Answer: ecosystem
An ecosystem is a community of living and non-living components. A coral reef is an aquatic ecosystem which is formed by a continuous walls of calcium carbonates released by living animals they get combine to form rocks. These rocks and walls are collectively called as hard stony corals. These hard stony corals provide shelter to many aquatic animals like fishes. As the water is the chief abiotic factor along with coral walls and rocks which help in the survival of living organisms therefore, ecosystem is the largest organizational level found in one coral reef.
No beacuse the other layer may be to cold or hot for humans to survive in
The answer is urticaria (also known as hives).
answer: it increases from left to right
explanation:
the electronegativity of atoms increases from left to right across a period in the periodic table; it also decreases as you move from top to bottom down a group in the periodic table