Cambridge IGCSE Biology, topic 19
Organisms and their environment
Organisms do not live alone. They depend on energy from the Sun and on each other for food. This topic looks at how energy flows through ecosystems along food chains and food webs, how nutrients are cycled, and how populations change in size.
Revision notes
Worksheet
FlashcardsSubtopics
Work through them in order. Each one has notes, exam questions and flashcards, and a PDF of each.
- 1Energy flow, food chains and food webs Spec 19.1, 19.2.1–19.2.10How energy flows from the Sun through producers, consumers and decomposers to the environment, and how food chains and webs show feeding links.NotesQuestions 7Flashcards 13
- 2Trophic levels and ecological pyramids Spec 19.2.11–19.2.19Trophic levels, pyramids of numbers, biomass and energy, and why energy transfer is inefficient so that food chains are short.NotesQuestions 7Flashcards 12
- 3Nutrient cycles Spec 19.3How carbon is cycled by photosynthesis, respiration, feeding, decomposition and combustion, and how bacteria move nitrogen through the nitrogen cycle.NotesQuestions 6Flashcards 10
- 4Populations Spec 19.4Populations, communities and ecosystems, the factors that affect population growth, and the phases of the sigmoid growth curve.NotesQuestions 6Flashcards 10
Whole topic
When you have done the subtopics: test yourself on everything, or print the lot.