Organisms and the Environment

Introduction

     The term ecology is derived from two Greek words (oikos - means 'house' or place to live and logos means 'a discussion or study'). Literally, ecology is the study of organism 'at home' in their native environment. The term was first introduced by Reiter in 1868, but was fully defined by Ernest Haeckel in 1869.

Organism and Environment

     Each and every living organism has its specific surrounding medium of environment with which it continuously interacts and remains fully adapted.

Habitat

     The surroundings or the localities in which a variety of plants and animals occur in nature is called habitat. The word habitat means living or dwelling place. Habitat of an organism is a part of the total environment of the region and it must offer the resident organism food, shelter and climatic conditions that are well suited for the organism to survive, reproduce and flourish.

Microhabitat

     The term microhabitat is defined as a small region or area within a given habitat with special features that suit some organisms better than others. The term microhabitat is used for a smaller and immediate habitat of an organism.

Abiotic Factors - Affecting an Organism

     The properties of temperature, pressure, humidity rainfall, sunshine cloud and wind in a given place and time is called weather. The average weather conditions of an area, which includes atmospheric conditions, seasons. etc. constitutes the climate.

Climatic Factors - Temperature

     Temperature is one of the essential and changeable environmental factors. It penetrates into every region of the biosphere and profoundly influences all forms of life by increasing or decreasing some of the vital activities of the organism. It is frequently a limiting factor for the growth or distribution of animals and plants.

Climatic Factors - Humidity

     It is the amount of water vapour present in the atmosphere. It can be measured by an Hygrometer. Humidity is greatly affected by intensity of solar radiation, temperature, altitude, wind exposure, cover and water status of soil.

Climatic Factors - Wind

     Air in motion is called wind. Wind velocity can be measured by an Anemometer. It is an important ecological factor of the atmosphere affecting variously the plant life on flat plains, along sea coasts and at high altitudes in mountains.

Climatic Factors - Rainfall and Water

     Rainfall is a source for ground water and relative humidity. The amount of rainfall greatly affects the vegetation as well as animal population of a particular region.

Climatic Factors - Atmospheric Gases

     The gases present in the atmosphere are chiefly oxygen, carbon dioxide and nitrogen which greatly influence the living organisms.

Edaphic Factors

     The word soil is derived from the Latin word solum meaning earthy material in which plants grow. The science which deals with the study of soil is called Soil Science, Pedology (pedos = earth) or edaphology (edaphos = soil).

Ecological Adaptations

     The phenotype is the physical expression of the organism. The phenotype shows variations due to differences in the environmental conditions in a habitat.

Aerial Habitat

     Some organisms have become secondarily adapted for aerial existence. Organisms that are capable to do their activities in the aerial environment are called as aerial or arboreal organisms.

Aquatic Habitat

     Water forms the habitat of an enormous variety of organisms. These organisms are called as aquatic organisms. The aquatic habitat may be fresh water or marine environment.

Terrestrial Habitat

     Land provides a wide variety of habitat for the organisms. Organisms that live on land are called as terrestrial organisms.

Hydrophytic Habitat

     It is a habitat with excessive water supply. The plants growing in such a habitat do not face the problems of water loss due to transpiration, wilting and drought, They are known as hydrophytes.

Ecological Adaptations - Mesophytes

     These are land plants which grow in moist habitats and need well aerated soils. They prefer soil and air with moderate humidity. They avoid soils with standing water and soils containing great abundance of salts.

Ecological Adaptations - Xerophytes

     These are plants adapted to grow in dry habitats. They are classified into three categories on the basis of their morphology and life - cycle pattern.

Ecological Adaptations - Halophytes

     The plants, which grow in saline habitats, are called Halophytes. There is high concentration of salts like sodium chloride, MgSO₄ etc. in these habitats. As the habitat is physiologically dry due to salts, the halophytes show characters similar to Xerophytes.

Adaptation to Environment In Animals

     Animals too have to face the problem of water scarcity or abundance. They also have to meet the various vagaries of nature. So, for their survival under these conditions, animals have developed a number of adaptations to meet the challenges.

Adaptation to Environment In Animals (Contd...)

     Adaptations for flight are called as volant adaptations. Bats, birds and insects are well adapted for an active flight.

Summary

     Ecology concerns with the associations and interactions of the organisms and the environment in general. The living place or dwelling place of an organism is called habitat. Within a given habitat there exists variations or micro habitats. In a given habitat we can observe physical (abiotic) environment and living organisms (biotic). There is an interdependence between organisms of a habitat.