Life history (biology)

“ In my judgment, the answer to these problems must come, if at all, from morphology, treated as the formal expression of the dynamics of organic growth, and from the history of its progress as portrayed by the embryology of the individual and the phylogeny of the race. The answer should tell us whether biology shall serve merely to record the phenomena of life, or whether, within its own sphere, it may reasonably hope to attain in some measure the dignity of prophet and master. ”

“ For example, a casual study of the facts of animal development is well calculated to show that life is not all progress, and that it includes retrogression as well as advance. Physiological history can readily be proved to tend in many cases toward backsliding, instead of reaching forward and upward to higher levels. This latter tendency, beginning now to be better recognized in biology than of late years, can readily be shown to exercise no unimportant influence on the fortunes of animals and plants. ”

“ It is the second and perhaps greater task of the biologist to study the organism from the historical point of view, considering it as the product of a continuous process of evolution that has been in operation since life began. ”

“ Stated concretely in regard to living creatures, the general doctrine of organic evolution suggests, as we all know, that the plants and animals now around us—with all their fascinating complexities of structure and function, of life-history, behaviour, and inter-relations—are the natural and necessary results of long processes of growth and change, of elimination and survival, operative throughout practically countless ages ”

“ Before starting, however, I ask the reader to bear in mind one consideration, which must reasonably prevent our anticipating that in every case the life-history of an individual organism should present a full recapitulation of the life-history of its ancestral line of species. ”

“ Of the sciences with which the nineteenth century has had much to do, those relating to organic life, classed under the general title of biology, stand prominent, which includes botany and zoology. Subsidiary to these are the sciences of anatomy, physiology, embryology, psychology, anthropology, and several others of minor importance. We have, here laid out before us a very large subject, which has made remarkable progress during the past hundred years, much too great to handle except in brief general terms. ”

“ Having now defined the meaning of the word Biology, and having indicated the general scope of Biological Science, I turn to my second question, which is—Why should we study Biology? Possibly the time may come when that will seem a very odd question. That we, living creatures, should not feel a certain amount of interest in what it is that constitutes our life will eventually, under altered ideas of the fittest objects of human inquiry, appear to be a singular phenomenon ”

“ The study of biology, which is the science of life, has provided an instructive viewpoint that enables us to see ourselves against the vast background built up by investigations into the nature of the earth and its ancient inhabitants. This science deals with living creatures as organisms—plants and animals so organized as to be capable of existence only in an environment which provides exact life requirements. ”

“ These researches have developed the science of physiology, or the laws of bodily action, on many accounts the most modern and extensive of our new acquisitions of natural learning. Through these studies we have come to know something of the laws or principles by which life is handed on from generation to generation, and by which the gradations of structure have been advanced from the simple creatures which appear like bits of animated jelly to the body and mind of man.
The greatest contribution which modern naturalists have made to knowledge concerns the origin of organic species. ”

“ During the immeasurable course of organic history, the many millions of years during which life was developing on our planet, secondary changes of the embryonic forms have taken place in most animals. ”

“ Preceding the forms of life which now exist, our observer would see animals and plants not identical with them, but like them; increasing their differences with their antiquity and, at the same time, becoming simpler and simpler; until, finally, the world of life would present nothing but that undifferentiated protoplasmic matter which, so far as our present knowledge goes, is the common foundation of all vital activity. ”

“ This survival of the fittest, which I have here sought to express in mechanical terms, is that which Mr. Darwin has called "natural selection, or the preservation of favoured races in the struggle for life." ”

“ Before closing the chapter, it will be useful to compare the definition of Life here set forth, with the definition of Evolution set forth in First Principles. Living bodies being bodies which display in the highest degree the structural changes constituting Evolution; and Life being made up of the functional changes accompanying these structural changes; we ought to find a certain harmony between the definitions of Evolution and of Life. ”

“ It is, curiously enough, among the professional biologists that objectors to the notion of biological progress and to its corollary, the distinction of higher and lower forms of life, have chiefly been found. ”

“ But, greater than all, is the difference in our philosophical conception of the teachings of Biology. In 1859 Darwin published his 'Origin of Species,' and from that date modern biology will recognise the commencement of a new period. ”

“ The animal organism is a higher kind of vegetable, whose development begins with those substances with the production of which the life of an ordinary vegetable ends.13 The fact, too, that embryonic man passes through ascending stages undistinguishable from those of lower creatures, is full of meaning. Does it not betoken a preserved epitome of the long history of slowly rising existence? ”

“ Now modern biological science, guided by the splendid genius and ceaseless research of Darwin, and the whole field of biologists, for the past quarter of a century, has been able for all practical purposes to discover and demonstrate a great ‘law’ or method, according to which all the varieties of living ‘species,’ animal and vegetable, have arisen; connecting the remotest ages of the life of the globe with the present flora and fauna in one unbroken continuity, by one unchanging method. The organic history of any individual becomes an analogue of the organic history of the world. ”

“ Perhaps some of the most impressive lessons on this subject will be found in connection with the history of the discovery of this great Law of Biogenesis, which says that life can come only from life. ”

“ Our prescribed limits only permit of briefly calling attention to some of the conclusions of Embryology, pointing out the manner in which they confirm the theory of the evolution of life as deduced from the structure and petrified remains of the vegetal and animal kingdoms. ”

