The heart sounds "lub" and "dup" result from the heart sounds "lub" and "dup" result from firing of the nodes of the intrinsic conduction system closure of heart valves blood rushing through the chambers contraction of the heart opening of the heart valves

Closure of heart valves

These are the first heart sound (S1) and second heart sound (S2), produced by the closing of the atrioventricular valves and semilunar valves, respectively.

If it doesn't have a nucleus its a prokaryote

Because the earth is not round ,but it may seem round when viewed from ,our planet but true some points earth is not round was an oblate spheroid -a square that it squashed as globe however is not even a perfect oblate spheroid.in fact isaac newton's first proposed that earth was not perfectly round but it was an oblate spheroid instead.that mean a square that is squashed as its poles and swollen at the