Plants can be divided into spore-producing plants, such as mosses and ferns, and seed-bearing plants, such as flowering plants.
There are now thought to be more than 400,000 identified species. But where did they first come from?
Plants originated as algae — simple organisms that live in water and feed off the Sun’s energy. The first algae lived in the sea. Over time, they spread into fresh water habitats and into damp places on land.
Moving onto land
More than 400 million years ago, plants started to grow on land. The first land plants were small, mosslike organisms and had no true leaves, roots, or flowers.
An unusual “seed”
Plants such as mosses and ferns have capsules that hold spores. Spores are a bit like seeds, but microscopic and not as hardy. Spores were a good means for early plants to reproduce, because an organism can produce millions of spores.
Land plants spread out
When plants such as Cooksonia evolved sturdier stems, plants began to grow taller and spread farther across land. Later, plants evolved the ability to produce seeds, which can sprout in much drier places than spores. Dense forests then sprang up, turning the land green.
This plant may look as if it’s producing fruits, but actually it is bearing seeds, each the size of an egg. Medullosa was the size of a small tree. It appeared about 350 million years ago.
A helping hand
As forests flourished, plants began to compete to reach the light. Woody stems evolved, allowing plants to reach higher. Plants similar to those we know today began to appear. Tree ferns, for instance, would have been familiar to the dinosaurs.
During the dinosaur era, forests were dominated by towering conifer trees. These have thin, needlelike leaves, which cope well with hot, dry climates. The monkey puzzle tree is a type of conifer that still survives from this period.
“With the spread of plants, more oxygen was released into the atmosphere. Plants were changing the planet”