Chemoautotrophs: Few bacteria such as sulfur bacteria, nitrifying bacteria, can be able to utilize free energy released from the chemical reactions to prepare organic food with it. They are called chemoautotrophs and the process is known as chemosynthesis. 

(ii) consumers: These are mainly the animals. They are unable synthesize their own food and depends on producers. They utilizes the oxygen being released from the producers as well. Several comsumers doesn’t get the food from the producers but they are depended on consumers it self. As a result, consumers are related to each other through multiple food chains. There are many types of consumers and we will discuss in details about these consumer in the subsequent lecture. The consumers are known as heterotrophs. 

 
(iii) decomposers: These are mainly bacteria and fungi. Their primary purpose in the ecosystem is to decompose the complex organic material into the simple inorganic material so that it can be use for producers to prepare food.

ABIOTIC COMPONENTS: These factors include the non-living physiochemical factors of the environment. Abiotic factors are as follows: 

(i) Inorganic substances: Inorganic substances like carbon, nitrogen, oxygen, water, carbon di-oxide, calcium, phosphorus and their inorganic compounds. These are available as free form or dissolved in water and may be adsorbed on the soil particles. 

 
(ii) Organic compounds: These are carbohydrates, proteins, lipids, nuceltic acids etc. This material is present in dead organic matter. These are broken into the simple compounds by decomposers in ecosystem for recycling of matter. 

(iii) Climatic factors: These are factors present in the environment such as temperature, humidity, light, wind, rainfall an atomospheric gaseous etc.

Study of specific Ecosystem:  Lets take a example of fresh water pond to understand the function of individual components.

1. Abiotic Components:  Non-living part of the pond includes: (1) water with dissolved gases, mineral and suspended organic matter. (2) air, CO₂ and O₂ on the water surface (3) sunlight. 

2. Biotic Components: The biotic constituents include the plants, animals and microorganisms. They play different role in ecosystem.