Chapter 18 Key Terms

Question 1

adaption

Answer 1

heritable trait or behavior in an organism that aids in its survival and reproduction in its present environment

Question 2

adaptive radiation

Answer 2

speciation when one species radiates to form several other species

Question 3

allopatric speciation

Answer 3

speciation that occurs via geographical separation

Question 4

allopolyploid

Answer 4

polyploidy formed between two related, but separate species

Question 5

aneuploidy

Answer 5

condition of a cell having an extra chromosome or missing one for its species

Question 6

autoploidy

Answer 6

polyploidy formed within a single species

Question 7

behavioral isolation

Answer 7

type of reproductive isolation that occurs when a specific behavior or lack of one prevents reproduction from taking place

Question 8

convergent evolution

Answer 8

process by which groups of organisms evolve in diverse directions from a common point

Question 9

gametic barrier

Answer 9

prezygotic barrier occurring when closely related individuals of different species mate, but differences in their gamete cells (eggs and sperm) prevent fertilization from taking place

Question 10

gradual speciation model

Answer 10

model that shows how a species evolves in small steps over time

Question 11

habitat isolation

Answer 11

reproductive isolation resulting when species’ populations are moved to a new habitat

Question 12

homologous structures

Answer 12

parallel structures in diverse organisms that share a common ancestor

Question 13

hybrid

Answer 13

offspring of two closely related individuals, not of the same species

Question 14

natural selection

Answer 14

reproduction of individuals with favorable genetic traits that survive environmental change because of those traits, leading to evolutionary change

Question 15

postzygotic barrier

Answer 15

reproductive isolation that occurs after zygote formation

Question 16

prezygotic barrier

Answer 16

reproductive isolation that occurs before zygote formation

Question 17

punctuated equilibrium

Answer 17

model for rapid speciation that can occur when an event causes a small portion of a population to be cut off from the rest of the population

Question 18

reinforcement

Answer 18

continued speciation divergence between two related species due to low fitness of hybrids between them

Question 19

reproductive isolation

Answer 19

situation that occurs when a species is reproductively independent from other species; behavior, location, or reproductive barriers may cause this to happen

Question 20

speciation

Answer 20

formation of a new species

Question 21

species

Answer 21

group of population that can interbreed and produce fertile offspring

Question 22

sympatric speciation

Answer 22

speciation that occurs in the same geographical area

Question 23

temporal isolation

Answer 23

differences in breeding schedules that act as a prezygotic barrier

Question 24

variation

Answer 24

genetic differences among individuals in a species

Question 25

vestigial structure

Answer 25

physical structure present in an individual that has no observed purpose and appears to be left from a ancestor

Question 26

vicariance

Answer 26

allopatric speciation that occurs when something in the environment separates a population into different groups