The great variety we see in some organisms is due to

asexual reproduction

mitosis

sexual reproduction

fission

What would be the most likely result if the ph of the stomach were increased to 5

Nucleic acid certain protein cell membranes certain carbohydrates

The concept of keystone species is controversial among ecologists because most organisms are highly interdependent. if each of the trophic levels is dependant on all others how can we say one is most important