FOOD CHAIN

A food chain is a linear sequence of links in a food web starting from a trophic species that eats no other species in the web and ends at a trophic species that is eaten by no other species in the web.
eg , if a bird feeds on a particular type of worm , the worm feeds on a special plant , and if the plant is extinct , the population of the worm will decrease , which will cause the population of bird to decrease and will also affect the other animals in the food chain.