Final answer:
In ecosystems, primary producers like plants create their own food, primary consumers are herbivores that eat producers, and secondary consumers are carnivores that eat primary consumers. Tertiary consumers eat other carnivores and are at the top of the food chain.
Step-by-step explanation:
In an ecosystem, the primary producers are photosynthetic organisms like plants or phytoplankton that form the base of the food chain. These producers create their own food using sunlight and are crucial because they are the source of energy for other organisms. Primary consumers are herbivores that eat these producers, and secondary consumers are usually carnivores that consume the primary consumers. In addition, there are tertiary consumers, which are carnivores that eat other carnivores, and they are often referred to as apex consumers - those at the top of the food chain.
In the context of Lake Ontario ecosystem described, primary producers are outlined in green, primary consumers in orange, secondary consumers in blue, and tertiary consumers in purple. For example, the Chinook salmon is an apex consumer that feeds on lower trophic levels, including secondary consumers.