The Garden's Web of Life
In a well-balanced garden the plants and animals are all interconnected. Green plants are essential for the life of all animals, either directly or indirectly. Some animals, known as herbivores, eat only plants. Herbivorous animals are in turn eaten by carnivores – meat eaters. Carnivorous animals are often referred to as predators and the animals they eat as their prey. The prey animal is usually smaller than the predator. The sequence of feeding is known as a food chain.
Leaf --------> earthworm --------> blackbird --------> sparrowhawk
In reality, the feeding relationships within a habitat are much more complicated than a simple chain. The blackbird eats many types of invertebrates, not only earthworms, and the sparrowhawk preys on different species of birds. Any living material may be part of many food chains and together the chains join to form a food web. Here is a simple food web involving plant material and a few animals you may find living in your garden:-
Notice that the sparrowhawk and the fox are not preyed upon – they are known as top carnivores. When they die, however, their bodies will be eaten by invertebrates such as fly larvae and beetles, and the remains acted on by decomposers, the resulting nutrients being used by living parts.
A food pyramid is sometimes used to represent the overall picture of food chains within a habitat. A pyramid also gives an idea of the build-up in numbers of animals within the food chain. There are always more animals at the bottom of the chains than at the top. This is because these animals are small in size and a larger predator needs to eat many of them in order to survive. Here is an example of a garden food pyramid:-
Read More: Pesticides and the Food Chain