Unit 7: Natural Selection

Question 1

Evolution

Answer 1

A change in the genetic makeup of a population over time

Question 2

Natural selection

Answer 2

The process by which individuals with favorable traits are more likely to survive and reproduce

Question 3

Adaptation

Answer 3

A heritable trait that increases an organism’s fitness in a particular environment

Question 4

Fitness

Answer 4

An organism’s ability to survive and reproduce in its environment

Question 5

Genetic variation

Answer 5

Differences in DNA sequences among individuals in a population

Question 6

Mutation

Answer 6

A change in DNA that can introduce new alleles into a population

Question 7

Gene pool

Answer 7

All the alleles present in a population

Question 8

Allele frequency

Answer 8

How often a particular allele appears in a gene pool

Question 9

Hardy-Weinberg equilibrium

Answer 9

A model stating that allele and genotype frequencies remain constant unless acted upon by evolutionary forces

Question 10

Conditions for Hardy-Weinberg

Answer 10

No mutations, random mating, no gene flow, infinite population size, and no selection

Question 11

Genetic drift

Answer 11

Random changes in allele frequencies, especially in small populations
-Leads to a loss of genetic variation

Question 12

Bottleneck effect

Answer 12

A sharp reduction in population size that can lead to reduced genetic variation.
-Often due to disaster

Question 13

Founder effect

Answer 13

Loss of genetic variation that occurs when a new population is established by a small number of individuals

Question 14

Gene flow

Answer 14

The movement of alleles between populations
“Gene/Allele migration”

Question 15

Natural selection that favors one extreme phenotype

Answer 15

Directional selection

Question 16

Stabilizing selection

Answer 16

Natural selection that favors intermediate phenotypes

Question 17

Disruptive selection

Answer 17

Natural selection that favors both extreme phenotypes over the intermediate

Question 18

Sexual selection

Answer 18

A form of natural selection based on an organism’s ability to attract mates

Question 19

Speciation

Answer 19

The process by which new species arise

Question 20

Reproductive isolation

Answer 20

When different populations can no longer interbreed and produce fertile offspring

Question 21

Prezygotic barrier

Answer 21

A reproductive barrier that prevents mating or fertilization

Question 22

Postzygotic barrier

Answer 22

A reproductive barrier that occurs after fertilization, often resulting in nonviable or sterile offspring

Question 23

Allopatric speciation

Answer 23

Speciation that occurs due to geographic isolation

Question 24

Sympatric speciation

Answer 24

Speciation that occurs without geographic isolation

Question 25

Fossil record

Answer 25

The ordered array of fossils within layers of rock that provides evidence for evolution

Question 26

Homologous structures

Answer 26

Structures in different species that are similar due to shared ancestry

Question 27

Vestigial structures

Answer 27

Structures that have lost their original function through evolution

Question 28

Molecular evidence

Answer 28

Similarities in DNA and protein sequences that suggest common ancestry

Question 29

Phylogeny

Answer 29

The evolutionary history of a species or group of related species

Question 30

Cladogram

Answer 30

A diagram used to show evolutionary relationships based on shared derived characteristics

Question 31

Common ancestor

Answer 31

An ancestral species from which two or more descendant species evolved