What Is an Autotroph? Definition and Examples

Autotroph Example
Trees are examples of autotrophs since they produce their own food.

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An autotroph is an organism that can produce its own food using inorganic substances. In contrast, heterotrophs are organisms that cannot produce their own nutrients and require consumption of other organisms to live. Autotrophs are important parts of the ecosystem known as producers, and they are often the food source for heterotrophs.

Key Takeaways: Autotrophs

  • Autotrophs use inorganic material to produce food through either a process known as photosynthesis or chemosynthesis.
  • Examples of autotrophs include plants, algae, plankton and bacteria.
  • The food chain is comprised of producers, primary consumers, secondary consumers and tertiary consumers. Producers, or autotrophs, are at the lowest level of the food chain, while consumers, or heterotrophs, are at higher levels.

Autotroph Definition

Autotrophs are organisms which create their own food using inorganic material. They can do so using light, water, and carbon dioxide, in a process known as photosynthesis, or by using a variety of chemicals through a method called chemosynthesis. As producers, autotrophs are essential building blocks of any ecosystem. They produce nutrients that are necessary for all other types of life on the planet.

How Do Autotrophs Produce Their Own Food?

Plants are the most common types of autotrophs, and they use photosynthesis to produce their own food. Plants have a specialized organelle within their cells, called a chloroplast, which allows them to produce nutrients from light. In combination with water and carbon dioxide, these organelles produce glucose, a simple sugar used for energy, as well as oxygen as a byproduct. Glucose not only provides nutrition for the producing plant but also is an energy source for consumers of these plants. Other examples of autotrophs that use photosynthesis include algae, plankton and some types of bacteria.

Different types of bacteria can use chemosynthesis to produce nutrients. Instead of using light in combination with water and carbon dioxide, chemosynthesis uses chemicals such as methane or hydrogen sulfide along with oxygen to produce carbon dioxide and energy. This process is also known as oxidation. These autotrophs are often found in extreme environments in order to find the chemicals necessary for food production. These environments include underwater hydrothermal vents, which are cracks in the seafloor that mix water with underlying volcanic magma to produce hydrogen sulfide and other gases.

Autotrophs vs. Heterotrophs

Heterotroph and autotroph vector illustration. Labeled biological division.
Heterotroph and autotroph vector illustration. Labeled biological division scheme for plants, bacteria, algae, animals and fungi. VectorMine / Getty Images

Heterotrophs differ from autotrophs in that they cannot produce their own food. Heterotrophs require consumption of organic material, rather than inorganic, to create nutrients necessary for life. Therefore, autotrophs and heterotrophs play different roles within an ecosystem. In any food chain, producers, or autotrophs, and consumers, or heterotrophs, are required. Heterotrophs include herbivores, carnivores and omnivores. Herbivores are primary plant eaters and consume autotrophs as primary consumers. Carnivores consume herbivores, and thus can be secondary consumers. Tertiary consumers are either carnivores or omnivores who eat smaller, secondary consumers. Omnivores are meat and plant eaters, and thus use autotrophs as well as other heterotrophs for food.

Autotroph Examples

The simplest example of autotrophs and their food chain includes plants like grass or small brush. Using water from the soil, carbon dioxide and light, these plants perform photosynthesis to provide their own nutrients. Small mammals, such as rabbits, are primary consumers that eat the surrounding flora. Snakes are secondary consumers that eat rabbits, and large birds of prey such as eagles are tertiary consumers that consume snakes.

Phytoplankton are the major autotrophs in aquatic ecosystems. These autotrophs live within oceans throughout the earth and use carbon dioxide, light and minerals to produce nutrients and oxygen. Zooplankton are primary consumers of phytoplankton, and smaller, filter fish are secondary consumers of zooplankton. Small predator fish are tertiary consumers in this environment. Larger predator fish or sea-dwelling mammals are other examples of tertiary consumers that are predators in this ecosystem.

Autotrophs that use chemosynthesis, such as the deep water bacteria described above, are one final example of autotrophs in the food chain. These bacteria use geothermal energy to produce nutrients from oxidation using sulfur. Other species of bacteria can act as primary consumers of autotrophic bacteria through symbiosis. Rather than consuming autotrophic bacteria, these bacteria derive nutrients from autotrophic bacteria by holding them within their bodies and provide protection from the extreme environment in exchange. Secondary consumers in this ecosystem include snails and mussels, which consume these symbiotic bacteria. Carnivores, like octopuses, are tertiary consumers that prey on snails and mussels.

Sources

  • National Geographic Society. “Autotroph.” National Geographic Society, 9 Oct. 2012, www.nationalgeographic.org/encyclopedia/autotroph/.