between populations (amalgamation)

Question 41

explain how diversity is impacted by natural selection

Answer 41

usually decreases diversity within populations (adaptation) can increase or decrease diversity between populations (speciation, convergent evolution)

Question 42

explain how diversity is impacted by genetic drift

Answer 42

decreases diversity within populations increases diversity between populations (speciation)

Question 43

what is the Hardy-Weinberg equilibrium?

Answer 43

type of equilibrium in populations that have constant allele and genotype frequencies from generation to generation because they are not evolving

Question 44

what are the conditions for a population to be in Hardy-Weinberg equilibrium?

Answer 44

absence of evolutionary influences: 1. no mutations 2. no gene flow 3. no natural selection 4. no genetic drift 5. random mating therefore, change will not happen and alleles will combine into genotypes based on the laws of probability

Question 45

what is the Hardy-Weinberg equilibrium good for?

Answer 45

if a population is in Hardy-Weinberg equilibrium, we can compute the frequencies of genotypes from the allele frequencies because p and q do not change

Question 46

what is the Hardy-Weinberg equilibrium equation?

Answer 46

p + q = 1 (allele frequency) p² + 2pq + q² = 1 (genotypic frequency) a population is not at equilibrium if equation does not equal 1