(i) A pyramid of numbers shows the total number of individual organisms at each level in the food chain of an ecosystem. The pyramids of numbers in Fig.1 and Fig. 2 are different shapes because in Fig. 1, an inverted pyramid of number is present with less number of producers than in Fig. 2.(ii) frogs: The trout from the lake in Fig. 2 were caught by fishermen. Trout eats frogs as a source of energy. If trout from the lake were caught by the fishermen, the population of trout (predator) will decrease which results in the increase in the population of the frogs. insects: Frogs eat insects as a source of energy. The trout from the lake in Fig. 2 were caught by fishermen which results in the increase in the population of frogs (predator). So to get energy, frogs will eat insects, which results in the decrease in the population of the insects.