Food Chain in Ecosystem

Food Chain:

Nutrition is one of the basic characteristics of living organisms.

The process of nutrition may be considered as a form of chain that brings different species of organisms into interaction.

For instance, a zebra will interact with different plants in the savanna biome for the purpose of food.

Similarly, a lion interacts with a zebra for the same purpose (food).

You can read on the Savanna and Tropical Rainforest Biomes here.

Note: The interaction of organisms for food will always commence with producers.

Producers in food chain refers to organisms that manufacture or produce their own food.

Producers also feed from the food they manufacture while other organisms will depend on them for ready made food, either directly or indirectly.

Organisms that manufacture their own food are referred to as autotrophic organisms or autotrophs. In food chain, we often refer to them as producers.

Please read on Autotrophic Mode of Nutrition here.

Examples of autotrophs or producers are the green plants, blue-green algae and chemosynthetic bacteria.

Note: When autotrophs require sunlight to make their food, they are referred to as photoautotrophs and the process involved is termed photosynthesis.

Examples of photoautotrophs are all green plants and the blue-green algae.

Conversely, when autotrophs utilizes chemicals for manufacturing their food, they are referred to as chemoautotrophs and the process involved is termed chemosynthesis.

Chemoautotrophs includes methanogenic archaea, aquificae and sulfur-oxidizing epsilon proteobacteria.

A Food Chain is a diagram that shows the relationship between plants and animals within a habitat on the basis of how they rely on each other for food.

Think of habitat as a place where organisms live. They are put into 3:

1. Terrestrial Habitat (Land)
2. Aquatic Habitat (Water)
3. Arboreal Habitat (Treetops)

Please read on Deserts and Swamp Forest with their Characteristics here.

The diagram below shows a Food Chain:

A food chain begins with the producers. These producers are usually consumed by other organisms (usually herbivores); and are referred to as consumers.

Note: Organisms that directly feed on producers in a food chain are preferably called primary consumers.

Examples of primary consumers are zebra, grasshopper, antelope, rabbit and other plant feeding organisms.

Please read on Differences between Plants and Crops here.

Next, the primary consumers are consumed or eaten by another sets of consumers called secondary consumers.

Secondary consumers include animals like rats, lion, cats and snakes. (They can be carnivorous or ominvorous organisms).

Please read on Reptiles and their Characteristics here.

Secondary consumers may be consumed by a third set of consumers called tertiary consumers.

Vultures and Eagles are examples of tertiary consumers.

Finally, the tertiary consumers are consumed by the last group of organisms called decomposers.

Decomposers in food chain are organisms that feed on dead organisms, bringing about their decomposition in the process. They may also be regarded as saprophytes.

Fungi and Bacteria are typical examples of Decomposers.

Please read on the Basic Introduction to Biology here.

Note: Producers begins the food chain while decomposers signifies the end of a food chain.

Food Web

Food chain can be interlinked in a habitat, giving rise to food web.

Consider the diagram below.

Using the above diagram as a point of reference, notice that the feeding pattern is interlinked.

Consider the explanations below (The diagram serves as our reference):

EXPLANATION 1:

• Grasshopper feeds on berries.
• The frog feeds on the grasshopper.
• A snake feeds on the frog.
• A titmouse feeds on the snake.
• The fox eats the titmouse.

The aformentioned observations are illustrated below:

Berries >> Grasshopper >> Frog >> Snake >> Titmouse >> Fox.

This illustration (above) is one food chain in the habitat. Notice that the food chain is linked to other food chains as illustrated in explanation 2.

EXPLANATION 2:

Recall that the food chain in explanation 1 began with the grasshopper.

Notice that apart from the grasshopper, the greenfly and butterfly also fed on the berries.

• The ladybird feeds on the greenfly.
• Dragonfly feeds on the ladybird.
• The frog feeds on the dragonfly.
• The snake eats the frog.
• The Buzzard eats the snake

This is another food chain although it has some links with the above food chain (in explanation 1).

Note: It is this linking of food chains that gives rise to a Food Web.

EXPLANATION 3:

• Also, you may have observed that apart from the dragonfly feeding on the ladybird, the titmouse also fed on the lady bird.
• Also, the butterfly and titmouse fed on the berries along side the greenfly and grasshopper.
• Similarly, the rabbit, mouse and grasshopper all fed on plantain.
• Again, the buzzard and fox feeds on the mouse and rabbit. We can go on and on but the point to note is:

A food web shows multiple food chains or multiple feeding relationships or multiple feeding connections all linked together.

Note: Food Web always consist of more than one food chain (at least, a minimum of 2 food chains linked together).

Food Pyramid

All organism get their energy from the food they eat.

A food chain that shows the movement of energy through it is termed a food pyramid.

Note: The food pyramid is always drawn in a triangular form with the narrow edge at the top. This narrowing at the top signifies the loss of energy as we go top of the food pyramid.

The image below shows a Food Pyramid:

From the above diagram, the primary consumers (grasshoppers) fed on the grasses and gained 1,000kcal of energy. Most of this energy would probably be used for their metabolic activities like hopping, respiration, movement, reproduction and so on.

All living organism must lose energy in the form of heat to their surroundings. This is as a result of their metabolic activities.

By the time the secondary consumers consumed the grasshoppers, it was only able to get 10kcal of energy simply because the grasshoppers had already lost some energy in the form of heat to it's surroundings.

Similarly, the secondary consumers will also use some of this energy (10kcal) for it’s metabolic activities; thus losing some energy in the form of heat to the surroundings.

Finally, the tertiary consumer consumed the secondary consumers and was able to get 1kcal of energy. This is because the secondary consumers had lost 9kcal of energy in the form of heat to its surroundings.

Note: As a student, you should be able to state the 2^nd law of thermodynamics because it has everything to do with the “loss of heat to the surroundings”.

Please read on the Concept of Heat and Temperature here.

The 2^nd Law of Thermodynamics, with regards to food chain states that:

In the course of energy transformation or transfer, some energy is lost in the form of heat to the surroundings.

Note: Energy is always lost as heat during metabolism.