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What's the Difference Between Food Chain and Food Web?

What is the Difference Between Food Chain and Food Web
Ecological community is the collection of individuals belonging to different species, occupying the same habitat, at the same time. The interaction between these individuals for their survival gives rise to various food chains, which ultimately give rise to various food webs. This ScienceStruck article does an analysis of food chain vs. food web by describing the different aspects surrounding it.
ScienceStruck Staff
Last Updated: May 8, 2018
Did You Know?
Keystone species are those whose presence has a significant impact on the survival of the ecological community.
Food chains and food webs serve as important tools in understanding how every individual of the ecological community, no matter how big or small, plays a role in the maintenance of the community as a whole. It helps us to understand how the reduction in the population of one individual causes a reduction in the population of other individuals. We also get to learn certain concepts like natural selection and behavioral adaptations of different plants and animals for their survival.
Food Chain
Food Chain
The food chain can be defined as a simple representation of who-eats-who. It is a chain of interdependence between different individuals of an ecology for their food. In other words, it is the feeding relationship between different individuals.
Food Web
Food Web
In nature, no food chain operates on its own. Every food chain is connected to other food chains by the individuals belonging to it. This interconnected network of food chains is called a food web. Each food chain is just one part of the food web.
How Does This Interconnection Arise?
A prey has an equal chance of being predated by more than one predator. Similarly, a predator has an equal chance of hunting down more than one type of prey. In a terrestrial ecosystem, a rat can be eaten by a snake, or by an eagle. Similarly, a snake can either eat a rat or a frog.
Trophic Levels
Every food chain or food web is made of different stages called trophic levels.
1st Trophic Level
The first trophic level comprises producers. Producers are plants. These utilize energy from the Sun and convert inorganic substances into organic food material, through the process of photosynthesis. In a way, they lock solar energy into a form that is more readily usable by other individuals. As these produce their own food, they are called producers.
2nd Trophic Level
All individuals that do not produce their own food, but depend on producers for their own food directly or indirectly are called consumers. The second trophic level comprises primary consumers. All herbivores (individuals that eat plants only) belong to this trophic level.
3rd Trophic Level
This trophic level comprises secondary consumers. Secondary consumers are individuals that feed on herbivores.
4th Trophic Level
This trophic level comprises individuals that feed on the secondary consumers and are called tertiary consumers. Sometimes, the tertiary consumer may be consumed by a higher-level consumer. Individuals who do not have any natural predators are called apex predators.
Only 10% of the total energy passes from one trophic level to the next trophic level, as most of the energy is consumed by the individual to do work. Due to this, a food chain is mostly made of 4 - 5 trophic levels only.

Another trophic level is occupied by decomposers. Decomposers grow on dead and decaying organic matter, and convert it into simple inorganic substances. They usually comprise detritivores (earthworms, termites, etc.), bacteria, and fungi.
Comparison Between Food Chain and Food Web
Although a food chain is a part of the food web, there are a few basic differences between the two.
1. Single Pathway Vs. Network
The food chain is a linear pathway, and it comprises only one pathway. For example: In a terrestrial habitat, grass is eaten by a grasshopper, the grasshopper is eaten by a frog, the frog is eaten by a snake, and the snake is eaten by an eagle. This makes one food chain. Similarly, the grass is eaten by the grasshopper, the grasshopper is eaten by a frog, and if the frog is eaten by an eagle, it makes for separate food chain.
The food web is an interconnected network of different food chains. For example: In a terrestrial habitat, grass is eaten by a grasshopper or a caterpillar, the grasshopper or the caterpillar is eaten either by a frog or a wasp, and the frog can be eaten by a snake or an eagle. So, there are many food chains that may participate in a food web.
2. Single Isolated Food Chains Vs. Complex Food Webs
Isolated food chains will decrease the stability of that ecological community. Suppose herbivore B solely depends on producer A for its food, a carnivore C completely depends on herbivore B for its food, and may be another carnivore say D depends solely on carnivore C for its food. Now, there is a chance that if any one of these die, the rest may starve to death, and ultimately the whole chain may collapse. As a result, there is a reduction in the number of species present in a particular ecological community, which will, thus, reduce its stability.
Complex food webs have greater stability. The complexity of a food web can be determined by the number food chains that are interconnected. Complexity increases as the number of interconnected food chains increase.

In complex food webs, an individual of a particular trophic level, carnivore C, depends on many other herbivores for its food. So, the scarcity of herbivore B will not be detrimental to the survival of carnivore C and thus, it will also not affect the survival of carnivore D.
3. One Individual-One Trophic Vs. One Individual-Many Trophic Levels
In a food chain, an individual will occupy only one trophic level. For example: In an aquatic habitat, phytoplankton is eaten by a zooplankton, the zooplankton is eaten by krill, the krill is eaten by blue whale, and the blue whale being eaten by Orca is one food chain. Here, krill will only occupy the third trophic level.
In a food web, an individual is capable of occupying more than one trophic level. This will depend on who it eats and who eats it. In the example mentioned above, krill can eat phytoplankton or it can eat zooplankton. So over here, krill can either occupy the second or third trophic level.
4. Less Fit Vs. More Fit
Isolated food chains do not help to increase the competitiveness and the adaptability of an individual. As only carnivore C is going to eat herbivore B, carnivore C does not have to compete with any other individual for its food. As a result, the carnivore does not need to adapt itself to get an edge over the other individuals of the same trophic level.
A complex food web increases an individual's ability to adapt and compete with other individuals of the same trophic level. In a world of survival of the fittest, every individual has to adapt to its environment so that it can compete with other individuals for food and mate. When herbivore B is being eaten by carnivore C, carnivore D, and carnivore E, then there is going to a competition between carnivores C, D, and E for herbivore B. The carnivore that has best adapted to its environment, wins.
Venn Diagram
Venn Diagram
By understanding how a food chain and, thereby, how a food web works, we are trying to understand the fine balance that exists in nature, which is essential for our very own survival.