7.11 Biodiversity, pollution and waste
5 exam questions worth 12 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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What is meant by biodiversity?
Mark scheme
the variety of (all the different) species (of organisms) on Earth / in an ecosystem
Model answer
Biodiversity is the variety of different species in an ecosystem or on Earth.
Explain why high biodiversity makes an ecosystem more stable.
Mark scheme
- species are less dependent on one other species (1)
- for food / shelter, so the loss of one species has less effect (1)
Model answer
With many species, each one depends less on any single other species for food and shelter, so losing one species does less damage to the ecosystem.
Fertiliser from a farm washes into a lake. Explain how this can cause fish in the lake to die.
Mark scheme
- nitrates / phosphates cause algae to grow rapidly (1)
- algae block light (1)
- plants below cannot photosynthesise and die (1)
- bacteria decompose dead plants (1)
- bacteria respire, using up oxygen (1)
- fish die from lack of oxygen (1)
Maximum 5 marks
Model answer
The nitrates and phosphates make algae grow rapidly on the surface. The algae block light, so the plants underneath cannot photosynthesise and die. Bacteria decompose the dead plants and use up the oxygen in the water as they respire, so the fish die from lack of oxygen.
Give one way humans pollute the land and one way they pollute the air.
Mark scheme
- land: landfill / toxic chemicals / pesticides / herbicides (1)
- air: smoke / acidic gases / sulfur dioxide / burning fossil fuels (1)
Model answer
Dumping waste in landfill pollutes the land, and burning fossil fuels releases smoke and sulfur dioxide into the air.
Explain why the growing human population is causing more pollution.
Mark scheme
- more resources used / more people (1)
- more waste produced (and not always handled properly) (1)
Model answer
More people with higher living standards use more resources and produce more waste, which is not always handled properly.
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