The dinoflagellates constitute a group within the protistan supergroup Alveolata, and can be referred neither to the plant nor the animal kingdom. They swim about using two flagella and orient using various stimuli. About half of the species are capable of oxygenic photosynthesis, but most of them complement this with capture of prey. Some live entirely by capturing small organisms, others are parasites. Some species are able to emit light. The group has a long evolutionary history, and almost as many extinct species as extant ones have been described. Remarkable is the way the photosynthetically potent dinoflagellates have acquired their chloroplasts by endosymbiosis with photosynthetic organisms from many different groups. In some cases repeated endosymbiotic events have taken place.