Human Impact on the Environment is one of 10 topics in the Grade 12 Life Sciences CAPS syllabus, covered across 3 lessons on Study Vault. Below are real practice questions from this topic with full worked answers.
Sample practice questions
Easy
1. The greenhouse effect is the process by which:
Greenhouse gases trap heat radiated from Earth's surface, keeping the planet warm enough to support life
All heat energy immediately escapes into space
Earth's surface reflects all incoming sunlight
Ozone destroys all incoming heat energy
Answer: Greenhouse gases trap heat radiated from Earth's surface, keeping the planet warm enough to support life — The natural greenhouse effect traps some outgoing heat energy in the atmosphere via greenhouse gases, keeping Earth warm enough to sustain life as we know it.
Easy
2. Which human activity is the primary source of the increased atmospheric carbon dioxide driving enhanced global warming?
Burning fossil fuels (coal, oil, and natural gas)
Ocean evaporation
Volcanic activity only
Photosynthesis by plants
Answer: Burning fossil fuels (coal, oil, and natural gas) — Burning fossil fuels for electricity, transport, and industry is the largest human contributor to rising atmospheric carbon dioxide levels since industrialisation.
Medium
3. How does deforestation contribute to the enhanced greenhouse effect?
It reduces the number of trees available to absorb carbon dioxide through photosynthesis, leaving more CO2 in the atmosphere
It directly releases large amounts of methane into rivers
It cools the atmosphere, counteracting global warming
It has no effect on atmospheric carbon dioxide levels
Answer: It reduces the number of trees available to absorb carbon dioxide through photosynthesis, leaving more CO2 in the atmosphere — Trees absorb carbon dioxide during photosynthesis; removing forests reduces this carbon absorption capacity, allowing more CO2 emitted from other sources to accumulate in the atmosphere.
