What is the difference between a food web and a food chain?
A food chain is a linear representation or description whereas a food web is not linear and therefore includes more connections within the organisms. The two are often used interchangeably, although they are not technically the same. A food web contains multiple food chains.
Here's an example of a food chain:
Here's a food web:
As you can see, the food web is more complex. The puffin doesn't just eat the salmon. It also eats the sand lace and the cephalopod. The puffin is eaten by the fox and the rat and the decomposer. Food webs are what we see in nature.
A food web consists of many food chains whilst a food chain is just one path of energy flow through an ecosystem.
A food chain is a linear sequence that involves links in a food web starting off with a producer (like a plant), primary consumer (herbivore), Secondary consumer and tertiary consumer. So it is this link that involves one organism eating another organism and so on.
A food web, however, is the natural connection of food chains through a graphical representation of what organism eats what in an ecological community. This is different to a food chain because, in a food web, a particular organism has the probability of being eaten/eat more than just one organism.
(Source, Difference btw, 2015)