Living components in a river ecosystem would include all plants, all animals, all microorganisms. Every fish species, every arthropod species, every reptile and amphibian species, all the birds, etc.
<span> B. A mutation can result in a change of function. </span>Not all mutations can cause negative effects, but a single mutation is capable of causing profound effect on the physiology and cellular structure of organisms. It can alter the function of proteins causing permanent diseases.
The answer is A. the presence or absence of an envelope
The answer is b gamete formation.