Chapter Four

Front 1

Directional Selection

Back 1

Natural selection that drives evolutionary change by selecting for greater or lesser frequency of a given trait in a population

Front 2

Stabilizing Selection

Back 2

Selection that maintains a certain phenotype by selecting against deviations from it

Front 3

Gene Flow

Back 3

Movement of genes between populations

Front 4

Inbreeding

Back 4

Mating between close relatives

Front 5

Genetic Drift

Back 5

Random changes in gene frequency in a population

Front 6

Founder Effect

Back 6

A component of genetic drift theory, stating that new populations that become isolated from the parent population carry only the genetic variation of the founders

Front 7

Genetic Bottleneck

Back 7

Temporary dramatic reduction in size of a population or species

Front 8

Sexual Selection

Back 8

Differential reproductive success within one sex of any species.

Front 9

Sexual Dimorphism

Back 9

Difference in size, shape, or color between the sexes

Front 10

Reproductive Potential

Back 10

The possible output of offspring by one sex

Front 11

Reproductive Variance

Back 11

A measure of variation from the mean of a population of one sex compared with the other

Front 12

Systematics

Back 12

Branch of biology that describes patterns of organismal variation

Front 13

Homology

Back 13

Similarity of traits resulting from shared ancestry

Front 14

Analogous

Back 14

Having similar traits due to similar use, not due to shared ancestry.

Front 15

Convergent Evolution

Back 15

Similar form or function brought about by natural selection under similar environment rather than shared ancestry

Front 16

Cladistics

Back 16

Method of classification using ancestral and derived traits to distinguish patterns of evolution within lineages

Front 17

Cladogram

Back 17

Branching diagram showing evolved relationships among members of a lineage

Front 18

Species

Back 18

An interbreeding group of animals or plants that is reproductively isolated through anatomy, ecology, behavior, or geographic distribution from all other such groups

Front 19

Speciation

Back 19

Formation of one or more new species via reproductive isolation

Front 20

Biological Species Concept

Back 20

Defines species as interbreeding populations reproductively isolated from other such populations

Front 21

Evolutionary Species Concept

Back 21

Defines species as evolutionary lineages with their own unique identity

Front 22

Ecological Species Concept

Back 22

Defines species based on the uniqueness of their ecological niche

Front 23

Recognition Species Concept

Back 23

Defines species based on unique traits or behaviors that allow members of one species to identify each other for mating.

Front 24

Reproductive Isolating Mechanisms (RIMs)

Back 24

Any factor--behavioral, ecological, or anatomical--that prevents a male and female of two different species from hybridizing

Front 25

Anagenesis

Back 25

Evolution of a trait or a species into another over a period of time

Front 26

Cladogenesis

Back 26

Evolution through the branching of a species or a lineage

Front 27

Allopatric Speciation

Back 27

Speciations occurring via geographic isolation

Front 28

Parapatric Speciation

Back 28

Speciation occurring when two populations have continuous distributions and some phenotypes in that distribution are more favorable than others

Front 29

Sympatric Speciation

Back 29

Speciation occurring in the same geographic location

Front 30

Gradualism

Back 30

Darwinian view of slow, incremental evolutionary change

Front 31

Macroevolution

Back 31

Evolution of major phenotypic changes over relatively short time periods

Front 32

Punctuated Equilibrium

Back 32

Model of evolution characterized by rapid bursts of change, followed by long periods of stasis

Front 33

Adaptionism

Back 33

A premise that all aspects of an organism have been molded by natural selection to a form optimal for enhancing reproductive success

Front 34

Reductionism

Back 34

Paradigm that an organism is the sum of many evolved parts and that organisms can best be understood through an adapationist approach

Front 35

Null Hypothesis

Back 35

The starting assumption for scientific inquiry that one's research results occur by random chance. One's hypothesis must challenge this initial assumption

Front 36

Hardy-Weinberg Equilibrium

Back 36

The theoretical distribution in the absence of evolution, expressed as a mathematical equation

Front 37

Group Selection

Back 37

Notion, largely discredited by the rise of Darwinian theory, proposing that animals act for the good of their social group of their species.

Front 38

Kin Selection

Back 38

Principle that animals behave preferentially toward their genetic kin; formulated by William Hamilton

Front 39

Inclusive Fitness

Back 39

Reproductive success of an organism plus the fitness of its close kin