Natural History and Fauna Exploration:
Natural history has been a primary developmental source of ecology since the time of Aristotle. Some of the important naturalists of late 17th, 18th and 19th centuries who contributed significantly for early growth of modem ecology are following:
Rene Reaumur (1683-1757), a noted French naturalist and physicist wrote a six-volume work entitled Memoires pour server Vhistoire des insects, in which he discussed the life habits and community patterns of social insects. He also investigated the natural history of crustaceans and molluscs.
The first great modern systematic, Carolus Linnaeus (1707-1778) a Swedish professor, physician and naturalist, in his classical work, entitled Systemic Natures, established the binomial system of nomenclature of organisms, furthered the sciences of plant and animal geography, and studied plant associations in different regions.
Georges Louis Leclerc Buffoia (1707-1788), an eminent French naturalist, wrote the forty-four volume Histotre naturally, generate particularly, a vast compendium of most of the natural history knowledge of the day. He considered that animals and plants developed adaptations which enabled them to favorably respond to their environment and termed this environmental induction.
He regarded climate as a variable compelling modification of plants and animals. Buffon explained how the great fertility of every species was counterbalanced by innumerable agents of destruction. In some ways his writings anticipated the evolutionary ideas of Darwin, but were not fully expressed or developed. He definitely opposed Linnaeus’ ideas of the fixity of species, and he amassed considerable evidence demonstrating variation and mutability in living organisms.
Gilbert White (1720-1793), an English naturalist, described the natural history of Southern England in his book “The Natural History of Selbourne.” An American naturalist James J. Audubon (1785- 1851) compiled the volume of “Birds of America.” Louis Agassiz (1807-1873), the Swiss American naturalist, compiled four volumes of Bibliographia Zoological, along with other books on fossil fishes, glacial activity, and naturalistic expeditions to Brazil.
He initiated the researches in marine ecology (oceanography) by establishing many laboratories for marine ecological researches. German naturalist Alexander Von Humboldt (1769-1859), after his extensive travels of tropical and temperate South America, in 1807 discussed the Geographical distribution of plants and animals in relation to climate.
Charles Darwin (1809-1882), a great British naturalist and evolutionist, wrote more than a dozen outstanding books and monographs on a variety of biological topics from 1842, when he published ‘Coral reefs’, to 1881, when he published ‘Action of earthworms on the processes of soil formation’.
His most famous works, of course, were the ‘Origin of Species’ (1859), and the ‘Descent of Man’ (1871), in which he presented his great interpretive theory of natural selection and evolution.
From ecological point of view, he increased our knowledge of island or insular life with their characteristically different types of environmental conditions. Edward Forbes (1815-1854), an English marine biologist, studied the dynamic relations existing between marine organisms and their environment.
Alfred Russell Wallace (1823-1913), a leading British naturalist of nineteenth century, wrote ‘Island life’ and several other leading books on the distribution of plants and animals in the Malay Archipelago.
Henri Fabre (1823-1915), a French naturalist, published ten volumes on the ‘Life of Insects.’ H.W.Bates (1825-1892), an English naturalist, wrote ‘Naturalist on the Amazon’ in 1863 and A. E. Brehm (1829- 1884), a German naturalist, published his thirteen volume compilation ‘Tierleben’ (Animal life) in 1911-1918. In 1838, a German botanist, August Grisebach, studied the plants and animals in the form of integrated communities.
Stephen A. Forbes (1844-1930), an American ecologist, published a series of papers on the concept of ecological communities. In one of his classical paper entitled, ‘The Lake as a Microcosm’.
Forbes suggested that the species assemblage in a lake was an organic complex and that by affecting one species one exerted some influence on the whole assemblage. He concluded that each species maintained a ‘community of interest with the other species and one should not limit his studies to a single species. C. Hart Merriam (1855-1942) devised a classification of major life zones- a system of habitat classification, still in wide use.
Mobius (1877), a German naturalist, investigated oyster banks and introduced the term “biocoenosis” to designate a group of organisms as an ecological unit. J.E.B. Warming, a Danish botanist, emphasized the unity of plant communities in 1895.
Animal ecologist C.C. Adams (1873-1955) in 1906 and 1909 recognized and described many animal communities in his ecological surveys of northern Michigan and Isle Royale in Lake Superior. In 1913, an American animal ecologist V.E. Shelford (1877-1968) presented a classical study of animal communities in temperate America.
