Let's imagine a world without plants. Oh that was really really scary. Never mind, don't imagine a world without plants. You know what we saw in that imaginary world? Nothing. Absolutely nothing. That's right. In our imagined, non-plant world, there was No. Life. At. All. (Gasp.) It was dark, and slimy, and surprisingly toxic to breathe.
But that is just an imaginary world anyway, right? In reality, life does not depend that much on plants. After all, vegetables are gross and we don't need grass lawns to play on anymore because we have iPhones and videogames, and football fields are all turf these days. Right?
Well…maybe that is a bit of an exaggeration. Maybe a few plants are okay. Like, palm trees are pretty scenic and strawberries are delicious. Also, chocolate is really tasty and it does technically come from a plant. It's also nice to be able to print something out on paper and put gas in the car, and those products come from plants. Yup, paper comes from trees and gasoline comes from dead plants that lived thousands of years ago. All right, so plants are not so bad after all. In fact, they are actually pretty useful.
Plants are not just useful; they can be interesting too. Interesting in the way that reading the dictionary is "interesting"? No…plants are sexually promiscuous. That's right. They spread their sperm all over the place trying to make babies. Because they spread their sperm, and sometimes their seeds, we have allergies, food, and an atmosphere with oxygen. The allergies are not so good, but the food and atmosphere aren't half bad.
The plants we see outside today have evolved over millions of years. The ancestors of plants lived in the ocean, as teeny, tiny bacteria that could photosynthesize. That is, they could convert sunlight into food. Those bacteria, called cyanobacteria, started living on land about 1.2 billion years ago. They made our atmosphere hospitable to more life. By making an atmosphere that we could breathe in, they paved the way for animal life, including humans.
Of course, plant evolution only started with cyanobacteria. Bacteria aren't plants but they did develop some crucial cellular machinery for photosynthesis. Then came algae, then mosses, and a bunch of other plants, and we couldn't help but noticing, but there are a lot of different plants out there. How many? Almost 300,000 kinds of plants. Whew. Hope you don't have to memorize them all for the test…