DP Biology (last assessment 2024)
Question 18M.3.HL.TZ2.15b
| Date | May 2018 | Marks available | [Maximum mark: 2] | Reference code | 18M.3.HL.TZ2.15b |
| Level | HL | Paper | 3 | Time zone | TZ2 |
| Command term | Describe | Question number | b | Adapted from | N/A |
b.
[Maximum mark: 2]
18M.3.HL.TZ2.15b
The interaction web shows top-down and bottom-up effects in a seagrass study system.
(b)
Describe how the sea otter indirectly affects seagrass.
[2]
Markscheme
a. sea otters have a positive «indirect» effect as sea otters feed on crabs that feed on isopods that feed on algae
b. less crabs means more isopods so less algae
c. less algae means more seagrass
OR
less competition between algae and seagrass
