Answer:
D
Explanation:
polysaccharides is NOT one of the four main groups of macromolecules of living things
B explained is that idek I just need points
Answer:
A
Explanation:
From what I know this could be wrong, but in the four stages of natural selection, the first step is overproduction, the second step is adaptation, and the third step is competition or survival of the fittest. This means that only the organisms with the best adaptations for their surroundings will survive. COULD BE WRONG SORRY IF IT IS
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.
