Glossary | D

Dead reckoning
the process of estimating one's current position based on a previously determined position, or fix, and advancing that position based on known speed, elapsed time, and course.
Debilitate
to weaken, deprive of strength
Decimate
organism such as a fungus or bacterium that causes decay of dead plants and animals
Decomposer
organism such as a fungus or bacterium that causes decay of dead plants and animals
Delayed implantation
fertilized egg remains free in the uterus prior to attachment to the uterine wall and placental formation
Demersal
living on or just above the bottom of a body of water
Dentin
a hard and bone-like tissue that forms most of the tooth
Dentin
a hard and bone-like tissue that forms most of the tooth
Deposit feeder
animal that feeds by consuming debris (detritus) on or in the seafloor
Dermal denticles
tooth like scales embedded in the skin (dermis of elasmobranches (sharks, rays, skates); placoid scales
Detritus
particles of organic and inorganic debris from decaying plants and animals
Diatom
flowering plant with two seed leaves
Dicot
flowering plant with two seed leaves
Dimorphism
biological differences between two or more types; having two different distinct forms in the same species, as in sexual dimorphism, where males and females have different characteristics
Dioecious
plants that have only male or only female flowers on individual plants
Disruptive coloration
type of camouflage where color patterns break up or disrupt body form to make an animal unrecognizable to predators or prey
Diurnal
occurring or active during the day
Diurnal tide
tide that has only one high and low tide instead of two in each tidal day of 24 hrs 50 min.
Diversity
richness of an area in relation to numbers of different types of organisms or groups of organisms in an area or zone
Dormancy
period of inactivity brought about by colder temperatures, where breathing and circulation slow slightly
Dorsal
pertaining to the back or upper surface
Downwelling
sinking of water or water masses below the surface
Drift algae
pieces of seaweed that break free of their attachment and drift