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The Earth was once a dark and stormy place, where everything alive was found in the ocean, cooking away in a big pot of primordial soup. Over time, early ancestors of plants and animals moved to land and developed lots of new traits that allowed them to survive above water. Before we jump into the grimy details of plant prototypes kicking and fighting their way out of the primordial ooze onto land, take a few minutes to review the basic principles of evolution here.
The ancestors of land plants were algae. There are red, green and brown algae. But even though they can be green, algae are not plants. Scientists usually distinguish plants from algae because plants are embryophytes: they develop an enclosed embryo on the plant body, usually in archegonia, which produce eggs. Algae do not make embryos. They make spores, which they don't nurture in enclosed, protected spaces. Geez, it's like they don't love their babies. The ancestor of land plants was most likely shared with a group of green algae called the charophytes. Now, we don't want everyone to go picking favorites among the algae, because there are lots of awesome algae out there. But charophytes are special because they share a few important traits with land plants:
In addition to the above traits, some charophytes also have a protein in their cell walls called sporopollenin, which was present in early land plants. The charophytes have DNA that is closer to land plants than other green algae. Together, these observations provide good evidence that land plants and charophytes shared a common ancestor.
Algae may not sound very exciting, but some people are betting that they will run our cars one day. Scientific research labs are working on extracting oils from algae for that very purpose.