Autotrophs and Heterotrophs

There are thousands of ecosystems of varying sizes on the earth's surface. All living beings as well as the physical and chemical factors such as sun, soil, climate and water, are part of some ecosystem and all these ecosystems are interconnected in some way or the other. Ecosystem is basically a unit consisting of biotic (living) and abiotic (non-living) factors in a particular area that are linked together through a nutrient cycle and flow of energy.The sun is the fundamental source of almost all ecosystems on this earth and the radiant energy from the sun flows through the various components of the ecosystem by a nutrient and energy cycle. The biotic or the living components of the ecosystem are divided into two categories - autotroph and heterotroph.

Autotrophs

Autotrophs are those organisms that are capable of synthesizing their own food, using the energy from the sun, by a process known as photosynthesis. All plants and some forms of bacteria come under this category. They are also known as producers in a food chain, as they are able to produce their own food and this food is directly or indirectly used by other members of the food chain.

Autotrophs are self-feeding or self-sustaining members of the ecosystem. They synthesize complex organic compounds such as carbohydrates, proteins and fats, from simple inorganic molecules, with the help of light energy or by inorganic chemical reactions. Depending on the method by which they synthesize their food, autotrophs are further classified into two categories:

• Phototrophs - These are mostly plants, that use light as source of energy.
• Chemoautotrophs - Bacteria or fungi that obtain their food by inorganic chemical reactions.

Heterotrophs

Those organisms which obtain energy from organic molecules that are made by autotrophs are known as heterotrophs. These organisms fail to synthesize their own food and are dependent on the producers or autotrophs, for the supply of organic compounds required for their growth. As heterotrophs obtain energy from producers, they function as consumers in the food chain. The complex organic compounds that are produced by the autotrophs are broken down into simple substances, that provide energy to the heterotrophs. Like autotrophs, heterotrophs are also classified as photoheterotrophs and chemoheterotrophs, depending on the energy source. Consumers are further classified into different categories, based on their mode of consumption.

• Herbivores - A heterotroph that obtains energy directly from plants.
• Carnivores - Those animals which feed on other animals.
• Omnivores - Animals that obtain their food from plants as well as from other animals.
• Saprobes - Organisms that obtain energy by breaking down remains of dead plants and animals.

Autotroph vs Heterotroph

Let us compare them and add to the debate of autotroph vs heterotroph.

Similarities

• Autotrophs, as well as heterotrophs, are living things and both are part of some ecosystem.
• The autotrophs and heterotrophs, together form various trophic levels in the food pyramid.
• Both require sunlight and water to live and obtain energy by conversion of chemical molecules.

Differences
The main difference between autotroph and heterotroph is that autotrophs can synthesize their own food, whereas, heterotrophs cannot. Most autotrophs contain the pigment chlorophyll, that plays a key role in synthesis of food. Chlorophyll is absent in almost all heterotrophs. Autotrophs obtain energy by converting inorganic raw materials into organic compounds, whereas, heterotrophs convert complex organic compounds into simpler ones to obtain energy.

So, this was all about autotroph and heterotroph. The movement of nutrients and energy from autotrophs through the various levels of heterotrophs, makes up a typical food chain. Autotrophs and heterotrophs, together, form an important part of all the ecosystems.