Chapter 8

Question 1

directional selection (p. 326)

Answer 1

selection that favours an increase or decrease in the value of a trait from the current population average

Question 2

stabilizing selection (p. 327)

Answer 2

selection against individuals exhibiting traits that deviate from the current population average

Question 3

disruptive selection (p. 328)

Answer 3

selection that favours two or more variations of a trait that differ from the current population average

Question 4

sexual selection (p. 328)

Answer 4

differential reproductive success caused by variation in the ability to obtain mates; results in sexual dimorphism, and mating and courtship behaviours

Question 5

genetic drift (p. 331)

Answer 5

changes to allele frequency as a result of chance; such changes are much more pronounced in small populations

Question 6

genetic bottleneck (p. 332)

Answer 6

a dramatic, often temporary, reduction in population size, usually resulting in significant genetic drift

Question 7

founder effect (p. 332)

Answer 7

genetic drift that results when a small number of individuals separate from their original population and establish a new population

Question 8

Hardy-Weinberg principle (p. 333)

Answer 8

In large populations in which only random chance is at work, allele frequencies are expected to remain constant from generation to generation.

Question 9

microevolution (p. 336)

Answer 9

changes in gene (allele) frequencies and phenotypic traits within a population and species

Question 10

speciation (p. 336)

Answer 10

the formation of new species

Question 11

reproductive isolating mechanism (p. 336)

Answer 11

any behavioural, structural, or biochemical trait that prevents individuals of different species from reproducing successfully together

Question 12

prezygotic mechanism (p. 336)

Answer 12

a reproductive isolating mechanism that prevents interspecies mating and fertilization (for example, ecological isolation, temporal isolation, and behavioural isolation)

Question 13

postzygotic mechanism (p. 336)

Answer 13

a reproductive isolating mechanism that prevents maturation and reproduction in offspring from interspecies reproduction

Question 14

allopatric speciation (p. 337)

Answer 14

the formation of a new species as a result of evolutionary changes following a period of geographic isolation

Question 15

sympatric speciation (p. 339)

Answer 15

the evolution of populations within the same geographic area into separate species

Question 16

adaptive radiation (p. 341)

Answer 16

the relatively rapid evolution of a single species into many new species, filling a variety of formerly empty ecological niches

Question 17

divergent evolution (p. 342)

Answer 17

the large-scale evolution of a group into many different forms

Question 18

convergent evolution (p. 343)

Answer 18

the evolution of similar traits in distantly related species

Question 19

coevolution (p. 344)

Answer 19

a process in which one species evolves in response to the evolution of another species

Question 20

macroevolution (p. 348)

Answer 20

large-scale evolutionary changes including the formation of new species and new taxa

Question 21

abiogenesis (p. 348)

Answer 21

the origin of life from non-living matter

Question 22

Cambrian explosion (p. 350)

Answer 22

the rapid evolution of most major animal phyla that took place over approximately 40 million years during the Cambrian period

Question 23

cladistics (p. 350)

Answer 23

a method of determining evolutionary relationships based on the presence or absence of recently evolved traits

Question 24

derived trait (p. 350)

Answer 24

a trait that has evolved relatively recently with respect to the species or groups being discussed

Question 25

synapomorphy (p. 350)

Answer 25

a derived trait shared by two or more species or groups

Question 26

theory of gradualism (p. 353)

Answer 26

a theory that attributes large evolutionary changes in species to the accumulation of many small and ongoing changes and processes

Question 27

theory of punctuated equilibrium (p. 353)

Answer 27

a theory that attributes most evolutionary changes to relatively rapid spurts of change followed by long periods of little or no change

Question 28

transitional form (p. 354)

Answer 28

a fossil or species intermediate in form between two other species in a direct line of descent

Question 29

primate (p. 358)

Answer 29

a group of relatively large-brained, mostly arboreal mammals that includes prosimians, monkeys, apes, and humans

Question 30

prosimian (p. 358)

Answer 30

the group of primates that includes lemurs, lorises, and tarsiers

Question 31

anthropoid (p. 358)

Answer 31

the group of primates that includes monkeys, apes, and humans

Question 32

hominid (p. 359)

Answer 32

all species descended fromthe most recent common ancestor of chimpanzees and humans that are on the human side of the lineage