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:
- Charophytes and land plants share certain enzymes that other green algae don't have. These enzymes help the cell hold onto organic products that it doesn't want to lose, like its cell phone and wallet. The enzymes in question are found in peroxisomes of charophytes and land plants, but not other algae. Coincidence? We think not.
- The proteins that make cellulose in both charophytes and land plants are arranged in circles. In other algae, they are arranged in lines.
- Sperm shape. Sperm of land plants looks much more like charophyte sperm than sperm of other algae.
- Cell division in land plants is more similar to charophyte cell division than other algal cell division.
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.