An aspect of biology which deals with the inter-relationship between biotic and a biotic component as well as the relationships among the individuals of the biotic component is called ecology.
Organisms form interacting systems or communities, these communities are coupled to their environments by transfer of matter and energy and so the communities and environment are interrelated.
A functional system formed by communities and their environment is called ecosystem. Thus ecology is a science of ecosystems or totality of reciprocal interactions between living organisms and their physical surroundings. (Clark, M.E. 1973).
The things of the world are classified into two major groups namely the living or biotic component and the non-living or a biotic component. The biotic component includes all types of living organisms, both plants and animals and the biotic component includes the non-living materials (soil, water, air, etc.) and the forces of nature (light, gravity and molecular energy). The living organisms exist in an environmental setting of which they are a part. Every aspect of life is influenced by the environment and the activities of organisms affect their environment.
Although the origin of the term Ecology is still uncertain, there is a general agreement that modem term Ecology is derived from “Oekologie”. The word ‘ecology’ (oekologie), first proposed by Earnst Haeckel (1869), a German Biologist, is derived from Greek words, oikos meaning the dwelling place or home and logos meaning the discourse or study; thus, the word ecology literally means the study of living organisms, both plants and animals in their natural habitats or homes.
It can also be defined as the study of life in relation to environment; the environment being the aggregate of all external conditions and influences which affect the life and development of organisms at a given spot. Recently, Eudgene Odum (1963) has defined ecology as the study of the structure and the function of nature. According to Charles J. Krebs (1972), Ecology is the scientific study of interactions that determine the distribution and abundance of organisms. Smith R.L. (1972) in his book Elements of Ecology and Field Biology has defined ecology as multidisciplinary science which deals with organisms and their environment, both biotic and abiotic.
The aggregate of all things; physical, chemical and biological and the influences which affect the life and development of organisms is called environment. This branch of science that seeks to determine the effects of environmental factors on the growth, distribution and migration of the organisms and also deals with some other aspects of relationship between organisms and those factors is called Environmental Science.
The concept of environment is as old as human civilization. Early people considered science of nature as Natural Philosophy. Now environmental science has emerged as interdisciplinary subject comprising Biosciences, Physics, Chemistry, Geology, Geography and Social Sciences.
Ecology, like biology, has been subdivided into plant ecology and animal ecology. Plant ecology deals with the relationship between plants and their environments and animal ecology is concerned with the study of relationship between animals and their environments. Ethology is the term now generally used by biologists to denote the scientific study of animal behaviour with special reference to the behaviour of animal in its normal environment.
In recent years there has grown an idea that in biological organisation the plants and animals are closely interdependent and they react with one another in many ways and at a particular place plants and animals share the same set of conditions and same environment. Therefore, these two subdivisions, plant ecology and animal ecology should be unified. In view of this reasonable fact, the authors of modem ecology have accounted for the study of both plants and animals in the environment.
Ecology and its divisions:
Ecology may be divided into autecology and synecology:
Autecology is concerned with the study of individual animal or plant species or its population throughout its life history in relation to the habitat in which it grows. In other words, it is a study of inter-relationship between individual species or its population and its environment.
The other area of ecology which deals with systems of many species—whole communities or major fractions of communities and ecosystems is termed Synecology in English speaking countries, or biocenology or bio-sociology by many Europeans. (Whittaker, R.H. 1970). It is concerned with the structure, nature, development and causes of distribution of communities. To understand the ecology of plant communities, the ecological life cycles (autecology) of at least most important plant species of the communities must first be studied. Thus, autecology forms a basis for synecology.
The study of plant community structure is called phytosociology or plant sociology. The study of plant ecology merges with plant geography or phytogeography. This is a science which deals with the distribution of plants on or near the surface of earth and water and it also deals with the migration of species.
Actually speaking there is no sharp line of distinction between plant ecology and plant geography. W.B. Turrill comments that plant ecology is intensive while plant geography is extensive in outlook, but both are concerned with plants and in attempting to correlate observed structure and behaviour of plants with causes, both refer to the same sum total of environmental factors though the emphasis varies.
Different fields of ecology:
Ecology involves study of organismal reactions i.e., movement, morphological adaptations, behaviour patterns, physiological activities, growth and reproductive behaviour, social and economic structure, life expectancy of the organisms in their natural habitats or under domestication. The integrated approach of such studies provides proper insight for a better management of natural resources for the benefit of man. Ecological studies are either organism based or habitat based and are conducted at various levels.
