Pumping blood in and out of the heart.
The correct answer is - No.
The Cambrian explosion is a term used for the big and rapid diversification of the animal species, but it is not the period in which the animal life started. The animal life started in the period between 620 and 550 million years ago, in what is known as the Vendian Period. In the Vendian Period, the first complex animal organisms appeared, started to develop and evolve, though it is not a period where there was a high diversification of the species. The later Cambrian Period provided better living conditions, and that resulted in a so called ''explosion of life'', which resulted in much more new species developing and evolving.
Phosphate groups are polar and allow the cell to exist in water.
One type of density change is mass over volume.
