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ADVANTAGES AND DISADVANTAGES OF MECHANIZATION

ADVANTAGES AND DISADVANTAGES OF MECHANIZATION ADVANTAGES OF MECHANIZED AGRICULTURE Farm mechanization has the following advantages 1. ...

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WHAT IS FOOD CHAIN, FOOD WEB AND TROPHIC LEVEL?


WHAT IS FOOD CHAIN, FOOD WEB AND TROPHIC LEVEL?

FOOD CHAIN

Food chain is defined as a feeding relationship involving the transfer of energy through food from producers to consumers. This is a linear feeding relationship; in which energy is transferred from producer/plants, through a series of organisms/trophic levels; in which each organism feeds on the preceding one, and provides food for succeeding one in the habitat.
During the process which occurs in food chain, food energy is transferred from one organism to another in a linear form. The arrows shows the direction in which the food is being transferred, even though most food chains begin with producers. There are few exemptions that start with dead plants or animals. For example, humus==earthworm==domestic fowl==man




FOOD WEB

Food web is defined as a complex feeding relationship among organisms in the same environment with two or more inter-related food chains.
Food web contains two or more food chains and therefore more organisms than food chain. In nature, the interaction in feeding are more complicated because a single plant could be fed upon by more than one or two organisms. When a consumer feeds on different types of plants or animals in a food web, it has a better chance of survival in its ecosystem.
In the food web in the picture, there are four food chains in the terrestrial habitat. Example of a food web in an aquatic habitat is illustrated below.

DIFFERENCES BETWEEN FOOD CHAIN AND FOOD WEB

FOOD CHAIN
1. It is a linear feeding relationship.
2. It involves one food chain.
3. It involves fewer organisms.
4. Organisms have lesser chance of survival.

FOOD WEB
1. It is a complex feeding relationship.
2. It involves two or more food chains.
3. It involves many organisms.
4. Organisms have greater chance of survival.

TROPHIC LEVEL

Trophic level, also called feeding level, is defined as the feeding level or each stage in a food chain or food web. In other words, trophic level is the number of links by which food energy is transferred from producers to final consumers. For example, in a food chain like the one below, we can have these levels.




PYRAMID OF NUMBER

Pyramid of number refers to the number of individual organisms at each trophic level which decreases progressively from the first to the last trophic level in a food chain. Pyramid is a diagrammatic representation of food chain in which producers form the base and the carnivores form the apex.
In a food chain or food web, there are relative number of organisms at different trophic levels. Normally, the number of organisms decreases progressively from the first to the last trophic level. For example, Grasses==Grasshoppers==Lizards==Hawks
The number of grasses eaten by grasshoppers is greater than the number of grasshoppers, while the number of grasshoppers eaten by lizards is greater than the number of lizards and finally the number of lizards eaten by hawks is greater than the number of hawks. From this explanation, one discovers that there is a progressive decrease in the number of organisms from the first to the last trophic level. The diagrammatic representation of this progressive decrease in the number of organisms along the food chain is called pyramid of number.




PYRAMID OF ENERGY

Pyramid of energy is defined as the amount of energy present in the living organisms at the different trophic levels of a food chain. In other words, the pyramid of energy represents a progressive decrease in energy from the first trophic level in a food chain or web.

Just like the pyramid of number, the producers at the first trophic level contain most of the energy. The primary consumers have lesser energy while the secondary or tertiary consumers have the least energy.
Just like the pyramid of numbers, the producers as in the grasses form the base of the pyramid while the tertiary consumers, e.g. hawks from the apex. Energy therefore decreases from the base of the pyramid to the apex.

PRINCIPLES GOVERNING TROPHIC LEVELS AND THE PYRAMIDS

1. Food chain starts with photosynthesis (producers) and ends with decay.
2. Shorter food chains are made more efficient than larger food chains in term of waste of energy.
3. Large population are characterized by more steps in food chain. This means that useful energy decreases so that little of it will be made available to the tertiary consumers.


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