Our Environment online mcq quiz
Our Environment boostup points
➔ Environment: It is the sum total of all external conditions and influences that affect the life and development of an organism, i.e., the environment includes all the physical or abiotic and biological or biotic factors.
➔ Biodegradable Substances are those substances which are broken down into simpler, harmless substances in nature in due course of time by the biological processes such as action of microorganisms.
Examples: Domestic waste products, urine and fecal matter, sewage, agricultural residue, paper, wood, cloth and cattle dung.
➔ Non-biodegradable Substances: are those substances which cannot be broken down into simpler, harmless substances in nature. These substances may be in solid, liquid or gaseous form and may be inert and accumulate in the environments or may concentrate in the food chain and harm the organisms.
Examples: DDT, plastics, polythene bags, insecticides, pesticides, mercury, lead, arsenic, aluminium, radioactive waste, etc.
➔ Ecosystem: It is the structural and functional unit of biosphere, comprising of all the interacting organisms in an area together with the non-living constituents of the environment. Thus, and ecosystem is a self sustaining system where energy and matter are exchanged between living and non-living components
➔ Biotic Component: It means the living organisms of the environment-plants, animals, human beings and microorganisms like bacteria and fungi, which are distinguished on the basis of their nutritional relationship.
➔ Abiotic Component: It means the non-living part of the environment – air, water, soil and minerals. The climatic or physical factors such as sunlight, temperature, rainfall, humidity, pressure and wind are a part of the abiotic environment.
➔ Types of Ecosystems: Ecosystems are of two types
I) Natural Ecosystem: The natural ecosystems are terrestrial (land) as well as aquatic. The common
examples of land ecosystem are forests, grasslands, deserts, etc. The common examples of aquatic ecosystem are ponds, lakes, rivers, ocean, etc.
II) Artificial Ecosystems: The artificial ecosystems are made by human beings. The common examples of artificial ecosystems are crop fields, gardens, parks, aquarium etc.
➔ Producers: Those organisms which produce food by photosynthesis, i.e., organisms which can make organic compounds like sugar and starch from inorganic substance using the radiant energy of the sin in presence of chlorophyll.
Examples: All green plants and certain blue-green algae are called producers.
➔ Consumers: those organisms which depend upon the producers for food, either directly or indirectly by feeding on other consumers for their sustenance. Consumers therefore feed upon those below it in a food chain and are called heterotrophs. It can be classified into primary consumer or herbivores, carnivores, omnivores and parasites.
➔ Herbivores are the animals that consume or eat vegetation or plants, e.g., cows, horses.
➔ Carnivores are the animals that eat meat of other animals, e.g., tigers, wolves.
➔ Omnivores are the animals that eat both plants and animals, e.g., humans, cockroaches.
➔ Parasites are those organisms that live on (ectoparasites) or in (endoparasites) the body of another
organism, e.g., host from which it obtains its nutrients, e.g., parasites of man includes fleas and lice
(ectoparasites) various protozoans (endoparasites) and tapeworms.
➔ Flow of Energy: The flow of energy through different steps in the food chain is unidirectional. This means that energy captured by autotrophs does not revert back to the solar input and it passes to the herbivores. It moves progressively through various trophic levels.
➔ Green plants capture 1% of energy of the sunlight that falls on their leaves and convert it into food
energy.
➔ When green plants are eaten by primary consumers, a great deal of energy is lost as heat to the
environment. On an average 10% of food eaten is turned into its own body and made available for
next level of consumers.
➔ Thus, 10% can be taken as average value, the amount of organic matter present at each step and
reaches the next level of consumers.
➔ As very less energy is available for next level of consumer, food chain consists of only three or four
steps. The loss of energy at each step is so great that very little energy remains after four trophic
levels.
➔ There are a greater number of individuals at lower trophic level, i.e., at the producer level of the
ecosystem.
➔ In an ecosystem, the Sun’s energy is transformed by producers into chemical energy by the process
of photosynthesis.
➔ In herbivores and carnivores this energy is then transformed further at various trophic levels.
➔ The chemical energy is transformed into mechanical energy and heat.
➔Thus energy flows from sun through producers to consumers in a single direction only.
➔ So, there is maximum energy at the producer level and further the energy goes on decreasing. The
herbivores get more energy with food than carnivores at third and fourth trophic levels.
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