AP BIOLOGY

Detailed explanation-1: -Saprophytes and decomposers have a great role in the food chain but they are not placed in any trophic levels.

Detailed explanation-2: -The first and lowest level contains the producers, green plants. The plants or their products are consumed by the second-level organisms-the herbivores, or plant eaters. At the third level, primary carnivores, or meat eaters, eat the herbivores; and at the fourth level, secondary carnivores eat the primary carnivores.

Detailed explanation-3: -Level 3: secondary consumers. Secondary consumers are comprised of animals that feed on primary consumers. Organisms that eat other animals are called carnivores (or predators). Predators occupy the trophic level 3 of a food chain or an ecological pyramid.