Different branches which are made to account for the various specific and detailed aspects of ecology are as follows:
I. Organism level:
Ecology of species and individual
2. Population ecology:
Study of population
3. Community ecology:
II. Habitat or Ecosm or Ecosystem level:
A. Terrestrial Ecosystems.
1. Forest ecology
2. Grassland ecology
3. Desert ecology
4. Wetland or Marsh ecology
B. Aquatic Ecosystems.
1. Marine ecology
2. Lagoon ecology
3. Estuarian ecology
4. Fresh water ecology or Limnology
(i) Lotic waters (running water bodies e.g., rivers and streams)
(ii) Lentic waters (standing water bodies like lakes and ponds)
III. Applied Ecology:
It deals with the applied aspects of ecology, i.e., application of ecological concepts in human welfare including conservation of natural resources, forestry, wild life management etc.
It includes the following:
1. Agricultural ecology:
Agricultural ecology or crop ecology.
It is concerned with the organisms and geological environments of the past Paleontology and radioactive dating have helped significantly in the study of Paleoecology.
It deals with the cytological details of the species or populations in relation to different environmental conditions.
4. System ecology:
It deals with the structure and working of ecological systems in relation to space and time and also with the analysis of components of ecosystem using applied mathematics, bioinformatics and statistics. In this, special emphasis is laid on the reciprocal relationship between living and non-living systems.
5. Conservation ecology or Resource ecology:
It is concerned with the proper management of plant animal, soil, water and mineral resources for human welfare.
6. Ecological energetic and Production ecology:
These modem branches of ecology are still in developing stage. These deal with the mechanisms and quantity of energy conversion and flow of energy through organisms. Energy production processes, rate of increase in organic weights of organisms in relation to space and time are also discussed in this branch of ecology.
7. Landscape ecology.
8. Radiation ecology.
10. Gene ecology.
Plant ecology and other branches of science:
Ecology is a synthetic branch of biological science which draws source materials from many other sciences. It is fundamentally related to morphology, taxonomy, physiology, biochemist, cytology genetics etc. Various other sciences, such as physics, chemistry, geology, geography, meteorology, climatology, hydrology, paleontology.
Anthropology, sociology, mathematics statistics are also being increasingly used in the study of ecological problems. Application of radioactive isotopes, use of many modem and advanced instruments like spectrometer, infrared gas analyzer, flame photometer, computers in the analysis of data, calorimeters, phytotrons for culturing the plants in environment controlled chambers and many other equipment’s are common in ecological researches. Besides botany, zoology, chemistry and physics, the knowledge of climatology, geography, pedology and geology is also essential in the study of complicated problems of plant ecology.
Application of plant ecology:
The study of plants in their environment has yielded a large body of knowledge which provides aids to the science of conservation of natural resources. The knowledge of ecology IS of great help in controlling soil erosion, reforestation, restoration of wild animals as well as grassland vegetation and flood control. Plant ecology is directly related to silvics and silviculture and other branches of forest biology.
In British Commonwealth Forestry Terminology (1953) silvics has been defined as the study of general characteristics and life history of forest trees and crops with particular reference to environmental factors as the basis for practice of silviculture while the silviculture has been defined as the art and science of culturing forest trees and crops. Every farmer or gardener is ecologist, since by such practices as cultivation, irrigation artificial pollination and spraying, he affects the plant behaviour.
Knowledge of ecology is being applied in agriculture, food production and horticulture. The soil conservation practices are in use these days in agronomy. The modem ecology revolves round the biological production processes and ecological energetic. The International Biological Programme (IBP) was launched since July 1, 1967 to study the biological basis of organic productivity and conservation of natural resources in relation to human welfare.
Launching of this programme has given impetus to the ecologists all over the world and over 70 nations including India have participated in the IBP at either national or international level. The future of ecology and indeed of biology is likely to be changed by some international programmes such as ‘Man and Biosphere’ (MAB).
The history of ecology in India is not very different from that of any other country in the world. Indeed, it has been much influenced by western school which provided the leadership Publications of botanical explorations by Dudgeon (1920), Saxton (1922), Bor (1942), Osmaston (1926) and Champion (1936) provided enough opportunity for ecological investigation in India Professor F.R. Bharucha, a student of Braun-Blanquet, established the first school of ecology at Bombay.
This school contributed a great deal of information’s on the biological spectra of different regions of India and on the phytosociology of grass and forest vegetation. The second school of ecology developed under the leadership of Professor R. Mishra first in Sagar and later at Varanasi At present, many secondary schools of ecology have emerged at Ujjain, Ahmedabad, Pilani Jodhpur, Pondicherry, etc. and ecologists in these centres are engaged in different fields of study.