Difference Between Autotrophs and Heterptrophs

The key difference between autotrophs and heterptrophs is that autotrophs are the organisms that obtain carbon from inorganic carbon sources such as carbon dioxide while heterotrophs are the organisms that obtain carbon from the organic carbon sources.

A living organism can only use two sources of energy in order to synthesize their organic requirements. These are light energy and chemical energy based on that there are two major groups of organisms namely phototrophs and chemotrophs.  Phototrophs use light energy as their energy source while chemotrophs use chemical energy as their energy source. 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. Autotrophs utilize inorganic carbon (carbon dioxide) as the source of carbon while heterotrophs utilize organic carbon as the source of carbon.

CONTENTS

1. Overview and Key Difference
2. What are Autotrophs
3. What are Heterotrophs
4. Similarities Between Autotrophs and Heterptrophs
5. Side by Side Comparison – Autotrophs vs Heterotrophs in Tabular Form
6. Summary

What are Autotrophs?

Autotrophs are the organisms that produce their own foods by utilizing carbon from inorganic carbon sources such as carbon dioxide. There are two main types of autotrophs as photoautotrophs and chemoautotrophs depending on the source of energy they use. Accordingly, photoautotrophs utilize light energy while chemoautotrophs utilize chemical energy. 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.

Chemosynthetic bacteria utilize carbon dioxide, but they obtain energy from chemical reactions by oxidizing inorganic materials such as ammonia and nitrite. Some chemoautotrophs carry out nitrification, playing an important role in the nitrogen cycle. Nitrosomonas and Nitrobacter are two chemoautotrophs involved in nitrification. Nitrification is a two steps process. In the first step, Nitrosomonas converts ammonia into nitrite while in the second step, Nitrobacter converts nitrite into nitrate. Both steps generate energy that can be utilized by the chemoautotrophs.

What are Heterotrophs?

Heterotrophs are organisms that cannot produce their food; hence, they depend on other organisms for food. Similar to autotrophs, there are also two subcategories of heterotrophs depending on the source of energy used. These are chemoheterotrophs and photoheterotrophs. Most bacteria are chemoheterotrophs. These bacteria obtain energy from chemicals in their food.

Moreover, there are three main groups of bacteria as saprotrophs, mutualists, and parasites. Saprotrophs obtain food from dead and decaying matter by carrying out extracellular digestion. They secrete enzymes onto the organic matter in order to digest it outside the organism and then absorb nutrients. 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. Rhizobium is a 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.

Photoheterotrophs are the second category of heterotrophs. They use light energy as the energy source, but obtain carbon from organic compounds. Examples for photoheterotrophs are purple non-sulphur bacteria.

What are the Similarities Between Autotrophs and Heterotrophs?

• Autotrophs and heterotrophs are two groups of living organisms categorized based on the carbon source.
• Both groups have two subcategories based on the energy source.
• They can use either light energy or chemical energy as their energy source.
• They are members of food chains and food webs.
• Both groups are vital for the balance of ecosystems.
• There are autotrophic as well as heterotrophic plants.

What is the Difference Between Autotrophs and Heterptrophs?

Autotrophs are organisms that utilize inorganic carbon and produce their own foods. On the other hand, heterotrophs are organisms that utilize organic carbon and cannot produce their own foods.  So this is the key difference between autotrophs and heterptrophs. In addition, there are two groups of autotrophs namely photoautotrophs and chemoautotrophs. Heterotrophs are also two categories namely photoheterotrophs and chemoheterotrophs. This is also a difference between autotrophs and heterptrophs.

A major difference between autotrophs and heterotrophs is the carbon source that they utilize.  Autotrophs use inorganic carbon as their source of carbon. On the other hand, heterotrophs use organic carbon as their source of carbon. Apart from that, the autotrophs are known as producers as they can produce their own food from inorganic, raw materials. Heterotrophs cannot produce their own foods. Hence, they extract organic nutrients from the outside source and known as consumers. Thus, it is another difference between autotrophs and heterotrophs.

Autotrophs mainly include plants, algae, and cyanobacteria. Heterotrophs mainly include animals. Some plants, fungi, and bacteria are also heterotrophs. Moreover, autotrophs are not dependent on other organisms for foods. But, heterotrophs depend on other organisms for food. Therefore it is another major difference between autotrophs and heterptrophs.

Summary – Autotrophs vs Heterotrophs

In summarizing the difference between autotrophs and heterptrophs, autotrophs and heterotrophs are two categories of organisms. Autotrophs produce their own foods while heterotrophs obtain foods from other organisms such as plants and animals. Furthermore, autotrophs utilize inorganic carbon sources while heterotrophs utilize organic carbon sources. In the food chains, autotrophs act as primary producers while heterotrophs work as secondary and tertiary consumers. Green plants, algae, and cyanobacteria are able to produce their own foods; hence they are autotrophs. On the other hand, animals including human, are heterotrophs. They cannot produce their own foods.

Reference:

1. “Autotroph.” Wikipedia, Wikimedia Foundation, 3 Mar. 2019, Available here.
2. “Heterotroph – Definition and Examples.” Biology Dictionary, Biology Dictionary, 28 Apr. 2017, Available here.

Image Courtesy:

1. “Auto-and heterotrophs” By Derivative by Mikael Häggström, using originals by Laghi l, BorgQueen, Benjah-bmm27, Rkitko, Bobisbob, Jacek FH, Laghi L and Jynto – Images used:GlucoseAnimalsCarbon dioxideGlucose (open form)OxygenPlantsFungiStarchWaterHumanFile:Upper body front.png (CC BY-SA 3.0) via Commons Wikimedia
2. “AutoHeteroTrophs flowchart” By Cactus0 – Own work (CC BY-SA 4.0) via Commons Wikimedia