The food chain illustrated below demonstrates the relationships between the organisms shown.

A food chain containing four organisms. From left to right, the organisms illustrated are algae, fish, grey heron, and alligator. An arrow points from algae to fish, from fish to grey heron, and from grey heron to alligator.
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Using the food chain pictured, answer the following questions.

Part 1: Explain the relationships in the food chain. Include the specific organisms shown and each trophic level. Label each organism as an autotroph or heterotroph, as well.
Part 2: What would happen to the ecosystem if the grey heron population was removed from this chain of organisms?