keystone

Abiotic

A term that describes a nonliving factor in an ecosystem.

Active Transport

The movement of particles from an area of low concentration to an area of high concentration that uses energy provided by ATP or a difference in electrical charges across a cell membrane.

Adenosine Triphosphate (ATP)

A molecule that provides energy for cellular reactions and processes. ATP releases energy when one of its high‐energy bonds is broken to release a phosphate group.

Adhesion

The tendency of water molecules to stick to other surfaces.

Agriculture

The artificial cultivation of food, fiber, and other goods by the systematic growing and harvesting of various organisms.

Allele

A version of a gene due to a variation in the nucleotide sequence.

Allele Frequency

How often an allele occurs in a population, its relative frequency.

Analogous Structure

A physical structure, present in multiple species, that is similar in function but different in form and inheritance.

Aquatic

A term that describes an organism associated with a water environment.

Atom

The smallest unit of an element that retains the chemical and physical properties of that element.

Biochemical Conversion

The changing of organic matter into other chemical forms such as fuels.

Bioenergetics

The study of energy flow (energy transformations) into and within living systems.

Biogeochemical Cycles

The movement of abiotic factors between the living and nonliving components within ecosystems; also known as nutrient cycles (i.e., water cycle, carbon cycle, oxygen cycle, and nitrogen cycle).

Biological Macromolecules

A group of biomacromolecules that interact with biological systems and their environments.

Biology

The scientific study of life.

Biome

A large area or geographical region with distinct plant and animal groups adapted to that environment.

Biosphere

The zone of life on Earth; sum total of all ecosystems on Earth.

Biotechnology

Any procedure or methodology that uses biological systems or living organisms to develop or modify either products or processes for specific use. This term is commonly associated with genetic engineering, which is one of many applications.

Biotic

A term that describes a living or once‐living organism in an ecosystem.

Carbohydrate

A macromolecule that contains atoms of carbon, hydrogen, and oxygen in a 1:2:1 ratio and serves as a major source of energy for living organisms (e.g., sugars, starches, and cellulose).

Carrier (Transport) Proteins

Proteins embedded in the plasma membrane involved in the movement of ions, small molecules, and macromolecules into and out of cells; also known as transport proteins.

Catalyst

A substance that enables a chemical reaction to proceed at a usually faster rate or under different conditions (e.g., lower temperature) than otherwise possible without being changed by the reaction.

Cell

The basic unit of structure and function for all living organisms. Cells have three common components: genetic material, cytoplasm, and a cell membrane. Eukaryotic cells also contain specialized organelles.

Cell Cycle

The series of events that take place in a cell leading to its division and duplication. The main phases of the cell cycle are interphase, nuclear division, and cytokinesis.

Cellular Respiration

A complex set of chemical reactions involving an energy transformation where potential chemical energy in the bonds of "food" molecules is released and partially captured in the bonds of adenosine triphosphate (ATP) molecules.

Chloroplast

An organelle found in plant cells and the cells of other eukaryotic photosynthetic organisms where photosynthesis occurs.

Chromosomal Mutation

A change in the structure of a chromosome (e.g., deletion, the loss of a segment of a chromosome and thus the loss of segment containing genes; duplication, when a segment of a chromosome is duplicated and thus displayed more than once on the chromosome; inversion, when a segment of a chromosome breaks off and reattaches in reverse order; and translocation, when a segment of one chromosome breaks off and attaches to a nonhomologous chromosome).

Chromosomes

A single piece of coiled DNA and associated proteins found in linear forms in the nucleus of eukaryotic cells and circular forms in the cytoplasm of prokaryotic cells; contains genes that encode traits. Each species has a characteristic number of chromosomes.

Cloning

A process in which a cell, cell product, or organism is copied from an original source (e.g., DNA cloning, the transfer of a DNA fragment from one organism to a self‐replicating genetic element such as a bacterial plasmid; reproductive cloning, the transfer of genetic material from the nucleus of a donor adult cell to an egg cell that has had its nucleus removed for the purpose of creating an embryo that can produce an exact genetic copy of the donor organism; or therapeutic cloning, the process of taking undifferentiated embryonic cells [STEM cells] for use in medical research).

Co‐dominance

A pattern of inheritance in which the phenotypic effect of two alleles in a heterozygous genotype express each phenotype of each allele fully and equally; a phenotype which would not be expressed in any other genotypic combination.

