Category: Biology Dictionary D

Diatom Definition Diatoms (pictured below) are a common type of unicellular phytoplankton that likely originated around the Jurassic period. Diatoms can form colonies characterized by particular shapes (e.g., stars, fans, and ribbons) and are encapsulated by a unique cell wall composed of silica, termed a frustule. The frustules of various diatom species are highly diverse […]

Diastole Definition Diastole is a phase in the cardiac cycle, during which the heart relaxes and allows blood to refill each atrium and each ventricle. Diastole is the longer of the two phases, and the contraction of the muscles in the heart happens rather quickly. The longer diastole phase is necessary to allow blood to return to the […]

Deuterostome Definition The Deuterostomes are a clade of animals that undergo deuterostomy during their embryonic development. They are a sister-clade of the Protostomes, and the two together with the Xenacoelomorpha form the major group of animals called the Bilateria—a major group animals which display bilateral symmetry and are mostly triploblastic. Deuterostomy During embryonic development, the fused gametes from the male and female—the sperm and the egg—form the zygote. […]

Detritivore Definition A detritivore is a heterotrophic organism, which obtains its nutrition by feeding on detritus. Detritus is the organic matter made up of dead plant and animal material. Detritivores may also obtain nutrition by coprophagy, which is a feeding strategy involving the consumption of feces. Detritivores are often invertebrate insects such as mites, beetles, butterflies and flies; mollusks […]

Desmosomes Definition Desmosomes are a type of anchoring junction in animal tissues that connect adjacent cells. Anchoring junctions are button-like spots found all around cells that bind adjacent cells together. Desmosomes have intermediate filaments in the cells underneath that help anchor the junction, while the other type of anchoring junction, an adherens junction, is anchored […]

Deoxyribose Definition Deoxyribose is the five-carbon sugar molecule that helps form the phosphate backbone of DNA molecules. DNA, or deoxyribonucleic acid is a polymer formed of many nucleic acids. Each nucleic acid is composed of a deoxyribose molecule bound to both a phosphate group and either a purine or a pyrimidine. Purines have two carbon and nitrogen rings, while pyrimidines […]

Density Independent Factors Definition Density independent factors, in ecology, refer to any influences on a population’s birth or death rates, regardless of the population density. Density independent factors are typically a physical factor of the environment, unrelated to the size of the population in question. Density independent factors vary depending on the population, but always […]

Density Dependent Factors Definition Density dependent factors affect a population through increasing or decreasing birth and death rates, in a way that is directly related to the density of the population. Unlike density independent factors, which are not tied to the population density, density dependent factors change how they affect the population as the population changes […]

Dendrite Definition Dendrites are projections of a neuron (nerve cell) that receive signals (information) from other neurons. The transfer of information from one neuron to another is achieved through chemical signals and electric impulses, that is, electrochemical signals. The information transfer is usually received at the dendrites through chemical signals, then it travels to the […]

Denature Definition Denaturing a biological molecule refers to the loss of its three-dimensional (3-D) structure. Since molecules like proteins and DNA depend on their structure to accomplish their function, denaturation is accompanied by a loss of function. However, denaturation has no impact on the amino acid sequence of the protein itself. Structure of Proteins The […]