<span>Comparative embryology is the study which determines the organisms that have the same and almost identical embryo development.
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While, comparative morphology is the scientific study of organisms where their structures, physical entities and elements are identified to be similar or dissimilar. Using only simple basis of empirical observation, a scientist can detect whether two animals are of the same family or not.</span>
I'm pretty sure it's primary growth. I might not have studied this type of biology yet, but secondary growth would definitely not be the answer.<span />