Cohesion

The intermolecular attraction between like molecules. Surface tension results from the cohesive properties of water.

Community (Ecological)

Different populations of organisms interacting in a shared environment.

Competition

When individuals or groups of organisms compete for similar resources such as territory, mates, water, and food in the same environment.

Concentration

The measure of the amount or proportion of a given substance when combined with another substance.

Concentration Gradient

The graduated difference in concentration of a solute per unit distance through a solution.

Consumer (Ecological)

An organism that obtains energy by feeding on other organisms or their remains.

Crossing‐over

An exchange of genetic material between homologous chromosomes during anaphase I of meiosis; contributes to the genetic variability in gametes and ultimately in offspring.

Cytokinesis

The final phase of a cell cycle resulting in the division of the cytoplasm.

Decomposer

An organism that obtains nutrients by consuming dead and decaying organic matter which allows nutrients to be accessible to other organisms.

Deoxyribonucleic Acid (DNA)

A biological macromolecule that encodes the genetic information for living organisms and is capable of self‐replication and the synthesis of ribonucleic acid (RNA).

Diffusion

The movement of particles from an area of high concentration to an area of low concentration; a natural result of kinetic molecular energy.

DNA Replication

The process in which DNA makes a duplicate copy of itself.

Dominant Inheritance

A pattern of inheritance in which the phenotypic effect of one allele is completely expressed within a homozygous and heterozygous genotype.

Ecology

The study of the relationships between organisms and their interactions with the environment.

Ecosystem

A system composed of organisms and nonliving components of an environment.

Embryology

The branch of zoology studying the early development of living things.

Endemic Species

A species that is found in its originating location and is generally restricted to that geographic area.

Endocytosis

A process in which a cell engulfs extracellular material through an inward folding of its plasma membrane.

Endoplasmic Reticulum (ER)

An organelle, containing folded membranes and sacs, responsible for the production, processing, and transportation of materials for use inside and outside a eukaryotic cell. There are two forms of this organelle: rough ER that has surface ribosomes and participates in the synthesis of proteins mostly destined for export by the cell and smooth ER that has no ribosomes and participates in the synthesis of lipids and steroids as well as the transport of synthesized macromolecules.

Endosymbiosis

A theorized process in which early eukaryotic cells were formed from simpler prokaryotes.

Energy Pyramid

A model that illustrates the biomass productivity at multiple trophic levels in a given ecosystem.

Energy Transformation

A process in which energy changes from one form to another form while some of the energy is lost to the environment.

Environment

The total surroundings of an organism or a group of organisms.

Enzyme

A protein that increases the rate of a chemical reaction without being changed by the reaction; an organic catalyst.

Eukaryote

A type of organism composed of one or more cells containing a membrane‐bound nucleus, specialized organelles in the cytoplasm, and a mitotic nuclear division cycle.

Evolution

A process in which new species develop from preexisting species (biological evolution or macroevolution); a change in the allele frequencies of a population of organisms from generation to generation (genetic evolution or microevolution).

Exocytosis

A process in which a cell releases substances to the extracellular environment by fusing a vesicular membrane with the plasma membrane, separating the membrane at the point of fusion and allowing the substance to be released.

Extinction

A term that typically describes a species that no longer has any known living individuals.

Extracellular

Located outside a cell.

Facilitated Diffusion

A process in which substances are transported across a plasma membrane with the concentration gradient with the aid of carrier (transport) proteins; does not require the use of energy.

Food Chain

A simplified path illustrating the passing of potential chemical energy (food) from one organism to another organism.

Food Web

A complex arrangement of interrelated food chains illustrating the flow of energy between interdependent organisms.

Forensics

The science of tests and techniques used during the investigation of crimes.

Fossils

The preserved remains or traces of organisms that once lived on Earth.

Founder Effect

A decrease in genetic variation caused by the formation of a new population by a small number of individuals from a larger population.

Frame‐shift Mutation

The addition (insertion mutation) or removal (deletion mutation) of one or more nucleotides that is not indivisible by three, therefore resulting in a completely different amino acid sequence than would be normal. The earlier in the sequence nucleotides are added or removed, the more altered the protein will be.

Freezing Point

The temperature at which a liquid changes state to a solid.

