Biology Vocabulary

Flashcards for key biology terms and definitions.

Abiotic factor

Nonliving component of an ecosystem, such as climate, light, temperature, and minerals.

Absorption spectrum

The range of a pigment's ability to absorb various wavelengths of light.

Accessory pigment

A pigment that absorbs light energy and transfers energy to chlorophyll a.

Activation energy

The amount of energy that reactants must absorb before a chemical reaction will start.

Active site

The specific region of an enzyme that binds the substrate and that forms the pocket in which catalysis occurs.

Allele

An alternative version of a gene.

Allosteric regulation

The binding of a regulatory molecule to a protein at one site that affects the function of the protein at a different site.

Amphiphatic

Having both a hydrophilic region and a hydrophobic region.

Anabolism

Pathways that consume energy to build complicated molecules from simpler ones.

Anaerobic metabolism

A metabolic process that does not require oxygen.

Analogous structure

Having characteristics that are similar because of convergent evolution, not homology.

Anticodon

A nucleotide triplet at one end of a tRNA molecule that base-pairs with a particular complementary codon on an mRNA molecule.

Apoptosis

A type of programmed cell death, which is brought about by activation of enzymes that break down many chemical components in the cell.

Aquaporin

A channel protein in a cellular membrane that specifically facilitates osmosis, the diffusion of free water across the membrane.

Autosome

A chromosome that is not directly involved in determining sex; not a sex chromosome.

Biodiversity

The number of different species in an area.

Biogeography

The study of the past and present distribution of species.

Biome

A major type of ecological association that occupies a broad geographic region of land or water and is characterized by its climate.

Biotic factor

Living component of an ecosystem.

Carbon cycle

The cycling of carbon in the environment.

Carrying capacity

The maximum population size that can be supported by the available resources.

Catabolism

Pathways that release energy by breaking down complex molecules to simpler compounds.

Catalyst

A chemical agent that selectively increases the rate of a reaction without being consumed by the reaction.

Cell cycle

An ordered sequence of events in the life of a eukaryotic cell, involving cell growth and nuclear division.

Cellular differentiation

The process by which a cell or group of cells becomes specialized in structure and function.

Chemiosmosis

An energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP.

Chemoautotroph

An organism that synthesizes organic molecules from inorganic raw materials by using energy from chemical energy.

Cline

A graded change in a character along a geographic axis.

Codominance

Situation in which the phenotypes of both alleles are exhibited in the heterozygote because both alleles affect the phenotype in separate, distinguishable ways.

Codon

A three-nucleotide sequence of DNA or RNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code.

Coenzyme

An organic molecule serving as a cofactor.

Coevolution

The joint evolution of two interacting species, each in response to selection imposed by the other.

Cofactor

Any nonprotein molecule or ion that is required for the proper functioning of an enzyme.

Compartmentalization

The presence of membrane-bound organelles in eukaryotic cells.

Convergent evolution

The evolution of similar features in independent evolutionary lineages.

Cyclic AMP

Cyclic adenosine monophosphate, a ring-shaped molecule made from ATP that is a common intracellular signaling molecule (second messenger) in eukaryotic cells.

Denaturation

A process in which a protein unravels and loses its native conformation, thereby becoming biologically inactive.

Density dependent factor

Referring to any characteristic in a population that varies with population density.

Detritivore

An organism that derives its energy and nutrients from dead organic matter.

DNA ligase

An enzyme that joins sugar-phosphate backbones of DNA fragments.

Ecological niche

The sum of a species' use of the biotic and abiotic resources in its environment.

Ecological pyramid

A representation of the trophic structure of an ecosystem (energy flow).

Ecological succession

The process of community development over time.

Ecosystem

All the organisms in a given area, as well as the nonliving (abiotic) factors with which they interact; a community and its physical environment.

Ecosystem stability

The ability of an ecosystem to resist changes.

Endergonic reaction

A reaction that absorbs free energy from its surroundings and is nonspontaneous.

Endosymbiosis

A process in which certain unicellular organisms engulf other cells, which become organelles in the host cell.

Entropy

A measure of disorder or randomness.

Evo-devo

Evolutionary developmental biology; a field of biology that compares the developmental processes of different multicellular organisms.

Exergonic reaction

A reaction that proceeds with a net release of free energy and is spontaneous.

Exponential growth

Growth of a population in an ideal, unlimited, environment, represented by a J-shaped curve when population size is plotted over time.

