The first member in any food chain must be an autotroph. Autotrophs are organisms that produce their food through photosynthesis or chemosynthesis, meaning they can synthesize organic compounds from inorganic materials like carbon dioxide, water, and sunlight or chemical energy. They are also known as producers since they produce the base of the food chain that other organisms rely on for survival.
For example, plants are autotrophs because they use sunlight to produce their food through photosynthesis. Herbivores, which are animals that eat only plants, rely on these plants for their energy needs. Carnivores, which are animals that eat other animals, rely on herbivores for their energy needs. Zooplankton, which are tiny aquatic animals, can either be herbivores or carnivores and also rely on autotrophs for their energy needs.
Therefore, autotrophs are the starting point of any food chain because they provide the energy source that sustains all other living organisms in the ecosystem.