Trace the water cycle and the structure of the atmosphere
Describe and draw the syllabus water cycle, identify the main atmospheric gases and layers, and distinguish the ozone layer from the natural greenhouse effect.
Exam scope and assessment notes
Original StudyForA teaching and practice, not Cambridge-authored questions, mark schemes or official grades. Cambridge expects candidates to study all eight topics, carry out investigative work and learn teacher-selected case studies. This course does not replace a centre's named case-study examples, current local environmental data, supervised fieldwork or the candidate's own investigation. Practice datasets are illustrative, not observations from a real place. No official assessment or certification is provided. The examples and practice datasets in these lessons are fictional and formative; learners must add their centre's verified case studies and current local evidence.
Before you begin
- Cambridge recommends prior environmental/science study equivalent to IGCSE or O Level. This is an AS-only qualification; use the exam-year syllabus and confirm centre entry details.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What makes environmental evidence useful?
What you will learn
- Label the water-cycle processes specified in the syllabus
- Name major atmospheric components and the four primary layers
- Explain the ozone layer's ultraviolet role and outline the natural greenhouse effect
Trace water between stores
The syllabus water-cycle processes are evaporation, transpiration, condensation, precipitation, interception, infiltration, surface run-off, through-flow and groundwater flow. Use arrows to show both movement and process; a diagram should distinguish surface and subsurface pathways.
The same amount of rainfall does not guarantee the same runoff or groundwater recharge. Soil, vegetation, slope, land cover and antecedent conditions affect how water moves through a catchment.
Separate atmospheric structure and processes
The syllabus names nitrogen, oxygen, carbon dioxide, argon and water vapour as major atmospheric components and identifies the troposphere, stratosphere, mesosphere and thermosphere as the four primary layers. The ozone layer is in the stratosphere and absorbs ultraviolet radiation.
In the natural greenhouse effect, shortwave solar radiation reaches and warms Earth's surface; the surface emits longwave infrared radiation, some of which greenhouse gases absorb and re-emit. This natural process maintains ambient temperature. The enhanced greenhouse effect is a separate topic about increased greenhouse-gas concentrations.
Sources for this lesson
Pause and explain
What is the location and role of the ozone layer?
Worked example
After heavy rain, a forested slope and a paved slope have different runoff. Trace two water-cycle pathways that could explain the difference.
Show the worked solution
- Identify the input from precipitation.
- Compare interception, infiltration and surface run-off.
- State one other factor that needs measuring.
Answer Forest vegetation can intercept some precipitation and roots and soil may permit greater infiltration and through-flow, while sealed paving can increase rapid surface run-off. Slope, soil condition and drainage also matter, so comparable rainfall and land measurements are needed before attributing the difference to vegetation alone.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Draw a water-cycle diagram containing all nine processes named in the syllabus.
Give me a hint
Start with evaporation and transpiration, then trace atmospheric and land pathways back to surface water.
Compare my reasoning
- Identify the relevant data, place or process in the prompt.
- Apply label the water-cycle processes specified in the syllabus to the stated context.
- Explain the inference and one limitation or trade-off.
A complete diagram labels evaporation and transpiration into the atmosphere, condensation, precipitation, interception by vegetation, infiltration into soil, surface run-off, through-flow within soil and groundwater flow. Arrows should show the direction between stores, not just list process names.
Look for these in your work
- Label the water-cycle processes specified in the syllabus
- Uses relevant evidence and explains the environmental mechanism
- Distinguishes observation, inference and limitation
Name the four primary atmospheric layers and state where the ozone layer is found.
Give me a hint
Order the layers from Earth's surface upward.
Compare my reasoning
- Identify the relevant data, place or process in the prompt.
- Apply name major atmospheric components and the four primary layers to the stated context.
- Explain the inference and one limitation or trade-off.
From the surface upward the layers are the troposphere, stratosphere, mesosphere and thermosphere. The ozone layer is within the stratosphere, where ozone absorbs ultraviolet radiation.
Look for these in your work
- Name major atmospheric components and the four primary layers
- Uses relevant evidence and explains the environmental mechanism
- Distinguishes observation, inference and limitation
A diagram shows incoming shortwave radiation and outgoing longwave radiation. Explain the natural greenhouse effect in two linked steps.
Give me a hint
Describe what the surface emits after absorbing incoming energy.
Compare my reasoning
- Identify the relevant data, place or process in the prompt.
- Apply explain the ozone layer's ultraviolet role and outline the natural greenhouse effect to the stated context.
- Explain the inference and one limitation or trade-off.
The surface absorbs shortwave solar radiation and emits energy as longwave infrared radiation. Greenhouse gases absorb some of this outgoing infrared and re-emit it, so not all energy escapes directly to space; this natural process helps maintain Earth's ambient temperature.
Look for these in your work
- Explain the ozone layer's ultraviolet role and outline the natural greenhouse effect
- Uses relevant evidence and explains the environmental mechanism
- Distinguishes observation, inference and limitation
Common mistakes
- Leaving arrows or process labels off a water-cycle diagram
- Putting the ozone layer in the troposphere
- Confusing the natural greenhouse effect with its human enhancement
What can you explain now?
What is the location and role of the ozone layer?
Compare with the explanation
It is in the stratosphere and absorbs ultraviolet radiation
Ozone depletion changes ultraviolet exposure; it is different from the enhanced greenhouse effect.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
How do the natural greenhouse effect and ozone-layer absorption differ in the radiation they act on?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.