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Do all life forms need to eat other life forms to exist?

  1. Sep 6, 2012 #1
    As you can tell from the question, my science knowledge is lacking. :confused:

    I can see that mammals, reptiles, etc. must eat other living creatures (mammals, insects, plants, etc.) for energy. But do plants, microbes and other types of life forms all depend on eating other life forms? For example, do the nutrients that plants get from the soil contain living organisms and are they essential? In other words, does every organism, simple or complex require eating another living organism for it's energy? If not, is there a term or classification for living organisms that don't eat other organisms for energy?

    Many thanks for taking the time to answer this question.
  2. jcsd
  3. Sep 6, 2012 #2


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    The nutrients that plants get from the soil don't generally include living organisms. For the most part, plants don't require eating other organisms as a source of energy, and animals do. Most plants get their energy from the sun instead of eating other organisms. There are some exceptions, like Venus fly-traps, which are plants that eat insects for nutrients (not for energy), and animals like worms that eat primarily dead organic matter.

    I think most plants could live in an environment that was completely sterile and contained no other organisms, as long as light, air, water, and the necessary inorganic nutrients were supplied.
  4. Sep 6, 2012 #3


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    Welcome to the forums, I believe the term you are looking for is autotroph.
  5. Sep 6, 2012 #4
    Ah! Thanks so much for both answers. The Wikipedia page for autotroph was very helpful, well written for the novice reader and the type of info I was looking for. It's a new term for me, plus, I also learned that "autos" is Greek for self and "trophe" is Greek for nutrition which is also good to know!
  6. Sep 6, 2012 #5
    By definition, an autotroph does not have to get its energy from another living thing. Most plants and some bacteria are autotrophs. The most well know autotrophs are phototrophs, getting their energy from light waves. However, some autotrophs get their energy from nonbiological chemicals. These include the lithotrophs and chemotrophs.
    Most plants, cyanobacteria and rhopsin bacteria are phototrophs. Iron reducing bacteria are chemotrophs. Those bacteria in the sea vents that eat sulfuric acid are chemotrophs.
    By definition, a heterotroph gets its energy from other living things. Animals, fungi and most bacteria are heterotrophs.

    “An autotroph[α] "(self-feeding)" or "producer", is an organism that produces complex organic compounds (such as carbohydrates, fats, and proteins) from simple substances present in its surroundings, generally using energy from light (by photosynthesis) or inorganic chemical reactions (chemosynthesis). They are the producers in a food chain, such as plants on land or algae in water. They are able to make their own food, and do not need a living energy or carbon source. Autotrophs can reduce carbon dioxide (add hydrogen to it) to make organic compounds. The reduction of carbon dioxide, a low-energy compound, creates a store of chemical energy. Most autotrophs use water as the reducing agent, but some can use other hydrogen compounds such as hydrogen sulfide. Phototrophs, a type of autotroph, convert physical energy from sun light (in case of green plants) into chemical energy in the form of reduced carbon.
    Autotrophs can be phototrophs, lithotrophs, or chemotrophs.”

    “Chemotrophs are organisms that obtain energy by the oxidation of electron donors in their environments. These molecules can be organic (chemoorganotrophs) or inorganic (chemolithotrophs). The chemotroph designation is in contrast to phototrophs, which utilize solar energy. Chemotrophs can be either autotrophic or heterotrophic.”
  7. Sep 7, 2012 #6
    Darwin123...thank you for the additional info. This is exciting stuff to learn about!
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