Chapter 15-16 Evolution

For Dr. Mrs. Kohler

Evolution

Change in a kind of organism over time; process by which modern organisms have descended from ancient organisms.

Theory

Well-tested explanation that unifies a broad range of observations

Fossil

Preserved remains or evidence of an ancient organism

Artificial selection

Selection by humans for breeding of useful traits from the natural variation among different organisms

Struggle for existence

Competition among members of a species for food, living space, and the other necessities of life

Fitness

Ability of an organism to survive and reproduce in its environment

Adaptation

Inherited characteristic that increases an organism's chance of survival

Survival of the fittest

Process by which individuals that are better suited to their environment survive and reproduce most successfully; also called natural selection

Natural Selection

Process by which individuals that are better suited to their environment survive and reproduce most successfully; also called Survival of the fittest

Descent with Modification

Principle that each living species has descended, with changes, from other species over time

Common descent

Principle that all living things were derived from common ancestors

Homologous structure

Structure that has different mature forms in different organisms but develop from the same embryonic tissues

Vestigial organ

Organ that serves no useful function in an organism

Gene pool

Combined genetic information of all the members of a particular population

Relative frequency

Number of times an allele occurs in a gene pool compared with the number of times other alleles occur

Single-gene trait

Trait controlled by a single gene that has two alleles

Polygenic trait

Trait controlled by two or more genes

Directional selection

Form of natural selection in which the entire curve moves; occurs when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end of the curve

Stabilizing selection

Form of natural selection by which the center of the curve remains in its current position; occurs when individuals near the center of a distribution curve have higher fitness than individuals at either end

Disruptive Selection

Form of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle

Genetic Drift

Random change in allele frequencies that occurs in small populations

Founder Effect

Change in allele frequencies as a result of the migration of a small subgroup of a population

Hardy-Weinberg Principle

Principle that allele frequencies in a population will remain constant unless one or more factors cause the frequencies to change

Genetic Equilibrium

Situation in which allele frequencies remain constant

Speciation

Formation of a new species

Reproductive isolation

Separation of species or populations so that they cannot interbreed and produce fertile offspring

Behavioral isolation

Form of reproductive isolation in which two populations have differences in courtship rituals or other types of behavior that prevent them from interbreeding

Geographic isolation

Form of reproductive isolation in which two populations are separated physically by geographic barriers such as rivers, mountains, or stretches of water

Temporal Isolation

Form of reproductive isolation in which two populations reproduce at different times