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Year 10
AQA
Higher

The importance of exchange surfaces and transport systems in humans

I can explain how exchange surfaces and transport systems enable cells in multicellular organisms to be quickly supplied with substances they need to stay alive.

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New
New
Year 10
AQA
Higher

The importance of exchange surfaces and transport systems in humans

I can explain how exchange surfaces and transport systems enable cells in multicellular organisms to be quickly supplied with substances they need to stay alive.

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Share activities with pupils
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Lesson details

Key learning points

  1. Consequences for living organisms of relationship between surface area:volume ratio and diffusion time.
  2. Reasons why a small surface area (relative to volume) could be a disadvantage to living organisms.
  3. The circulatory system minimises diffusion distance for oxygen and food molecules so cells can be supplied quickly.
  4. Examples of exchange surfaces in humans (e.g. alveoli in lungs, villi in digestive system).
  5. The exchange surfaces are adapted to maximise surface area for diffusion of particles of essential substances and waste.

Keywords

  • Surface area - The total area of the surface of an object.

  • Surface area to volume ratio - The relationship between the surface area and the volume of a shape.

  • Diffusion - The net movement of particles from an area of higher concentration to an area of lower concentration.

  • Exchange surfaces - A specialised surface which enables the efficient exchange of substances.

Common misconception

Pupils may think that villi and alveoli increase surface area without changing volume.

These ideas are explored in detail with examples and demonstrations using cube animals. The issue of surface area to volume ratio and diffusion rate is covered thoroughly, along with solutions to the issues in humans.

Use stackable cubes or building blocks to help show how breaking a large block up into smaller pieces increases surface area without reducing volume. Wrapping them in paper to show the surface area changing also works, but might be best done in advance.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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Starter quiz

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6 Questions

Q1.
The role of the circulatory system is to deliver and nutrients to cells and take away waste products.
Correct Answer: oxygen, O2
Q2.
Where in the lungs does gas exchange take place?
An image in a quiz
Correct Answer: alveoli, alveolus
Q3.
Which of the following statements about diffusion are correct?
molecules move in one direction
it requires energy from respiration
Correct answer: it is a passive process
Correct answer: molecules move randomly
Q4.
Where are nutrients absorbed into the bloodstream?
oesophagus
Correct answer: small intestine
stomach
Q5.
Which blood vessel is only one cell thick?
Correct Answer: capillaries, capillary
Q6.
What is the surface area to volume ratio of this shape?
An image in a quiz
2 : 4 : 4
8 : 2
8 : 4
Correct answer: 2 : 1
32 : 32

Exit quiz

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6 Questions

Q1.
Which factors does the surface area and volume affect?
Correct answer: rate of diffusion
Correct answer: diffusion distance
which substances can diffuse in and out of a cell
Q2.
True or false? Large living organisms have a large surface area to volume ratio.
true
Correct answer: false
Q3.
Why is a small surface area a disadvantage to organisms?
Correct answer: Decreasing SA : V decreases diffusion rate.
Decreasing SA : V increases diffusion rate.
Q4.
Having many villi the surface area over which diffusion can take place.
An image in a quiz
Correct answer: increases
decreases
does not impact
Q5.
What are the advantages of a circulatory system?
An image in a quiz
It means substances don't have to diffuse.
Correct answer: It moves nutrients and waste products around the body.
Correct answer: It reduces the time taken for substances to diffuse from the blood to the cells.
Correct answer: It brings blood near to the surface of cells which reduces diffusion distance.
It means active transport will occur instead of diffusion.
Q6.
How are the alveoli adapted for efficient diffusion?
Correct answer: good blood supply
Correct answer: large surface area
Correct answer: thin cells
thick cells
small surface area