circulatory system, fish, mammal,insects difference

Mammals and fish both have circulatory systems that consists of a heart, blood and blood vessels. Insects have an open circulatory system, where the haemolymph circulates freely among the body cavity and not enclosed in vessels, unlike the closed circulatory, where the blood is transported via the blood vessels. Mammals have a double loop circuit, meaning that the blood passes through the heart twice in each circuit of the blood that is pumped around the body. Fish, however, have a single loop system, unlike mammals, blood only goes through their heart once in each circuit. Haemoglobin is an iron based molecule that binds oxygen to the red blood cells for transport, thus giving it the red colour. Blood in mammals and fish carry nutrients, waste products, small amounts of carbon dioxide, and oxygen that are transported to the heart. However, haemolymph in insects also carries nutrients and waste products but does not carry oxygen. Insects have a different system for a gas exchange, where the oxygen is transported via tracheal tubes. Haemolymph contains about 90% plasma, which is clear, and is involved in clotting and internal defence. Unlike vertebrae blood, insects lacks red blood cells, this is because the oxygen is delivered directly to the tracheal systems. Blood transports nutrients, wastes, hormones and respiratory gasses. It also regulates the body temperature by distributing heat and defends against infection. The three animals all have some sort of heart/pump with one way valves to stop blood backflowing. Mammals have a four-chambered heart ,where as fish have a two chambered heart. Insects have a tubular heart where the haemolymph is pumped and goes through short vessels into the large body cavity and re-enters through ostia. Open systems cannot develop high blood pressure but muscle contraction help to circulate the haemolymph. Closed systems have higher pressure than insects because the blood is being delivered directly to the capillary beds of the