Answer:
The populations become adapted to different environments and eventually become so different that they cannot interbreed to produce fertile offspring.
Speciation is the evolution of one species into two different kinds, and when they become isolated, that is the final step, since they cannot interbreed any longer.
Answer:
If you're talking about the cell: The nucleus contains the cell's chromosones
If you're talking about the atom: The nucleus contains protons and neutrons.
Explanation:
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I believe the answer is that;Corals are stressed and more likely to die without zooxanthellae; the zooxanthellae grow best when associated with the corals.
The corals and the algae have a mutualistic relationship. The coral provides the algae with a protected environment and compounds they need for photosynthesis. In return, the algae produce oxygen and help the coral to remove wastes. Most importantly, zooxanthellae supply coral with glucose, glycerol, and amino acids, which are the products of photosynthesis.