Most animals in a habitat can be classified as predators, prey or both. A predator is an animal which kills another animal (the prey) for food. For example, a snake is a predator because it eats frogs (prey). However, the frog is also a predator (however unintimidating it seems!) because it eats grasshoppers. With so many animals having differing diets, even a small environment can produce a food web such as this one.
Because the grass eats no other species, only consuming nutrients from the soil, we call it a producer. The fox and snake are called top consumers because no other species eats them within this habitat. But in certain habitats, large birds of prey eat snakes.
Food webs can be affected by even the most subtle increase or decrease in the number of any species. If, for example, the population of frogs increased in the above food chain, then several changes might take place:
1) The number of grasshoppers would decrease because there are more frogs to eat them.
2) More snakes would come to the habitat and prosper because there are more frogs to eat.
3) Because there are more snakes, the number of rabbits will deplete as they will be eaten by the higher population of snakes.
Consider what might happen if:
a) The population of mice increased
b) The population of rabbits decreased
c) A drought led to a poor crop of grass
Whether their population increases or decreases, each species within a habitat will be affected by changes in population to some degree.
If your class is interested in getting to grips with food chains, our app Pairing for Early Science introduces them with the foundation science vocabulary to get them started!
Below: predator extraordinaire, office cat, aka Mr Worthington