Adaptation
Change in a species resulting from natural selection; a structure which is the result of such selection.

Adaptive radiation
The rapid speciation from a single or a few species to many, filling many open ecological niches, such as following colonization of new islands.

Allele
For a given location on a chromosome, one of two (or more) slightly different molecular forms of a gene. Alleles code for different versions of the same trait. Humans have two alleles for each gene locus, one from each parent.

Allopatric speciation
(Meaning "different place") speciation that occurs when a population becomes geographically isolated from other populations and adapts to local conditions.

Altruism
Behaviour benefits other individual, at a cost to altruist. The costs and benefits are measured in terms of reproductive success; fitness.

Amino acid
An organic molecule that contains both amine and carboxyl functional groups; Amino acids are the building blocks of proteins.

Biogeography
The study of geographic patterns of species distribution and the processes that result in such patterns.

Carbohydrate
A family of organic molecules consisting of carbon (carbo), hydrogen (hydr) and oxygen (ate). A source of energy and a structural component of living cells.

Carnivore
An organism that eats animals, getting its energy from the 2nd trophic level or higher. Most carnivores are animals.

Cell cycle
Complete sequence of steps a cell undergoes in order to replicate itself. Most of the cycle consists of a growth period in which the cell grows and replicates its DNA..

Cell wall
Rigid structure deposited outside the cell membrane. Found in plants, algae and certain protists, but not animals.

Cellulose
Carbohydrate polymer of glucose, found in the cell walls of plants and green algae.

Character
Trait possessed by an organism.

Chlorophyll
The green-colored pigment that absorbs light during photosynthesis, found in plants, algae, and some bacteria.

Chloroplast
A chlorophyll-containing structure found in algae and plant cells. Photosynthesis takes place here.

Chromosome
A tightly-wound, rod-shaped or threadlike DNA-containing structure, with many associated proteins. Chromosomes are located in the nucleus of eukaryotic cells, and come in homologous pairs, one from each parent. Humans have 23 pairs of chromosomes.

Comparative Anatomy
The study of similarities and differences in the anatomy of organisms.

Consumer
An organism which gets its energy from the tissues of other organisms.

Convergence
Similar adaptations which have evolved independently in different lineages, such as wings of pterosaurs, birds, and bats, or the eyes of vertebrates and octopuses.

Cytochrome c
A small protein found loosely associated with the inner membrane of the mitochondrion. It is an essential component of the cell's energy production system.

Decomposer
An organism that eats dead or decaying organisms

Desiccation
The drying out of a living organism

Detritus
Particles of organic material. It typically includes the bodies of dead organisms, fragments of organisms, and fecal material.

Detrivore
Any organism which obtains its energy from detritus.

Diploid
Having two sets of chromosomes in each cell.

Dispersal
The more or less permanent movement of individuals (including seeds) away from an existing population or away from the parent organism.

Disturbance
A change in average environmental conditions, sometimes resulting in the removal of large amounts of biomass. Ecological disturbances include fires, flooding, and volcanic activity.

Diurnal
Active during daylight.

DNA
Deoxyribonucleic acid. A nucleic acid which contains the genetic instructions for the biological development of an organism. DNA is a long polymer of nucleotides (a polynucleotide) that encodes the sequence of amino acid in proteins.

Dominance hierarchy
A social system by which individuals within a population or group control access to resources within the community. In some hierarchies, one individual dominates. In others, each individual has a rank in the hierarchy.

Dominant allele
Allele that is expressed regardless of its ‘partner’ allele on the homologous chromosome.

Ecosystem
An ecological community of various plants, animals, and other organisms, interacting with each other and with the nonliving resources in their environment.

Embryology
The study of the embryo and its development from a single-celled zygote following fertilization.

Endosymbiosis
A mutualistic relationship in which an individual(s) from one species lives within the body or cells of another organism, such as nitrogen-fixing bacteria which live in root nodules on roots of many legumes. It is generally agreed that certain organelles of the eukaryotic cell, especially mitochondria and chloroplasts, originated as bacterial endosymbionts.

Eukaryote
An organism whose cells have their DNA contained in a nucleus, separated from the other contents of the cell.

Eusociality
A social system of reproductive specialization found in some animals. The basic group is the colony, headed by a reproductive queen, and includes classes of sterile members which carry out specialized tasks, including caring for the queen and her offspring, defense, and foraging. The most familiar examples are insects such as ants, bees, and termites, but there are two mammal species (mole rats) as well.

Fitness
The genetic contribution of an individual to future generations, typically measured as the number of offspring that reach reproductive age.

