The biosphere , the part of the earth where we live is about 20 km thick. It extends from the ocean floor to the highest point in the atmosphere where life is found. Autotrophs are organisms that can use inorganic compounds to make organic nutrients. Most carry on photosynthesis and a few carry on chemosyntheses. Heterotrophs are divided into groups depending on what they eat and how they obtain food.
Herbivores eat plants.
Carnivores eat other animals. Predators kill and eat their prey. Scavengers feed an dead animals. Omnivore seat both plants and animals. Saprophytes break down dead plants and animals.