OCR GCSE (9-1) Geography A: Geographical Themes (J383) · Spec 2.1.1, 2.1.2, 2.1.4 and 2.1.5
Ecosystems: components, distribution and coral reefs
Read the notes, then try the questions. Each one is marked the moment you press Check, and shows the right answer and why.
Key ideas
- Abiotic parts of an ecosystem are non-living: sunlight, soil, water and climate. Biotic parts are living: plants, animals and people.
- Plants are producers, animals are consumers and fungi and bacteria are decomposers. A food web links many food chains, so changing one species can affect many others.
- Hot deserts lie mainly near the tropics, about 15 to 30 degrees north and south, not on the Equator. Air sinks there and brings dry weather. They get under 250 mm of rain a year and have hot days and cold nights.
- Polar areas are very cold and dry, with little precipitation that mostly falls as snow.
- Adaptations: a cactus stores water in its stem and has long or wide roots. A camel's hump stores fat. Polar animals have thick fur and blubber.
- Warm-water coral reefs need warm, clear, shallow, sunlit seas, mostly within about 30 degrees of the Equator.
- Coral polyps live with tiny algae that make food by photosynthesis. If the sea gets too warm, the coral expels the algae and turns white. This is bleaching.
Key terms
- Abiotic
- The non-living parts of an ecosystem.
- Biotic
- The living parts of an ecosystem.
- Producer
- An organism that makes its own food from sunlight, such as a green plant.
- Decomposer
- An organism that breaks down dead matter and returns nutrients, such as a fungus.
- Interdependence
- Parts of an ecosystem relying on each other, so a change in one affects the others.
- Adaptation
- A feature that helps a plant or animal survive in its environment.
- Coral bleaching
- Coral expels its algae and turns white because the sea water is too warm.
Common mistakes
- Saying grass is abiotic because it is not an animal. Grass is a living thing, so it is biotic.
- Placing hot deserts on the Equator. They are mostly near the tropics, where air sinks.
- Saying a camel stores water in its hump. It stores fat.
- Blaming pollution as the cause of coral bleaching. Bleaching comes from warmer water. Pollution is a different threat.
Exam tip
Paper 2 often opens with a climate table or graph. Calculations on this paper are usually 1 mark with an answer only, and there is no margin for error, so check the units and decimal places. In a climate description, use only the data: temperatures and rainfall with values. Landscape and plants are not climate.
Free practice questions
8 questions, 17 marks. Answer, then press Check. The marking guide explains how the marks are worked out. Nothing is saved.
- Question 1 · Multiple choice[1 mark]
Which of these is an abiotic component of a tropical rainforest ecosystem?
- Question 2 · Fill the gaps[3 marks]
Green plants are ___, animals are ___, and fungi that break down dead matter are ___.
Word bank: producers · predators · decomposers · consumers
- Question 3 · Matching[3 marks]
Match each ecosystem role to its job.
- Question 4 · True or false[3 marks]
Decide whether each statement about food webs is true or false.
1. If foxes die out, rabbit numbers fall.
2. Arrows show energy passing from the eaten to the eater.
3. Changing one species can affect many others.
- Question 5 · Multiple choice[1 mark]
Which statement best describes where most hot deserts are found?
- Question 6 · Sort into groups[3 marks]
Sort each adaptation into the right group.
Spines
Waxy skin
Active at night
- Question 7 · Multiple choice[1 mark]
What is the main cause of coral bleaching?
- Question 8 · Choose more than one[2 marks]
Which TWO conditions are needed for warm-water coral reefs to grow?
Choose 2.