Plants and animals are not the entirely separate entities we often like to picture. Plants evolved from single-celled animals that engulfed cyanobacteria. In a special case of symbiosis, the cyanobacterium was not digested and eventually became an integral part of the host animal, which we subsequently call plant.

There are many examples of single-celled animals that are seemingly stuck in this evolutionary transition and display trophic modes characteristic of both animals and plants (e.g. dinoflagellates and stramenopiles), multi-cellular animals that simply mirror this evolutionary coup (e.g. many Cnidaria and molluscs), and plants that returned to their primal animal lifestyle (e.g. dinoflagellates and parasitic land plants). The first two of these groups are broadly referred to as mixotrophs, animals that are also plants or plants that are also animals. A special case of mixotrophy, which you have encountered in the video, is called kleptoplasty, where the symbiotic chloroplast is first stolen from a plant.

These lifeforms have puzzled humans for well over 2000 years because they cannot be squeezed into oversimplified and widely used sets of categories such as our traditional “animal, vegetable or mineral” or its contemporary equivalent “animals, plants and fungi”. Perhaps it is time to adapt our views and embrace the fact that plants and animals are not as segregated as we think and explore the yet hidden diversity of those organisms with a mixed lifestyle.

Next Section »