Ecology: Definition, Scope and History | Biology

In this article we will discuss about:- 1. Definition of Ecology 2. Study of Ecology 3. History 4. Branches 5. Scope.

Definition of Ecology:

Ecology is a Greek word which means the study of the habitation of living organisms (oikos=habitation, logos=discourse). The word ecology has been defined variously by different authors. Some prefer to define it as “scientific natural history” or “the science of community population” or the “the study of biotic communities”.

The most comprehensive definition of ecology will be “a study of animals and plants in their relation to each other and to their environment”.

The word ‘ecology’ was first proposed in the year 1869 by Ernst Haeckel, although many contributions to this subject was done much earlier. However, much later, in the 1900s ecology was recognised as a distinct field of science.

Initially it was rather sharply divided into plant and animal ecology, but later the understanding of the biotic commu­nity concept, the food chain, material cycling concept etc., helped to establish the basic theory for a unified field of general ecology.

Ecology till recently was considered in academic circles to be a branch of biology, which, along with molecular biology, genetics, developmental biology, evolution etc. was by no means always considered as one of the subjects of biological sciences only.

However, presently the emphasis has shifted to the study of environmental systems of the entire ‘household’, which in fact relates to its core meaning. Thus, ecology has grown from a subdivision of biological sciences to a major interdisciplinary science that links together the biological, physical and social sciences.

Study of Ecology:

Ecology is studied with particular re­ference to plants or to animals, hence the topics Plant ecology and Animal ecology. Since plants and animals are intimately interrelated, study of plant ecology or animal ecology alone is bound to be imperfect and inadequate.

So plant and animal ecology are to be given equal emphasis and it is better to study them under the term Bio-ecology. The term Synecology denotes ecological studies at the community level while the term Autecology denotes ecological studies at the species level.

History of Ecology:

In a sense ecology is the new name of ‘Natural history’. Man’s interest in natural history dates back to prehistoric times. The carving and pictures discovered in France and Spain speak on the observation of the cave-dwellers about the fauna and flora around them.

The writings of Romans and Greeks bear evidences of their interest in natural history. ‘The Histories of Ani­mals’ of Aristotle (384-322 B.C.) is a famous contribution in this line.

The first naturalist to give a systemised knowledge about the relation existing bet­ween living organisms and environment was Buffon. In a series of work in 1749, he stressed on habits and adaptations. After this, outstanding advances were made in the study of natural history in the eighteenth and nineteenth centuries.

Darwin’s Natu­ralistic voyage round the world, Wallace’s Island of life and many other work stimu­lated the knowledge of Biology to a great extent. However, the term ecology was first coined by German Biologist, Haeckel in 1878.

The science of ecology after undergoing a several hundreds of years gestation period has emerged today as a matured, honoured and scholarly discipline in biolo­gical science.

Branches of Ecology:

Ecological studies focus on how various organisms interact with their environment. There are a number of fields within ecology, either focusing on specific areas of interest or using particular approaches to address eco­logical problems.

The sub-fields or branches of ecology are:

i. Behavioural Ecology:

It is concerned with explaining the patterns of behaviour in animals.

ii. Physiological Ecology or Eco-Physiology:

It deals with how organisms are adapt­ed to respond to temperature, maintain prop­er water and salt balance, balance levels of oxygen and carbon dioxide, or deals with other factors of their physical environment. Studies of eco-physiology play an important role in agriculture since crop yield is very much dependent on the performance of indi­vidual plants.

It also plays an important role in conservation studies. For example, the decline of migratory bird species focuses on how changes in the environment affect the physiological mechanisms that prepare birds for long-distance migration.

iii. Molecular Ecology:

The use of mole­cular biology to directly tackle ecological problems is the focus of molecular biology.

iv. Evolutionary Ecology:

Evolutio­nary ecology emphasises the impact of evo­lution on current patterns and human induced changes. It relates to how animals choose mates, determine the sex of their off­spring, forage for food and live in groups, or how plants attract pollinators, disperse seeds, or allocate resources between growth and reproduction. Evolutionary ecologists are particularly interested in how form and func­tion adapt organisms to their environment.

v. Ecosystem Ecology:

Organisms obtain energy either through photosynthesis or by consuming other organisms. These ener­gy transformations are associated with the movements of materials within and between organisms and the physical environment.

Thus, the interaction between the biotic and abiotic components called an ecosystem is the sub-field of ecology called ecosystem ecology. Issues of interest at this level is how human activities affect food webs, energy flow and global cycling of nutrients.

vi. Population Ecology:

Population ecology constitutes organisms of the same species living in the same place and same time. It may comprise of the dynamics of a single population of any living thing (earth­worm, fox, whale, pine tree etc.) or may focus on how two populations (predator and its prey or parasite and its host) interact with each other.

