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The Collaborative International Dictionary

Unicellular \U`ni*cel"lu*lar\, a. [Uni- + cellular.] Having, or consisting of, but a single cell; as, a unicellular organism.

Douglas Harper's Etymology Dictionary

1858; see uni- + cellular.


a. (context biology English) Describing any microorganism that has a single cell n. A single-celled organism; a unicell.


adj. having or consisting of a single cell

Usage examples of "unicellular".

In the multicellular organisms the organs of the body are made up of cells, and the different organs are produced by a differentiation of cells, but in the unicellular organisms the organs are the results of the differentiation of the parts of a single cell.

Among unicellular animals are some which are large enough for direct manipulation, and it is found that if these cells are cut into pieces the different pieces will behave very differently in accordance with whether or not they have within them a piece of the nucleus.

This has long been believed, but has now been clearly demonstrated by the experiments of cutting into fragments the cell bodies of unicellular animals.

Whether we consider the plant that multiplies by buds or the unicellular animal that simply divides into two equal parts, or the larger animal that multiplies by eggs, we find that in all cases the fundamental feature of the process is division.

In the simplest case, that of the unicellular animals, the cell divides, giving rise to two animals, each of which divides again, producing four, and these again, giving eight, etc.

If two similar unicellular organisms are placed under different conditions they become unlike, since their unstable protoplasm is directly affected by the surrounding conditions.

Among some of the lowest forms of unicellular organisms it is not known, but in most others some form of such union is universal.

They were developments of the original unicellular amoeba, quite large and with a highly-organized nervous system, but still amoeba, with pseudopodia, reproducing by binary fission, and in the main offensive to Terran settlers.

From the unicellular creatures will come sea-beings with vertebrae, then amphibiae, and true reptiles.

Those who examine the main facts of animal and vegetable organisation without bias will, no doubt, ere long conclude that all animals and vegetables are derived ultimately from unicellular organisms, but they will not less readily perceive that the evolution of species without the concomitance and direction of mind and effort is as inconceivable as is the independent creation of every individual species.

Those who accept evolution insist on unbroken physical continuity between the earliest known life and ourselves, so that we both are and are not personally identical with the unicellular organism from which we have descended in the course of many millions of years, exactly in the same way as an octogenarian both is and is not personally identical with the microscopic impregnate ovum from which he grew up.

Whether sentient or barely capable of the feeblest unicellular reaction-formation, Trente passed along from his faceted cubicle invisible against the backdrop of the changing stars, unhappiness and misery in proportions too complexly arrived at to be verbalized.

The vegetation which actually oxidized the saturated hydrocarbons of Mesklinite biological waste and gave off free hydrogen was represented by a variety of unicellular species corresponding as nearly as might be expected to terrestrial algae.

Three, on the unicellular level, the biosensor readings showed no evidence of any life with an Earth-type chromosomal structure.

Even unicellular creatures and protozoans have nuclei which act in the same central organizing manner as the brains of higher creatures.