A gastrovascular cavity is a digestive sac with only a single opening. An alimentary canal has two openings (a mouth and anus) between its digestive tubes unlike the gastrovascular cavity in which food is ingested and eliminated through the same opening.
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Human dna was completely mapped
Most macromolecules are polymers of simple molecules (monomers). There is not a great variety of simple molecules, but their structure determines the macromolecule. For example, proteins are macromolecules synthesized from amino acids. There are only 20 amino acids and a great number of proteins made of different combinations of those 20 amino acids.
Explanation:
making hypotheses is a scientific method