SESSION-18: School Students
PAPER-4: Eco Systems and its Balance with Nature
Bharath H.Aithal

Abstract:

An ecosystem is the most complex level of organisation in nature.   It is made up of a community and its abiotic (non-living and physical) environment, including climate, soil, water, air, nutrients and energy. The elements that make up an ecosystem can be grouped into 6 main parts based on flow of energy and nutrients they are: The sun, Abiotic substances, Primary producers, Primary consumers, Secondary consumers and Decomposers.

The sun provides energy that primary producer's need to make food.   Primary producers mainly consist of green plants, such as grass, trees, which make food by the process of photosynthesis.   Plants also need abiotic substances, such as phosphorus, water, etc. to grow.   Primary consumers include mice, rabbits, and grasshopper's etc. and other plant eating animals.   The predators i.e. secondary animals which include foxes, weasels etc. eat animals.   Decomposers such as bacteria and fungi, break down dead plants and animals into simple nutrients.   The nutrients go back into the soil and plants again use it.

The series of stages energy goes on through in the form of food is called a food chain.   A simple food chain would be one in which grass is a primary producer.   A primary consumer's such as rabbit eats the grass.   A hawk or a vulture may eat the rabbit, which is a secondary consumer.   Decomposing bacteria break down the uneaten remains of dead grass, rabbits and hawks as well as body water produced by them.   Most ecosystems have a variety of producer's, consumer's and decomposers, which forms an overlapping network known as food web.

Most organisms have a low ecological efficiency.   This means they are able to convert any small fractions of the available energy into stored chemical energy.   The energy remaining from the activity is burned up. Because a lot of energy escapes as heat at each step of food chain, all ecosystems develop a pyramid of energy.   In many land ecosystem's the pyramid energy results in pyramid of biomass.

Cycling of materials

All living things are composed of certain chemical elements and compounds.   Chief among them is water, carbon, hydrogen etc. All of these materials cycle through eco-system again and again. The cycling of phosphorus provides an example of this process.   Plants take up phosphorus compounds from the soil or other animals that they eat.   Decomposers then return phosphorus to soil.

Changes in Ecosystem

In the past, the concept of balance, largely unchanging ecosystem was thought to be especially descriptive of climax communities.   But modern studies of ecosystem have altered the studies.

Further ecological studies indicate the changes in the food plants and nutrients may be as important in regulating the predator and prey population.   Natural systems are filled with compensating mechanisms that help stabilise nature.   This necessitates to understand the intra and inter linkages of biotic and abiotic components of an ecosystem