The answer is B. Population
If you look at two species in their embryogenic stage. their bones and their forms look similar and you can differentiate too.
if you look at a fish and a human...
humans wont have the the fins protruding in the fishes embryo, showing how different they are. <span />
Answer:
C. A concentration gradient must exist.
An acid has <em><u>c. more </u></em> hydrogen ions than a base.
The abiotic factor is the amount of oxygen. Abiotic means non-living, and all the other answer choices reference living things.
If you need more help, comment below and I'd be happy to assist.
