Scientists currently know about three hundred thousand (300,000) species of plants, and there are probably many more that we don't yet know about. The real number is probably about a million.

That is a very interesting question. There are many many different types of plants on Earth. They can grow almost anywhere as long as there is enough water, sunlight and the temperature isn't too cold. Plants are grouped by shared features, especially how they appear when they flower or reproduce. That means that some trees are more closely related to dandelions (for example) than they are to other trees. Some plants are very ancient in their origin and others only came about very recently in time. There are thought to be 300,000 different species of plants on Earth. That's around the number of individual hairs on 3 people's heads! That's a lot of plants!