Question EXEX.2.HL.TZ0.4
| Date | Example questions Example questions | Marks available | [Maximum mark: 4] | Reference code | EXEX.2.HL.TZ0.4 |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | Explain, Outline | Question number | 4 | Adapted from | N/A |
The gas exchange system of terrestrial animals becomes more developed as organisms increase in size.
[Source: Image by Natfot from Pixabay https://pixabay.com/photos/earthworm-soil-dirt-macro-686593/.
Image by Ilo from Pixabay https://pixabay.com/photos/frog-water-frog-lily-pads-amphibian-2211972/.
Image laurent marx from Pixabay https://pixabay.com/photos/elephant-safari-animal-defence-1421167/.]
Explain one reason gas exchange is more challenging in larger species of organisms.
[2]
Reason:
- (as organisms get larger) distance to centre of the body increases
OR
the surface area for diffusion relative to the volume/ surface area to volume ratio becomes smaller/ decreases;
Explanation: - which causes gas exchange/ diffusion of oxygen in/ carbon dioxide out to be too slow
OR
there is less area/space for diffusion to occur;
Explanation must match reason to award marking point b
Outline the role of the following during gas exchange in mammalian lungs:
secretion of of surfactant.
[1]
(surfactant) reduces surface tension, preventing water from causing the walls of alveoli to adhere during exhalation/ alveoli from collapsing;
dense network of capillaries.
[1]
increases the surface over which gases diffuse;