... , stable, and self-regulating, even though it interacts with other units at the same level and at higher and lower levels. One such hierarchy of levels is identified structurally: quark, nucleus, atom, molecule, macromolecule, organelle, cell, organ, organism, and ecosystem. Other hierarchies are identified functionally: the reproductive hierarchy (gene, genome, organism and population), or the neural hierarchy (molecule, synapse, neuron, neural network, brain, and body). Human beings ... , too, the laws of chemistry limit the combinations of atoms that are found in DNA, but do not determ...

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• Grade Level: Undergraduate