DATA: Information gathered during an experiment. It is sometimes called experimental results.
DECOMPOSERS: Organisms, such as fungi or bacteria, that break down and absorb nutrients from dead organisms.
DENSITY: The amount of matter (stuff) in a given volume (space). Density is equal to mass divided by volume.
DENSITY-DEPENDENT FACTOR: Limiting factors such as disease, parasites, or food availability that affect growth of a population.
DENSITY-INDEPENDENT FACTOR: Limiting factors such as temperature, storms, floods, drought, or habitat disruption that affects all populations, regardless of their density.
DEOXYRIBONUCLEIC ACID: See DNA.
DEOXYRIBOSE: The sugar (carbohydrate) found in DNA.
DEPENDENT VARIABLE: The thing that is being measured; it depends on the independent variable; the effect
DIFFUSION: A form of passive transport that moves substances from a high concentration to a low concentration. This does not require energy!
DIPLOID (2N): The total number of chromosomes in a cell. Most diploid cells are somatic cells created during a process called mitosis.
DISINFECTANT: Something that helps kill bacteria and other microorganisms. Chlorine or UV rays are examples of disinfectants that are used in water treatment.
DISSOLVED OXYGEN: The amount of oxygen present in a liquid.
DIVERGENT EVOLUTION: Evolution in which species that once were similar to an ancestral species diverge; occurs when populations change as they adapt to different environmental conditions; eventually resulting in a new species.
DNA (DEOXYRIBONUCLEIC ACID): DNA is a nucleic acid that is composed of nucleotides. DNA contains four types of nitrogen bases called adenine, thymine, guanine and cytosine. DNA contains a sugar called deoxyribose. DNA is the molecule that codes for proteins in all living things.
DNA REPLICATION: See replication
DOMINANT ALLELE: Dominant alleles are always represented by a capital letter. Dominant alleles are stronger than recessive alleles, and are always expressed when paired with a recessive allele.
DOWNS SYNDROME (TRISOMY 21): A genetic disorder caused by an extra chromosome on the 21st pair.
DOUBLE HELIX: Shape of a DNA molecule formed when two twisted DNA strands are coiled into a spring-like structure and held together by hydrogen bonds between the bases.
DYNAMIC EQUILIBRIUM: Result of diffusion where there is continuous movement of particles but no overall change in concentration.