Autotrophs are organisms (green plants and some basic bacterial which can use sunlight or chemical to manufacture their food from inorganic substances during the process of Photosynthesis). In other words, autotrophies are organisms capable of synthesizing their own food, hence they are called Producers.
Autotrophys provide food for the other organisms in the habitat. Examples of autotrophys are Grasses, Trees and Shrubs while aquatic autotrophies are Phytoplankton, Water cyacinths, Sea weeds e.t.c.
Heterotrophys are organism, mainly animals which cannot manufacture their own food but depend directly or indirectly on plants for their food, hence they are called Consumer.
Animals that feed directly on green plants (Producer) are called Herbivoresor primary consumers while animals or organisms that feed on the primary consumers are called Carnivores or secondary consumers. Hetetrophys include all Animals, Carnivores Plant, Fungi, Most Protists and Some -Bacterial.
Consumers are Heterotrophys that feed on other organisms they include halozoic organism such as herbivorous, carnivorous omnivorous, decomposers and parasite. Some examples of consumers or hetetrophys in terrestrial ecosystem are Caterpillar, Cow, Dog, Lion, Toad, Hawk, Lizard, Man e.tc. While aquatic, Heterotrophys include water fleas, tadpoles, larvae of insects and fishes.
Decomposers are organism that feed on dead organism and other decaying organic material. Decomposers help to break organic matter and release simple chemical which plants can absorb and use again.
Examples of decomposer are insects such as Termite, Larvae of Housefly, Bacteria and Fungi.
Food chain is defined as a feeding relationship involving the transfer of energy through food from producers to consumers.
Examples of food chain in terrestrial habitat are:
- Guinea grass (Producer).
- Grasshopper (Primary Consumer).
- Toad (Secondary).
- Snake, Hawk (Tertiary Consumer).
- Grass (Producer).
- Antelope (Primary Consumer).
- Lion (Secondary Consumer).
Every food chain usually begins with a producer (green plant) that is fed on by a herbivorous (Primary consumer) which is in turn feed on by a carnivore, e.g toad and the carnivore is again feed on by the snake and the snake is feed on by a bigger carnivore such as the Hawk.
Example of a food chain in aquatic habitat:
- Diatoms (Producer).
- Mosquito Larvae (Primary Consumer).
- Tilapia Fish (Secondary).
- Whales (Tertiary Consumer).
During the process which occurs in food chain, food energy is transferred from one organism to another in a linear form.
The line shows the direction in which the food transferred, even though most food chains begin with producer, there are few examples that start with dead plants or animal e.g.
Human >> Earthworm >> Domestic fowl >> Man
Food web is defined as a complex feeding relationship among organism in the same environment with two or more inter-related food chains.
Food web contains two or more foods chains and therefore more organisms than food chain. In nature, the interaction in feeding are more complicated because a single plant could be feed upon by more than one or two organism.
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 above food web, there are three food chains in the habitat.
DIFFERENCES BETWEEN FOOD CHAIN AND FOOD WEB
|S/N||FOOD CHAIN||FOOD WEB|
|1.||It is linear feeding relationship.||It is a complex feeding relationship.|
|2.||It involves one food chain.||It iinvolves two food chain.|
|3.||It involves fewer organisms.||It involves many organisms.|
|4.||Organisms have lesser chances of survival.||Organisms have greater chance of survival.|
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 link by which food energy is transferred from producers to final consumers.
For examples in a food chain like the one below:
- Guinea Grass (1st Trophic level).
- Grasshopper (2nd Trophic level).
- Toad (3rd Trophic level).
- Lizard (4th Trophic level).
- Hawk (5th Trophic level).
There are five trophic of feeding level. In other words, there are given links by which energy is transferred from producers, e.g. (Guinea grass) to final consumers (Hawks). Guinea grass is at the first trophic level to Grasshopper at the second trophic level, Toad at the third, Lizard at the fourth and Hawk ay the fifth.
PYRAMID OF NUMBER
Pyramid of number refers to the number of individuals organism 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 from the base and the carnivorous from 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.
Grasses >> Grasshoppers >> Lizards >> Hawks
The number of grasses eaten by the grasshopper is greater than the number of grasshopper, while the number grasshoppers eaten by Lizards is greater than the number of lizards, and finally the number of lizards eaten by the hawks is greater than the number of the hawks.
Below is how the pyramid of energy decreases in the number of an organism:
- Grasses 40
- Grasshoppers 12
- Lizards 5
- Hawks 2
Pyramid of energy is defined as the amount of energy present in the living organisms at the different level of food chain.
In other words, the pyramid of energy represents a progressive decrease in energy from the trophic level to the last trophic level in a food chain or web.
Below is how the pyramid of energy decreases in energy:
- Grasses 500 Joules
- Grasshoppers 300 Joules
- Toads 100 Joules
- Lizards 20 Joules
- Hawks 5 Joules
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