transport in animals 3.1.2

what is the need for transport systems?

• as organisms get bigger, the distance between the cells get greater

• as diffusion is only effective over very short diffusion distance, the organism won’t survive

• organisms therefore need a specialised transport system to move substance around the body

how are exchange systems adapted to maximise effectiveness?

• thin for short diffusion distance

• large surface area so lots of a substance can diffuse at once

• good blood supply to maintain a concentration gradient

what are the features of a transport system?

• transport medium

• vessels to transport

• pump to transport medium

• medium which flows in one direction (valves)

• anility to control flow of medium suit the changing needs of the organism

what are the 3 types of circulatory systems?

• single closed

• double closed

• open circulatory system

• closed circulatory system

what is the single closed circulatory system?

• only passes through the heart once for each complete circuit of the body

• the heart had 2 chambers

• because it goes through 2 sets of narrow vessels, the pressure is low which limits exchange process

what is the double closed circulatory system?

• the blood travels twice through he heart each circuit

• this ensures relatively high pressure and fast flow of blood

what are advantages of double circulation?

• the blood only travels through 1 capillary network before retuning to heart

• this maintains high pressure and steep concentration gradient

what is the close circulatory system?

• the blood is enclosed in blood vessels and doesn't come in direct contact with cells

• the blood is pumped under pressure and things leave through walls of the blood vessels

• the volume of blood flowing can be adjusted by widening or narrowing blood vessels

what is the open circulatory system?

• the blood (haemolymph) flows freely from the heart into body cavities (haemocoel) and comes into direct contact with the cells

• this is where change takes place before returning to heart through open-ended vessels

• no transport of O₂ or CO₂ directly exchanged from tracheoles