Honors Biology Evolution

9th Grade

species are fixed

A pre-Darwinian idea that all species of organisms have remained the same since they first appeared on the planet.

adaptations

Features that allow an organism to better survive in its environment; can lead to genetic change in a population over time.

allele frequency

A measure of how common a certain allele is in a population, calculated as the number of times an allele occurs in a gene pool divided by the total number of alleles.

analogous structures

Structures performing similar functions but not similar in origin; do not have close common ancestry.

artificial selection

The process by which humans change a species by breeding it for certain traits.

binomial nomenclature

Scientific naming of species where each species has two names written in Latin: the genus and specific epithet.

biogeography

The study of the distribution of species and ecosystems in geographic space and through geological time.

bottleneck effect

Genetic drift caused by an event that drastically reduces the population size and variation.

catastrophism

Theory that states that natural disasters shaped earth’s landforms and caused extinctions.

cladogram

A diagram used to show relationships among organisms, representing a hypothesis about their evolutionary history.

directional selection

A type of selection that favors phenotypes at one extreme of a trait’s range.

disruptive selection

Occurs when both extreme phenotypes are favored while individuals with intermediate phenotypes are selected against.

evolution

The process of biological change by which descendants come to differ from their ancestors.

fitness

A measure of ability to survive and produce more offspring relative to other members of the same population.

fossils

Traces of organisms that existed in the past, showing evidence of species changing over time.

founder effect

Genetic drift that occurs after a small number of individuals colonizes a new area.

gene flow

Movement of alleles from one population to another; exchange of genes with another population.

gene pool

Combined alleles for every type of allele at every locus of all individuals in a population.

genetic drift

Change in allele frequencies due to chance alone, often occurring in small populations.

genus

A classification grouping that consists of a number of similar species.

Hardy-Weinberg equilibrium

Condition in which a population's allele frequencies for a given trait do not change from generation to generation.

heritability

The ability for a trait to be passed down from one generation to the next.

homologous structures

Similar structures found in more than one species that share a common ancestor.

hybridization

The crossing of two different species that share common genes.

inheritance of acquired characteristics

Hypothesis that changes in the environment lead to changes in behavior, enhancing or reducing traits inherited by offspring.

interspecific variation

Differences among individuals from different species.

intraspecific variation

Differences among individuals from the same species.

microevolution

The observable change in allele frequencies of a population over time.

mutation

Random changes in DNA of a gene that can form a new allele.

natural selection

Mechanism by which individuals with beneficial adaptations produce more offspring on average.

normal distribution

Type of variation where frequency is highest near the mean value and decreases towards each extreme end of the range.

paleontology

The study of fossils or extinct organisms.

phenotype

The expression of a trait, produced by one or more genes.

population

Individuals that belong to the same species that are in the same place at the same time.

recombination

Shuffling of alleles resulting in different genetic combinations, mostly occurring during meiosis.

species

Group of organisms so similar to one another that they can reproduce and have fertile offspring.

specific epithet

The second part of the scientific name in the binomial nomenclature system.

stabilizing selection

The intermediate phenotype is favored and becomes more common in the population.

uniformitarianism

Theorized geological processes that shape the Earth occur at a constant rate.

variation

Differences in the physical traits of an individual from others in the same group.

vestigial structures

Remnants of structures that may have had important function in ancestors but have no clear function in modern species.