Ans: Biotic Components of an Ecosystem
The biotic components comprise the living part (organisms) of the ecosystem. Biotic components are further classified as producers, consumers and decomposers. Figure 16.1
i)Producers: The producers are the autotrophs present in an ecosystem. Producers include plants, algae and photosynthetic bacteria. These organisms are able to synthesize complex organic' compounds (food) from inorganic raw materials. Producers form the basis of any ecosystem. In terrestrial ecosystems, plants are the main producers. In aquatic ecosystems, the main producers are the floating photosynthetic organisms (mainly algae) called phytoplankton and shallow water rooted plants.
ii)Consumers: The consumers are heterotrophs. They cannot synthesize their food and so depend upon producers for food. Consumers include all animals, fungi, protozoans and many of the bacteria. The animals are the major consumers of ecosystems.
Consumers are further classified as herbivores and carnivores.
(a) Primary consumers: Herbivores e.g. cattle, deer, rabbit, grasshopper etc. feed on plants. They are the primary consumers. They feed directly on plants or products of plants.
• (b) Secondary consumers: Carnivores feed on other animals. Primary carnivores (secondary consumers) feed on herbivores. Fox, frog, predatory birds, many fishes and snakes etc. are primary carnivores.(c) Tertiary consumers: Secondary carnivores (tertiary consumers) feed on primary carnivores. Wolf and owl etc. are secondary carnivores. Tertiary carnivores e.g. lion, tiger etc. feed on secondary carnivores. Tertiary carnivores are not eaten by any other animals. They are also called top carnivores.
(d) Omnivores: Omnivores are the consumers that eat animal flesh as well as plants and plant products.
Ill) Decomposers: Decomposers or reducers break down the complex organic compounds of dead matter (of plants and animals) into simple compounds. They secrete digestive enzymes into dead and decaying plant and animal remains to digest the organic material. After digestion, decomposers absorb the products for their own use. The remaining substances are added to environment. Many types of bacteria and fungi are the principal decomposers of biosphere. The minerals, which are released by decomposers, are used as nutrients by the producers