Eli5: How does a single cell multiply into exact copies of itself yet somehow knows to start building into different body parts? They are all in the same environment with the same DNA yet behave differently.
In: Biology
Because they’re not in the same environment. Once your original cell divides enough times, you’ve become a ball of cells.
Originally yes, the new cells were in the same environment but now, as a ball, you have got inside cells surrounded by other cells and outside cells forming the surface of the ball.
The inside cells start doing different things compared to the outside cells because they’re in a different environment.
Because of this, the ball changes shape and stops being bally and round and starts having a different elongated bean shape.
Now the outside cells are different from each other. Some are at the ‘top’ and others at the ‘bottom’ and they start doing different things. Inside cells nearer the top outside cells start doing things differently to the inside cells near the bottom outside cells.
This continues with each iteration of change creating new environments for the cells which now react differently to their parent cell, and so on and so forth until you have all your body parts.
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