Chapter 16 Vocab

Front 1

Microevolution –

Back 1

a change in the collective genetic material of a population

Front 2

Gene pool –

Back 2

the genes (all of the alleles) for all the traits in a population; the total genetic information
in a population

Front 3

Bell curve –

Back 3

many traits in a population follow the pattern of a bell curve.

Front 4

allele frequency

Back 4

(the percentage of an allele in a gene pool)

Front 5

H-W genetic equilibrium

Back 5

– a condition in which the frequency of alleles in a population remains the
same over generations.

Front 6

a. Immigration

Back 6

– the movement of individuals into a population (new genes added)

Front 7

b. Emigration

Back 7

– the movement of individuals out of a population (genes lost)

Front 8

Gene flow –

Back 8

the process of genes moving from one population to another.

Front 9

Genetic drift

Back 9

- a shift in allele frequencies in a population due to chance; the fluctuation in gene
frequency occurring in an isolated population, presumably due to random variations from
generation to generation.

Front 10

Nonrandom mating

Back 10

– mating should occur w/o regard for genetic make-u

Front 11

Sexual selection –

Back 11

the preferential choice of a mate based on a specific phenotypic trait

Front 12

5. Natural selection

Back 12

– the most significant factor that disrupts genetic equilibrium

Front 13

Stabilizing selection

Back 13

– a type of natural selection in which the average form of a trait causes an
organism to have advantage in reproduction = more fit (most common)

Front 14

Directional selection

Back 14

– when an individual w/ an extreme form of a trait has greater fitness than
the individuals with the average form.

Front 15

Disruptive selection

Back 15

– where individuals with 2 extreme forms of a trait have an advantage and
the intermediate form is eliminated.

Front 16

Speciation –

Back 16

the process by which a new species is formed; when members of similar populations no
longer interbreed to produce viable (fertile) offspring.

Front 17

Morphology –

Back 17

the study of the internal and external structure and form of an organism.

Front 18

1. Geographic isolation

Back 18

– the physical separation of populations

Front 19

e. Allopatric Speciation

Back 19

– when new species arise as a result of geographic isolation

Front 20

2. Reproductive isolation –

Back 20

the inability of formerly interbreeding organisms to produce offspring.

Front 21

Prezygotic isolation

Back 21

– a barrier to successful breeding that occurs before fertilization,
such as differences in mating time or behavior.

Front 22

Postzygotic isolation –

Back 22

a barrier to successful breeding that occurs after fertilization,
such as the production of nonviable or sterile offspring.

Front 23

Sympatric Speciation

Back 23

– when two subpopulations become reproductively isolated within the
same geographic area

Front 24

Punctuated equilibrium –

Back 24

a theory that speciation occurs during brief periods of rapid genetic
change with long periods of genetic equilibrium in between (Stephen J. Gould)

Front 25

Graduated equilibrium –

Back 25

a theory that speciation occurs at a gradual, stable rate.