ECOSYSTEMS: AN INTRODUCTION

 Ecosystem is a broad term which includes all organisms and the environment they live, i.e. it includes all living and non living things, and their interactions. In other words it is a community of organisms along with their physical environment. The study of ecosystems is called Ecology. It was Sir A G Tansley, who was an English Botanist, who introduced the concept of 'Ecosystem". The living and non-living components of the ecosystems are interlinked by means of energy transfer and biogeochemical cycles. Ecosystem can be defined as 'the living community of plants, animals and microbes in an area and their surrounding environment such as soil, air and water.' The basic living components of the ecosystem are producers, consumers and decomposers.

Ecosystems are broadly divided into terrestrial or land based ecosystems, and aquatic ecosystems in water.

1. AQUATIC ECOSYSTEMS

Aquatic ecosystems are water based ecosystems in which water acts as the surrounding environment for the living organisms. Aquatic ecosystems are further classified in to the following categories. - marine ecosystem, estuarine ecosystem and freshwater ecosystem, based on the salinity of water.

Marine ecosystem: When the salinity of the water is equal or more than 35ppt (parts per thousand), the ecosystem is considered to be marine. 

Freshwater ecosystem: When the salinity is 0.5 ppt or less, it is considered as freshwater ecosystem.

Estuarine ecosystem: When the salinity keeps varying between 0.5 to 30 ppt it is considered to be estuarine.

2. TERRESTRIAL ECOSYSTEMS

All the ecosystems which are seen on the land are called terrestrial ecosystems. They can be further divided based on the the types of plants and animals inhabiting. Some features of terrestrial organisms are the following; they are exposed directly to air, hence developed respiratory system for gaseous exchange; the plants have extensive root system for finding water in the soil and absorbing it; animals have developed mechanisms to combat with heat or cold.

Forest ecosystem: Terrestrial ecosystem in which trees are the dominant vegetation. They can be further subdivided into tropical forests, temperate forests and boreal forests.

Grassland ecosystem: When the vegetation is dominated by grasses, the ecosystem is called grassland ecosystem. They can be further divided into tropical grasslands and temperate grasslands. Tropical grasslands are called savannah and temperate grasslands are called prairies, steppes, pampas, veldts etc. in different places.

Desert ecosystem: Desert is a region which receives very less rainfall, which is usually less than 25 cm per year. There are two types of deserts: hot deserts and cold deserts.