Question 19M.2.HL.TZ1.7c
| Date | May 2019 | Marks available | [Maximum mark: 4] | Reference code | 19M.2.HL.TZ1.7c |
| Level | HL | Paper | 2 | Time zone | TZ1 |
| Command term | Outline | Question number | c | Adapted from | N/A |
Outline the features of ecosystems that make them sustainable.
[4]
a. recycling of nutrients/elements/components/materials ✔
b. carbon/nitrogen/another example of recycled nutrient/element ✔
c. decomposers/saprotrophs break down organic matter/release «inorganic» nutrients ✔
d. energy supplied by the sun
OR
energy cannot be recycled «so ongoing supply is needed»
OR
energy is lost from ecosystems as heat ✔
e. energy flow along food chains/through food web/through trophic levels ✔
f. photosynthesis/autotrophs make foods/trap energy
OR
autotrophs supply the food that supports primary consumers ✔
g. oxygen «for aerobic respiration» released by autotrophs/photosynthesis/plants ✔
h. carbon dioxide «for photosynthesis» released by respiration ✔
i. populations limited by food supply/predator-prey/interactions/competition
OR
populations regulated by negative feedback
OR
fewer/less of each successive trophic level «along the food chain»/OWTTE ✔
j. supplies of water from rainfall/precipitation/rivers/water cycle ✔
There were some vague answers to this question but also some impressive ones that explained ecological processes including nutrient recycling, energy flow and regulation of population sizes.
