What is the food chain?

In nature, there are ‘producers’ that build the biological mass, and ‘consumers’ that eat. Producers are the plants, which grow and create energy with the help of photosynthesis. They are eaten by a consumer, and that consumer is often eaten by another consumer. This chain of consumers is called the ‘food chain’. A short food chain is grass – cow – man. A longer one is algae – water flea – herring – seal – polar bear: A water flea eats algae, a herring eats many water fleas, a seal eats herrings, and the polar bear eats the seal. Ultimately, a lot of algae are needed to feed a polar bear. When the polar bear dies, its meat is either eaten by other animals or it is decomposed into nutrients by bacteria. These nutrients are again used by the algae to create energy, and thus the food chain gets completed.