Carbon Cycle
Overview
The Earth is a closed box: almost no new atoms arrive from space. So every carbon atom in your body, and every nitrogen atom in your proteins, has been used before, perhaps by a dinosaur, a fern or a bacterium. Nutrient cycles are the routes these atoms take as they pass endlessly between the air, the soil, living things and back again.
In this lesson you will follow carbon through photosynthesis, respiration, feeding, decomposition, fossil fuels and combustion, and then trace nitrogen through the bacteria that fix it, turn it into nitrates and return it to the air. Understanding these cycles explains everything from why we add fertiliser to fields to why burning fossil fuels is warming the planet.
Objectives
- Describe the carbon cycle, limited to: photosynthesis, respiration, feeding, decomposition, formation of fossil fuels and combustion
- [Supplement] Describe the nitrogen cycle with reference to: decomposition of plant and animal protein to ammonium ions nitrification nitrogen fixation by lightning and bacteria absorption of nitrate ions by plants production of amino acids and proteins feeding and digestion of proteins deamination denitrification
- [Supplement] State the roles of microorganisms in the nitrogen cycle, limited to: decomposition, nitrification, nitrogen fixation and denitrification (generic names of individual bacteria, e.g. Rhizobium, are not required)
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Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Carbon Cycle. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- During daylight, which process carried out by green plants takes carbon dioxide out of the air? A. respiration B. transpiration C. photosynthesis D. decomposition Answer: C
- Carbon locked in coal and oil is returned to the air mainly by: A. photosynthesis B. combustion C. nitrification D. transpiration Answer: B
- Plants absorb nitrogen from the soil in the form of: A. nitrogen gas B. ammonia gas C. nitrate ions D. protein Answer: C
- Which bacteria convert ammonium ions into nitrates? A. denitrifying bacteria B. nitrifying bacteria C. decomposer fungi D. nitrogen-fixing bacteria Answer: B
- Denitrifying bacteria are harmful to soil fertility because they: A. fix nitrogen gas B. make nitrates from ammonium C. turn nitrates into nitrogen gas D. decompose protein Answer: C
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