DNA was not a type of evidence Darwin had available in his time!!
Feathers<span> vary considerably in structure and </span>function<span>. </span>Contour feathers<span> form most of the surface of the bird, streamlining it for flight and often waterproofing it. The basal portion may be downy and thus act as insulation.
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Answer:Exocrine glands are glands that secrete substances onto an epithelial surface by way of a duct.
