a large oxygen-carrying protein (blood pigment).
a social structure in which different classes are determined by heredity.
regions in particular geographical locations with similar climates and vegetation types.
an organelle that occurs in the cytoplasm of both plant and animal cells. It is made from stacks...
a substance that consists of two or more chemically joined atoms.
blood that has no antigens (blood group O) and can be given to a person with any blood group....
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