Test (biology)

Biologists call test the hard shell of some sphaerical marine animals, notably sea urchins and microorganisms such as testate foraminiferans, and sometimes radiolarians and testate amoebae.

Origin of the word

In an anatomical context, the word "test" is not linked to the empirical definition of "Test (assessment)" : the first one comes from the latin "testa" (which means a rounded bowl, amphora or bottle), and the latter one from "testis", related to the idea of testimony.

The anatomical "test" is hence comprised in the same etymological field as "testicle", which also refers to the idea of a small, rounded bottle. It also gave the word for "head" in most roman languages (French tête, Italian testa...).

Structure

The test is a skeletal structure, made of hard material such as calcium carbonate, silica, chitin or composite materials. As such, it allows the protection of the internal organs and the attachment of soft flesh.

In sea urchins

The test of sea urchins is made of calcium carbonate, strengthened by a framework of calcite monocristals, in a characteristic "stereomic" structure. These two ingredients provide sea urchins with a great solidity and a moderate weight, as well as the capacity to regenerate the mesh from the cuticle. According to a 2012 study, the skelettal structures of sea urchins consist in "92% of bricks of calcite monocristals (conferring solidity and hardness) and 8 % of a "mortar" of amorphous lime (allowing flexibility and lightness). This lime is constituted itself of 99,9 % of calcium carbonate, with 0,1 % only of structure proteins, which make sea urchins animals with an extremely mineralized skeleton (which also explains their excellent conservation as fossiles).

Test

Test, TEST or Tester may refer to:

Science and technology

People

Biology

Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, evolution, distribution, and taxonomy. Modern biology is a vast and eclectic field, composed of many branches and subdisciplines. However, despite the broad scope of biology, there are certain general and unifying concepts within it that govern all study and research, consolidating it into single, coherent fields. In general, biology recognizes the cell as the basic unit of life, genes as the basic unit of heredity, and evolution as the engine that propels the synthesis and creation of new species. It is also understood today that all organisms survive by consuming and transforming energy and by regulating their internal environment to maintain a stable and vital condition.

Subdisciplines of biology are defined by the scale at which organisms are studied, the kinds of organisms studied, and the methods used to study them: biochemistry examines the rudimentary chemistry of life; molecular biology studies the complex interactions among biological molecules; botany studies the biology of plants; cellular biology examines the basic building-block of all life, the cell; physiology examines the physical and chemical functions of tissues, organs, and organ systems of an organism; evolutionary biology examines the processes that produced the diversity of life; and ecology examines how organisms interact in their environment.