Every living organism needs energy to survive. Energy can be gained by consuming food. There are two main ways living organisms can get food and they are grouped as either being an autotroph or heterotroph.
Autotrophs, also known as producers, have the unique ability to manufacture their own food. Autotrophs can either be photoautotrophs or chemoautotrophs. Phototrophs gain their nourishment by absorbing the energy they need from the sun. Photoautotrophs take this solar energy and convert it into glucose, a type of sugar, through a process called photosynthesis. Photoautotrophs transform light energy into chemical energy and then turn that energy into sugar bonds through the use of chlorophyll. Photosynthesis can also be described as 6CO2 + 6H20 (solar energy) -> C6H1206 + 6O2. On the other hand, chemoautotrophs manufacture energy by oxidizing inorganic materials such as iron, sulphur, and ammonia. Autotrophs provide the foundation for the ecosystem.
While autotrophs are mostly made up of plants and algae, animals, fungi, most prokaryotes, nearly all protists, and some parasitic plants are all heterotrophs. Heterotrophs make up nearly all the other organisms in the ecosystem. Heterotrophs are unable to manufacture their own energy from the sunlight or inorganic materials like autotrophs so they must ingest biomass for their energy. It is for this reason that while most autotrophs contain chlorophyll which aids in synthesizing their own food, this pigment is not found in the vast majority of heterotrophs. Heterotrophs eat other heterotrophs and autotrophs. Their bodies break down complex compounds such as carbohydrates, fats, and proteins into simpler compounds. Carbohydrates break down into glucose, fats break down into fatty acids and glycerol, and proteins break down into amino acids.
Heterotrophs are divided up into four major categories: herbivores, carnivores, omnivores, and saprobic organisms. Herbivores are animals that only consume plants. Examples include cows, goats, and horses. Carnivores are animals that only eat other animals like sharks, lions, and hawks. Omnivores eat plants and animals; examples include bears and humans. Saprobic organisms absorb energy from the environment. An example would be fungi.
Autotrophs and heterotrophs play essential roles in the ecosystem. In a food chain autotrophs, or producers, make up the foundation. Primary consumers like birds, mice, tortoises, ants, and other herbavores are the next level up and are referred to as primary consumers. Small carnivores like snakes, some birds, some fish, and tarantulas are secondary consumers. At the top of the food chain are the top predators of the ecosystem and can be large carnivores such as lions, sharks, and bears. Decomposers like fungi break down waste materials and dead organisms for food which are then returned to the soil and used by the autotrophs again. While autotrophs and heterotrophs are very different from each other, they are both essential for a healthy ecosystem.