There are also a few animals that carry out photosynthesis, and this is the story of how they came about. Animals and fungi are heterotrophic and generally require organic molecules, whereas algae are autotrophic, and can make organic molecules from carbon dioxide, water and sunlight. Oddities also exist: Some single-celled animals called protozoa are mixotrophic, that is able to live both as food-eating or photosynthetic organisms, depending on access to light. Clams and corals are symbiotic with photosynthetic algae to obtain food from sunlight, but this partnership is reversible. Fun fact: these animals are also hermaphrodites, capable of making both eggs and sperm, although they do not self-fertilize.