Animal Circulatory Systems An efficient circulatory system has: a fluid, e.g., blood, to carry the materials to be transported; a system of vessels to distribute the blood; a pump to push the blood through the system; exchange organs to carry out exchanges between the blood and external environment, e.g., lungs and intestine to add materials to the blood; lungs and kidneys to remove materials from the blood. The most crucial demand on the circulatory system is the transport of oxygen and carbon dioxide to and from a gas exchange organ: lungs or gills and the tissues. All exchanges between blood and cells occur in the capillaries. The force of the pump that pushes blood through the arteries is dissipated as the blood flows through capillaries.
If they were land animal and could not swim then the only logical reasoning would be that the two pieces of land drifted apart from each other and the fossils were in between them and that´s why they ended up in the ocean.
<span>"Cytoplasmic determinates" are the proteins and rnas which perform a greatly significant role of vital importance in oocyte maturation, essential to organ formation of an organism's development very early on in the process which takes place in the mother's ovary.</span>
