Definition of EcologyVery often a word has a precise well-defined meaning in scientific literature but is loosely used in everyday language. It is, therefore, necessary for you to be clear about a few concepts and definitions before we begin the study of ecology.
Ecology is a familiar term today. Although ecological studies have been going on for many - years. however, it is only recently that people have become aware of ecology as a part of their daily life. These days newspapers and magazines provide ample space to highlight the nature and the consequences of man’s impact on nature—deforestation, soil erosion, the : Bhopal gas tragedy, the Chambly disaster, ozone hole, global writing and many other problems. Public outcry about such problems clearly emphasizes the relevance of ecology for our society. Ecology is now a well-developed branch of science having increasing importance to human welfare and survival.
The term ecology was coined oily as late as 1868. It has been derived from two Greek F words namely, ‘Oikos’ meaning home or estate and ‘logos’ meaning study. Literally it means the study of the home or household of nature. Ecology is defined ‘as the scientific study of the relationship of the living organisms with each other and with their environment.’
Ecological studies are aimed to understand the relationships of organisms with their environment. This could be best achieved by extensive field observations and experimental studies to verify the field observations.
History of EcologyThe roots of ecology lie in Natural History,’ which is as old as human civilization itself. As a matter of fact man indulged in ecology in a practical sort of way, though unknowingly, since early history. In primitive societies every individual was required to have intimate knowledge of his environment for survival, i.e., of the forces of nature and of plants and animals around him. Primitive tribes, which were dependent on hunting, fishing and food gathering needed detailed knowledge of their environment to obtain their sustenance. Later, the adoption of settled agricultural life further stressed the need to learn practical ecology for the successful domestication of plants and animals.
Our ancient Indian texts arc full of references to ecological principles. The classical texts of the Vedic period (1500 BC-600 BC) such as the Vedas, the Samhita, the Brahmanas and ‘the Aranyakas-Upanishads contain many references to ecological concepts.
The Indian treatise on medicine, the Caraka’Samhita (lst Century AD-4th Century AD) Charakai.c. ‘ and the surgical text Susruta.Samhita (1st Century AD-4th Century AD), show that people during period had a good understanding of plant and animal ecology. These texts contain classification of animals on the basis of habit and habitat, land in terms of nature of soil, climate and vegetation; and description of plants typical to various localities. Caraka Samhita contains information that air, land, water and seasons were indispensable for life and that polluted air and water were injurious for health.
Similar awareness of ecological issues was prevalent in Europe in the 4th Century BC. The early Greek philosophers were well aware of the importance of environmental studies. Hippocrates in his work ‘On Airs, Waters and Places’ stressed the need for ecological background for medical students, as he emphasized the effect of water, air and locality on health and diseases in man. Aristotle classified animals on the basis of habit and habitat.
Theophrastus (370-250 BC) was the first person to introduce ecological approach long ‘before the Terni ecology was coined, 11e studied plant types and forms in relation to altitude, moisture and light exposure.
After a gap of several centuries European naturalists made significant contribution to ecological thinking. The French Naturalist Georges Buffon (1707-1788) in his book Natural History (1756) made a serious attempt to systematize the knowledge concerning the relation of animals to environment.
In the early eighteenth century Anton-van Leeuwenhoek (1632-1723), the microscopic, pioneered the study of food chain and population regulation which have grown into the major areas of modem ecology.
It was Hanns Reiter who in 1868 appears to hav6 coined the term ‘ecology’ by combining the two Greek words Oikos (home) and Logos (study). However it was the German biologist Ernst Haeckel (1866-1870) who for the first time elaborated the definition of ecology as follows;
“By ecology we mean the body of knowledge concerning the economy of nature — the investigations of the total relations of animal both to its inorganic and to its organic environment including above all, its friendly and inimical relation with ‘ those animals and plants with which it comes directly or indirectly into contact — in a word, ecology is the study of all the complex interrelations referred to by Darwin as the conditions of the struggle for existence.”
A few years earlier to Haeckel, the French zoologist Isodore Geoffrey St. Hillarie and the English naturalist St George Jackson Mivart had proposed the terms “ethology” and “hexicology” respectively, which are almost similar to ‘ecology’. A British zoologist Charles Eton (1927) in his pioneering book “Animal Ecology’ defined ecology as scientific natural history.
The concept of community in ecology was applied by Karl ‘Mobius (1877) to animal Whereas Forbes (1887), Waning (1909), Cowles (1899), Clements (1916) and many others made notable contributions to the study of plant and animal communities. The concept of ‘population’ and its several related aspects developed in the early part of the twentieth century. Mathematical techniques were used for understanding community ecology. These mathematical and statistical methods have since been applied for an understanding of population dynamics.
