Chapter 6

Question 1

A process of evolutionary change in which traits that confer survival or reproductive advantages tend to increase in frequency in a population over time.

Answer 1

adaptive evolution

Question 2

An event in which a group of organisms gives rise to many new species that expand into new habitats or new ecological roles in a relatively short time.

Answer 2

adaptive radiation

Question 3

One of two or more forms of a gene that result in the production of different versions of the protein that the gene encodes.

Answer 3

allele

Question 4

A pattern of gradual change in a characteristic of an organism over a geographic region.

Answer 4

cline

Question 5

Selection that favors individuals with one extreme of a heritable phenotypic trait.

Answer 5

directional selection

Question 6

Selection that favors individuals with a phenotype at either extreme over those with an intermediate phenotype.

Answer 6

disruptive selection

Question 7

(1) Change in allele frequencies in a population over time. (2) Descent with modification; the process by which organisms gradually accumulate differences from their ancestors.

Answer 7

evolution

Question 8

A branching diagram that represents the evolutionary history of a group of organisms.

Answer 8

evolutionary tree

Question 9

(1) The uptake of the gaseous form of a compound, including CO2 in photosynthesis and N2 in nitrogen fixation, by organisms for use in metabolic functions. (2) With respect to the genetic composition of a population, an allele frequency of 100%.

Answer 9

fixation

Question 10

The transfer of alleles from one population to another via the movement of individuals or gametes.

Answer 10

gene flow

Question 11

A process in which chance events determine which alleles are passed from one generation to the next, thereby causing allele frequencies to fluctuate randomly over time; the effects are most pronounced in small populations.

Answer 11

genetic drift

Question 12

The genetic makeup of an individual.

Answer 12

genotype

Question 13

An event in which a large proportion of Earth’s species are driven to extinction worldwide in a relatively short time.

Answer 13

mass extinction

Question 14

Change in the DNA of a gene.

Answer 14

mutation

Question 15

The process by which individuals with certain heritable characteristics tend to survive and reproduce more successfully than other individuals because of those characteristics.

Answer 15

natural selection

Question 16

The observable characteristics of an organism.

Answer 16

phenotype

Question 17

Rearrangements of genetic material during sexual reproduction that result in the production of offspring that have combinations of alleles that differ from those in either of their parents.

Answer 17

recombination

Question 18

The process by which one species splits into two or more species.

Answer 18

speciation

Question 19

Selection that favors individuals with an intermediate phenotype.

Answer 19

stabilizing selection

Question 20

An organism’s allocation of its limited energy or other resources to one structure or function at the expense of another.

Answer 20

trade-off