Carnivorous plants don't count as they don't use their prey for energy. Photoheterotrophs don't seem to fit based on a quick read as they use light and carbon in the same reaction. I'm looking for something that both eats for energy and does photosynthesis for energy. A select few animals that are symbiotic with algae barely fit. But is there a reason why 99.9999999% of organisms choose one or the other?

As an example, why couldn't some seaweed evolve to catch plankton like an anemone?

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    $\begingroup$ Welcome to Biology StackExchange! You seem to somehow mix up the terminology. Auto- and heterotrophy relates to the source of carbon (inorganic vs organic), not the source of energy. I suggest reading the article about Primary Nutritional Groups on Wikipedia which also have several examples of different groups. $\endgroup$
    – Domen
    May 22 at 10:08
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    $\begingroup$ Carnivorous plants don't count as they don't use their prey for energy. Of course they do. Why else would they eat them if not for the energy they provide? $\endgroup$
    – MattDMo
    May 23 at 16:50
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    $\begingroup$ @MattDMo As a source of nitrogen and other nutrients? Maybe there are exceptions but I thought that was the primary impetus for evolving carnivory in plants. $\endgroup$
    – Bryan Krause
    May 24 at 22:42
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    $\begingroup$ @MattDMo carnivorous plants normally grow in nutrient poor environments, typically nitrogen and/or phosphorus limited, such as in acidic bogs or as epiphytic plants, though other environments exist too. The consume the animals as a nitrogen source. It's all energy when you come down to it, just one particular form of energy in this case! $\endgroup$
    – bob1
    May 24 at 23:28
  • $\begingroup$ @bob1 that's kind of what I was referring to. Thanks for clarifying it! $\endgroup$
    – MattDMo
    May 25 at 21:43

1 Answer 1


It is because there is no need for developing such as a system like this.

Some recent research depict that some organelles were independent organisms in ancestors. If we assume that consuming energy from other organisms, and gain energy through photosynthesis are two different paths of evolution, they separated in history. Possibly, two different branches of gaining energy formed.

Obviously, having two systems of obtaining energy would be brilliant, but it may bring a lower efficiency in the body. <<#i am not sure>>

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    $\begingroup$ Welcome. Please cite relevant literature that support your claims; if you are not sure as you write, then refrain from posting. Maybes, perhapses, academic guesses and guesstimated numbers are OK, but only when supported by appropriate and credible sources. $\endgroup$
    – AliceD
    May 25 at 13:13

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