Concept : Food Chain and Food Web
The chain that shows the transfer of matter and energy from one organism to another
in the form of food is called a food chain.
- Every organism needs energy for survival.
Plants depend on the sun for energy whereas, animals obtain energy from plants and other animals.
- Green plants utilise the energy from the sun for producing
food by the process of photosynthesis and are therefore called autotrophs.
Characteristics of a food chain:
- Plants lie at the base of all food chains-
This is because plants can synthesise their food by photosynthesis using water and
minerals in the presence of sunlight and chlorophyll. They are also called producers.
- Consumers lie at the second and successive trophic levels of a food chain—-
- The second trophic level is generally occupied by plant-eating animals (herbivores), also called primary consumers.
- In the following successive trophic levels lie the carnivores and omnivores.
- The organisms at third and fourth trophic levels are called secondary and tertiary consumers, respectively.
- The position of an organism in a food chain is defined as the trophic level.
The number of trophic levels in a food chain is not less than three and not more than five.
- The reason behind this is that energy is lost at each trophic level of a food chain,
and there is no energy or little energy left for transfer after five trophic levels.
- Shorter the food chain, the greater is the available energy.
The dead plants and animal bodies are decomposed by the decomposers and are converted into simple nutrients.
These nutrients then get mixed with the soil.
Passage of Energy in a food chain:
Energy is transferred along food chains from one trophic level to the next. The amount of energy decreases with each successive trophic level as energy is lost at every trophic level for essential life processes.
A food web is the diagrammatic representation of the overall food relationships and interdependence between organisms in an ecosystem.
Features of the food web:
- A food web contains all the constituent food chains of an ecosystem.
- It comprises multiple food chains that can vary in the number of trophic
levels; some may be short while the others may be long.
- A food web comprises similar trophic levels as that of a food chain.
- There are five main trophic levels—
- Producers: Plants are called producers as they can make their own food.
- Primary consumers: Heterotrophs that feed on producers.ExamplesCaterpillar, grasshopper.
- Secondary consumers: Heterotrophs that feed on primary consumers.Examples: Frog, mouse.
- Tertiary consumers: Heterotrophs that feed on primary and secondary consumers.Examples: Lion, tiger, humans.
- Apex predators: Animals who hunt and feed on other animals. Examples: Fox, eagle.
Ecosystem: It is the smallest unit of environment where
the living and non-living components interact with each other.
Bioaccumulation: It is the build-up of toxic materials inside living organisms.
Biomagnification: It refers to the significant increase in the amount of a
toxic substance every time it moves up the levels of the food chain.
Did You Know?
The concept of the food chain was first put forward by the Arab scientist Al-Jahiz in the 9th century,
and the scientist who first proposed the idea of the food web was Charles Elton in 1927.