In 1927, Charles Elton published an outstanding analysis of community dynamics. F.E. Clements and V.E. Shelford (1939) emphasized the significance of early investigation of J.G. Cooper (1859) that whole community is one biotic unit, rather than one unit of plants and another of animals.
In recent years many workers such as D. Ramon Margalef, Robert MacArthur, and others have analyzed the structure of these biotic communities in respect to such phenomena as species diversity, niches and how they came about through evolution (Kendeigh, 1974).
Environmental Physiology and the Study of Responses to Environmental Changes:
Environmental physiology or physiological ecology had its historical beginnings in the correlation of biological phenomena with variations in temperature stimulated by Galileo’s invention of a hermetically sealed thermometer about 1612 A.D. Rene Reaumur and Georges Buffon were primarily naturalists of the eighteenth century, but they were also interested in the responses of organisms to temperature, light and altitude.
Reaumur summed the mean daily temperatures for April, May, and June in 1734 and again in 1735, and correlated the earlier maturing of fruit and grain during the first year with the greater accumulation of heat.
A discovery of parallel significance was of oxygen in 774 by the English clergyman, Priestley, and the finding by Lavoisier, a Frenchman, in 1777 that oxygen was an essential part of air. The observations of Priestley and Scheele that plants produce oxygen led to an understanding of the inter-relationship of plants arid animals.
The discovery that green plants use carbon dioxide and water to form organic matter for the use of animals and result in the release of oxygen and water as wastes provided the concept of food-chains.
Justus von Liebig (1803-1873) initiated the idea of carbon and nitrogen cycles in nature. He also developed his analysis of limiting-factors (1840). He was interested primarily in physical factors which limit the distribution and abundance of plant and animal life. We recognize his basic contribution today in Liebig’s Law of Minimum, which states that an organism will be limited by that factor most closely approaching its minimum life supporting requirements.
Jacques Quetelet (1796-1874) studied dormancy and hibernation in plants and animals in relation to temperature (1846), and shortly thereafter Alphonse de Candolle (1806-1893) studied plant germination in relation to temperature and moisture (1865). Claude Bernard, a French physiologist, enunciated the principle of homeostasis in 1876.
This concept originally referred to regulatory mechanisms which maintained the “internal environment” of body constant in the phase of changing external conditions. Later the concept came to be applied also to maintenance of community inter-relations. Vant Hoff, a Dutch scientist, contributed to physiological ecology in 1884 in describing how the speed of chemical reactions increased two or three fold with each rise of 10°C.
Two men who gave environmental physiology its greatest advance in the nineteenth century were K.G. Semper (1832-1893) and Charles Davenport (1866-1944). Semper wrote an important ecological treatise in 1881, entitled Animal Life as affected by the Natural conditions of Existence, in which established the ‘principle of food chains’ and what we now ‘pyramid of numbers’.
He was interested in predator-prey interactions, protective colouration, and the spatial relations of animals. He showed that pond snails and fresh-water isopods would he stunted if crowded in a small volume of water, and he postulated the existence of chemical factors passing between animals in the environment and influencing growth and development.
We now recognize these as “exocrine” or environmental hormones, and they represent a major area of current research. Davenport wrote two volumes in 1897 and 1899, entitled Experimental Morphology.
He studied animal behaviour and development in a variety of artificial environments and media, and he analyzed a wide range of environmental responses to chemicals, light, moisture, temperature and gravity.
More recent summaries of know ledge and methods in physiological ecology have been made by V.E. Shelford in Laboratory and Field Ecology, Samuel Brody in Bioenergetics and Growth (1945) and by F.J. Vernberg and W.B.Vernberg in The animal and the Environment (1970). J. L. Clondseley-lfcompson (1956, 1975) worked “extensively on the ecology of terrestrial arthropods such as centipede, scorpions, beetles, etc., of arid environments (deserts) and he specifically studied, effect of high temperature on them.
Evolution and Theories of Natural Selection:
The growth of evolutionary theories of 18th and 19th centuries paved the way to the early development of ecology. Georges Buffon had developed the ideas of evolutionary change in his Histoire in 1749 which stated ‘if we again consider each species in different climates we shall find obvious varieties both as regards size and form, all-are influenced more or less strongly by the climate.
These changes only take place slowly and imperceptibly, the great workman of nature is time: he walks always with even strides, inform and regular, he does nothing by leaps; but by degrees, by gradations, by succession, he does everything; and these changes at first imperceptible, little by little become evident……”
Jean Baptiste de Lamarck (1744—1829) was environmental evolutionist of the 18th and early 19th century. Like Buffon he believed that plants and animals were changed by environmental influence. In his two major books Philosophic Zoologique in 1809, Sans Vertebras in 1815 Lamarck presented his evolutionary ideas—”the use and disuse theory” and “inheritance of acquired characteristics.
