Our Environment | Class 10 Science Notes

13.1.1 Food Chains and Webs

A food chain is a linear sequence of organisms where each organism is eaten by the next member in the chain, showing the flow of energy and nutrients. It always starts with producers (autotrophs) that convert solar energy into chemical energy through photosynthesis. Consumers follow: primary consumers (herbivores) feed on producers; secondary consumers (small carnivores) feed on herbivores; tertiary consumers (larger carnivores) feed on secondary consumers. Each step in a food chain is called a trophic level. Energy flow in an ecosystem is unidirectional, starting from the sun to producers, then to consumers and decomposers. At each trophic level, energy is lost as heat, digestion, and work, with only about 10% of energy transferred to the next level, limiting food chains to 3-4 levels. Food webs are complex networks of interconnected food chains, showing multiple feeding relationships among organisms, reflecting the complexity of natural ecosystems.

📊 Diagram: Figure 13.1 Food chain in nature (a) in forest, (b) in grassland and (c) in a pond; Figure 13.2 Trophic levels; Figure 13.3 Food web, consisting of many food chains; Figure 13.4 Diagram showing flow of energy in an ecosystem

🧪 Activity: Activity 13.3: Debating pesticide levels in food, sources of pesticides entering food chains, and methods to reduce pesticide intake.

🔗 Connection: Introduces the concept of biological magnification and human impacts on ecosystems.