Final answer:
Producers in a food web are typically photosynthetic organisms like plants or phytoplankton, which are outlined in green in the given figures. They make their own food through photosynthesis and are essential for the energy flow through the ecosystem.
Step-by-step explanation:
The producers in a food web are organisms that can make their own food using energy and simple inorganic molecules to create organic compounds. In the descriptions of the figures provided, these producers are typically photosynthetic organisms like plants or phytoplankton, which are outlined in green. They serve as the foundation of the food chain by transforming energy from the sun through the process of photosynthesis into glucose, providing energy and nutrients to the rest of the ecosystem, including the herbivores (primary consumers) and various carnivores (secondary and tertiary consumers).
According to the information given, in the Lake Ontario ecosystem, primary producers are outlined in green in Figure 37.6 and Figure 46.6. This indicates that you would need to identify the organisms colored in green in the provided figures to determine the specific producer organisms in the food web.