He believed, for example, that the giraffe’s neck had become long because he continually stretched higher for leaves to feed on, and thus each generation was born with a slightly longer neck as a result of stretching. Similarly, he believed that blind cave fish lost their eyes because they failed to use them.
Although we can recognize elements of truth in these theories, we now know that Lamarck’s understanding of the mechanism was incorrect. It is well established now That environmental changes affecting only somatic cells of the body are not transmitted to subsequent generations.
However, some environmental changes which affect germ cells, such as radiation or certain chemicals (mutagens) can produce genetic changes that are passed on to later generations. So in this sense, environmental factors can influence subsequent generations.
The evolutionary theories of Charles Darwin and Alfred R. Wallace, which emerged about 40 years after Lamarck, were similarly ecological in emphasis, but radically different in their explanation of how evolution occurred.
They developed their views independently and almost concurrently, placing emphasis on population pressure and struggle for existence as the driving forces of evolutionary change. They envisaged survival of the fittest and natural selection as the mechanism of evolution, working on the foundation of inherited variations in plants and animals.
Population Studies and Demography:
From the sixteenth century onward, a few scholars were worried about population growth and pressures. Machiavelli (1469-1527), Botero (1540-1617), Buffon, and Franklin (1707-1790) all partially anticipated Malthus by expressing concern about population growth, starvation, disease and war. However, Malthus was primarily responsible for focusing controversial attention on these topics.
Thomas Robert Malthus, a professor of history and political economy at Hailey bury College, Reverend, published his controversial book, An essay on population (1798), in which he observed that human populations tend to increase geometrically (I, 2, 4, 8, 16, 32…) and thus exceed the means of subsistence, which increase arithmetically (1, 2, 3. 4, 5, 6, 7…). He felt that unless populations were controlled by voluntary constraint they surpassed their level of support and were then decimated by starvation, disease, war and poverty.
Malthusian theory produced a storm of protest and has remained controversial to modern times. Many scholars believed that Malthus failed to give any cognizance to the great potential of modern science to overcome famine and disease. Some felt it presented too dismal a view of human potential.
Doubleday (1841) contradicted Malthusian idea by stating that whenever a species was threatened, nature made a corresponding effort to preserve it by increasing the fertility of its members. Human populations that were undernourished had the highest fertility; those that were well fed had the lowest fertility.
He explained these effects by the oversupply of mineral nutrients in well-fed populations. Recently, however, Malthusian doctrine has come back into favour, and it is being taken more seriously now than in the 1930’s (Hardin, 1964).
Now- a-days, even many writers who believe in the potential of science and technology to solve the problems of population pressure admit that the Malthusian fears of starvation, war and disease still haunt the earth.
Incidentally, it is an odd quirk ol scientific history that Darwin was favorably influenced by Malthus, and relied heavily on his doctrine to establish his theory of natural selection. Subsequently, Darwin’s theories accepted in scientific circles long before those of Malthus.
Population studies resumed great importance in the twentieth century with the work of Raymond Pearl (1925), Lotka (1925), Volterra (1931), Thomas Park (1933), Charles Elton (1933) Nicholson (1933), Gause (1935), Andrewartha and Birch (1954) and many others.
Pearl analyzed mathematically the characteristics of population growth. Lotka and Voltera developed theoretical mathematical equations to show the manner in which populations of different species interact.
Nicholson (1933) studied the factors that stabilize populations at particular levels. Gause (1935) studied interacting populations of predators and prey. Andrewartha and Birch emphasized the importance of climate and other factors in determining the size of populations.
Ecological Geography and Conservation:
Modern geographic ecology dates back to the generalizations on the worldwide distribution of animals made by Buffon and the explorations of Humboldt. There was lively interest and many important contributions in this general field during the nineteenth century; notably, the life-zone concept of C. Hart Merriam (1890-1910) needs special mention.
During the present century the concept of biotic provinces is identified with L.R. Dice (1943) and the biome concept with F.E. Clements and V.E. Shelford (1939). The broad survey of ecological animal geography made by R. Hesse in 1924 exerted considerable influence.
