Section B: The Living World
Overview
Cut a tropical rainforest down and the soil underneath is almost worthless within three or four harvests. That single fact confuses more students than any other in this section, because everything about a rainforest looks rich: the tallest trees on Earth, more species than anywhere else, rain almost every afternoon. The wealth is real. It is just not in the ground. It is in the living things, and when they go it goes with them.
In this lesson you will learn to read an ecosystem as a system: what feeds what, what recycles what, and what happens when a single component is pulled out. Then you will apply that to the two ecosystems this specification names. You will study a tropical rainforest in enough detail to use it as a case study, watch what deforestation does to it and weigh the strategies meant to slow it. And you will cross to the opposite extreme, the hot desert, where the limit is water rather than nutrients, and see how the fringes of those deserts are turning into desert themselves.
Objectives
- Ecosystems exist at a range of scales and involve the interaction between biotic and abiotic components.
- Tropical rainforests Tropical rainforest ecosystems have a range of distinctive characteristics.
- Deforestation has economic and environmental impacts.
- Tropical rainforests need to be managed to be sustainable.
- Hot deserts Hot desert ecosystems have a range of distinctive characteristics. of climate, water, soils, plants, animals and people; how plants and
- Areas on the fringe of hot deserts are at risk of desertification.
- An example of a small-scale ecosystem to illustrate the concept of interrelationships within a natural system, an understanding of producers, consumers, decomposers, food chain, food web and nutrient cycling. The balance between components. The impact on the ecosystem of changing one component. An overview of the distribution and characteristics of large-scale natural global ecosystems.
- The physical characteristics of a tropical rainforest.
- The interdependence of climate, water, soils, plants, animals and people. How plants and animals adapt to the physical conditions. Issues related to biodiversity. Changing rates of deforestation.
- A case study of a tropical rainforest to illustrate:
- causes of deforestation - subsistence and commercial farming, logging, road building, mineral extraction, energy development, settlement, population growth
- impacts of deforestation - economic development, soil erosion, loss of biodiversity, contribution to climate change. Value of tropical rainforests to people and the environment.
- Strategies used to manage the rainforest sustainably - selective logging and replanting, conservation and education, ecotourism and international agreements about the use of tropical hardwoods, debt reduction.
- The physical characteristics of a hot desert; the interdependence
- animals adapt to the physical conditions.
- Issues related to biodiversity. Use examples to illustrate:
- Causes of desertification - climate change, population growth, removal of fuel wood, overgrazing, over-cultivation and soil erosion.
- Strategies used to reduce the risk of desertification - water and soil management, tree planting and use of appropriate technology.
Mind map
This topic is mapped out so you can see how the ideas connect.
Open the mind map in the app
Lesson Note
Complete Note Available on the Green Bridge App
Get the Green Bridge CBT app on your phone or computer for the complete IGCSE library: past papers, mark schemes, mind maps, flashcards and audio lessons.
Lesson Evaluation
Congratulations on completing the lesson on Section B: The Living World. 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.
- Which one of the following is a producer in an ecosystem? A. A fungus B. A grazing antelope C. A green plant D. A soil bacterium Answer: C
- Which soil type is typical of a tropical rainforest? A. Chernozem B. Latosol C. Podzol D. Peat Answer: B
- What is the maximum annual rainfall normally used to define a hot desert? A. 100 mm B. 250 mm C. 500 mm D. 1000 mm Answer: B
- Which of the following is a cause of desertification rather than a strategy to reduce it? A. Building stone lines along the contour B. Planting shelter belts of trees C. Using solar cookers instead of fuel wood D. Grazing more animals on the same land Answer: D
- Why do many rainforest trees have buttress roots? A. To store water for the dry season B. To support a tall tree whose roots are shallow C. To shed heavy rain from the trunk D. To reach groundwater many metres down Answer: B
Work through these questions in the app
Work through these questions in the app
Recommended Books
Practice Mock Questions
Want to practice mock questions on Section B: The Living World? Download the Green Bridge CBT app to access mock questions and full practice assessments for this topic.
Download The App On Google Playstore
Everything you need to excel in your exams
