Mixotrophy even cuts both ways: an alga called Tripos furca can consume several microscopic animals a day, allowing it to survive in darkness for weeks.
All the plants we know today descended from the same ancestor: a teeny-tiny green alga — that's the singular for algae — that existed around 500 million years ago.
Researchers have not been able to find traces of the compounds in rocks older than that, despite the existence of fossils of a red and a green alga — both eukaryotes — dating back about one billion years.