Food webs normally start at the bottom and work their way up. Like the plants will be at the bottom, and then each level shows the animals getting bigger while losing energy. You continually lose energy as you work your way up an ecosystem, so normally there are only three or four levels. I hope this helps!
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The reason why toxic chemicals are classified as hazard because they can do as much damage as hazard things and can cause a serious of problems to one's health, for something to be hazard it can be flammable, and toxic chemicals are just that.
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Explanation: The basic unit of a DNA is a Nucleotide. The nucleotide comprises of: the nitrogenous bases, a deoxyribose sugar and a phosphate group. The nitrogenous bases are the purines and pyrimidines . The include, Adenine, guanine, Thymine and cytosine
