There are animals that are also plants.
Elysia Chlorotica is a slug that looks like a leaf. She’s the one on the top left in the image above.
Part of what makes a plant a plant is that it can make its own food out of inorganic materials like sunlight and water.
Slugs like Elysia are mixotrophs. They eat food like other animals but they can also synthesize part of their energy from sunlight. Elysia can go as long as a year without having to eat food.
Mixotrophs do this by munching on plants and keeping the chloroplasts in the algae or leaves they eat intact. These little plant cells then continue to photosynthesize inside their new host’s translucent digestive system.
Apparently there are about 70 species of slug that steal chloroplasts like this.
And it’s not just slugs, other organisms like corals and sponges also have symbiotic relationships with algae that allow them to live off of sunlight.
Mixotrophy goes both ways. An alga called Tripos Furca eats microscopic animals all day long, allowing it to survive in darkness for weeks. Pitcher plants and the Venus fly trap that catches and digests little inspects are other more commonly known mixotrophs.
It’s always nice when a sharp line between something that feels black and white turns out to be much blurrier than we first thought.
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Learned all this from a Ted Ed video by Luka Seamus Wright. Best Ted Ed video I’ve seen in ages. https://youtu.be/fSaHVHTqDY0