Solution:
Producers are those that convert the Sun's energy into organic carbon bonds such as sugars (molecules). The main producers are plants, algae, and cyanobacteria (blue-green algae).
Animals that eat plants are called primary consumers, while animals that eat other animals are called secondary consumers or even tertiary consumers.
According to the above information, we can conclude that the correct answer is:
1. Producer (bottom of the pyramid): Large blue-stemmed grass
2. Primary Consumer: Bison
3. Secondary consumer: wolf
