Natural Environment

In an ecosystem, living organisms interact among themselves and also with the surroundings. Ecosystem is divided into two basic categories - terrestrial and aquatic. Humans can also make ecosystems. For example, aquarium, gardens and agricultural fields are examples of man-made ecosystem.

The various components of an ecosystem function as a complete unit and have definite relationships with each other. The living organisms are directly or indirectly dependent on each other and use various natural resources for their survival.

Ecosystem = Non-living Component (Abiotic) + Living Component (Biotic)

All components of a biotic community are connected through food and energy available. They also form a web of inter-relationships. 

A number of controlled processes occur in an ecosystem. Plants use nutrients from the soil. Their availability is largely dependent upon decomposition and mineralization of organic detritus. Animals found in an ecosystem are delicately balanced by the number of herbivores and the degree to which they are being eaten.

Nutrients like carbon, nitrogen, water, sulphur and phosphorus are present in definite amounts in the ecosystem. Saprophytes help in recycling the nutrients back into the atmosphere by feeding on the dead and decaying organic matter and in the process also help in cleaning the environment.

Energy flow is unidirectional. Only part of the energy is transferred to the next trophic level.

Environmental problems may arise due to natural disasters or due to human activities. Natural disasters like floods, earthquake, volcano, cyclone, tsunami, cloud-burst, landslide, forest-fire are not within human control.

Increased population, mindless over-exploitation of resources and human negligence has adversely affected our environment. The excessive use of fertilizers and pesticides to increase agricultural yield has led to eutrophication and biomagnification.

Global warming is caused by high concentration of carbon dioxide accumulated in the environment, which traps heat and increases atmosphere temperature. 

Ozone provides a protective layer against the ultra-violet rays coming from the sun. The excessive use of chemicals like CFCs have resulted in the depletion of the ozone layer.