N Which structures are most similar in birds and mammals based on their functions?
air sacs in birds and rib cages in mammals
air sacs in birds and mammary glands in mammals
gizzards in birds and teeth in mammals
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crops in birds and teeth in mammals

What discovery would weaken the primordial soup hypothesis of the origin of life? question 19 options: lightning was common on early earth. earth’s early atmosphere contained carbon dioxide, water, and trace gases. earth’s early oceans were warm and shallow. asteroid impacts were uncommon when life is presumed to have begun.