Chapter 23

Question 1

micro evolution

Answer 1

the change in allele frequencies in a population over generations

Question 2

what are three things that cause allele frequency change?

Answer 2

• natural selection
• genetic drift
• gene flow

Question 3

what causes adaptive evolution?

Answer 3

natural selection

Question 4

what is essential to have in a population in order for evolution to occur

Answer 4

variation in heritable traits

• you get variation from different genes
• you need a gene to make a certain protein which causes a phenotype
• if you don’t have the gene to a trait then you can’t have the trait

Question 5

Both ____ and _____ characters contribute to variation within a population

Answer 5

• discrete

- quantitative

Question 6

true or false:

discrete characters can be classified on an either - or basis

Answer 6

true

Question 7

true or false:

quantitative characters vary along a continuum within a population

Answer 7

true

Question 8

average heterozygosity

Answer 8

measures the average percent of loci that are heterozygous in a population

Question 9

how is nucleotide variability measured?

Answer 9

measured by comparing the DNA sequences of pairs of individuals

Question 10

geographic variation

Answer 10

most species exhibit this.

-differences between gene pools of separate populations

Question 11

cline

Answer 11

which is a graded change in a trait along a geographic axis

Question 12

how can new genes and alleles arise?

Answer 12

by mutation or gene duplication

Question 13

what is a mutation?

Answer 13

a change in nucleotide sequence of DNA

Question 14

only mutations in cells that produce _____ can be passed to offspring

Answer 14

gametes

Question 15

what is a point mutation

Answer 15

a change in one base in a gene

Question 16

what are the possible effects of point mutations?

Answer 16

• can be harmless
• mutations in a genes can be neutral because of redundancy in the genetic code
• result in a change in protein production are often harmful
• result in a change in protein production that can sometimes be beneficial

Question 17

what type of chromosomal mutations are typically harmful?

Answer 17

mutations that delete, disrupt, or rearrange many loci

Question 18

what type of chromosomal mutations are less harmful?

Answer 18

duplication of small pieces of DNA increases genome size and is usually less harmful

Question 19

what can shuffle existing alleles into new combinations?

Answer 19

sexual reproduction

Question 20

population

Answer 20

a localized group of individuals capable of interbreeding and producing fertile offspring

Question 21

gene pool

Answer 21

consists of all the alleles for all loci in a population

Question 22

how is a locus fixed?

Answer 22

if all individuals in a population are homozygous for the same allele

Question 23

how can frequency of an allele in a population be calculated for diploid organisms

Answer 23

p + q = 1

Question 24

what is the hardy-weinberg principle

Answer 24

• describes a population that is not evolving

- frequencies of alleles and genotypes in a population remain constant from generation to generation

Question 25

if a hardy weinberg equation is not in equilibrium what does this mean?

Answer 25

-if a population does not meet the criteria of the Hardy-Weinberg principle, it can be concluded that the population is evolving

Question 26

what equation is used to find the genotypic ratio of alleles?

Answer 26

p^2 + 2pq + q^2 =1 - p is dominant - 2pq is heterozygous - q is recessive

Question 27

what does the hardy weinberg theorem describe?

Answer 27

a hypothetical population that is not evolving | FYI in real populations, allele and genotype frequencies do change over time

Question 28

what five conditions have to occur for nonevolving populations?

Answer 28

1. No mutations 2. random mating 3. no natural selection 4. extremely large population size 5. no gene flow

Question 29

true or false: | natural populations can evolve at some loci, while being in Hardy-weinberg equilibrium at other loci

Answer 29

TRUE

Question 30

what three major factors alter allele frequencies and bring about most evolutionary change:

Answer 30

- natural selection - genetic drift - gene flow

Question 31

genetic drift

Answer 31

describes how allele frequencies fluctuate unpredictably from one generation to the next

Question 32

what does genetic tends to reduce what?

Answer 32

genetic variation through losses of alleles

Question 33

the smaller a sample of population, the greater the chance of____

Answer 33

deviation from a predicted result

Question 34

founder effect

Answer 34

occurs when a few individuals become isolated from a larger population -allele frequencies in the small founder population can be different from those in the larger parent population

Question 35

bottleneck effect

Answer 35

a sudden reduction in population size due to a change in the environment -the resulting gene pool may no longer be reflective of the original population's gene pool

Question 36

if the population remains small, it may be further affected by ______

Answer 36

genetic drift

Question 37

what are 4 things to know about genetic drift?

Answer 37

1. significant in small populations 2. causes allele frequencies to change at random 3. can lead to a loss of genetic variation within populations 4. can cause harmful alleles to show up

Question 38

gene flow

Answer 38

consists of movement of alleles among populations | -alleles can be transferred through the movement of fertile individuals or gametes

Question 39

gene flow tends to reduce ______

Answer 39

variation among populations over time

Question 40

gene flow can decrease _____

Answer 40

the fitness of a population

Question 41

gene flow can increase____

Answer 41

the fitness of a population

Question 42

evolution by natural selection involves both _____ and ______

Answer 42

- change | - sorting

Question 43

new genetic variations arise by _____

Answer 43

chance

Question 44

beneficial alleles are sorted and favored by

Answer 44

natural selection

Question 45

how does natural selection bring about adaptive evolution

Answer 45

acting on an organism's phenotype

Question 46

what does survival of the fittest really mean?

Answer 46

reproductive success

Question 47

relative fitness

Answer 47

the contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals -selection favors certain genotypes by acting on the phoenotypes of certain organisms

Question 48

directional selection

Answer 48

favors individuals at one end of the phenotypic range

Question 49

disruptive seleciton

Answer 49

favors individuals at both extremes of the phenotypic range

Question 50

stabilizing seleciton

Answer 50

favors intermediate variants and acts against extreme phenotypes

Question 51

natural selection increases _____

Answer 51

frequencies of alleles that enhance survival and reproduction

Question 52

sexual selection

Answer 52

natural selection for mating success

Question 53

sexual dimorphism

Answer 53

marked differences between the sexes in secondary sexual characteristics

Question 54

intrasexual selection

Answer 54

competition among individuals of one sex for mates of the opposite sex (usually males)

Question 55

intersexual selection

Answer 55

often called mate choice, occurs when individuals of one sex are choosy in selecting their mates (usually females)

Question 56

neutral variation

Answer 56

genetic variation that does not confer a selective advantage or disadvantage

Question 57

how does diploidy maintain genetic variation?

Answer 57

in the form of hidden recessive alleles through heterozygotes

Question 58

balancing selection

Answer 58

occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a populations

Question 59

what does balancing selection include?

Answer 59

- heterozygote advantage | - frequency-dependent selection

Question 60

heterozygote advantage

Answer 60

occurs when heterozygotes have a higher fitness than do both homozygotes -natural selection will tend to maintain two or more alleles at that locus

Question 61

frequency dependent selection

Answer 61

the fitness of a phenotype declines if it becomes too common in the population -selection can favor whichever phenotype is less common in a population

Question 62

why can natural selection not fashion perfect organisms? (4)

Answer 62

1. selection can only act on existing variations 2. evolution is limited by historical constraints 3. adaptations are often compromises 4. chance, natural selection, and the environment interact