Food web
A ‘map’ of the exchanges of energy and nutrients among species in different trophic levels in an ecosystem.

Fossil
Anything that once lived and has been permanently preserved, typically the mineralized remains or impressions preserved in stone.

Fungi
Kingdom of eukaryotic organisms. Fungi are heterotrophic organisms characterized by a chitinous cell wall, and in the majority of species, filamentous growth as multicellular hyphae forming a mycelium.

Gamete
Reproductive cells which fuse to form a zygote. Gametes are haploid, differentiated into egg and sperm in animals.

Gene
A hereditary unit consisting of a sequence of DNA that occupies a specific location on a chromosome and determines a particular characteristic in an organism.

Genetic drift
A change in the genetic makeup of a small population that takes place strictly by chance.

Genome
The hereditary information of an organism encoded in the DNA (or, for some viruses, RNA). This includes the genes and the non-coding sequences of the DNA.

Genotype
The genetic makeup of an organism or cell (the various alleles of its many genes), determines its expressed features (its phenotype).

Gradualism
A model of evolution that assumes slow, steady rates of change.

Habitat
The place and conditions in which an organism lives.

Haplodiploidy
A phenomenon in which one of the sexes has haploid cells (usually male) and the other has diploid cells. The male develops from unfertilized eggs, the female develops from fertilized eggs: the sperm provides a second set of chromosomes when it fertilizes the egg.

Haploid
Having a single set of chromosomes in the nucleus of each cell. Mosses, and many protists and fungi, are haploid, as are some insects, bryophytes, and the gametes of all diploid organisms.

Herbivore
An organism that eats plants or algae, getting its energy from the 1st trophic level.

Heterozygous
Refers to an individual with two different alleles of the same gene

Hibernation
A state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate.

Homologous chromosomes
A pair of chromosomes containing the same gene sequences, each derived from one parent. Each of the homologous pair contains the same genes, but may possess differing alleles.

Homology
Traits or structures in different organisms which have their origin in a common ancestor. Homologies been modified from the original structure or trait of the common ancestor and may not necessarily perform the same functions in each organism, nor perform the functions it did in the common ancestor.

Homozygous
Refers to an individual with two identical alleles of the same gene

Hypothesis
A proposed explanation for an observation.

Independent assortment
Mendelian principle in which alleles at different loci tend to assort into gametes independently.

Inheritance
The transmission, from parents to offspring, of structural and functional traits that have a genetic basis.

Interspecific competition
Competition among members of different species.

Intraspecific competition
Competition among members of the same species.

Intuition
A quick and ready insight, akin to “common sense.”

Larva
Stage in the development of many animals (eg, insects, amphibians), occurring after birth or hatching and before the adult form is reached. These immature, active forms are structurally different from the adults and are usually adapted to a different environment.

Meiosis
A two-stage type of cell division in sexually reproducing organisms. In meiosis, a diploid cell divides to produce four haploid cells, each with half the original chromosome content.

Metabolism
The complete set of chemical reactions that occur in living cells, allowing cells to grow and reproduce, maintain their structures, and respond to their environments.

Mitochondria
Membrane-enclosed organelle in most eukaryotic cells; they generate adenosine triphosphate (ATP), used as a source of chemical energy.

Mitosis
The process of nuclear division in eukaryotes. Mitosis occurs as the first step in cell division, so each resulting daughter cell has a full complement of chromosomes.

Molecular Biology
The branch of biology that studies the structure and activity of molecules essential to life, in particular the biochemistry of DNA.

Monera
The kingdom of unicellular prokaryotes (bacteria and cyanobacteria) characterized by the lack of a nuclear membrane enclosing the DNA.

Monogamy
Mating system in which females and males form exclusive mating pairs, either for one mating season or for life.

Morphology
The form and structure of an organism.

Mutation
A change to the base pair sequence of genetic material (either DNA or RNA).

Niche
The functional role of organism in the biotic environment and its relations to food and enemies.

Nocturnal
Active at night.

Notochord
A flexible rod that extends most of the length of the body. Lying ventral (away from the back) to the central nervous system, it stiffens the body and acts as support during locomotion. In lower vertebrates, it persists throughout life, while in higher vertebrates it is replaced by the vertebral column as the embryo develops.

Nucleic acid
Class of biochemical compounds which includes DNA and RNA.

Nucleotide
The basic structural unit of nucleic acids (DNA or RNA). It contains a sugar, a phosphate group, and an organic base. ATP is a nucleotide.

Nucleus
Membrane-bound organelle in eukaryotic cells, which contains DNA in the form of chromosomes.

