Class 7 Science - ICSE-BIOLOGY
Ecosystems
The chapter 'Ecosystems' in Class 7 ICSE Biology introduces students to the fascinating interactions between living organisms and their physical environment. You will explore the structural and functional units of nature, learning about biotic and abiotic components, producers, consumers, and decomposers. The chapter details how energy flows through food chains and food webs, and highlights the delicate balance maintained in nature through nutrient cycles. This topic is vital for board exams as it forms the foundational base for environmental science and ecology in higher classes, frequently appearing in both objective and descriptive sections.
Start Learning FreeKey Concepts
Ecosystem
A self-contained community of living organisms interacting with each other and with their non-living physical environment.
Biotic and Abiotic Components
Biotic components are the living parts like plants and animals, while abiotic components are the non-living physical factors like sunlight, temperature, and water.
Producers, Consumers, and Decomposers
Producers make their own food via photosynthesis, consumers eat other organisms for energy, and decomposers break down dead organic matter to recycle nutrients.
Food Chain and Food Web
A food chain is a linear sequence of who eats whom, whereas a food web is a complex, interconnected network of multiple food chains in an ecosystem.
Ten Percent Law
Only about 10 percent of energy is transferred from one trophic level to the next in a food chain, while the rest is lost as heat.
Important Formulas
Board Exam Info
In ICSE Biology exams, this chapter typically carries around 6 to 8 marks. Questions usually include defining key ecological terms, differentiating between food chains and food webs, constructing a food chain from a given set of organisms, and explaining the role of decomposers.
Frequently Asked Questions
A food chain is a single, straight-line path of energy transfer, whereas a food web consists of many interconnected food chains showing multiple feeding relationships in an ecosystem.
Why do food chains rarely have more than four or five trophic levels?
Because of the 10 percent energy rule, very little energy is available at higher trophic levels, leaving insufficient energy to sustain organisms beyond the fourth or fifth level.
Are bacteria considered producers or decomposers?
Most bacteria act as decomposers because they break down dead plants and animals, though certain bacteria like cyanobacteria can produce their own food.
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