You might have played the game called “animal, vegetable, mineral”. One player thinks of an object or organism and the other players ask questions to try to guess what it is – starting with this simple classification. But nature isn’t this simple. There are dozens of groups of living species that are neither plants nor animals.
We tend to think of plants as organisms that stand still and use photosynthesis to produce energy from sunlight and make their own organic molecules from the soil. And we see animals as creatures that move and feed on other organisms to obtain the energy and molecules they need.
But many organisms challenge those descriptions. The Venus flytrap, despite being a plant, feeds on other organisms – and some of its parts move faster than its unfortunate animal prey. Many groups of animals do not move and live attached to a surface for most of their life, including sponges, corals, mussels and barnacles to name a few.
It’s still relatively easy to say whether these creatures are plants or animals. But there are other organisms whose nature is more mystifying. Here are a few of the most intriguing creatures who defy our simple categories.
Hungry sea anemones
Sea anemones are technically animals, but they look so much like plants that they are named after a group of flowers. Even Aristotle, the ancient Greek who produced one of the world’s first systems for categorising life, was puzzled by them. He classified anemones as “zoophytes”, organisms bearing traits of both groups.