Which is NOT an example of how an ecosystem can change suddenly?

good one: produce hormones that plants grow.

bad one: the problem with organic matter is that while plant nutrients are needed for crop growth, they can also stimulate excessive growth of the wrong plants – mainly, algae.

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".