Organic
Pertaining to compounds containing carbon.

Paleontology
The study of prehistoric life forms on Earth through the examination of fossils.

Parthenogenesis
An asexual form of reproduction found in females where growth and development of an embryo or seed occurs without fertilization by males.

Phenotype
The outward expression (physical, behavioral or physiological traits) of a genotype.

Photosynthesis
The process by which plants, algae and some bacteria absorb light energy and use it to synthesize carbohydrates.

Phylogeny
The evolutionary history of a taxonomic group.

Phylogenetic tree
A diagram illustrating the evolutionary relationships among species with common ancestry.

Plankton
Any drifting organism that inhabits the open waters of oceans, seas, or bodies of fresh water.

Polyandry
Mating system in which females mate with multiple males.

Polygyny
Mating system in which males mate with multiple females.

Polyploidy
The condition of having more than two homologous sets of chromosomes in each cell.

Population biology
The study of populations of organisms, especially in terms of demography (life history, birth and death rates).

Population
A group of (potentially) interbreeding individuals of the same species that occupy a given place at a given time

Predator
Organism which hunts and eats other organisms.

Producer
Organism that synthesizes its own food, rather than consuming the tissues of other organisms.

Prokaryote
“Before the nucleus,” the term applies to single-celled organisms, such as bacteria, without a nucleus segregating the DNA from the rest of the cell.

Protein
Biochemical molecules constructed from amino acids. Proteins may be structural, such as those that make up hair and cartilage, or they may be reactive, such as enzymes.

Protista
The kingdom of eukaryotic unicellular organisms. It includes the protozoa (e.g. parameciums and amoebas), unicellular eukaryotic algae and some special forms of fungi.

Pseudogenes
Genes that have lost their protein-coding ability or are otherwise no longer expressed.

Recessive allele
Allele expressed only when the same allele is present on both homologous chromosomes.

Recombination
The re-arrangement of genes that results in a new combination of chromosomes that is capable of creating a unique gamete.

Reproductive success
The relative production of fertile offspring by an individual or a colony.

Reproductive isolation
The inability of two or more populations to interbreed and exchange genes.

RNA
Ribonucleic acid. Any of various single-stranded polynucleotides that plays a role in transferring information from DNA to the protein-forming system of the cell and in controlling certain chemical processes in the cell; RNA is the genetic material of some viruses.

Rubisco
Protein which fixes carbon in photosynthetic organisms. Rubisco is the most common protein on earth.

Ruminant
An Artiodactyl (hoofed mammal with an even number of toes) that digests its food in two steps, first by eating the raw material, then regurgitating and chewing a semi-digested form known as cud, which is then re-swallowed and digested.

Secondary sexual characters
Traits which are found in one gender only but are not directly connected to the act of reproduction, such as antlers, lion's manes, or a peacock's tail.

Segregation
Mendelian principle in which alleles at one locus separate into different gametes; see Independent Assortment.

Self-fertilization
Fusion of male and female gametes (sex cells) produced by the same individual. Self-fertilization occurs in most flowering plants, numerous protozoans, and many invertebrates.

Skepticism
The method of suspended judgment, systematic doubt, or criticism.

Stasis
A period of little or no discernible evolutionary change in a lineage.

Stigma
The terminal portion of a flower's female reproductive structure (carpel), that is fitted to receive pollen

Stomates
Small openings (primarily) on the underside of leaves. Their function is to allow CO2 into the leaf and the waste products of photosynthesis out, and to regulate passage of water vapor out of the leaf.

Survivorship
The likelihood of surviving to the next round of reproduction.

Symbiosis
“The living together of unlike organisms.” A relationship between individuals of different species which improves the fitness of at least one of them; includes mutualism (both organisms benefit, they rely on each other for survival), parasitism (one organism benefits at its host's expense) and commensalism (one partner benefits and the other neither benefits nor is harmed)

Systematics
The study of phylogenies and the evolutionary relationships among living things.

Taxon
Any unit used in the science of biological classification, or taxonomy. (plural taxa).

Taxonomy
The science of naming and classifying organisms.

Theory
A testable explanation of a broad range of related phenomena; a body of interconnected statements that explains a variety of observations.

Trophic level
The feeding level or position that an organism occupies in a food chain, based on origination and flow of energy through that chain.

Vestigial
Something that is a vestige (remnant) of a primitive, homologous structure, which has lost all or most of its original function.

Zygote
The product of gamete fusion. In organisms with a haploid life cycle, the zygote immediately undergoes meiosis, but in organisms with a multicellular diploid stage, the zygote is merely the first stage in the diploid portion of the life cycle.