Show your math and tell the fraction or percent of geologic time that land plants have been present on Earth?

Question

Geological Time Scale Mural

Answer 1

Well, that depends. There is evidence of algae at 3.5 billion, probably photosythetic cells by 2.0, and clear plants by 400 million. With a 4.6 billion year old earth, that's 76%, 43%, or 8.7% of the time.