Food Chain – nature’s critical network for survival
A food chain is a directed graph which links together the eating habits of organisms in an ecosystem. Depends on the scale of the ecosystem, the network of a food chain can be consisted of either only a few nodes and easily traceable paths, or a complex graph with complex edges.
Having the idea of a breadth-first search, a food chain network graph can be analyzed using breadth-first search as the food chain is mainly made up of three “trophic levels” – producers, consumers, and decomposers. Take the pond for example, the seaweed and water plants in the pond are the first level of the food chain network as they produce food for primary consumers – fish and water organisms that consume plants. Seaweed and water plants gain nutrition and live through the process of photosynthesis which does not consume other organisms. The primary consumers are then consumed by secondary consumers such as fish and turtles. Similarly secondary consumers are eaten by tertiary consumers and so on until it reaches the level called “apex predator” where at this level they cannot be preyed while living. The fungus and bacteria living in the soil at the bottom of the soil becomes the decomposer which allows the search to reach its end. In a simple ecosystem, its food chain can be interrupted if there exists a weak edge which is no longer connected. This would break the food chain and have severe consequences. If the edge which connects seaweed and primary consumers in the pond broke, this would end up in the fact that only the producers can survive in this broken food chain.
One thing I tend to think about a food chain is that while strong edge can represent a direct and usual consumption to an upper level, a weak edge might indicate that it is not common for this level of consumers to consume its upper level, or this level of consumers have multiple choices of consumption. In a more complex food chain network, on the other hand, it is possible to have a few disconnected edges, yet since there exists multiple producers, consumers which consume different producers and consumers, the network can still be connected and maintain its function.
http://education.nationalgeographic.com/encyclopedia/food-chain/