W2 Ch.17 Definitions

Question 1

Microevolution

Answer 1

Small-scale genetic changes within populations, often in response to shifting environmental circumstances or chance events
ex. the antibiotic resistance in bacteria

Question 2

Phenotypic Variation

Answer 2

Heritable variation in appearance and/or function

Question 3

Phenotypic Plasticity

Answer 3

Ability of an organismto change phenotype due to the environment

Question 4

Quantitative Variation

Answer 4

Variation that is measured on a continuum (such as height in human beings) rather than in discrete units or categories
Ex . if you weighed everyone in class, mass varies almost continuously from the lightest to heaviest

Question 5

Qualitative Variation

Answer 5

Variation that exists in 2 or more discrete states, with intermediate forms often being absent
Ex. snow geese have either white OR blue feathers, none in between…

Question 6

Polymorphism

Answer 6

The existence of discrete variants of a character among individuals in a population
ex. humans have either Type A, B, AB, or O blood

Question 7

Genetic Variation

Answer 7

Genetic variation due to production of new alleles (mutations) and recombination of the existing ones (crossingover, independent assortment, etc.)

Question 8

Gene Pool

Answer 8

The sum of all alleles at all loci in all individuals of a population

Question 9

Genotype Frequency

Answer 9

The percentage of individuals in a population possessing a particular genotype

Question 10

Phenotype Frequency

Answer 10

The percentage of individuals in a population possessing a particular phenotype

Question 11

Allele Frequency

Answer 11

The abundance of one allele relative to others at the same gene locus in individuals of a population

Question 12

Diploid

Answer 12

An organism or cell with two copies of each type of chromosome in its nucleus

Question 13

Haploid

Answer 13

An organism or cell with only one copy of each type of chromosome in its nuclei

Question 14

Null Model

Answer 14

A conceptual model that predicts what one would see if a particular factor had no effect

Question 15

Genetic Equilibrium

Answer 15

The point at which neither the allele frequencies nor the genotype frequencies in a population change in succeeding generations

Question 16

Mutation

Answer 16

Spontaneous heritable variation in DNA oRare event, significant over long time scales
Major source of heritable variation

Question 17

Neutral Mutation

Answer 17

A mutation that has no advantageous/disadvantageous effect on the organism

Question 18

Advantageous Mutation

Answer 18

Benefits an organism
Natural selection may favor organisms with mutation

Question 19

Gene Flow

Answer 19

The transfer of genes from one population to another through the movement of individuals or their gametes

Question 20

Population Bottleneck

Answer 20

An evolutionary event that occurs when a stressful factor reduces population size greatly and eliminates some alleles from a population

Question 21

Genetic Drift

Answer 21

Random fluctuations in allele frequencies as a result of chance events; usually reduces genetic variation in a population

Question 22

Founder Effect

Answer 22

An evolutionary phenomenon in which a population that was established by just a few colonizing individuals has only a fraction of the genetic diversity seen in the population from which it was derived

Question 23

Natural Selection

Answer 23

Increase in traits that enhance reproduction from one generation to the next
If a phenotype is successful, all alleles in organism are selected

Question 24

Sexual Selection

Answer 24

A form of natural selection established by male competition for access to females and by the females’ choice of mates

Question 25

Locus

Answer 25

Location of a gene on a chromosome

Question 26

Heterozygote Advantage

Answer 26

When heterozygotes have higher relative fitness than either homozygote

Question 27

Relative Fitness

Answer 27

Describes the total number of offspring an organism has compared to the average number of offspring for the population

Question 28

Directional Selection

Answer 28

A type of selection in which individuals near one end of the phenotypic spectrum have the highest relative fitness

Question 29

Stabilizing Selection

Answer 29

A type of natural selection in which individuals expressing intermediate phenotypes have the highest relative fitness

Question 30

Disruptive Selection

Answer 30

A type of natural selection in which extreme phenotypes have higher relative fitness than intermediate phenotypes

Question 31

Inbreeding

Answer 31

A special form of nonrandom mating in which genetically related individuals mate with each other

Question 32

Balanced Polymorphism

Answer 32

The maintenance of two or more phenotypes in fairly stable proportions over many generations

Question 33

Frequency-Dependent Selection

Answer 33

A form of natural selection in which rare phenotypes have a selective advantage simply because they are rare

Question 34

Adaptive Traits

Answer 34

Any product of natural selection that increases relative fitness of an organism in its environment