A simple way to see how evolution works
Lets make a cell, and call it Blobb
Every Blobb has the genetic code telling it: “Eat 4 foods → reproduce.”
The environment has less and less food, so many Blobbs die before finding enough.
Random mutation creates a Blobb that only needs 3 food.
That small change means it reproduces sooner and leaves behind more offspring.
Over generations, more 3-food Blobbs exist than 4-food ones.
A scientist grows Blobbs in a tank, letting them reproduce normally.
Then the environment is suddenly altered (like flushing the tank with nitrogen).
Most Blobbs die because their normal traits can’t handle nitrogen.
A few Blobbs randomly had mutations making them resistant.
Only those survivors pass their traits on, so the next generation is more nitrogen-resistant.
Repeating this process quickly “steers” evolution toward nitrogen resistance.
Blobb gets attached to an altered Blobb, the altered Blobb is much larger.
Food in this new environment is rare, so Blobb struggles to reproduce.
A random mutation gives Blobb a tiny spike. It is now called Blokk
By chance, the spike pokes the host, releasing food.
Blokk with spikes reproduce more because they get more food.
Over generations, the spike trait strengthens and spreads.
The larger Blobb, lets call it BLOBB gets a layer of skin
Blokk’s spike no longer works on hosts with tougher skin.
Most Blokks fail to feed and die.
A few Blokks randomly have sharper spikes that can pierce the new skin.
Those survive and reproduce, passing down the sharper spike trait.
The host may evolve even tougher skin later, restarting the cycle.
One day, a simple Blobb gains a trait that allows them to detect Blokk, which will kill the Blobb, let's call them Slokk. However, they cannot defend themselves.
Eventually, they attach to a BLOBB.
The BLOBB’s normal skin cannot protect it from a Blokk, so when it feels a Blokk, it stiffens its skin, which makes it unpierceable.
However, this takes a lot of energy, so whether they do it in time is up to chance.
However, when the Slokk attaches, it evolves to send a signal to the BLOBB that tells it to stiffen its skin, and evolves to send that signal when Blokks are close.
So. They now rely on each other, and evolve into multicellular life.