BIO1 Current

Atom

The smallest unit of an element that retains the element’s properties.

Molecule

Two or more atoms held together by chemical bonds.

Macromolecule

A very large molecule, such as a protein, nucleic acid, or polysaccharide.

Cell

The basic structural and functional unit of life.

Tissue

A group of similar cells that perform a common function.

Organ

A structure composed of two or more tissue types that performs a function.

Organism

An individual living entity.

Population

A group of individuals of the same species living in the same area.

Community

All populations of different species living and interacting in an area.

Ecosystem

A community plus its nonliving physical environment.

Biosphere

All regions of Earth where organisms live.

Evolution

Change in the characteristics of populations over generations.

Microevolution

Evolutionary change within populations, usually involving allele frequencies.

Macroevolution

Evolutionary change at or above the species level.

Species

A group of organisms that share a common gene pool and are reproductively compatible.

Molecular evolution

Evolutionary changes in DNA and protein sequences.

Empirical thought

Knowledge based on observations and experiments rather than speculation.

John Ray

Naturalist who developed an early biological species concept and classification system.

Carolus Linnaeus

Developed a hierarchical classification system and binomial nomenclature.

Georges Buffon

Early thinker who proposed that species could change and share common ancestors.

Jean-Baptiste Lamarck

Proposed evolution through use and disuse and inheritance of acquired characteristics.

Catastrophism

The idea that Earth's geological features resulted from sudden catastrophic events.

Uniformitarianism

The principle that the same gradual geological processes operate today as in the past.

Thomas Malthus

Argued that populations can increase faster than available resources.

Alfred Russel Wallace

Naturalist who independently developed the idea of evolution by natural selection.

Natural selection

Individuals with advantageous heritable traits leave more offspring.

Adaptation

A heritable trait that increases reproductive success in a particular environment.

Transitional forms

Fossils showing intermediate characteristics between ancestral and descendant groups.

Tiktaalik roseae

A transitional fossil with both fish and early tetrapod characteristics.

Pakicetus

Early whale relative showing the terrestrial ancestry of modern whales.

Odontoceti

Toothed whales, including dolphins and sperm whales.

Mysticeti

Baleen whales that filter-feed using baleen plates.

Biogeography

The study of the geographic distribution of organisms.

Endemic

Restricted to a particular geographic area.

Island fox

An endemic fox species found on the California Channel Islands.

Convergent evolution

The independent evolution of similar traits in distantly related organisms.

Analogous structures

Structures that have similar functions but evolved independently and do not share a common ancestral structure.

Selective breeding

The deliberate breeding of organisms with desired traits.

Artificial selection

Evolutionary change produced by humans selecting which organisms reproduce.

Homology

Similarity among traits resulting from common ancestry.

Homologous structures

Structures that share an underlying anatomical similarity because of common ancestry, even if their functions differ.

Vestigial structures

Reduced or modified structures inherited from ancestors that have little or no current function.

Developmental homology

Similarity in developmental patterns among related organisms resulting from common ancestry.

Molecular homology

Similarity in DNA or protein sequences resulting from common ancestry.

p53 protein sequence

A molecular sequence used as evidence of evolutionary relationships because similarities and differences in the protein reflect common ancestry.

Population genetics

The study of genetic variation and allele frequencies within populations.

Gene pool

All of the alleles present in a population.

Polymorphism

The presence of two or more genetic variants within a population.

Polymorphic gene

A gene that has two or more alleles in a population.

Monomorphic gene

A gene for which only one allele is present in a population.

SNP

A single-nucleotide polymorphism; a variation involving one nucleotide position in DNA.

Allele frequency

The proportion of a particular allele in a population's gene pool.

Genotype frequency

The proportion of individuals in a population with a particular genotype.

Homozygote

An individual with two identical alleles for a particular gene.

Heterozygote

An individual with two different alleles for a particular gene.

