Answer:A checkpoint is a stage in the eukaryotic cell cycle at which the cell examines internal and external cues and "decides" whether or not to move forward with division.
Explanation: Easy Peasy
<span> C) It was once underwater; now it is not. </span>
Organisms compete for the resources they need to survive- air, water, food, and space. In areas where these are sufficient, organisms live in comfortable co-existence, and in areas where resources are abundant, the ecosystem boasts high species richness.
