A food chain demonstrates the feeding relationship between living organisms in an ecosystem.
It consist of a sequence of organisms starting with a producer (i.e. plants), followed by a primary consumer, the secondary consumer and ending with the tertiary consumer.
A simple food chain could start with the grass (producer), which is consumed by rabbits (primary consumer), who get consumed by foxes (secondary consumer).
A simple food chain could start with the grass (producer), which is consumed by rabbits (primary consumer), who get consumed by foxes (secondary consumer).
Grass -> Rabbit -> Foxes
Sometimes, you may find that a food chain can appear more complex than the one above.
Take a look at the below illustration.
GRASS -> Grasshopper -> Rat -> Snake -> Hawk -> Mushroom -nutrient-> GRASS
After the hawk dies, fungi (like mushrooms and other decomposers break down the carcass and turn the remains of the hawk into nutrients, which are released into the soil.
The nutrients (with other factors like sunshine and water) will cause the grass to grow.
It's an interesting circle of life!