Hardy-Weinberg equilibrium

A condition in which allele and genotype frequencies remain constant from generation to generation in the absence of evolutionary forces.

Hardy-Weinberg equation

The equations p + q = 1 and p² + 2pq + q² = 1, used to calculate allele and genotype frequencies in a population at equilibrium.

p²

The expected frequency of homozygous individuals with two copies of allele p.

2pq

The expected frequency of heterozygous individuals with one p allele and one q allele.

q²

The expected frequency of homozygous individuals with two copies of allele q.

Hardy-Weinberg assumptions

Large population size, random mating, no mutation, no migration, and no natural selection.

Microevolution

A change in allele frequencies within a population over generations.

Natural selection

A process in which individuals with heritable traits that improve reproductive success leave more offspring.

Reproductive success

The relative contribution of an individual to the next generation through surviving and reproducing offspring.

Directional selection

Natural selection that favors individuals at one extreme of a range of phenotypes.

Stabilizing selection

Natural selection that favors intermediate phenotypes and selects against extreme phenotypes.

Diversifying selection

Natural selection that favors individuals at both extremes of a range of phenotypes.

Balancing selection

Natural selection that maintains two or more alleles in a population.

Heterozygote advantage

A form of balancing selection in which heterozygotes have greater reproductive success than either homozygote.

Negative frequency-dependent selection

Selection in which a phenotype or allele has greater fitness when it is rare.

Sexual selection

Selection resulting from differences among individuals in their ability to obtain mates or achieve reproductive success.

Intrasexual selection

Competition among members of the same sex for access to mates.

Intersexual selection

Mate choice in which individuals of one sex select mates based on particular traits.

Genetic drift

Evolutionary change in allele frequencies caused by random sampling of individuals.

Random genetic drift

Random changes in allele frequencies caused by chance events rather than differences in reproductive success.

Bottleneck effect

Genetic drift resulting from a drastic reduction in population size.

Founder effect

Genetic drift that occurs when a small group establishes a new population.

Neutral variation

Genetic variation that does not significantly affect an organism's reproductive success.

Gene flow

The movement of alleles between populations through the movement of individuals or gametes.

Random mating

A mating pattern in which individuals choose mates without regard to their phenotypes or genotypes.

Nonrandom mating

A mating pattern in which individuals choose mates based on particular traits or relationships.

Assortative mating

Nonrandom mating in which individuals with similar traits are more likely to mate.

Disassortative mating

Nonrandom mating in which individuals with different traits are more likely to mate.

Inbreeding

Mating between individuals that are more closely related than randomly selected individuals in a population.

Inbreeding depression

Reduced reproductive success resulting from increased homozygosity caused by inbreeding.

Speciation

The evolutionary process by which new species arise.

Morphology

The form and structural characteristics of an organism.

Reproductive isolation

The inability of populations to successfully interbreed and produce fertile offspring.

Species concept

A definition or framework used to identify and distinguish species.

Biological species concept

The concept that defines a species as a group of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups.

Evolutionary lineage concept

The concept that defines a species as a lineage of populations that maintains its identity from other lineages and has its own evolutionary tendencies and historical fate.

Lineage

A sequence of populations or organisms connected through ancestor-descendant relationships.

Ecological species concept

The concept that defines a species according to its ecological niche.

General lineage concept

The concept that defines a species as a separately evolving lineage of organisms or populations.

Reproductive isolating mechanisms

Biological mechanisms that prevent populations from successfully reproducing with one another.

Interspecies hybrid

An offspring produced by reproduction between individuals from two different species.

Habitat isolation

Reproductive isolation that occurs when populations live in different habitats and therefore rarely encounter each other.

Temporal isolation

Reproductive isolation caused by populations reproducing at different times.

Behavioral isolation

Reproductive isolation caused by differences in courtship or other reproductive behaviors.

Mechanical isolation

Reproductive isolation caused by differences in reproductive structures that prevent mating or pollen transfer.