Final answer:
Food chains always begin with a producer, which is an organism that can make its own food through photosynthesis. Producers provide energy for all other organisms in the ecosystem.
Step-by-step explanation:
A food chain always begins with a producer. Producers are organisms that can make their own food through the process of photosynthesis. They convert sunlight, water, and carbon dioxide into glucose and oxygen. Examples of producers include plants on land and phytoplankton in aquatic ecosystems. Producers are the base of the food chain because they provide energy for all other organisms in the ecosystem.