At the level of population, evolu­tionary changes take place. It is also related directly to the management of fish and game populations, forestry and agriculture. Popu­lation ecology is also fundamental to our understanding of the dynamics of disease.

vii. Community Ecology:

Populations of many different organisms in a particular place are tied to one another by feeding rela­tionships and other interactions. These rela­tionships of interacting populations are called ecological communities and their study is under the purview of community ecology.

Community studies is principally on how biotic interactions such as predation, herbivory and competition influence the numbers and distributions of organisms. It has particular relevance in our understand­ing of the nature of biological diversity.

viii. Landscape Ecology:

These are of ecological fields whose study requires the synthesis of several other sub-fields of ecology. Landscape ecology is one that emphasizes the inter-connections among ecosystems of a region.

The values of land­scape ecology are:

(a) It emphasises on larger land areas of interacting ecosystems, i.e., next higher level of organisation above the local ecosystem, and

(b) Its tendency to compartmentalize. We study a lake or forest ecosys­tem but landscape ecology considers the con­nections between them. For example, herons forage in the lake, nest in the forest and, thus, the herons move nutrients from water to land.

ix. Conservation Biology:

This sub- field of ecology blends the concepts of gene­tics with population and community ecology. It takes a landscape approach and is related to the maintenance of biodiversity and the preservation of endangered species.

x. Restoration Ecology:

It relates to the re-establishing of the integrity of natural sys­tems that have been damaged by human activity.

xi. Ecotoxicology:

It is the study of the fate and action of human-made substances, such as pesticides and detergents, in the natural world. Ecotoxicology focuses on the way in which human-made substances affect human health. Eco-toxicologists often use other animals, such as fish or small inverte­brates, as models for the action of the parti­cular toxic substance under study.

Environmentalism, conservationism and preservationism are social or political move­ments and not branches of ecology. Roadside trash pickups and city tree planting drives are well-intentioned public beautification and cleanup activities, but such activities are not science. Although everyone applauds such civic responsibilities, they however, do not increase our understanding of the natu­ral world.

The subfields of ecological studies pro­vide ways to think about the various approaches in ecology. However, in many cases, individual ecologists conduct work that crosses boundaries of these subfields. The natural curiosity of most ecologists, along with the complexity of nature, often encour­ages broad approaches. Ecological study, thus, is an integrative science, one that requires great innovation, breadth and curiosity.

Scope of Ecology:

The solution of a particular ecological problem requires several lines of approach. None of this constitute an end in itself but each one of these makes important contribution in making the picture com­plete.

These various lines of approach towards the ecological problem can be translated as:

(a) Biotic

(b) Quantitative

(c) Climatic (both physical and chemical)

(d) Taxonomic

(e) Genetic and evolutionary.

Biotic factors are the direct outcome of the various types of activities amongst the animals. A competition for food and shelter always exists amongst the members of a community. This competition de­mands various types of activity amongst the animals.

Quantitative study includes an assessment of the population density in a given area and also an estimation of the number of members present in different communities. Information of this kind is of immense value in solving many problems like food availability and movement within a parti­cular colony.

Climatic factors include both physical and chemical conditions present in a habitat. These factors are ever changing in nature. Physical factors include mainly temperature, light and humidity. Chemical factors include acidity or salinity that are specially present in aquatic habitat. Some animals are so sensitive that a minute climatic change becomes fatal to them. Climatic factors play an important role in the distribution of animals.

Taxonomy means classification, naming and description of organisms. A mere naming of a large number of animals of a given area, as was done earlier in ecolo­gical surveys, is meaningless without a consideration of the circumstances that enable them to live there. Thus a com­plementary observation of the various eco­logical factors together with taxonomy is emphasized in ecology.

The genetic and evolutionary aspects have taken a rightful place in ecological problems. In recent years the knowledge of heredity and the mechanism of the opera­tion of Natural Selection have increased to a considerable extent.

Evolution is no longer regarded as a thing of the past and it has been proved that evolution is a dynamic process though the progress is very slow. In certain circumstances it has become possible to detect and to measure the rate of evolution in wild population.

The above subdivisions form the back­bone of the study of ecology. The inter­relationship existing between these sub­divisions can be best understood with the help of an example. Let us assume that we want to study the ecology of a given spe­cies of edible fish inhabiting a large lake, with an object of establishing a new colony of these fishes to be started else­where.

In so doing, the first information that we need is that whether the food available in the new place is to be taken by these fishes. Our second enquiry would be to find out whether predators are pre­sent in the locality.

These two are included within the biotic factors. We will have to determine the number of fishes that are to be let loose in the new locality and the number is to be determined in such a way that they can live there without being overcrowded.

Herein lies the involvement of the quantitative aspect. We will have to study the water itself and to find out the extent of the fluctuations in its constitution such as salt content, acidity or alkalinity in order to determine the tolerance of the fishes in the changing factors.

If the first lake is a very old one and the fish in question had been isolated there for a great period of time, it is possible that a subspecies or local race might evolve there. In such cases the taxonomist might come forward and help identifying the species. Such a situation opens up a case for the Geneticists and Evolutionists to find out how and at what rate the new forms have evolved.