1. Producers: These are autotrophic organisms that can make their own food through the process of photosynthesis or chemosynthesis. Plants are the primary producers in most terrestrial food webs, while phytoplankton are the main producers in aquatic food webs.
2. Primary Consumers: Also called herbivores, these organisms consume only plants. They are the first level of consumers in the food web and are directly dependent on producers for their food. Common examples of primary consumers include insects, rabbits, and deer.
3. Secondary Consumers: These organisms are carnivores or omnivores that consume primary consumers. They are the second level of consumers in the food web and obtain their energy by feeding on herbivores. Examples of secondary consumers include spiders, frogs, and birds.
4. Tertiary Consumers: Also known as top predators, these organisms are carnivores or omnivores that feed on other carnivores. They are the highest level of consumers in the food web and have few or no predators. Examples of tertiary consumers include hawks, wolves, and sharks.
5. Decomposers: These organisms break down dead plants and animals, recycling their nutrients back into the environment. Decomposers include bacteria, fungi, and insects like earthworms.
The levels of a food web are interconnected, with energy flowing from one level to the next. As energy is passed up the food chain, it is lost as heat and used for the various activities and processes of the organisms involved. This results in a decrease in energy available at higher trophic levels, which limits the number of levels that a food web can support.