Autotrophs vs Heterptrophs
Nutrition is the process by which organisms obtain energy and materials. Living organisms are grouped based on their energy source and the carbon source. Carbon is the most fundamental material required for growth. Living organism can only use two sources of energy in order to synthesize their organic requirements. Those are light energy and chemical energy. Organisms that use light as their energy source are known as phototrophs, and organisms that use chemical energy as their energy source are known as chemotrophs. Phototrophs are the organisms that carry out photosynthesis. Organisms can also be autotrophic or heterotrophic depending on whether their source of carbon is organic or inorganic. If the source of carbon is inorganic (carbon dioxide), those organisms are said to be autotrophs and if the source of carbon is organic those organisms are said to be heterotrophs.
Autotrophs can be divided into two subcategories depending on the source of energy used by them. Those are photoautotrophs and chemoautotrophs. Cyanobacteria or blue green algae, algae, and plants are good examples of photoautotrophs. They all carry out photosynthesis and use carbon dioxide (inorganic carbon) as the source of carbon. Chemoautotrophic bacteria are usually called chemosynthetic bacteria. Similar to photoautotrophs their carbon source is carbon dioxide, but they obtain energy from chemical reactions. The energy is obtained by oxidizing inorganic materials such as ammonia and nitrite. Some carry out nitrification, playing an important role in the nitrogen cycle. There are two steps involved in nitrification. In the first step, ammonia is converted to nitrite and energy is released. This is carried out by nitrosomonas. In the second step, nitrite is converted to nitrate and again energy is released. This is carried out by nitrobacter.
Similar to autotrophs heterotrophs can also be divided into two subcategories depending on the source of energy used by them. Those are chemoheterotrophs and photoheterotrophs. Most of the bacteria are chemoheterotrophs. These bacteria obtain energy from chemicals in their food. There are three main groups. Those are saprotrophs, mutualists, and parasites. Saprotrophs obtain food from dead and decaying matter. Enzymes are secreted onto the organic matter in order to digest it outside the organism. Mutualists are organisms involved in any form of a close relationship between two living organisms in which both partners benefit. A good example of a bacterial mutualist is Rhizobium nitrogen fixing bacteria living in the root nodules of legumes. A parasite is an organism which lives in a host from which it obtains food and shelter. Examples for photoheterotrophs are purple non – sulphur bacteria.
What is the difference between Autotrophs and Heterptrophs?
• Autotrophs use inorganic carbon as their source of carbon and heterotrophs use organic carbon as their source of carbon.
• The autotrophs are known as producers as they can produce their own food from inorganic, raw materials, but heterotrophs cannot do so. They extract organic nutrients from the outside source, and known as consumers.
• Autotrophs mainly include plants. Heterotrophs mainly include the animals.
• Autotrophs usually require an external source of energy where as heterotrophs do not require an external source of energy.