Biology

Biology, from the Greek bios, life, logos, science, is a modern name for the science of living beings, whether animal or vegetable, expressing in its comprehensiveness the recently-acquired conviction of students of Nature that there is a fundamental unity in the life of plants and animals. Botany and zoology are but subdivisions of this science, and, as it is difficult to distinguish some of the lowest plants from the lowest animals, they are indefinite subdivisions. Modern biology concerns itself less with the detailed classification of plants and animals or with the study of their dead remains than with their life, growth, development, and mutual relations as living beings. We can here only indicate the leading questions or groups of questions which form the subject-matter of the science.

Firstly, in defining the province of biology we have to attempt to explain the nature of life itself, which we do by investigating the general properties of living bodies, and especially those distinguishing them from non-living bodies. Thus, true or active vitality is unknown to us in the absence of a certain extremely complex chemical substance, or rather mixture of substances, containing carbon, hydrogen, oxygen, nitrogen, and traces of sulphur, and known as protoplasm (q.v.). This substance is unknown except in living beings. Protoplasm is during active life constantly decomposing into such simpler substances as carbonic acid, water, and ammonia, which may be excreted by the organism. This decomposition, known as katabolism (q.v.), is, however, accompanied by a power of self-restoration, by the taking in of suitable simple nutritive matters and the building of them up (anabolism) into new protoplasm. This is the chemical aspect of life, and such life can only occur at certain temperatures (varying with the kind of organism) and in the presence of moisture, oxygen, and other food-material. If the anabolism, or building up of protoplasm, does not equal the katabolism, we have death, local or systemic; if it exceeds the katabolism, we have growth. The growth of living beings differs from that of inanimate matter (accretion) in that it almost invariably results in the production of a variety or heterogeneity of structure, which we term organisation, and this organisation is accompanied by a variety of function, or physiological division of labour. Living beings have commonly curved surfaces, which contrast with the plane faces of crystalline minerals. That division of biology that deals with form is termed Morphology (q.v.); that which deals with structure, Anatomy (q.v.); and that which deals with function, Physiology (q.v.). When the growth of a living being has reached a certain stage it may become discontinuous, the separated portion forming a new individual. This is Reproduction (q.v.). All the functions of an organism may be classified as those of nutrition (including alimentation and growth), those of reproduction, and those of relation (including sensation, the senses and motion), which are subsidiary to the others, bringing the living being into relation with its surroundings. The latter, as more distinctive of animals, are sometimes called the animal functions.

Whilst the protoplasm of living beings gives rise to many chemical compounds unknown in inanimate nature, a yet more striking characteristic which it generally exhibits is that of being divided up into more or less distinct minute masses or structural units known as cells (q.v.). Plants differ from animals in having their cells commonly enclosed by a membrane or cell wall of simpler composition. Similar cells may be grouped together into what are termed tissues, and that branch of anatomy which deals with cells and tissues is termed histology (q.v.).

The lowest plants and animals consist of a single cell, or are unicellular, and multiply by simple fission [Schizophyta], and the higher plants and animals all begin their individual existence as a single cell, ovum, or egg-cell. In these latter this cell by division gives rise to more complex structures, certain parts or organs being gradually shaped for the performance of certain functions. Whilst the germs or embryos of large classes of plants or animals resemble one another, as they develop they become more and more unlike, resembling, that is, the members of smaller and smaller sub-classes. This is Von Baer's law that ontogeny, or individual development, recapitulates phylogeny, or the history of the evolution of the race. It is no contradiction of this principle of progressive evolution that we find cases of degeneration (q.v.), parasites, for instance, often losing many organs which their easy mode of life renders superfluous. Thus biology has to deal with embryology (q.v.), and with classification (q.v.) as the tabulated result of phylogeny. This study is facilitated by that of the fossil remains of organisms now extinct, the ancestors of those now living.

Whilst nutrition serves to maintain the life of the individual, and reproduction to provide one or more new individuals to succeed it at its death, the increase thus brought about inevitably leads to dispersal, and organisms have many structures, such as organs of flight, adapted to that end. Thus the struggle for existence has led to the existing geographical distribution of plants and animals.

Biology has also to deal with many complex questions as to the relations of different classes of organisms to one another, such as those of symbiosis, parasitism, protective mimicry, the pollination of flowers by insects, etc., referred to under these various heads.

Lastly we have the great problems of aetiology, or the causes of biological phenomena, such as the origin of living matter, the possibility of spontaneous generation or abiogenesis (q.v.) at the present time, and the origin of the existing specific differences between organisms whether by creation (q.v.) or by descent with variation.

The practical study of biology in this country generally begins with the examination, both anatomical and physiological, of selected types of the great divisions of the animal and vegetable kingdoms, noting their likenesses and unlikenesses.