2.1 gas exchange in humans

Question 1

respiration

Answer 1

organisms undergo respiration for energy
- take in oxygen
- produce carbon dioxide

Question 2

why don’t single-called organisms need a gas exchange system?

Answer 2

they have a large surface area to volume ratio, can do everything via diffusion
- gets water and oxygen from air and surroundings
- less demand for nutrients and energy

Question 3

why do larger organisms need transport systems?

Answer 3

1. larger transport distances:
   - larger organisms have specialised organ systems that need delivery of nutrients and removal of waste
   - the organs are important exchange sites and they are far away within the organism
   - diffusion is non-viable since it wouldn’t be fast enough to meet the metabolic requirements of cells
2. smaller SA : VO ratio:
   - less surface area for absorption of nutrients and gases + removal of waste
   - greater volume = longer diffusion distances
3. higher levels of activity:
   - more physically active + more cells = higher metabolic activity
   - they have higher demand for oxygen and nutrients, plus there is more waste produced