In 1864, George Perkins Marsh of North America, published a book Man and Nature, or Physical Geography as Modified by Human Action and laid the foundations for ecological geography and conservation Marsh’s basic theme in Man and Nature was that man’s economic progress has often disrupted the balance of nature to his own detriment. He clarified the reciprocal interaction of man and environment.
He traced the history of civilizations, particularly those in the Mediterranean area, in terms of physical geography, natural resources, and land changes induced by man. He first called attention to the striking effects of deforestation and land scarring on erosion, agriculture, and water resources. He thus forced his readers to look upon man in a different perspective- not as a conqueror but as a despoiler.
Another American, John Muir (1838-1914) developed a philosophy of conservation similar to Marsh. He extensively travelled throughout the world, and wrote poetically of the values and beauties of natural wilderness.
Through articles, books, and lectures, he worked effectively for the conservation of lands and forests and was ultimately influential in the designation of 148,000,000 acres, as reserve forests in the United States.
Through his painstaking efforts many national parks such as Yosemite and Sequoia National Parks, Mt. Rainier, King’s Canyon, and Grand Canyon National Parks were established in U.S.A. in 1890. Later on, certain staunch supporters of Marsh and Muir but political man like Gifford Pinchot (1865-1947) and President Theodore Roosevelt (1858-1919) spearheaded the environmental conservation movement in U.S.A.
In regards to other divisions of ecology, the crystallization of studies in oceanography may be credited to Edward Forbes (1843), Maury (1855), Alexander Agassiz(1888), Peterson and his colleagues (1911), and Murray and Hjort (1912); limnology to Forel (1869), Birge (1893), Juday (1896), Ward and Whipple (1918), Thienemann (1913,1935) and Naumann (1918-32) and wildlife management to Aldo Leopold (1933).
Attention to ecological succession though began in 1685, but, in modern context it started only in 1899 when the American plant ecologist Henry Cowels (1869-1938) studied succession of plants on the sand dunes at the South end of Lake Michigan.
In 1916, another American plant ecologist, Frederis E. Clements (1874-1945) worked on plant succession. C. C. Adams (1906, 1909) and V.E. Shelford (1913) were among the first to apply the concept of ecological succession to animals.
In the 1930’s, attention to biological productivity began in connection with practical pond-fish culturing and the immunological studies of Thienemann m Europe and of Birge and Juday at the University of Wisconsin, out the modern crystallization of the Subject came with the freshwater and marine investigations of Lindcman, Hutchinson, Riley at Yale University (1945) and of Eugene and Howard Odum. An early study of energy relation within terrestrial communities is that of Stanchinskv (1931).
Further development of ecology during 20th century has been greatly stimulated by organization of ecologists. The British Ecological Society was founded in 1913 and had a membership of about 2000 in 1974. Following the British, the Ecological Society America was founded in 1915 and in 1974 had a membership of 4700.
The Society in America has given birth to several offspring’s; the Wildlife Society, Society of Limnologists and Oceanographers, the Nature Conservancy, the Animal Behaviour Society, in 1971, the Inter-American Institute of Ecology was established in U.S.A.
The Ecological Society of America publishes three periodicals-Bulletin, Ecology, and Ecological monographs. The British Ecological Society also publishes three periodicals: Journal of Ecology, Journal of Animal Ecology, and Journal of Applied Ecology. Oikos began publication in 1949 to represent ecologists in Denmark, Finland, Iceland, Norway and Sweden.
The International Society for Tropical Ecology, including ecologists of India and adjacent countries, was founded in 1960 and publishes Tropical Ecology. The New Zealand Ecological Society came into existence in 1952 and the Ecological Society of Australia in 1960, and both Societies publish their annual proceedings.
The Japanese Journal of Ecology, begun in 1954, is the official publication of The Ecological Society of Japan. Researches on population Ecology, started in 1959, are published by the Japanese Society of Population Ecology.
In 1968, an International Association for Ecology was formed within the International Union of Biological Sciences to coordinate ecological work in various countries. It started publishing the Intecol Bulletin in 1969.
Research papers of Ecological nature usually also appearing in the following biological journals : Science, Nature, Evolution, Bioscience, Endeavour, Journal of Soil and Water Conservation, Advance Ecological Research, Archivio di Oceanographia Limnologia, Biological Bulletin, Journal of Experimental Botany, Journal of Experimental Zoology, Biological Review, Journal of Wildlife Management, Geographical Review, Marine Biology, Journal of Parasitology, Scientific American, New Biology, Journal of Theoretical Biology, Turtox News, Canadian Journal of Research, Annals of Entomological Society of America, Journal of Morphology, etc.