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a chemical messenger produced and released by a cell or a gland in one part of the body of the organism that affect cells in other parts of the organism. In essence, it is a chemical messenger that transports a signal from one cell to another. Only a small amount of hormone is required to alter cell metabolism. Hormones in animals are most often transported in the blood.
birds without a keel on their breastbones and therefore unable to fly, for example ostriches....
microscopic canals running longitudinally through compact bone tissue that contain blood vessels...
the process whereby nutrients that have been absorbed from the digestive system are taken up by...
compounds that consist of any combination of elements, but do not usually contain carbon and...