3.2.1 - The need for Transport Systems in Animals

Question 1

Why do larger organisms require specialised transport systems?

Answer 1

• increasing transport distances
• SA:V ratio
• increasing levels of activity

Question 2

How are there increasing transport distances in animals?

Answer 2

• in larger, more complex organisms, their exchange sites tend to be further away from other cells in the organism.
• higher levels of metabolic activity
• they cannot rely on simple diffusion, as it would not fast enough to meet the metabolic requirements of cells.

Question 3

How does a high SA:V ratio benefit smaller organisms?

Answer 3

• allows for exchange of substances to occur via simple diffusion
• large SA allows for maximum absorption of nutrients and gases and secretion of waste products.
• small volume means diffusion distance is shorter

Question 4

Why does SA:V ratio decrease as organisms increase in size?

Answer 4

• there is less SA for the absorption of nutrients and gases and secretion of waste products
• the greater the V, the longer the diffusion distance to the cells and tissues in the organism

Question 5

What is a mass transport system?

Answer 5

The bulk movement of materials. It is directed movement, so involves some sort of force. In larger organisms. There is still some diffusion involved at specific exchange sites, e.g. the lungs. An example being a circulatory system.

Question 6

What do mass transport systems help with?

Answer 6

• brings substances quickly from one exchange site to another
• maintains diffusion gradient at exchange sites + between cells + surrounding fluids
• ensure effective cell activity