Food chain

The pathway along which food energy is transferred from trophic level to trophic level, beginning with producers.

Food web

A network of interconnecting food chains.

Gamete

A haploid reproductive cell, such as an egg or sperm.

Gel electrophoresis

A technique for separating nucleic acids or proteins on the basis of their size and electrical charge, both of which affect their rate of movement through an electric field in a gel.

Gene expression

The process by which information encoded in DNA directs the synthesis of proteins or, in some cases, RNAs that are not translated into proteins and instead function as RNAs.

Gene flow

The transfer of alleles from one population to another, resulting from the movement of fertile individuals or their gametes.

Gene pool

The aggregate of all copies of every type of allele at all loci in every individual in a population.

Genetic bottleneck

Genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer genetically representative of the original population.

Genetic code

The set of rules by which information encoded in genetic material (DNA or RNA sequences) is translated into proteins (amino acid sequences) by living cells.

Genetic drift

A process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next.

Genetic engineering

The direct manipulation of genes for practical purposes.

Genetic equilibrium

The condition describing a non-evolving population (one that is in Hardy-Weinberg equilibrium).

Genetic transplantation

The branch of medical science that deals with the transplantation of human genes and tissues.

Genomic imprinting

The expression of certain genes is determined by whether it is inherited from the male or female parent.

Glycolipid

A lipid covalently attached to a carbohydrate.

Glycoprotein

A protein with one or more carbohydrates covalently attached to it.

Greenhouse gas

Any gas that absorbs infrared radiation in the atmosphere.

Greenhouse effect

The warming of Earth due to atmospheric accumulation of greenhouse gases, which absorb infrared radiation and reradiate some of it back to Earth.

Gross primary productivity

The total primary production of an ecosystem.

Habitat

The physical environment where an organism lives.

Haploid

A cell containing only one set of chromosomes (n).

Homeotic genes

Any of the master regulatory genes that control placement and spatial organization of body parts in animals, plants, and fungi by controlling the developmental fate of groups of cells.

Homologous chromosomes

A pair of chromosomes of the same length, centromere position, and staining pattern that possess genes for the same characters.

Homologous structures

Structures in different species that are similar because of common ancestry.

Hox genes

A group of homeotic genes that are arranged in a linear order in eukaryotic chromosomes, controlling development.

Hybrid

An offspring of parents differing in one or more heritable characters.

Hypertonic

Referring to a solution that, when surrounding a cell, will cause the cell to lose water.

Hypotonic

Referring to a solution that, when surrounding a cell, will cause the cell to take up water.

Incomplete dominance

Type of inheritance in which the phenotype of a heterozygote (Aa) is intermediate between the phenotypes of the two types of homozygotes (AA and aa).

Independent assortment

Each pair of alleles segregates independently of each other pair of alleles during gamete formation

Independent variable

The one factor that is changed by the person doing the experiment.

Inducible gene

A gene that is only expressed when a specific inducer molecule is present.

Interspecific competition

Competition between individuals of different species for the same limited resources.

Intraspecific competition

Competition between individuals of the same species for the same limited resources.

Introduced species

A species deliberately or accidentally carried to a new habitat by humans.

Introns

A noncoding, intervening sequence within a eukaryotic gene.

Isotonic

Referring to a solution that, when surrounding a cell, causes no net movement of water into or out of the cell.

K-selection

Selection that selects for life history traits that are sensitive to population density and environmental conditions.

Keystone species

A species that is not necessarily abundant in a community yet exerts strong control on community structure by the nature of its ecological role or niche.

Ligand

A molecule that binds specifically to another molecule, usually a larger one.

Limiting factors

Environmental factor that restricts population growth.

Logistic growth

Description of idealized population growth that is slowed by limiting factors as the population size increases, represented by an S-shaped curve when population size is plotted over time.

Macromolecule

A giant molecule formed by the joining of smaller molecules.

Metabolic pathway

A series of chemical reactions that either builds a complex molecule or breaks down a complex molecule into simpler compounds.

Monohybrid cross

A cross between two organisms that are heterozygous for the gene that is being followed (Aa x Aa).

Morphogenesis

The cellular and molecular processes by which an animal body takes shape.

Multiple alleles

The case in which more than two alleles exist for a particular gene locus.

Mutation

A rare change in the DNA of a gene, ultimately creating genetic diversity.

Mutualism

A symbiotic relationship in which both participants benefit.