Chemoheterotroph

Chemoheterotroph Definition

It may surprise you to learn this, but you are actually a chemoheterotroph!

“Chemoheterotroph” is the term for an organism which derives its energy from chemicals, and needs to consume other organisms in order to live. That means you: your body gets its energy from food, and you must consume other organisms such as plants and animals in order to survive.

All organisms must solve two problems in order to survive: they must be able to obtain energy, and they must be able to obtain cellular “building materials” such as proteins, lipids, and carbohydrates.

Most organisms that consume organic material use it for both energy and building materials. Animals and fungi both, for example, obtain energy by breaking down our food, and also get the building materials for our own cells from the food we eat.

A few rare organisms, however, use inorganic chemicals for energy, and yet cannot make their own building materials. These organisms – almost always bacteria – require both inorganic chemical energy sources, and other organisms whose organic materials they can consume, in order to survive.

All animals are chemoheterotrophs. So are fungi – although fungi may look like plants, they don’t perform photosynthesis, but rather derive their energy by breaking down organic material in soil.

Many bacteria are also chemoheterotrophs, including many bacteria that live inside the human body, many infectious bacteria, and some sulfur bacteria.

The chart below may be useful for determining whether a given organism is a chemoheterotroph:

Troph flow chart

Function of Chemoheterotrophs

Chemoheterotrophs play a big role in most ecosystems.

While “producers” at the bottom of an ecosystem’s energy pyramid make energy and organic materials from scratch, the upper levels of the pyramid are usually chemoheterotrophs who feed on those producers. Herbivores, carnivores, scavengers, and decomposers are all chemoheterotrophs.

Chemoheterotrophs take materials from plants and chemoautotrophs and recycle them in a complex web of life, where materials are used over and over again.

Types of Chemoheterotrophs

Chemoorganoheterotrophs – Eaters of Living Things

“Chemoorganoheterotroph” is a mouthful. But we’ve seen what “chemotroph” and “chemoheterotroph” mean.

“Chemoorganoheterotroph” just adds the term “organo,” for “organic” molecules. Organic molecules are carbon-containing molecules such as proteins, lipids, sugars, etc. that are usually associated with life.

Chemoorganoheterotrophs, then, are eaters of organic molecules – and where do you find organic molecules? Inside of living or dead organisms.

Chemoorganoheterotrophs, then, include herbivores, carnivores, scavengers, and decomposers. They include all fungi and animals.

Chemolithoheterotrophs – Stone Eaters

Just as “organo” is the Greek root word for organic materials, “litho” is the Greek word root for “stone.”

Chemolithoheterotrophs are organisms that derive their energy from inorganic minerals or other geological processes. Food sources for chemolithotrophs can include elemental sulfur and elemental gas.

Chemolithoheterotrophs are generally bacteria. Because deriving energy from inorganic minerals is not as efficient is digesting sugars using cellular respiration, organisms that use this energy source are generally small and simple.

Chemolithoheterotrophs can be found in places such as the sea floor or underground water sources, where both their chemical food sources and organic materials are found.

They may obtain their organic compounds be feeding on other bacteria, or on dead material that settles in sea floors and river beds from other organisms.

Examples of Chemoheterotrophs

Humans

It is easy to see how humans are chemoheterotrophs! We eat food every day. That food is made from animals, plants, and other organisms. We break down the organic chemicals from their cells to both obtain our own energy, and building materials for our own bodies.

Mushrooms

Mushrooms and other fungi may look like plants, but they are actually more like animals than like plants.

Fungi derive their energy from breaking down organic material. Often it’s organic material that is already dead, or is not well-defended by its host immune system.

Mushrooms can commonly be found growing in rich soil – which is made rich by the breakdown of the bodies of dead plants and animals – or on dead trees, old fruits, and other sources of organic material that do not have an immune system to fight the fungus off.

Some fungi can even attack living animals and infect them despite the immune response, though these are fairly rare. The Ophiocordyceps fungus, for example, attacks and digests living insects. Very rarely – usually in people whose immune systems are not healthy and strong – fungi can even attack healthy humans and cause dangerous infections.

Lithotrophic Bacteria

Almost all chemolithotrophs are autotrophs that do not need to consume other organisms to survive.

Likewise, almost all heterotrophs are organochemotrophs, organisms which obtain energy and organic compounds from the same source.

But a few species of bacteria that derive their energy from minerals have also developed the ability to use organic materials made by other organisms instead of making their own.

A few may even have lost the ability to make their own organic materials, meaning that they now require the presence of other organisms as well as their mineral energy source in order to survive.

Related Biology Terms

  • Chemotroph – Any organism that obtains its energy from chemicals. This includes chemoautotrophs such as sulfur bacteria, and chemoheterotrophs such as animals and funig.
  • Energy pyramid – A diagram which shows how energy flows through different types of organisms within an ecosystem.
  • Heterotroph – Any organism which must each other organisms in order to survive. This includes animals and fungi, and some bacteria.

Quiz

1. Which of the following root words is NOT found in “chemoheterotroph?”
A. “Chemo” for “chemical”
B. “Hetero” for “other”
C. “Troph” for “food” or “to eat”
D. “Auto” for “self”

Answer to Question #1

2. Which of the following is NOT true of chemolithoheterotrophstrophs:
A. They derive their energy from inorganic chemicals.
B. They rely on other organisms for organic materials.
C. They solve the problems of obtaining energy and organic materials separately.
D. They obtain their energy and organic materials from the same source.

Answer to Question #2

3. Which of the following is NOT an example of a chemoheterotroph?
A. A dog.
B. A daisy.
C. A sulfur bacteria that can’t make its own organic molecules.
D. A mushroom.

Answer to Question #3
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