This is my FAVOURITE diagram. Have I posted this before?? Gonna post it again.
Most diagrams of geologic time periods just display the dates, order and names. It blew my mind seeing it laid out like this. Look how fast everything happens once complexity starts to accelerate. Look how long things were small and simple compared to the time that anything we focus on showed up.
Over half of life's history is unicellular?? Nearly half is prokaryotic??
And - I cannot properly emphasize that eukaryotes are a BIG DEAL. Highschool bio did not drive home what a big deal they are. Like, yeah, they have a nucleous, ok, they store their dna in a little membrane bundle good for them, but — they can do that because they have internal membrane systems PERIOD. Prokaryotes don't. Those membranes are a SUPER POWER.
These guys are like 10x bigger than prokaryotes because having membranes inside lets them majorly hack the surface-area-to-volume-ratio issue that is like the #1 problem of every living thing. The reason elephants have big ears and lungs are spongy and leaves are broad and flat, and a billion other things. Not enough surface area on the outside?? Add surfaces on the inside!!
It also lets them compartmentalize reactions that wouldn't be able to happen otherwise. The nucleous isn't just some superficial difference under a microscope - it lets them fiddle with the messages from their dna before reading them out to make proteins, because the protine machines aren't just sitting loose in the same soup as the dna strands and have to wait their turn. This opens up a whole new avenue for nuanced and adaptable gene expression.
And with them, all along, are the efficient little bacteria being so so so good at cellular respiration to give the cells energy to do all this!! The little friends...!!!
(there's some chicken-vs-egg debate about whether those first archaea cells could let in the useful respiring bacteria because they had wonky cell membranes, or whethet they were able to develope those membranes because their little friends gave them so so much energy, but either way!! )
And also: for ANY of that to happen, some photosynthetic little buddies had to spend like 900 million years producing enough oxygen to rust the entire surface of the earth???? 900 million years.... That's longer than plants have lived on land. That's so so long. Oh my god.
(also. Plants. Plants are eukaryotes that have extra little friends because those photosynthetic little buddies?? They moved in and beame chloroplasts.)
And now we are a pile of cells doing fancy adaptable gene expression powered by tiny bacteria that are one with our cells and our guts are full of bacteria we would probably die without and did you know dogs came over to the Americas with the first humans because dogs have been beside us for longer than there have been people on the continent, and -
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