1. 4.1 Cell Biology
Lesson 12

2. Baseline (flightpath D): Know that as the
size of the organism increases the SA:Vol ratio decreases which
reduces the efficiency of diffusion and active transport.
Further (flightpath C): Describe several examples of cellular adaptations which larger organisms use to increase diffusion and active transport.
Challenge (flightpath B&A): Explain why there are limits to the size individual cells and how larger organisms overcome this barrier.

3. Limitations of diffusion and active transport
Diffusion only works efficiently if the distance over which the substances have to diffuse is small. Diffusion is a slow process and the larger the distance the longer it takes.
And an organism must have a large surface area to volume ratio for diffusion to be efficient.
This is only the case for small organisms
Larger more complex organisms have a bigger distance from the surface to the cells inside the body

4. Cellular adaptations – inside the small intestine

5. Cellular adaptations – inside the lungs

6. Cellular adaptations – inside the gills

7. Cellular adaptations – inside the roots

8. Cellular adaptations – inside the leaves

9. Sailors’ eyeballs Valonia ventricosa, also known as
bubble algae or sailors' eyeballs.
They are one of the largest
single-celled organisms and can
grow up to 5 cm in diameter. 
Discuss why there is a limit to
how big they can grow.