Circulatory System

Question 1

What transport system is used for efficient supply of materials over large distances?

Answer 1

Mass Transport, since diffusion is fast enough for transport over short distances

Question 2

What do all organisms do?

Answer 2

Exchange materials between themselves and their environment

Question 3

Why are specialist exchange surfaces required?

Answer 3

• With Increasing size, surface area to volume ratio decreases to a point where needs of the organism cannot be met by body surface alone
• Specialist exchange surfaces are required to absorb nutrients and respiratory gasses and remove excretory products

Question 4

Where must materials be transported?

Answer 4

• Materials have to be transported between exchange surfaces and the environment
• Transported between different parts of the organism

Question 5

Why is a transport system required?

Answer 5

• Required to take materials from cells to exchange surfaces and from exchange surfaces to cells

Question 6

Whether there is a specialised transport system or whether it is circulated by a pump depends on which factors?

Answer 6

• Surface area to volume ratio
• How active the organism is
Lower the surface area to volume ratio and the more active the organism, the greater the need for a specialised transport system with a pump

Question 7

What are some common features of transport systems?

Answer 7

• Suitable medium in which to carry materials ( for example blood ), normally liquid based on water because water readily dissolves substances and can be moved around easily, but can be a gas breathed in and out of the lungs
• Form of mass transport in which the transport medium is moved around in bulk over large distances, faster than diffusion
• Closed system of tubular vessels that contains the transport medium and forms a branching network to distribute it to all parts of the organism
• Mechanism for moving the transport medium within vessels
• Mechanism to maintain the mass flow movement in one direction
• Means of controlling rate the flow of transport medium to suit the changing needs of different parts of the organism
• Mechanism for the mass flow of water or gasses, for example intercostal muscles

Question 8

What are the two ways in which the mechanism for moving the transport medium within vessels is achieved?

Answer 8

• Animals can use muscular contraction of either body muscles or of a specialised pumping organ such as the heart
• Plants rely on natural passive process such as the evaporation of water

Question 9

What type of circulatory system do mammals have?

Answer 9

• Closed double circulatory system.

* In which blood is confined to vessels and passes twice through the heart for each complete circuit

Question 10

Why does blood pass twice through the heart in double circulatory systems?

Answer 10

• When blood is passed through the lungs, pressure is reduced.
• If it were to pass immediately to the rest of the body its low pressure would make circulation very slow
• Blood is returned to the heart to boost pressure before being being circulated to the rest of the tissues
• Substances are therefore delivered to the rest of the body quickly

Question 11

Why is it required to deliver substances to the rest of the body very quickly?

Answer 11

• Mammals have a high body temperature, and a very high metabolism

Question 12

What are the vessels which make up the circulatory system?

Answer 12

• Arteries
• Veins
• Capillaries

Question 13

What is a direct consequence of blood passing twice through the heat?

Answer 13

• Substances are delivered to the rest of the body quickly due to a boost in pressure of blood before being circulated to the rest of the tissues

Question 14

What form of transport is used in order to enter cells?

Answer 14

• Diffusion

Question 15

Why is the final exchange into cells rapid?

Answer 15

• Final exchange from blood vessels into cells is rapid is because it takes place over a large surface area across short distances, and there is a steep diffusion gradient