MODEL QUESTIONS
(Essay/Long type)
• What are the six classes of the components of the ecosystem? Describe in brief.
Ans :
a) components of Eco-system
There are two components (parts) of an Eco-system.
• Biotic : .They are living organisms. They are distinguished on the basis of their nutritional relationships.
The organisms living, on the land masses are different from those in sea-water. Climate condition bring about variations in the types of plants and animals found in different land masses.
• Abiotic : They are non-biological of Eco-System. They influence the living organism in the area.
They are also called non-living components of the Eco-system. Examples are chemical substances found in the soil, water, oxygen, carbon dioxide and minerals like phosphates, nitrates or organic materials like carbohydrates, fats, proteins and vitamins. Other abiotic elements of the climate are temperature, rain fall, duration of sunlight, winds ,nature of soil, slope of the land, composition of the bodies, etc.
The six classes of an Eco-system are as follows :
• Primary consumers. Herbivores feeding on plants. Example : Rabbit etc.
• Secondary consumers : carnivores feeding on animals. Examples : Lion
3) Tertiary consumers : Omnivores feeding both plants and animals. Example ; man
4) Consumers of decomposed tissues of plants. . Decomposers, Example: bacteria and fungi.
• Nutrients in soil and water.
• Energy from sun and from photosynthesis.
• Describe the ecosystem with reference to a pond as an example.
Ans : A pond is a good example of a small, fresh - water, aquatic ecosystem, which is self-sufficient and self-regulating. In fact, one of the best ways to start the study of ecology is to study a small pond, where all the basic components of an ecosystem can be conveniently examined.
Abiotic Components : The Abiotic components of a pond ecosystem consist of the physical and chemical parameters of pond water such as color, odour, taste, turbidity, electrical conductivity, temperature, pH (hydrogen ion concentration), suspended solids, dissolved solids, dissolved oxygen, alkalinity, chemical oxygen demand (COD), biochemical oxygen demand (BOD), nitrate, sulphate, phosphate, chloride, etc., and certain minerals like sodium, potassium, calcium, magnesium, iron, manganese, nickel, cobalt, lead, mercury and arsenic. Water samples can be collected from the pond and ail the above-mentioned physico-chemical parameters can be determined in a well-equipped laboratory.
Biotic Components : In a pond, the auto-trophic (self-nourishing) green plants and some species of photosynthetic bacteria are the producers . The green plants are mainly the macrophytes and phytoplanktons present in the pond water. The macrophytes are the rooted larger plants, which may be partly or completely submerged, emergent or free-floating. The phytoplanktons, on the other hand, are extremely small, floating or suspended lower plants. Diatoms form a major part of phytoplakton ok. Other types of phytoPlanktons are the green algae such as oscillatoria, volvox, spirogyra, etc.
In a pond, the majority of consumers are the herbivores. There are also a few insects and fishes which are carnivores. They depend on herbivores for their food. The primary consumers are either benthos or zooplarlktons (microscopic anirnals). Benthos are the organisms present at the bottom of the pond, but some are associated with the living plants. The common examples of benthos are fishes, beetles or insect larvae. Zooplanktons are mainly rotifers, protozoans and crustaceans. They feed on phytoplanktons. Some fishes, insects and frogs come under the category of secondary consumers . They feed on zooplanktons or on small fishes. The large fishes that eat small fishes and water snakes that feed on fishes come under the category of tertiary consumers .
In a pond, there are some microorganisms that decompose the dead and decaying bodies of both consumers and producers. They are known as decomposers . Some bacteria, fungi and actinomycetes belong to this category of the biotic components of a pond. Their main function is to bring about the decomposition of dead and decaying organisms of the pond ecosystern. Thus, within the small area of a pond, all the important feature of an ecosystern can be observed.
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