Gamete

A specialized cell (egg or sperm) used in sexual reproduction containing half the normal number of chromosomes of a somatic cell.

Gene

A sequence of nucleotides composing a segment of DNA that provides a blueprint for a specific hereditary trait.

Gene Expression

The process in which a nucleotide sequence of a gene is used to make a functional product such as protein or RNA.

Gene Recombination

A natural process in which a nucleic acid molecule (usually DNA but can be RNA) is broken and then joined to a different molecule; a result of crossing‐over.

Gene Splicing

A type of gene recombination in which the DNA is intentionally broken and recombined using laboratory techniques.

Gene Therapy

The intentional insertion, alteration, or deletion of genes within an individual's cells and tissues for the purpose of treating a disease.

Genetic Drift

A change in the allele frequency of a population as a result of chance events rather than natural selection.

Genetic Engineering

A technology that includes the process of manipulating or altering the genetic material of a cell resulting in desirable functions or outcomes that would not occur naturally.

Genetically Modified Organism

An organism whose genetic material has been altered through some genetic engineering technology or technique.

Genetics

The scientific study of inheritance.

Genotype

The genetic composition of an organism with reference to a single trait, a set of traits, or the entire complement of traits of an organism.

Golgi Apparatus

An organelle found in eukaryotic cells responsible for the final stages of processing proteins for release by the cell.

Gradualism

A proposed explanation in evolutionary biology stating that new species arise from the result of slight modifications (mutations and resulting phenotypic changes) over many generations.

Habitat

An area that provides an organism with its basic needs for survival.

Homeostasis

The regulatory process in which an organism regulates its internal environment.

Homeostatic Mechanism

A regulatory mechanism that contributes to maintaining a state of equilibrium (e.g., thermoregulation, water regulation, and oxygen regulation).

Homologous Structure

A physical characteristic in different organisms that is similar because it was inherited from a common ancestor.

Hypothesis

A proposed, scientifically testable explanation for an observed phenomenon.

Impermeable

Not permitting passage of a substance or substances.

Incomplete Dominance

A pattern of inheritance in which two alleles, inherited from the parents, are neither dominant nor recessive. The resulting offspring have a phenotype that is a blending of the parental traits.

Inheritance

The process in which genetic material is passed from parents to their offspring.

Interphase

The longest‐lasting phase of the cell cycle in which a cell performs the majority of its functions, such as preparing for nuclear division and cytokinesis.

Intracellular

Located inside a cell.

Isolating Mechanisms

Features of behaviors, morphology, or genetics which serve to prevent mating or breeding between two different species (e.g., temporal isolation, in which individuals are active at different times of the day, seasons, or mating periods; ecological isolation, in which individuals only mate in their specific habitat; behavioral isolation, when there are no sexual cues between representatives of the species; mechanical isolation, when there is no sperm transfer during an attempted mating; and gametic incompatibility, when there is sperm transfer without fertilization occurring).If mating can take place, there are four factors that prevent hybrid viability: zygotic mortality (fertilization but no zygote), hybrid inviability (embryo is not viable), hybrid sterility (resulting adult is sterile), and hybrid breakdown (first generation is viable but future generations are not).

Law (Scientific)

A law that generalizes a body of observations. At the time it is made, no exceptions have been found to a law. It explains things but does not describe them; serves as the basis of scientific principles.

Limiting Factor

Chemical or physical factor that limits the existence, growth, abundance, or distribution of an individual organism or a population.

Lipids

A group of organic compounds composed mostly of carbon and hydrogen including a proportionately smaller amount of oxygen; are insoluble in water, serve as a source of stored energy, and are a component of cell membranes.

Macromolecule

A polymer with a high molecular mass. Within organisms there are four main groups: carbohydrates, lipids, proteins, and nucleic acids.

Mechanism (Scientific)

The combination of components and processes that serve a common function.

Meiosis

A two‐phase nuclear division that results in the eventual production of gametes with half the normal number of chromosomes.

Migration (Genetics)

The permanent movement of genes into or out of a population resulting in a change in allele frequencies.

Mitochondrion

A membrane‐bound organelle found in most eukaryotic cells; site of cellular respiration.

Mitosis

A nuclear division resulting in the production of two somatic cells having the same genetic complement as the original cell.