Chapter 17

Question 1

adaptation

Answer 1

a modification in the form, physical functioning, or behavior of organisms in a population over generations in response to environmental change

Question 2

allele

Answer 2

one of the alternative forms of a single gene

Question 3

bottleneck effect

Answer 3

a change in allele frequencies in a population due to chance following a sharp reduction in the population’s size. One of the factors that potentiates genetic drift

Question 4

directional selection

Answer 4

in evolution, the type of natural selection that moves a character toward one of its extremes

Question 5

disruptive selection

Answer 5

in evolution, the type of natural selection that moves a character toward both of its extremes, operating against individuals that are average for that character. This type of selection seems to be less common in nature than either stabilizing or directional selection

Question 6

evolution

Answer 6

any genetically based phenotypic change in a population of organisms over successive generations. Evolution can also be thought of as the process by which species of living things can undergo modification sometimes resulting in the formation of new species

Question 7

fitness

Answer 7

in evolution, the success of an organism, relative to other members of its population, in passing on its genes to the next generation of offspring

Question 8

founder effect

Answer 8

the phenomenon by which an initial gene pool for a population is established by means of that population migrating to a new are. One of the conditions that potentiates genetic drift

Question 9

gene flow

Answer 9

the movement of genes from one population to another

Question 10

gene pool

Answer 10

the entire collection of alleles, or variant forms of genes, in a population

Question 11

genetic drift

Answer 11

the chance alteration of allele frequencies in a population, with such alterations having greatest impact on small populations

Question 12

genotype

Answer 12

the genetic makeup of an organism, including all the genes that lie along its chromosome

Question 13

macroevolution

Answer 13

evolution that results in the formation of new species or other large groupings of living things

Question 14

microevolution

Answer 14

a change of allele frequencies in a population over a short period of time. The basis for all large-scale evolution (macroevolution)

Question 15

migration

Answer 15

movement of individuals from one population into the territory of another

Question 16

natural selection

Answer 16

the process through which traits that confer a reproductive advantage to individual organisms grow more common in populations of organisms over successive generations

Question 17

phenotype

Answer 17

a physiological feature, bodily characteritstic, or behavior of an organism

Question 18

polygenic

Answer 18

having multiple genes affecting a given character, such as height in humans

Question 19

population

Answer 19

all the members of a species that live in a defined geographic region at a given time

Question 20

sexual selection

Answer 20

a form of natural selection that produces differential reproductive success based on differential success in obtaining mating partners

Question 21

species

Answer 21

a group of actually or potentially interbreeding natural populations that are reproductively isolated from other such populations

Question 22

stabilizing selection

Answer 22

in evolution, the type of natural selection in which intermediate forms of a given character are favored over either extreme. This process tends to maintain average traits for a character