Question 8
Differences: a pond and a river ecosystem; renewable and non-renewable sources of energy
10 marks
- Time to write
- About 20 minutes
Question
Question 8 · 10 marksDifferentiate between any two of the following: (5 + 5)
- The hydrosphere and the lithosphere
- A pond ecosystem and a river ecosystem
- Renewable and non renewable sources of energy
Reworded from the university paper; the task is the same. The original paper belongs to the University of Delhi. See DU's question bank.
Before you write
Read off the question and its marks
Read from the question
- any twoAnswer any 2 of the 3, 5 marks each. Only 2 are marked: a third earns nothing.
- (5+5)The paper splits the marks itself: 5 + 5. Give each part its share.
- Differentiate betweenSet the differences out in a table, basis by basis, not as two separate essays.
Write it in this order
The parts stand alone: start with the one you are surest of.
- Read; underline the asks; jot your points 1 min
- 1 Pond and river ecosystems 5 marks 9 min
- 2 Renewable and non-renewable energy 5 marks 9 min
- Check: every ask answered, key terms underlined 1 min
Easy marks
- Choose the ones you know best: each carries the same marks.
Short on time? A few lines on every part beat a full answer to one: each part is capped at its own marks.
Try it first. About 20 minutes for 10 marks. Write it out, then open the solution.
Solution
Hover or tap a marked figure, like 72,000, to see how it is made and where else it appears.
Two of the three pairs are answered, as the question allows.
(b) A pond ecosystem and a river ecosystem
Both are freshwater aquatic ecosystems with producers (algae, water plants), consumers (insects, snails, fish, birds) and decomposers. They differ mainly because one holds still water and the other moves.
| Basis | Pond ecosystem | River ecosystem |
|---|---|---|
| Water | Still (standing) water in a small, shallow basin | Flowing water that moves continuously downstream |
| Permanence | Many ponds are seasonal: they fill in the monsoon and dry up afterwards, when land plants spread over them | Large rivers flow all year; hill streams may turn seasonal where catchments are deforested |
| Adaptations of life | Organisms survive the dry phase dormant in the mud and reappear when the pond refills | Plants and animals are adapted to the speed of flow: snails and burrowing animals withstand fast hill streams, water beetles and skaters need slow water |
| Food chain | Algae, eaten by microscopic animals, then small fish, larger fish and fish-eating birds such as kingfishers and herons | Drifting and attached algae, insects and fish; some fish migrate, such as the Mahseer, which goes upstream to clear hill streams to breed |
| Self-containment | A fairly self-sustaining unit in which productivity, decomposition, energy flow and nutrient cycling are easy to observe | An open system: it carries water, silt and nutrients from the catchment to the sea |
| Example (ours) | A village pond in Haryana that fills each July | The Yamuna as it flows past Delhi |
(c) Renewable and non-renewable sources of energy
| Basis | Renewable sources | Non-renewable sources |
|---|---|---|
| Meaning | Resources that nature constantly replaces | Resources formed over very long periods that are used up faster than they can form again |
| Examples | Hydropower, solar, wind, geothermal, and energy from biomass and garbage | Coal, oil and natural gas, the fossil fuels formed from prehistoric plant life |
| Availability | Not exhausted by use, but some (such as biomass or water) can still run down if used faster than they renew | Limited stocks: at present rates of use there is coal for a long time, but oil and gas are likely to be used up within about 50 years |
| Pollution | Usually less polluting | Burning releases greenhouse gases and other pollutants; coal is the world's single largest source of greenhouse gases |
| Example (ours) | Rooftop solar panels on a house in Jaipur | A coal-fired thermal power station in Jharkhand |
Note: nuclear energy is usually treated separately, because it uses such small quantities of uranium that supply is effectively limitless, though the fuel itself is a mineral.
Where the 10 marks sit
| # | Component | Marks |
|---|---|---|
| 1 | Pond and river ecosystems | 5 |
| 2 | Renewable and non-renewable energy | 5 |
| Total | 10 |
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