Ch 23: Evolution of Populations

Question 1

What is microevolution?

Answer 1

changes in gene frequencies that occur over generations in a population of organisms (Evolution on the smallest scale)

Question 2

What is a genetic mutation?

Answer 2

a random change in the nucleotide sequences of an organism’s DNA. Must occur in gametes (transcription and translation)

Question 3

What are the two sources of genetic variation?

Answer 3

genetic mutation (translation and transcription) and sexual reproduction (meiosis)

Question 4

What is the one thing that natural selection needs to occur?

Answer 4

natural selection can only act on variation with a genetic component

Question 5

What is a mutation?

Answer 5

a random change in nucleotide sequence of DNA

Question 6

What is a point mutation?

Answer 6

change in one base in a gene

Question 7

What factors can influence mutation rate?

Answer 7

generation time, which is how long it takes for animals to produce offsprig and how long it takes for them to produce offspring

Question 8

Generation time example for plants and animals:

Answer 8

plants and animals have a relatively long generation time so they have a low mutation rate

Question 9

Generation time example for micro organisms:

Answer 9

micro organisms have short generation time so they have a very high mutation rate

Question 10

What is a population?

Answer 10

a group of individuals of the same species that occur in a defined area that reproduce with eachother and reproduce fertile offspring

Question 11

What is a gene pool?

Answer 11

all alleles of all genes that occur in a population

Question 12

What is allele frequency?

Answer 12

how common an allele is in a population

Question 13

What is the Hardy-Weinberg equation?

Answer 13

p^2+2pq+q^2=1
(p+q)^2=1

Question 14

What are the five Hardy-Weinberg assumptions?

Answer 14

1. Infinite population size
2. No migration (ex. gene flow)
3. No mutations
4. Random mating
5. No natural selection

Question 15

What are the five causes of microevolution?

Answer 15

genetic drift, mutation, gene flow, non-random mating, and natural selection

Question 16

What is genetic drift?

Answer 16

random changes that occur in the gene pool of a generation to generation

Question 17

When is genetic drift strongest?

Answer 17

in smaller populations and it will eventually reduce the genetic variability of the population

Question 18

What is the “bottleneck” effect?

Answer 18

a phenomenon in which a population is reduced in size due to natural disasters, habitat loss, or overhunting. A consequence of the bottleneck effect is the loss of variation in a population caused by the reduction of allele frequencies

Question 19

What is the founder effect?

Answer 19

genetic drift that occurs when a new habitat is colonized by a single or a few individuals

Question 20

What is gene flow?

Answer 20

gene flow consists of the movement of alleles among populations

Question 21

What is directional selection?

Answer 21

a mode of negative natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype

Question 22

What is disruptive selection?

Answer 22

occurs when both extreme traits are favored in an environment. Disruptive selection increases genetic and phenotypic diversity in a population, since more than one phenotype, or physical trait, is favored

Question 23

What is stabilizing selection?

Answer 23

a form of natural selection wherein individuals with moderate or average phenotypes are more fit (more likely to survive and reproduce)

Question 24

What is sexual dimorphism?

Answer 24

marked differences between the sexes in secondary sexual characteristics

Question 25

What are the two subcategories of sexual selection?

Answer 25

intrasexual selection and intersexual selection

Question 26

What is intrasexual selection?

Answer 26

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

Question 27

What is intersexual selection?

Answer 27

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

Question 28

What is the good gene hypothesis?

Answer 28

if a trait is related to male genetic quality or health, both the male trait and female preference for that trait should increase in frequency

Question 29

What is diploidy?

Answer 29

maintains genetic variation in the form of hidden recessive alleles (Rr)

Question 30

What is balancing selection?

Answer 30

natural selection maintains stable frequencies of two or more phenotypic forms in a population

Question 31

What is heterozygous advantage?

Answer 31

occurs when heterozygous have a higher fitness than do both homozygotes (ex sickle cell anemia)

Question 32

What is frequency-dependent selection?

Answer 32

the fitness of a phenotype declines if it becomes too common in the population