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This document discusses food chains in nature. It explains that plants like phytoplankton and algae are producers at the start of the food chain, obtaining energy through photosynthesis. Zooplankton and other organisms then consume the plants as primary consumers. Secondary consumers feed on the primary consumers, and in some ecosystems there are tertiary consumers that feed on both. Decomposer bacteria break down dead organisms, recycling nutrients. Each link in the food chain is important for the survival of the whole chain.Read less