In 1935 a distinguished British botanist, Sir Arthur Tansley introduced the concept of the ecosystem or ecological system. This was a major development in the history of ecology. The concept of ecosystem along with the ideas on the trophic-dynamic aspect of community developed by Lindeman (1942), and biogeocoenoses by Sukachev (1944) stimulated investigations on the organism — environment complex from a holocoenotic standpoint and led to a major breakthrough in the progress of ecology. Recently, an American ecologist Eugene P Odum (1971) has defined ‘ecology as the study of the structure and function of nature’.
In India, ecological studies began as elsewhere with the descriptive phase at the end of the. nineteenth century. Descriptive accounts of the forests. Were prepared by the forest officers (1875-1929). However, the first comprehensive ecological contribution was made in 1921 by Prof P. Dudgeon of Allahabad University who described the role of environment in the succession of communities.
By the l940s there was sufficient ecological information of the descriptive and observational kind. There was now a need for precise determination of the behavior and distribution of plants (individually or in groups) in relation to specific environmental factors. This led to the experimental approach (1940-1965). Extensive gynecological studies were carried out on forest and grassland communities and autecological studies on trees, herbs and grasses under the guidance of Prof. R. Mishra, who established a flourishing school of ecology at the Banaras Hindu University, by the l960s. In the early sixties the need for developing a better understanding of the structure and function of different ecosystems was considered necessary for the effective management of natural resources, especially in view of the growing human population.
With This view, the International Biological Programme (IBP) was launched (1964-1974) with a focus on the biological basis of productivity and human welfare. Under the aegis of this programme, productivity of different terrestrial and aquatic ecosystems was evaluated apart from studies on human adaptability, conservation of ecosystem and the use of biological resources.
Much of the recent interest ecology stems from the problems caused by rapid population growth and widespread deterioration of environment due to pollution of air soil and water. Ecological studies are now increasingly geared to promote conservation and rational utilization of natural resources through international efforts such as Man and biosphere programme of UNESCO (MAB), United Nations Conference oh Human Environment held at Stockholm in 1972, United Nations Environment Programme (UNEP), International Union for Conservation of Nature and Natural Resources, (IUCN) and World Wide Fund for Nature (WWF). The science of ecology has much to contribute in solving the problem of environment.
Subdivisions of EcologyEcology was earlier Divided into plant and animal ecology. However, modem ecology doesn’t make any such distinction since plants and animals are intimately interconnected and interdependent amongst themselves and on their environment.
The three main subdivisions of ecology today are given below: i) Autecology, ii) Synecology, iii) Habitat ecology.
- Autecology: It is the study of individual species or individuals in relation to the environment. There are two approaches to autecological studies (a) autecology of .species where individual species are studied (b) population ecology where individuals of the same species are studied.
- Synecology:It is the study of the community of living organisms as a unit. The , difference between autecology and synecology could be explained by the following. example. If a neem tree (or several neem trees)or a crow(or.several crows) are studied in relation to the environment then this would be an autecological study. However, if the Ecobgy and Ecvysten study deals with a forest community as a whole in which many different birds, tree and . animals share the sane area, then it would be called a synecological approach. Synecological studies can be of two types. a) Community ecology is concerned with the study of biotic (living) community comprising of interdependent plants and animals in a particular area, b) ecosystem ecology which is a recent development in ecology. It deals with the community of living organisms and their environment as an integrated unit of nature.
- Habitat ecology : It is the study of the habitat or environment of organisms and its effect on the organisms. In this approach different types of habitats such as terrestrial, fresh water, marine, and estuarine are the focus of study.
Relationship of Ecology with Other Disciplines of BiologyIn order to understand the scope and relevance of ecology let us consider its position in relation to other biological disciplines, with the help of a diagram in the shape of a cake see This hypothetical biological cake has several horizontal layers representing the ‘basic’ divisions of biology, common to all organisms — morphology, physiology, genetics, ecology, evolution, molecular biology, developmental biology etc. These horizontal layers are divided vertically into unequal ‘taxonomic slices’ of biology as well, Each such slice is labelled by the specific kinds of organism. The thicker slices represent large divisions of ‘biology and are labelled Zoology, Botany, Bacteriology etc. The thinner slices are labelled a Phycology, Ornithology, Protozoology as they deal with specific type of organisms.
Let us consider slice ‘A’, i.e. ornithology — the ‘study of birds. This slice with its horizontal layers of molecular biology, developmental biology, genetics, ecology etc. indicates that there are different approaches to the study of birds. The approach may be molecular or ‘ ecological, or of any other type, or a combination of two or more approaches. The ‘biological cake’ analogy helps us appreciate their ecology is a basic division of biology.
It is often important to restrict work to certain taxonomic species or groups because different kinds of organisms require different methods of study. For example, one cannot study pigeons and bacteria using the same methods. However, the modern ecological principles have provided many unifying concepts such as energy flow, nutrient cycling and population dynamics for comparing diverse ecosystems .