Tracheophytes— Flowering Plants (Angiosperms)
What factors have contributed to the success of seed plants?
Scientists do not know for certain which was the world’s first flowering plant, and their analysis changes every year based on new fossils or genetic studies. Still, based on current fossil evidence, many paleobotanists believe the first angiosperms arose 140 to 190 million years ago.
Another group of researchers believes the first flower plants may have evolved even earlier—about 215 million years ago. They base their theory on the genetic comparisons between living plants and clues from fossils to reconstruct the relationships between more than 150 terrestrial plant species. Their results showed that the dates corresponded with our knowledge of vascular and seed plants, but they had a much older date for the origin of angiosperms—dates that did not correspond (so far) with the fossil record.
Seed plants became prolific over time for many reasons. For example, seed plants do not require water for sperm to swim to an egg during reproduction; pollen and seeds have allowed them to grow in almost all terrestrial habitats; the sperm of seed plants is carried to eggs in pollen grains by the wind or animal pollinators such as insects; the seeds themselves are fertilized eggs that are protected by a seed coat until conditions are proper for germination and growth; and finally, the smallness of most seeds make them easily dispersed by wind or animals.