short answer: The apple tree is the producer, the cardinal is the consumer, and the caterpillar is the decomposer.
Long answer: The tree produces energy, and when the caterpillar eats the leaves/apples, that keeps the caterpillar fed, then the cardinal comes along and eats the caterpillar, then when the cardinal dies, an apple tree can grow in it's place, keeping the cycle going. hope that hels!p
