The contradiction between my brain capacity and the genius that went into Mao's writings gave me a headache. I need an adult please.

Lets start by asking, in reference to:

"It is evident that purely external causes can only give rise to mechanical motion, that is, to changes in scale or quantity, but cannot explain why things differ qualitatively in thousands of ways and why one thing changes into another. As a matter of fact, even mechanical motion under external force occurs through the internal contradictoriness of things. Simple growth in plants and animals, their quantitative development, is likewise chiefly the result of their internal contradictions."

I kind of understand what is meant here, but isn't plant and animal growth governed by multiple different chemical reactions?

I don't have a biology degree but there aren't just two chemical reactions acting in opposition to each other, or a set of pairs of chemical reactions, right?

How can something so complex be reduced to pairs of opposites? Doesn't that impose a limitation? What if instead of a dialectic its an n-alectic where n can possibly reach the thousands or millions (since things "differ qualitatively in thousands of ways")? Is this really what Mao wanted to convey?

Obviously his ideas were "right" because they helped develop a correct understanding of reality such that Mao won wars. I just don't understand what is meant.