Biology - 4BI1 PearsonEdexcel

Cycles Within Ecosystems

Overview

Carbon and nitrogen are essential to every living organism, yet there is a fixed amount of each element on Earth. If these elements were not recycled, life would have run out of raw materials long ago. Instead, natural processes move carbon and nitrogen through the atmosphere, soil, water and living things in continuous loops.

In this lesson you will trace the carbon cycle from photosynthesis through respiration, decomposition and combustion, and then follow the nitrogen cycle through the specialised bacteria that convert nitrogen into forms plants can absorb. Both cycles are tested regularly on Edexcel papers, and understanding them will also help you explain human impacts on the environment.

Objectives

  1. Describe the stages in the carbon cycle, including respiration, photosynthesis, decomposition and combustion
  2. Describe the stages in the nitrogen cycle, including the roles of nitrogen fixing bacteria, decomposers, nitrifying bacteria and denitrifying bacteria

Lesson Note

The carbon atoms in your body have been recycled countless times. Some may once have been part of a dinosaur, a prehistoric fern, or a molecule of volcanic gas. Unlike energy, which flows through ecosystems and is eventually lost as heat, chemical elements are endlessly reused. The carbon and nitrogen cycles describe the routes these atoms take - and human activity is now changing both cycles in ways that affect the whole planet.

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Lesson Evaluation

Congratulations on completing the lesson on Cycles Within Ecosystems. 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.

  1. Which process removes carbon dioxide from the atmosphere? A) Respiration B) Combustion C) Photosynthesis D) Decomposition Answer: C
  2. Which type of bacteria converts nitrates back into nitrogen gas? A) Nitrogen-fixing bacteria B) Nitrifying bacteria C) Denitrifying bacteria D) Decomposers Answer: C
  3. Where are nitrogen-fixing bacteria found in leguminous plants? A) In the leaves B) In the stem C) In the root nodules D) In the flowers Answer: C
  4. Which of the following returns carbon dioxide to the atmosphere? A) Photosynthesis B) Absorption by oceans C) Respiration D) Nitrogen fixation Answer: C
  5. What do nitrifying bacteria convert ammonium compounds into? A) Nitrogen gas B) Proteins C) Nitrates D) Carbon dioxide Answer: C

Available on the Green Bridge App

Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.

Full lesson notes with diagrams
AI-powered learning assistant
Study offline, anytime, anywhere
Available on Android, Windows, macOS, and Linux

Available on the Green Bridge App

Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.

Full lesson notes with diagrams
AI-powered learning assistant
Study offline, anytime, anywhere
Available on Android, Windows, macOS, and Linux

Practice Mock Questions

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