Chapter 23 Microevolution

Question 1

What is microevolution?

Answer 1

Change of life in allele frequencies in a population over generations

Question 2

What are the 3 mechanical causes of allele frequency change?

Answer 2

• natural selection
• genetic drift
• gene flow

Question 3

What can only cause adaptive evolution?

Answer 3

Natural selection

Question 4

What is a prerequisite for evolution?

Answer 4

Genetic variation in heritable traits

Question 5

What is genetic variation?

Answer 5

Among individuals it’s caused by differences in genes or other DNA segments

Question 6

What is a phenotype?

Answer 6

Physical appearance of genes

Question 7

What is a genotype?

Answer 7

Genetic makeup code

Question 8

What are some phenotypic differences determined by?

Answer 8

Determined by a single gene

Question 9

What are other phenotypic differences determined by?

Answer 9

The influence of two or more genes, and varies along a continuum within a population

Question 10

What is measured as gene variability or nucleotide variability?

Answer 10

Genetic variation

Question 11

What also can cause a change in phenotypic variation?

Answer 11

Environmental influences

Question 12

What kind of variation can only have evolutionary consequences?

Answer 12

Only genetically determined variation

Question 13

When does the recombination of existing alleles happen?

Answer 13

Happens during the process of meiosis

Question 14

What is a mutation?

Answer 14

Random change in nucleotide sequence of DNA

Question 15

What is a point mutation?

Answer 15

Change in one base in a gene

Question 16

What are the effects of a point mutation?

Answer 16

• Varies in mutation can be harmful, beneficial, or neutral
• Usually are hidden in recessive alleles

Question 17

What is neutral variation?

Answer 17

Conferring no selective advantage or disadvantage in mutation

Question 18

Where can neutral variation happen?

Answer 18

It can happen in point mutations in the noncoding region

Question 19

Chromosomal Mutation

Answer 19

Mutations that delete, disrupt, or rearrange many loci that are typically harmful

Question 20

Duplication Mutation

Answer 20

Increases genome size and is usually less harmful
- can take on new function by further mutation

Question 21

Why are mutations rates higher in viruses compared to prokaryotes?

Answer 21

Due to rapid reproduction

Question 22

What is a population?

Answer 22

Localized group of individuals that’s capable of interbreeding and producing fertile offspring

Question 23

What is a gene pool?

Answer 23

Consists of all the alleles for all loci in a population

Question 24

What is a diploid organism?

Answer 24

The total number of alleles at locus is the total number of individuals times 2

Question 25

What is the Hardy-Weinberg formula?

Answer 25

* p + q = 1 * p^2 + 2pq + q^2 = 1

Question 26

What does the Hardy-Weinberg equation describe?

Answer 26

Describes the genetic makeup we expect for a population that's not evolving at a particular locus.

Question 27

How do we know if a population may be evolving?

Answer 27

If the observed genotype of population differs from expectations under Hardy-Weinberg

Question 28

What is the Hardy-Weinberg Equilibrium?

Answer 28

Alleles and genotype frequencies remain constant from generation to generation

Question 29

What are the 5 conditions for a nonevolving population that are rarely met?

Answer 29

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

Question 30

What is genetic drift?

Answer 30

Describes how allele frequencies fluctuate unpredictably from one generation to the next - tends to reduce genetic variation thru loss of alleles

Question 31

What is the founder effect?

Answer 31

Occurs when a few individuals become isolated from a larger population

Question 32

What is the bottleneck effect?

Answer 32

Sudden reduction in population size due to change in the environment (such as changes due to natural disasters)

Question 33

What is relative fitness?

Answer 33

Contribution of an individual makes to the gene pool of the next generation - relative to the contributions of other individuals

Question 34

What is gene flow?

Answer 34

Consists of the movement of alleles among populations

Question 35

What are some effects of genetic drift?

Answer 35

- significant in small populations - can cause allele frequencies to change at random - can lead to a loss of genetic variation within populations - can cause harmful alleles to become fixed

Question 36

What are some effects of gene flow?

Answer 36

- can increase or decrease the relative fitness of a population - reduces genetic variation over time

Question 37

What are the 3 modes of selection?

Answer 37

- directional selection - disruptive selection - stabilizing selection

Question 38

Directonal Selection

Answer 38

favors individuals at one extreme end of the phenotypic range

Question 39

Disruptive Selection

Answer 39

Favors individuals at both extreme ends of the phenotypic range

Question 40

Stabilizing Selection

Answer 40

Favors immediate variants and acts against extreme phenotypes

Question 41

Sexual selection?

Answer 41

natural selection for mating success that results in sexual dimorphism

Question 42

sexual dimorphism

Answer 42

Marked differences b/w the sexes in secondary sexual characteristics

Question 43

intrasexual selection

Answer 43

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

Question 44

intersexual selection

Answer 44

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

Question 45

Balancing Selection

Answer 45

Occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population - includes: heterozygous advantage and frequency dependent selection

Question 46

Heterozygote Advantage

Answer 46

Occurs when heterozygotes have a higher fitness than do both homozygotes - results from stabilizing or directional selection

Question 47

Frequency-Dependent Selection

Answer 47

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

Question 48

Why natural selection cannot fashion perfect organisms? (4 things)

Answer 48

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