Food Chain vs Food Web
All plants and animals (including human beings) need food to live and to have energy to do work. Sun is the primary source of energy for all living things and plants make the most of the energy from the sun as they convert it into their food with the help of photosynthesis. Plants are thus called producers. They are eaten by herbivores who in turn are eaten up by carnivores. This is a simple food chain but there are many food chains and these are interconnected to make up a food web. Energy is passed from one organism to another in this complex network like a spider’s web. There are similarities in a food chain and food web but there are far more differences that will be talked about in this article.
All living beings need food to have energy to live, to move, and to grow. Food, by the process of digestion, releases energy that is used for various purposes. It is sun that provides food to the plant world as they convert it into food. Some of this food is stored for use in stem, roots and leaves and it is this food that is a source of energy for all other organisms. Even carnivores that eat herbivores are dependent upon this energy of plants as herbivores get energy from plants and carnivores get this energy when they eat herbivores. Thus, plants are the only producers in this food chain which begins with sun, while rest of the organisms are consumers. While herbivores are primary consumers, carnivores are called secondary consumers. There are also decomposers such as bacteria and fungi. They convert dead matter into gases like carbon dioxide and nitrogen that is released back into the air, water and soil. They play an important role in this food chain as they recycle the nutrients to be used again by producers (plants). So actually the food chain begins with these decomposers.
Decomposers—producers—primary consumers—secondary consumers
However, there is not a single food chain but many as animal world is interconnected with one another.
A hawk eats a snake that eats a frog that eats a grasshopper that eats grass
However, a hawk might also eat a mouse, a frog, a squirrel or some other animal. This means that a particular animal may be a part of many chains instead of one and thus there are many food chains that are interconnected in the form of a food web. A food web is thus many food chains connected with each other in the form a spider’s web.
However, one should not think that the entire energy that a herbivore gets from plants gets transferred to the carnivore that eats this herbivore. The herbivore uses some of the food to move and grow while only a small fraction is stored in its body to make a body mass. Similarly when the carnivore eats it, it also utilizes the energy and only a small fraction of this energy remains in its body when it is eaten by a tertiary consumer. This explains why there are more herbivores than carnivores. The amount of energy that is transferred up the chain gets smaller and smaller as we go up the chain. Thus a large number of plants are needed to support herbivores while a large number of herbivores are needed to support fewer carnivores. Food chains often have 4-5 links but not more than this because animals at the end of the chain would not get enough food to stay alive with a large number of links.
Difference between Food Chain and Food Web
• There is not one food chain but scores of food chains that are cross linked with many more chains. This makes a food web of interconnected chains that look like a spider’s web.
• Food chains show a single path as animals eat each other to have a large carnivore at the top
• Food web shows how plants and animals are interconnected by different paths.
• Food web shows how animals are interconnected and are not dependent upon a single food chain.