Short Answer 
To illustrate an ecosystem’s food web, begin by identifying producers, such as plants and algae, which capture solar energy. Next, classify consumers into primary (herbivores), secondary (carnivores/omnivores), and tertiary predators, followed by mapping energy flow between them, optionally including decomposers to show nutrient recycling.
Step 1: Identify Producers
Begin by identifying the producers in the ecosystem, which are typically plants or algae. These organisms form the base of the food web because they capture energy from the sun through photosynthesis. Examples include:
- Grass
- Phytoplankton
- Algae
Step 2: List Consumers
Next, classify the consumers in hierarchical order. Start with primary consumers, which are herbivores that feed on the producers. Following them, add secondary consumers, which can be either carnivores or omnivores that prey on herbivores. Examples include:
- Zooplankton (primary consumers)
- Sardines (secondary consumers)
- Top predators like tuna and killer whales (tertiary consumers)
Step 3: Connect and Illustrate
Finally, draw arrows between organisms to indicate the direction of energy flow, highlighting the feeding relationships. Optionally, you can include decomposers, which recycle nutrients back into the ecosystem. Ensure the diagram visually represents the complex interactions, as this illustrates the interconnectedness of various organisms in the food web.