To determine the number of trophic levels in the given food chain, we need to identify each distinct level in the sequence of energy transfer from plants up to the top predator. Let's break down the food chain:
1. Grass: This is the producer, the first trophic level. Plants like grass produce their own food through photosynthesis and form the base of any food chain.
2. Grasshopper: This is a primary consumer and herbivore, feeding directly on the producers. It occupies the second trophic level.
3. Frog: This is a secondary consumer, which preys on the primary consumers (grasshoppers). Hence, it is at the third trophic level.
4. Snake: This is a tertiary consumer, preying on secondary consumers (frogs). It represents the fourth trophic level.
Each organism represents a distinct level in the food chain through which energy flows from producers to higher-level consumers.
So, there are a total of 4 trophic levels in this food chain:
1. Grass (Producer)
2. Grasshopper (Primary Consumer)
3. Frog (Secondary Consumer)
4. Snake (Tertiary Consumer)
Therefore, the number of trophic levels is:
Answer: B. 4
