Answer: Cell
Explanation: Cells make up all living things. Atoms make up all things that are not living.
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
Answer:Ecological succession is the process that describes how the structure of a biological community (that is, an interacting group of various species in a desert, forest, grassland, marine environment, and so on) changes over time. The structure of this community becomes more complex as new species arrive on the scene.
Explanation:
Gas exchange in humans is the delivery of oxygen lungs to the bloodstream, and the elimination of carbon dioxide from the bloodstream to the lungs.
