The main responsible for the delay among the atrial and
ventricular contractions is the action potential conduction velocity of the AV
node cells. If the atria and ventricles contract simultaneously, atria cannot
give any help in filling the ventricles, which is needed, especially in those
with stiff ventricles as in the elderly. Hence atria have to contract first and
then the ventricles.
<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>
A. The arrangement of particles within the watermelon changed.
<span>prorostomes and deuterostomes is your answer</span>