“ These are the functions and capacities of living organisms in general, and in particular those of variation and inheritance, of development and self-differentiation. What is, and whence comes this mysterious power of the organism to build itself up from the smallest beginnings, from the germ? And the equally mysterious power of faithfully repeating the type of its ancestors? And, again, of varying and becoming different from its ancestors? Even the “mechanical” theory of selection is forced to presuppose the secret of life. ”

“ Biogenesis, or life generated by life, is the distinctive feature of organic Nature. We are linked to living creatures of higher or lower nature by the power of educating or subduing them, and by all those varying relations involved in the mystery of life.
The distinctive position of man, as an animal placed at the head of the animal world, necessarily creates serious responsibility on the part of the higher towards the lower creature. ”

“ To trace out the progressive development of animal life, from its humblest phases; and to mark, as they become visible in the intermediate grades, the first rudiments of organs and instincts which are destined to attain their maximum in the higher ones, embody but a small portion of what it is the naturalist's mission to investigate. ”

“ Physiology is also the first science in which we recognise the influence of habit—the tendency of something to happen again, merely because it has happened before. From physiology, too, we get our clearest notion of what is meant by development, or evolution. The growth of a plant or animal from the first germ is the typical specimen of a phenomenon which rules through the whole course of the history of man and society—increase of function, through expansion and differentiation of structure by internal forces. ”

“ We should have less right, or perhaps none, if this theory of life were really of a purely “biological” nature, built up entirely from the expert knowledge and data which the biologist alone possesses. ”

“ In the next place, however minute the supposed gradations which you trace backward from a recognizable organism to the primal protoplasmic substance, out of which you suppose it to have been gradually evolved, and through whatever extent of time you imagine these gradations to have been worked out by the operation of the forces of Nature, modifying successive beings, you must find an organism to which you can attribute life. ”

“ It clings to all our conceptions of living things: quite as much, for example, to the evolution of an animal, with all its parts from a one-celled germ, or to the connection of brain-cells with the manifestations of intelligence. ”

“ THE FUNDAMENTAL LAW OF ORGANIC EVOLUTION
The field of natural phenomena into which I would introduce my readers in the following chapters has a quite peculiar place in the broad realm of scientific inquiry. There is no object of investigation that touches man more closely, and the knowledge of which should be more acceptable to him, than his own frame. But among all the various branches of the natural history of mankind, or anthropology, the story of his development by natural means must excite the most lively interest. ”

“ If we contemplate a single specimen of the human race, we find a bodily organism, endowed with life like that of other animals, and acted upon by physical laws throughout the whole period of its existence. ”

“ That the first germs of the animal and plant having been formed in appropriate places and circumstances, the faculties of a beginning life and of an organic movement established, have necessarily gradually developed the organs, and that with time they have diversified them, as also the parts;
“4. That the power of growth in each part of the organized body being inherent in the first created forms of life, it has given rise to different modes of multiplication and of regeneration of individuals ”

“ If the famous suggestion, that all animal and vegetable life results from a single vital germ, and that all the different animals and plants now existent were developed by a natural process of evolution from that germ, were a demonstrated truth, we should still be able to point to the evidence of intelligence displayed in the measured and progressive development, in those exquisite forms so different from what blind chance could produce, and in the manifest adaptation of surrounding circumstances to the living creature, and of the living creature to surrounding circumstances. ”

“ Before passing to a connected story of the gradual emergence of higher and higher forms of life in the course of the successive ages--the procession of life, as it may be called--it will be useful to consider the evolution of animal behaviour.
Evolution of Mind
A human being begins as a microscopic fertilised egg-cell, within which there is condensed the long result of time--Man's inheritance. ”

“ In proof of all these statements concerning the immediate effects of the promulgation of the theory of evolution, we have only to glance at the marvelous development during the past fifty years of anatomy, embryology, histology, cytology and physiology, both human and comparative, and of paleontology, chorology, ethology and taxonomy, both botanical and zoological. ”

“ Can any one conversant with the works of the first of evolutionists, particularly with his First Principles, Principles of Psychology, and Principles of Biology, gainsay the fact that organic evolution implies a tendency in organisms to advance, when under the influence of physical conditions, from the simpler to the more complex? ”

“ Darwin's theory of the descent of man as an animal consists in assigning to him a certain pedigree, which traces his organism through a long series of other animals back to the lowest and crudest form of animal life ”

“ Thus Bionomics is treated in such articles as Evolution, Heredity, Variation, Mendelism, Reproduction, Sex, &c.; Zoo-dynamics under Medicine, Surgery, Physiology, Anatomy, Embryology, and allied articles; Plasmology under Cytology, Protoplasm, &c.; and Philosophical Zoology under numerous headings, Evolution, Biology, &c. ”

“ Construed in terms of evolution, every kind of being is conceived as a product of modifications wrought by insensible gradations on a pre-existing being; and this holds as fully of the supposed commencement of organic life, or a first organism, as of all subsequent developments of organic life. ”

“ Until there had been such systematic descriptions of different kinds of organisms, as made it possible to compare the connexions, and forms, and actions, and modes of origin, of their parts, the Science of Life could make no progress. ”