What is definition of ecology in biology? And type of ecology.

-: Introduction

Before going to study ecology, We should know about life and environment. Life originated in our earth around four billion years ago. It is generally agreed that all life forms of today evolved by a common descent from a single primitive life form. It is not known how this early life form came into existence, but scientists think that it was a natural process which took place perhaps 3,900 million years ago. They were found in iron and silica rich rocks which were once hydrothermal vents in the Nuvvuagittuq greenstone belt of Quebec, Canada. If this is the oldest record of life on earth, it suggests 'an almost instaneous emergence of life' after oceans were formed 4.4 billion years ago. Moreover a scientific study showed that geological formation of stromatolites of 3.45 billion years old contain fossilized cyanobacteria and stromatolites were also the oldest known life records on earth.

-: CONCEPT OF ECOLOGY

After knowing about life, living organisms, biosphere and environment,we will now come to ecology . Ecology is the branch of biology that deals with the relations of organisms to one another and to to their physical surrounding or environment. It is also the scientific analysis and study of interactions among organisms and their environment, perticularly of the abiotic components. Ecology in an interdisciplinary field that includes biology (botany and zoology), geography, genetics, earth science and environmental science.

Definition of ecology

The term 'oekologie' (ecology), coined in 1866 by the German biologist, Ernst Haeckel was from the Greek oikos meaning "house" or "dwelling", and logos meaning"science" or "study" . Thus, ecology is the "study of the house of nature" . 

According to him ecology is the study of reciprocal relationships between organisms and their environment. A contemporary definition of ecology is : The scientific study of the distribution and abundance of organisms and their interactions with the environment that determine their distribution and abundance.

-: SOME IMPORTANT ECOLOGICAL TERMS

The term environment refers to the sum total of physical and biotic conditions that influence an organism.

Ecosystem . It is perhaps the most widely used term in ecology. It is defined as the system of organisms and physical factors under study or consideration.

Habitat . It is the sum total of the environmental conditions under which a species, species population, or assemblage of species or community lives.

Niche . The niche is the set of biotic and abiotic conditions of the environment in which a species is able to persist and maintain stable population sizes. It is further subdivided into fundamental and realized.

Population . Population is a group of potentially inbreeding individuals of a single species.

Community . In ecology, community is an assemblage or association of population of two or more different species occupying the same geographical area and in a perticular time.

Autecology . Autecology is the ecological study of a perticular species. It is also known as population ecology, or species ecology.

-: SCOPE OF ECOLOGY

-: HISTORY OF ECOLOGY

Although the term ecology was coined only 150 years ago and the science of ecology started from 1866, history of ecological subject started much earlier. A brief history of ecology is furnished below :

A. Carolus Linnaeus and Binomial Nomenclature

Carolus Linnaeus, a Swedish naturalist, is well known for his work with taxonomy but his ideas helped to lay the groundwork for modern ecology . He developed a two part naming system for classifying plants and animals. Binomial nomenclature was used to classify,describe, and name different genera and species.

B. Darwinism, E. Haeckel and the science of ecology

The roots of scientific ecology may be traced back to Charles Darwin. His book 'On the Origin of Species'(1859) is full of observations and proposed mechanisms that clearly fit within the boundaries of modern ecology and because the term ecology was coined in 1866 by a strong proponent of Darwinism, Ernst Haeckel.

-: BRANCHES OF ECOLOGY

1. Habitat ecology : It deals with ecological study of different habitats on planet earth and their effects on the organisms living there. According to kind of habitat, ecology is subdivided into marine ecology, estuarine ecology, fresh water ecology, terrestrial ecology.

2. Behavioral ecology : It is the study of the evolutionary basis of organism's behaviour due to ecological pressure.

3. Population ecology : It deals with the study of the manner of growth, structure and regulation of populations of organisms.

4. Community ecology : It deals with the study of the local distribution of organisms (plant and animals) in various habitats, the structure, abundance, demography and composition of community units and succession.

5. Ecosystem ecology : Ecosystem ecology is the integrated study of the living and non-living components of the ecosystems and their interactions within an ecosystem framework.

-: LEVELS OF ORGANIZATION (ECOLOGICAL HIERARCHY)

-: INTER-RELATIONSHIP BETWEEN THE LIVING WORLD AND THE ENVIRONMENT

There is a close, interactive relationship between the living organisms and the environment. Life is unthinkable without a suitable, sustainable, environment. Living organisms also have influence on the environment, perticularly an the atmosphere, hydrosphere and lithosphere and vice versa. The study of interactions between organisms and their physical and biotic environment as known as ecology.

-: THE FOUR SPHERES OF ENVIRONMENT

The environment has four 'spheres' i.e. atmosphere, lithosphere, hydrosphere and biosphere which are discussed below :

A. Structure of atmosphere

In this way, earth's atmosphere can be divided into five main layers. Excluding the exosphere, the atmosphere has four primary layers, which are the troposphere, stratosphere, mesosphere, and thermosphere. From highest to lowest, the five main layers are :

1. Exosphere: 700 to 10,000 km

2. Thermosphere : 80 to 700 km

3. Mesosphere :    50 to 80 km

4. Startosphere :  12 to 50 km

5. Troposphere :  0 to 12 km

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