Food Chains and Food Webs

A Food Chain is a series of organisms that are dependent on the next as a source of food. Organism feed on each other. These organisms take part at various biotic levels and form food chains. A trophic level is each step or level in the food chain. They show the direction of energy in an environment. The producers or autotrophs which produce food by the process of photosynthesis are at the first trophic level. Autotrophs or producers fix up the solar energy & make it available for consumers, which are also known as Heterotrophs.

What is Food Chain?

The food chain is the straight chain of organisms that starts with the producer and then the energy is transferred from the producer to the carnivores and ends with the decomposer in the food web. The food chain explains the feeding relationship of organisms.

Those who produce their own food by changing the organic energy into chemical energy are known as autotrophs and in the process known as photosynthesis that organisms have chlorophyll for making food. Thus, they are called Producers or Autotrophs. Some organisms which are dependent on the producers as a source of food are termed, consumers. Consumers are also known as herbivores. Those who feed on the producers are known as primary consumers and place on the second trophic level and they occupy the second trophic level. Those who feed on primary consumers are known as small carnivores or secondary consumers and secondary consumers occupy the third trophic level. Large carnivores which feed on secondary consumers or small carnivores are known as tertiary consumers and they form the fourth trophic level.

The food chain has four main components those are:

1. Sun: Plants use solar energy for the process of photosynthesis. 
2. Producer: These are the organisms that produce food themselves through the process of photosynthesis. Producers are also known as Autotrophs. Solar energy is converted into chemical energy which transfers from one trophic level to the other as a source of energy. Producer Example-Algae, green plants, cyanobacteria, etc.
3. Consumer: These are the organisms that consume the food produced by the producers, also known as heterotrophs. Heterotrophs are those organisms that cannot make their own food and depends on other for food. The consumer can be herbivores, i.e., that organism that feeds upon green plants, or carnivores i.e., organisms that feed upon another organism. Consumers are the largest part of any food chain. 
4. Decomposers: Organisms that break down complex organic substances into simple inorganic substances, which then go into the soil and they are an important part of maintaining the nutrients cycle in the environment.

The food we consume acts as fuel to our body and it provides energy and helps in maintaining homeostasis. Due to the interactions among the components of the environment energy flows from one component of the system to another component. Autotrophs absorb energy from sun rays and convert it into chemical energy. It is this energy that supports all the activities. The energy pass in a unidirectional upward movement from producer to decomposer. When one form of energy is converted into another form of energy, some amount of energy or a huge amount of energy is lost to the environment and can’t be used again.

Another aspect of the food chain is that some chemicals enter our body through the food chain and start accumulating in the body this is known as Biomagnification. Humans use various chemicals and pesticides to protect crops from pests and other diseases. These chemicals reach soil or water bodies when they are washed off. On the one side, from the soil, these are absorbed by the plants along with water & minerals. On the other side, the water bodies, are taken up or consumed by aquatic plants & animals. In this way, chemicals enter the food chains. These chemicals are not degradable. So they go on accumulating at each trophic level. It’s human beings who occupy the topmost level of the food chain. It can also be defined as a  process in which the maximum concentration of chemicals gets accumulated in the body of organisms occupying the topmost trophic level. This is the reason wheat, rice, fruits, vegetables, and meat contains varying amount of chemicals.

Key Points

• When sunlight falls on the leaves of green plants they capture 1% of the energy of sunlight and convert it into food energy.
• When green plants are consumed by herbivores or primary consumers, a certain amount of energy is lost to the environment in the form of heat. The remaining energy would be used up by the herbivores for other activities like digestion, growth, and reproduction.
• Around 10% of the food eaten is turned into its own body and would be made available for secondary consumers.
• The food chain is generally up to 4-5trophic levels. A great amount of energy is lost at each trophic level as heat loss thus, very little energy remains for the consumers of the next trophic level. Consumers or organisms at third and fourth trophic levels receive less energy than the organisms at first and second trophic levels.
• On a normal basis, we see the food web very commonly instead of the food chain.

Law of Leinweber

This is also known as the 10% rule.

• This law states that the energy passed from one trophic level to the next level will only the 10% of the previous tropic level.
• The flow of energy is unidirectional and always in the upward direction.
• There is a max. loss of energy as heat loss so for the next level they have less amount of energy to transfer.

Types of Food Chain

Food chains are of two types on the basis of the beginning of the food chain. Detritus and Grazing Food chain.

Grazing Food Chain

The food chain in which the producers are autotrophs i.e, they make their own food by photosynthesis. Autotrophs are later on consumed by herbivores. Herbivores by the carnivores. The energy is passed on with each tropical level. Primary energy is taken from the sun.

Sun-> Autotrophs-> Herbivores-> Small Carnivores-> Large Carnivores-> Top Predator

Detritus Food Chain

This food chain starts with dead organic material. The Detritus food chain starts with the different organisms i.e, bacteria, algae, fungi, etc, which decompose the organic material like the detritus of plants, and decomposing animals. The decomposer gains energy from decomposition, the decomposer is later on eaten by the small carnivores and the energy is restored.

• Primary consumers of the detritus food chain are decomposers
• The Detritus food chain helps in regulating nutrient cycling.
• They have larger energy transfers in terrestrial habitats.

Food Web

The length and complexity of the food chain differ greatly. In our environment, one organism can be eaten by two or more kinds of organisms which are then eaten by others. So instead of a straight-line food chain, this relationship can be shown as a series of branching lines, this graphical representation is known as the Food Web. The Food web also can be defined as an interconnection of food chains.

The energy captured by producers or autotrophs is passed on to the secondary consumers, then to tertiary consumers, and so on. So the flow of energy is said to be unidirectional and it doesn’t revert back. As we already discussed, some amount of energy is lost from each trophic level in the form of heat loss to maintain their temperature. so for the next transfer, the energy is less and energy goes on decreasing. Thus, the top trophic level receives less energy than the previous ones.

FAQs on Food Chain

Question 1: What are the first organisms in a food chain?

Answer: 

The food chain starts with the producer. On the basis of producer, the food chain is classified into two types: Detritus and Grazing food chain.

Question 2: What is a Food chain? 

Answer: 

A food chain is a series of organisms which are dependent on the next as a source of food.These organisms take part at various biotic levels and form food chains.

Question 3: Define trophic level.

Answer:

 A trophic level is formed by each step or level of the food chain.

Question 4: What are food web?

Answer: 

In our environment one organism can be eaten by two or more kind of organisms which are then eaten by others.So instead of a straight line food chain, this relationship can be shown as a series of branching lines,this graphical representation is known as Food web.

Question 5: What is the difference between a food chain and a food web?

Answer:

The food chain is the linear line that represents the feeding relationship of the organisms. Whereas in the food web multiple food chains are interconnected and show how different plants and animals are connected. 

Question 6: Which organisms occupy the first trophic level and why?

Answer:

The producers or autotrophs occupy the first trophic level. Because they produce food by themselves by the process of photosynthesis and autotrophs or producers fix up the solar energy and they are the one who make it available for consumers of the next trophic levels.