A fiel trip trough plant evolution : blue green algae

People usually think of plants as fairly passive, since they don’t move, or make sounds, or look at you, so it’s very easy to not think about them and the life that they live.

But they can't just sit there and do nothing, being a plant isn't easy. Just imagine, you have to defend yourself from things that want to eat you, you have to deal with changing, sometimes extreme temperatures, you have to compete with other plants trying to get the same sunlight and water as you, and you have to reproduce with others of your species, all of that without moving an inch.

In order to achieve all of this, plants have had to adapt a lot throughout millions of years , and today I wanna talk about that. 

This is the beginning of a little series of blogs that I’d like to make about plant evolution and about some interesting species that illustrate it, starting with blue-green bacteria. 

¿Where do plants come from?

Okay, let’s start  from the beginning, specifically 3500 million years ago, at this time in earth’s history living things are simple, primitive bacteria living in the ocean under an atmosphere with little to no oxygen. This last thing is a big deal, because metabolism with oxygen produces way more energy than that with other chemicals, meaning that without it you can’t maintain a big, multicellular animal like me or you.

or this thing

In comes photosynthesis, now, photosynthesis is VERY complex so keep in mind this is the simplified version. 

3500 million years ago one group of bacteria figured out how to break a molecule of H2O, with the help of sunlight, resulting in energy for the cell, this process releases a molecule of oxygen. This group were the blue-green bacteria or cyanobacteria, and they were so successful they started changing the chemistry of the atmosphere by dumping tons of oxygen into it. 

What does this have to do with plants?

Well some time after that something happened, an amoeba-like organism ate a cyanobacteria, swallowing it whole but not digesting it, by mistake just keeping it inside. So the bacteria kept doing its thing, taking sunlight, turning it into energy and now, giving some excess energy to its captor,this created a symbiotic relation where the amoeba brought movement and protection while the cyanobacteria gave energy. 

An illustration of said events, by me :3

This one anonymous organism, in one unknown portion of the ancient ocean thus became, by complete coincidence the ancestor of all living plants, a pretty big deal. This is known as endosymbiosis and it’s the same thing that happened with mitochondria 

Modern plants have chloroplasts, organelles which are responsible for all of the photosynthesis process, and inside those chloroplasts there’s DNA which allows us to see the connection between the organelle and the bacteria, like a strange paternity test.

Plant cells full of chloroplasts 

And what happened to cyanobacteria?

After making the atmosphere breathable and giving rise to all living plants, this group did not retire, they are in fact still alive and kicking, and are doing great actually!

Now (almost) all bacteria are individually, too small to see with the naked eye, but cyanobacteria are so numerous and successful they can sometimes be seen forming colonies of thousands or millions of individuals.

Despite being arguably the most simple and primitive photosynthetic organisms, they are majorly successful and a large part of the oxygen that you still breathe comes from them.

Left: shitty blurry picture of some Rivularia bullata i took at a local beach

Right: image stolen from google of the same species, alongside a closeup that shows the individual organisms (string like green stuff).

Now it’s not all fun and games, because some species produce toxins to avoid being eaten, and when they form great blooms in the ocean, something that’s become more common with climate change, these toxins can accumulate and become lethal or accumulate in the seafood we eat (which is bad).

Trichodesmium blooms (microalgas de mierda, para los canarios) as you can see in the image they can become so massive as to be seen from space, remember, the individual bacteria are much smaller than the width of a human hair 

There’s a lot more to talk about with this topic, but I don't want this blog to be 500 pages long, so that’s all for now. I hope you’ve gained some appreciation for the green scum you see on the shoreline or the water because it’s been a major player in shaping the world that you live in now.