Chapter 21

Question 1

A process in which traits that enhance survival or reproduction tend to increase in frequencies in a population over time

Answer 1

Adaptive evolution

Question 2

Natural selection that maintains two or more phenotypic forms in a population

Answer 2

Balancing selection

Question 3

Genetic drift that occurs when the size of a population is reduced, as buy a natural disaster or human actions. Typically, the surviving population is no longer genetically representative of the original population

Answer 3

Bottleneck effect

Question 4

Natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully then do other individuals

Answer 4

Directional selection

Question 5

Natural selection in which individuals on both extremes of a phenotypic range survive or reproduce more successfully than do individuals with intermediate phenotypes

Answer 5

Disruptive selection

Question 6

Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population is gene pool composition is not reflective of that original population

Answer 6

Founder effect

Question 7

Selection in which the fitness of a phenotype depends on how common is a phenotype is in a population

Answer 7

Frequency-dependent selection

Question 8

The transfer of alleles from one population to another, resulting from the movement of fertile individuals or their gametes

Answer 8

Gene flow

Question 9

The aggregate of all copies of every type of a allele at all loci in every individual in a population. The term is also used in a more restricted sense as the aggregate of alleles for just one or a few loci in a population

Answer 9

Gene pool

Question 10

A process in which chance events cause unpredictable fluctuations an allele frequencies from one generation to the next. Effects of this are most pronounced and small populations

Answer 10

Genetic drift

Question 11

Differences among individuals in the composition of their genes or other DNA segments

Answer 11

Genetic variation

Question 12

The state of a population in which frequencies of alleles and genotypes remain constant from generation to generation, provided that only Mendelian segregation and re-combination of alleles are at work

Answer 12

Hardy-Weinberg equilibrium

Question 13

Greater reproductive success of heterozygous individuals compared with homozygotes; tends to preserve variation in a gene pool

Answer 13

Heterozygote advantage

Question 14

Revolutionary change below the species level; change in the allele frequencies in a population over generations

Answer 14

Micro evolution

Question 15

Genetic variation that does not provide a selective advantage or disadvantage

Answer 15

Neutral variation

Question 16

A group of individuals of the same species that live in the same area and interbreed, producing fertile offspring

Answer 16

Population

Question 17

The contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals in a population

Answer 17

Relative fitness

Question 18

Differences between the secondary sex characteristics of males and females of the same species

Answer 18

Sexual dimorphism

Question 19

A process in which individuals with certain inherited characteristics are more likely than other individuals of the same sex to obtain mates

Answer 19

Sexual selection

Question 20

Natural selection in which intermediate phenotype survive or reproduce more successfully then do extreme phenotypes

Answer 20

Stabilizing selection