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1. Environment

The environment is defined as ‘the sum total of living, nonliving components; influences and events, surrounding an organism’. Everything that surrounds or affects an organism during its life time is collectively known as its environment which comprises both living (biotic) and nonliving (abiotic) components.

Biosphere

 Biosphere is the life supporting layer which surrounds the earth and makes existence of life possible without any protective layer.

 The biosphere consists of living organisms, physical environment and energy. It is the zone of assemblage of lithosphere, atmosphere, hydrosphere and living organisms together.

There are three components of biosphere, are:

 Biotic or organic components: It includes micro-organisms, plants and animals including man.

 Inorganic or abiotic component: It includes physical environment of soil, water, air, temperature and sunlight.

 Energy component: Solar and geothermal energy etc.Biosphere is termed as an open system as there is continuous inward and outward flow of energy and matter.Biosphere always tends to maintain equilibrium between 

flow of energy and output of the matter. If this equilibrium is maintained environmental and ecological balances are also maintained. Disturbances in the biosphere equilibrium bring ecological and environmental disturbances which have long term or short term effects on the very existence of living beings.

2. Ecology 

Ecology deals with the inter-relationships amongst organisms and interactions between organisms and their environment. In other words, Ecology is the study of organism in relation with the surrounding in which they live. The surrounding is the environment of the living organisms and nonliving things in the vicinity.The term Ecology is being derived from two Greek words namely,’Oikos’ meaning home or place to live in and ‘logos’ means study. It means the study of the home of nature.Levels of organization in ecology:The various ecological levels of organisation are described below:

Individual:

 An individual organism is a distinct unit of life in nature. It is the basic unit of ecological hierarchy. Ex: Plant, Animal, Bacteria. Population: It is a group of individuals of a plant or animal species inhabiting a given area at a particular time. Ex: All the frogs living in a pond constitute a population. Community: It is an assemblage of populations of plants, 

animals, bacteria, and fungi that live in an area that show interaction and interdependence. 

Ex : A gross land community dominated by grasses, it may contain herbs,shrubs, and 

trees along with associated animals of 

different species

3. Ecosystem

An ecosystem is defined as a structural and functional unit of biosphere consisting of community of living beings and physical environment, both interacting and exchanging materials between them. Ecosystem is a self-contained, dynamic system composed of a natural community along with its physical environment. Components of ecosystem:

 Abiotic Components: Abiotic components or abiotic factors are non-living chemical and physical parts of the ecosystem that affect living organisms and the functioning of ecosystems. Ex: Soil, Topography, Water, Atmosphere etc.

 Biotic Components: Biotic components, 

or biotic factors, can be described as any 

living component that affects another organism thatshapes the ecosystem. Ex: Green Plants, Non-Green Plants, Animals, Parasites, Decomposers etc.

 The environment is not static. Both biotic and abiotic

 4. Ecotone

An ecotone is a zone of junction or a transition area between two biomes (diverse ecosystems). Ecotone is the 

zone where two communities meet and integrate.For e.g. the mangrove forests represent an ecotone between marine and terrestrial ecosystem. Other examples are grassland (between forest and desert), 

estuary (between fresh water and salt water) and riverbank or marshland (between dry and wet).Characteristics of Ecotone

 It may be narrow (between grassland and forest) or wide (between forest and desert).

 It has conditions intermediate to the adjacent ecosystems. Hence it is a zone of tension.

 Usually, the number and the population density of the species of an outgoing community decreases as we move away from the community or ecosystem.

 A well-developed ecotone contains some organisms which are entirely different from that of the adjoining communities.Ecocline

 Ecocline is a zone of gradual but continuous change from one ecosystem to another when there is no sharp boundary between the two in terms of species composition.

 Ecocline occurs across the environmental gradient (gradual change in abiotic factors such as altitude, temperature (thermocline), salinity (halocline), depth, etc.).Edge Effect – Edge Species

 Edge effect refers to the changes in population or community structures that occur at the boundary of two habitats (ecotone).

 Sometimes the number of species and the population density of some of the species in the ecotone is much greater than either community. This is called edge effect.

 The organisms which occur primarily or most abundantly in this zone are known as edge species.

 In the terrestrial ecosystems edge effect is especially applicable to birds.

 For example, the density of birds is greater in the ecotone between the forest and the desert.

5. Ecological Niche

 Niche refers to the unique functional role and position of a species in its habitat or ecosystem.

 The functional characteristics of a species in its habitat is referred to as “niche” in that common habitat.

 In nature, many species occupy the same habitat, but they perform different functions:

1. habitat niche – where it lives, food niche – what is eats or decomposes & what species it competes with,

2. reproductive niche – how and when it reproduces,

3. physical & chemical niche – temperature, land shape, land slope, humidity & another 

requirement.

 Niche plays an important role in the conservation of organisms. If we have to conserve species in its native habitat, we should have knowledge about the niche  requirements of the species.

Difference between niche and habitat

 The habitat of a species is like its ‘address’ (i.e. where it lives) whereas niche can be thought of as its “profession” (i.e. activities and responses specific to the species).

 A niche is unique for a species while many species share the habitat.

 No two species in a habitat can have the same niche. This is because of the competition with one another until one is displaced.

 For example, a large number of different species of insects may be pests of the same plant, but they can co-exist as they feed on different parts of the same plant.

Functions of Ecosystem

 Ecological succession or ecosystem development.

 Homeostasis (or cybernetic) or feedback control mechanisms.

 Energy flow through the food chain.

 Nutrient cycling (biogeochemical cycles). factors are in a flux and keep changing.

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