Photosynthesis: The Most Important Thing On Earth
And for the first time, after a dusty red sheen;
from the Earth emerged, a little bit of green.
There are a lot of animals doing a lot of things on Earth. If most of them disappeared, the Earth would be fine. In fact, if humans disappeared, the rest of the planet would probably sigh in relief. However, there is one process that almost the entirety Earth’s creatures rely on, and that is photosynthesis. Photosynthesis is where plants absorb light from the Sun to get energy. Life relies on it so much, because almost every living thing on the planet, is a plant, eats plants, or eats things that eat plants. That means, if plants suddenly disappeared, it would be pulling the ground out from under life on Earth, and pretty quickly, most life on the planet would cease. Understanding the origins of photosynthesis is very important. Let’s dive in, to photosynthesis.
Photosynthesis: What is it?
Put simply, photosynthesis is a biological solar panel. Plants take in energy from the sun and use it to build sugar, which they then use to fuel themselves to grow, repair cells, build new roots and leaves and do all the other things that plants do. It is their main source of energy, most plants don’t really “eat” like animals do. The underlying chemical reaction is very simple – the plants take in carbon dioxide and water and give off oxygen and sugar. This is why plants are so good for the environment, as they offset a lot of the carbon that human machines belch into the atmosphere.
However, photosynthesis is actually quite complex. While the chemical reaction is quite simple, it is very hard to make it happen. It doesn’t happen in one big leap, it has an enormous number of intermediate steps. Plants have engineered all sorts of different processes to make these intermediate steps more efficient. Enormous amounts of human time and money are put into study these processes, trying to breed plants to make them slightly more productive, as even a slight improvement in the effectiveness of these processes, could increase crop yields and leave to and massively improve the quality of life in the poorer regions of our planet. Teleportation and black holes are cool and all, but making photosynthesis work is really the science that helps people.
The Great Oxygenation: Photosynthesis Evolves
Photosynthesis is the first thing in the evolution of early life for which we have a really clear date. As discussed previously, the early earth’s atmosphere was very different from its current atmosphere, it had lots of carbon and very little oxygen (see our post here). However, about 2.5 billion years ago, a billion years into the history of life, the amount of oxygen in the Earth’s atmosphere massively increased and the amount of carbon decreased.
This increase in oxygen is very easy to see in the geological record. At about 2.5 billion years ago, there is a sudden band of iron rust that turns up all across the world. At this stage of the Earth’s life, there was still a lot of exposed metal on the surface. However, this exposed metal hadn’t rusted in any way, because there was no oxygen in the air. Then suddenly, the first photosynthetic organisms appeared and they started consuming carbon dioxide and producing oxygen. This oxygen then combined with the exposed iron to create a thick band of iron rust which covered a lot of the Earth. This iron rust band is still visible today, across the planet.
This “Great Oxygenation” of the atmosphere, particularly important in the history of life on Earth. The amount of oxygen in the Earth’s atmosphere increased by 100 fold, these organisms dominated the planet and re-engineered the entire atmosphere. In fact, a lot of other organisms almost certainly died out, not being able to cope with the sudden change brought about by this new form of life. Also, it’s quite likely that oxygen-rich atmospheres are much easier for life. Before the Great Oxygenation, the atmosphere was almost all nitrogen and carbon dioxide, a much more hostile environment. There were some species surviving but it is difficult to imagine the great diversity of life on Earth today without oxygen. These organisms laid the bedrock for all life as we know it.
In the modern world, photosynthesis is generally associated with plants. However, plants had not evolved yet. Instead, all this oxygenation was done by “Cyanobacteria” – weird little green bacteria that photosynthesis. Most people know them as “Blue-Green Algae” (that’s what the cyan bit means in their name – blue bacteria). In fact, even today, most of the removal of carbon dioxide and production of oxygen on earth continues to be done by cyanobacteria, floating in the ocean. They just don’t have as good a PR team as plants.
Why does this all matter?
Photosynthesis is the most important thing going on Earth. It’s fundamental to understanding every ecosystem on the planet, and life on the planet would crumble if it was removed.
But perhaps, even more importantly, it teaches us how fundamentally interconnected all systems of our planet are. It’s a bit of a cliche to say “everything is connected”. But it’s actually true. The entire planet relies on photosynthesis to survive. Photosynthesis provides food for the food chain, cleans the ocean and the atmosphere, even tries to offset the damage us humans do.
Most people have some concept of life being connected – they understand the idea of an ecosystem. But it goes even deeper. The plants and other photosynthesizing organisms remade the very planet itself. The atmosphere went from a noxious nitrogenous hell to the pleasant summer breeze we know today because early life cleaned it. And when doing this, they left an iron band deep within the Earth that we can still see today. The entire Earth is one deeply interconnected system, between the environment, living and non-living things all giving and taking and playing their part in a finely balanced ballet. It is a truly beautiful thing. We should appreciate it all so much more.
