Habitat is a specific physical place or locality occupied by an organism, population or community which has a particular combination of abiotic or environmental factors.
It is the sum total of environmental factors which determine the existence of an individual, population or community in a particular locality. Animals generally show habitat specificity with a few exceptions e.g. Hilsailisha(Indian shad) can live in both fresh-water and sea water.
It is generally occupied by the entire community e.g. a pound with many individuals of different species showing cohabitation.
Variety of habitats
Annelid Tubifex is found in running and well aerated fresh-water bodies with abundant organic matter. Plasmodium (malaria parasite) found in RBCs and liver cells of man, and in stomach and salivary glands of female Anopheles mosquito.
Oryctolagus(rabbit) found in the grasslands and open woodlands. Scoliodon(Indian shark) found in the sea all along the Indian coast.
Reasons for differential habitats
Rotation of earth around the sun and tilt of its axis are responsible for annual Variations in the intensity and duration of temperature, resulting in distinct seasons. The annual temperature and precipitation variations, in turn, result the formation of different types of biomes.
Subdivisions of a habitat having different environmental conditions and different kinds of organisms are called microhabitats e.g. forest floor, tree canopy, muddy bottom, surface of a pond, burrow, center of a pond etc.
Elton (1927) defined the ecological niche as “Anecological niche refers to animals Place in the biotic environment and its relation to its food and enemies or its functional role in an ecosystem”. In other words, if habitat is the address of an organism then ecological niche is the Profession of an organism. It is also called “way of life”. Examples: O. Neill (1967) reported seven different species of millipedes in forest floor of a maple oak tree. All these seven species are found in same habitat (e.g. forest floor) and belong to same trophic level.
Conclusion: This shows that no two species can occupy the same ecological niche. If they do occur in the same geographical area, and then they use different food items or are active at different times or are occupying somewhat different niches. In case, two different species found in same ecological niche, then only one survives while other is excluded.
Significance: Ecological niche helps in avoiding continuous intense competition for the place of living. It also helps in diversification of species into sub-species.
VARIOUS LEVELS OF BIOLOGICAL ORGANISATION
Organization is the arrangement of smaller components of any structure into larger ones and so on in a hierarchy or a pyramid in which components of each level coordinate with one another towards a common function.
Molecular organization is found in one-celled protozoan’s e.g. Amoeba, Paramecium, etc. which show the division of labour at the level of cell-Organelles.
Individual level of organization(Biological hierarchy)
In multicellular organisms, division of labour is at the level of tissue or organ level. In such organisms though each cell type is specialized for a specific function but no Cell can show independent existence and the cells show interdependence.
Cells Tissues Organs Organ Systems Organism.
Higher level of organization(Ecological hierarchy)
Ecological hierarchy includes a graded series of ecological categories of ecological hierarchy. Ecological hierarchy involves the following categories. Organism, Population, Species, Biotic community, Ecosystem, Biome and Biosphere
ORGANISM AND ENVIRONMENT
All organisms, including plants are not independent of themselves but depend upon some sort of surrounding medium known as environment. There is a continuous Interaction between the organisms and the environment. The environment can be defined as the sum total of all the physical and biotic conditions which influence the responses of organisms. The place where the organism lives is called its habitat, while the conditions and Resources for its life activities constitute the environment.
Ecological factors are those components of environment which determine the Variation in the physical and chemical nature of different habitats. These ecological factors are classified into two major groups.
Direct factors: These factors influence the organisms directly e.g. light, temperature, humidity, soil, moisture, soil nutrients and soil air etc.
Indirect factors: These factors affect organisms indirectly by modifying other factors e.g. soil structure, precipitation, wind, soil organisms, altitude, slope etc.
These include the non-living physico-chemical factors of environment. These are divided into the following categories: Climatic Factors & Edaphic Factors.
Climatic Factors (weather): These include the physical factors of environment like Light, Temperature, Humidity, Wind, Rainfall, Water & Atmospheric gases.
CLIMATIC FACTORS: Climate is average weather of an area. Climate is of two types: Microclimate and Macroclimate.
Microclimate: It represents the climatic conditions which are present at local scale(i.e. within area of limited size).For example-immediate surroundings of various organisms. Macroclimate: Forest is an example of macro-climate. Here, dense foliage retards the quantity of light falling on ground. It also changes the prevailing temperature.