Determination
The progressive restriction of developmental potential, causing the possible fate of each cell
to become more limited as the embryo develops.
Detritus
Dead organic matter.
Detritivores
Organisms that live on dead and discarded organic matter; include large scavengers, smaller
animals such as earthworms and some insects, as well as decomposers (fungi and bacteria).
Deuterostome
One of two distinct evolutionary lines of coelomates, consisting of the echinoderms and
chordates and characterized by radial, indeterminate cleavage, enterocoelous formation of
the coelom, and development of the anus from the blastopore.
Development
The progressive production of the phenotypic characteristics of a multicellular organism,
beginning with the fertilization of an egg.
Diadelphous
Having the filaments of a flower united into two groups
Diakinesis
In cell division the stage of first meiotic prophase, in which the nucleolus and nuclear
envelope disappear and the spindle fibers form.
Diaphragm
A sheet of muscle that forms the bottom wall of the thoracic cavity in mammals; active in
ventilating the lungs.
Diastole
The stage of the heart cycle in which the heart muscle is relaxed, allowing the chambers to
fill with blood.
Diatoms
Any of numerous microscopic, unicellular, marine or freshwater algae of the phylum
Chrysophyta, having cell walls containing silica.
Diastolic pressure
The pressure in an artery during the ventricular relaxation phase of the heart cycle.
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