why do food chains only have 4-5 levels
Food web In a pyramid of numbers, the number of consumers at each level decreases significantly, so that a single top consumer, (e.g., a polar bear or a human), will be supported by a much larger number of separate producers. There is usually a maximum of four or five links in a food chain, although food chains in aquatic ecosystems are more often longer than those on land. Eventually, all the energy in a food chain is dispersed as heat.[4]
Consumer (food chain) Within an ecological food chain, Consumers are categorized into primary consumers, secondary consumers, and the tertiary consumers.[2] Primary consumers are herbivores, feeding on plants. Secondary consumers, on the other hand, are carnivores, and prey on other animals. Omnivores, who feed on both plants and animals, can also be considered a secondary consumer. Tertiary consumers, sometimes also known as apex predators, are usually at the top of food chains, capable of feeding on secondary consumers and primary consumers. Tertiary consumers can be either fully carnivorous or omnivorous.