The circulatory system has evolved over time from simple diffusion through cells, in the early evolution of animals, to a complex network of blood vessels that reach all parts of the human body. Made of specialized and unique cardiac muscle, it pumps blood throughout the body and to the heart itself.
Claps shut at birth. Evolutionary changes in the vertebrate heart are tied to change from single to double-circuit heart, with increased separation of oxygenated and deoxygenated blood, allowing more efficient respiration and circulation to fuel high activity and increased oxygen demands associated with endothermy.
Hypotonic solutions are those with less solute (again read as higher water potential). Isotonic solutions have equal (iso-) concentrations of substances. Water potentials are thus equal, although there will still be equal amounts of water movement in and out of the cell, the net flow is zero.
(1) Digestive System gets nutrients (good) from food and hands it over to the blood and Circulatory System then carries those nutrients where they need to go. (2) Filters out waste from food and pushes it through intestines and out the body (and you know how and where it gets out).
