OUR ENVIRONMENT
ECOSYSTEM
– WHAT ARE ITS COMPONENTS?
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Organisms and physical
surroundings interact with each other and maintain a balance in nature.
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All the interacting
organisms in an area together with the non-living constituents form an ecosystem.
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Biotic components: Include all living organisms.
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Abiotic components: Include physical factors like temperature, rainfall, wind, soil
and minerals.
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Natural ecosystems: Forests, ponds, lakes etc.
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Humanmade (artificial)
ecosystems: Gardens, crop-fields, aquarium
etc.
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Aquarium is a self-sustaining system because it includes biotic factors
(fishes, aquatic plants, animals, etc.) and abiotic factors (free space, water,
oxygen & food).
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Organisms can be grouped
as producers, consumers and decomposers.
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Producers: They make food from inorganic compounds. E.g. Green plants and
some bacteria.
Green plants make organic
compounds (sugar & starch) from inorganic substances using the solar radiant
energy in presence of chlorophyll. It is called photosynthesis.
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Consumers: Organisms that directly or indirectly depend on the producers
for food. They consume the food from producers or by feeding on other
consumers.
Types of Consumers:
o Herbivores: E.g. Grasshopper,
Rabbits, Deer etc.
o Carnivores: E.g. Frog, Tiger, lion
etc.
o Omnivores: E.g. Human, bears,
birds, dogs etc.
o Parasites: E.g. Roundworms,
tapeworms, leech etc.
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Decomposers: They break-down dead remains & waste products of organisms
(complex organic substances) into simple inorganic substances. Inorganic
substances go into the soil and are used up by the plants.
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If the aquarium is not
cleaned, fishes and plants will be died. The microorganisms (bacteria &
fungi) break-down the dead remains and waste products of organisms.
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If decomposers are
absent, the garbage, dead animals and plants will not decompose. It leads to
accumulation of organic materials thereby causes pollution.
Food Chains and
Webs
- A food chain is the series of organisms feeding on one
another or organisms taking part at various biotic levels.
- Each step or level of the food chain forms a trophic level.
o Autotrophs (producers): First
trophic level.
o Herbivores (primary consumers): 2nd trophic level.
o Small carnivores (secondary consumers): Third trophic level.
o Larger carnivores (tertiary
consumers): Fourth trophic level.
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- Autotrophs capture solar energy and convert into chemical
energy.
- From autotrophs, energy goes to heterotrophs and decomposers.
- The study of flow of energy reveals that
o Green plants in a terrestrial
ecosystem capture about 1% of the solar energy that falls on their
leaves and convert it into food energy.
o
o Food chains generally consist of only 3 or 4 steps since so
little energy is available for the next trophic level.
o There are generally so many individuals at the lower trophic
levels. Producers are in greatest number.
o Each organism is generally eaten by two or more kinds of
organisms which in turn are eaten by several other organisms. This series of
branching relationship of food chains is called a food web.
- Energy flow diagram shows the following features:
1.
Energy flow is unidirectional.
It does not revert back from autotroph to the Sun or consumer to autotroph.
2.
Energy available at each
trophic level gets diminished progressively due to loss of energy at each
level.
- Some harmful chemicals may enter the bodies through the food chain.
E.g. Pesticides and other chemicals are washed down into the soil or water.
From the soil, plants absorb them. From the water bodies, aquatic plants &
animals take up them. Thus they enter the food chain.
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The non-degradable
chemicals get accumulated at each trophic level. This is called biological
magnification. Thus cereals, vegetables, fruits & meat contain
pesticide residues. Their concentration is
maximum in human body because humans occupy the top level in any food
chain.
- Methods to reduce intake of pesticides:
o Minimise the use of chemical pesticides.
o Wash fruits & vegetables thoroughly before use.
o Use organic fruits and vegetables.
