Difference Between Food Chain and Food Web

The main difference between food chain and food web is that the food chain is a linear sequence of organisms through which the energy and nutrients pass whereas the food web is a complex of interconnected food chains of a particular ecosystem. Furthermore, a food web is a more realistic representation of the energy flow within each component of the ecosystem when compared to a food chain. 

Food chain and food web are two types of ecological concepts that interpret the flow of energy in a particular ecosystem. 

Key Areas Covered 

1. What is a Food Chain
     – Definition, Trophic Levels
2. What is a Food Web
     – Definition, Interconnections of Trophic Levels
3. What are the Similarities Between Food Chain and Food Web
     – Outline of Common Features
4. What is the Difference Between Food Chain and Food Web
     – Comparison of Key Differences

Key Terms 

Ecosystem, Energy Flow, Food Chain, Food Web, Trophic Levels 

What is a Food Chain 

A food chain is a series of events in the ecosystem where one organism eats another and is then eaten by another organism.  These various levels of organisms in a food chain are referred to as trophic levels. The two main types of trophic levels in a food chain are autotrophs and heterotrophs. A food chain is the link of autotrophs to heterotrophs. 

Autotrophs – Autotrophs are the primary producers of an ecosystem; hence, they represent the primary trophic level of each food chain and food web. The two types of autotrophs are photoautotrophs, which use energy from the sunlight to produce simple organic compounds such as plants, algae, and cyanobacteria, and, chemoautotrophs, which use energy from chemicals to produce simple organic compounds such as bacteria. 

Heterotrophs – The other organisms that feed on primary producers are collectively known as heterotrophs. They are unable to capture energy to produce organic compounds; hence, they consume organic compounds produced by primary producers. The herbivores represent the primary consumer level since they directly feed on the plant matter. Carnivores are the secondary consumers since they consume both plant matter and animal matter for obtaining energy. Omnivores represent the final consumer level since they only consume animal matter. They are the tertiary consumers. Some food chains have an apex consumer that represents the quaternary consumer level. 

Figure 1: A Complete Food Chain

Decomposers represent another important trophic level of a food chain though they always do not appear in a food chain. Sometimes, decomposers are considered in a separate trophic level since they consume decaying plant and animal matter.  

What is a Food Web 

A food web is a collection of all trophic levels in a particular ecosystem that can interact with each other. It is made up of a collection of interconnected food chains. A particular trophic level of a food chain has equal chances to be predated by a higher trophic level. By this, each trophic levels of the food chains in a food web can interconnect with the other trophic levels, making a web. As an example, a squirrel of a particular ecosystem can be eaten by a fox or raccoon. On the other hand, fox also eats mice and grasshoppers.  

Figure 2: A Marine Food Web

Similarities Between Food Chain and Food Web 

• Food chain and food web are two types of ecological concepts that describe the flow of energy in a particular ecosystem. 
• They start with a producer and then flow through the primary and secondary consumers.  
• All trophic levels of both the food chain and food web occupy the same habitat at the same time. 

Difference Between Food Chain and Food Web 

Definition 

Food chain refers to a feeding hierarchy in which organisms in an ecosystem are grouped into trophic (nutritional) levels and are shown in a succession to represent a linear flow of food energy and the feeding relationships between them while food web refers to a graphical model showing the interconnecting food chains in an ecological community. 

Energy Flow 

A food chain is a single, linear pathway of energy flow while food web consists of a number of interconnected pathways through which the energy flows within an ecosystem. 

Number of Food Chains 

A food chain is a single unit while a food web is a collection of several interconnected food chains. 

Number of Trophic Levels 

Food chain may consist of 4-6 trophic levels while food web consists of numerous trophic levels. 

Feeds upon 

A member of a higher trophic level can only feed upon a single type of organism in its lower trophic level in a food chain while a member of a higher trophic level in a food web can feed upon several types of organisms in its lower trophic level. 

Disturbance 

A disturbance on a single trophic level/organism definitely disturbs the whole food chain while a disturbance on a single organism does not disturb the whole food web. 

Stability 

The food chain increases the instability of an ecosystem while a food web increases the stability of an ecosystem. 

Adaptability and Competitiveness of Organisms 

Food chain does not improve the adaptability and competitiveness of organisms while food web improves the adaptability and competitiveness of organisms. 

Conclusion 

A food chain is a single, linear chain of organisms through which the energy flows in one direction. On the other hand, a food web is a collection of interconnected food chains. Therefore, the main difference between food chain and food web is the direction of energy flow. 

Reference:

1. “Food Chains & Food Webs.” Khan Academy, Khan Academy, Available Here

Image Courtesy:

1. “Complete-circle-foodchain” By Junjira saetae – Own work (CC BY-SA 4.0) via Commons Wikimedia    
2. “Chesapeake Waterbird Food Web” By Matthew C. Perry – US Geological Survey.”Chapter 14: Changes in Food and Habitats of Waterbirds.” Figure 14.1. Synthesis of U.S. Geological Survey Science for the Chesapeake Bay Ecosystem and Implications for Environmental Management. USGS Circular 1316. (Public Domain) via Commons Wikimedia