Adaptations for transport in animals

Adaptations for transport in animals

Features of a transport system

Animals have the following features:

• A suitable medium to carry materials
• A pump, e.g. the heart which moves the blood
• Valves to maintain the flow in one direction

Some systems also have:

• A respiratory pigment, e.g. haemoglobin which allows a higher volume of oxygen to be transported
• A system of vessels with a branching network to distribute the transport medium to all parts of the body

Open circulatory systems

• Blood doesn't move around the body in blood vessels, it bathes the tissue directly
• Blood is held in a cavity which is called the haemocoel and it's found in insects
• They have a long, dorsal, tube-shaped heart which runs the length of the body
• It pumps blood at lower pressure into the haemocoel
• Here materials are exchanged between the blood and body cells
• The blood slowly returns to the heart and the open circulation stars again
• Oxygen diffuses directly into the tissues from the tracheae so blood doesn't transport oxygen and has no respiratory pigment

Closed circulatory systems

The blood moves in blood vessels. There are two types of closed systems: single circulation and doule circulation.

Single circulation

• Blood moves through the heart once in its passage around the body. e.g. in the earthworm
• Blood moves forward in the dorsal vessel and back in the ventral vessel
• Five pairs of pseudohearts, thickened, muscular blood vessels, pump the blood from the dorsal to the ventral vessel and keep it moving 
• e.g. fish. The ventricle of the heart pumps deoxygenated blood to the gills, where its pressure falls
• Oxygenated blood is carried to the tissues
• From there, deoxgenated blood returns to the atrium of the heart
• Blood moves to the ventricle and the circulation starts again

Double circulation

• Blood passes through the heart twice in its circuit around the body 
• e.g. mammals:
• Blood is pumped by a musclar heart at a high pressure and this gives a rapid flow rate through the vessels
• Organs aren't in direct contact with the blood, they're bathed in tissue fluid
• This seeps out of capillaries
• They have a blood pigment - haemoglobin which carries oxygen
• When blood…