Science [2 Mark Questions]

• Pesticides and other chemicals are used in order to protect the crops from diseases or pests.
• Such chemicals are non-biodegradable.
• The amount of these chemicals increases in the soil or water bodies due to uncontrolled use of it.
• From soil or water they enter in the body of plants and then it passes in trophic levels of food chain.
• They get accumulated progressively at each trophic level as these chemicals are not degradable.
• Due to bio-magnification, high concentration of such chemical causes lethal effects on higher level carnivores animals. Some such chemicals prove lethal for organisms of lower trophic level too.
• These chemicals reach upto human beings too through food.
• Thus, it is necessary to prevent the uncontrolled use of pesticides and other chemicals.

• In nature, organisms are interlinked for food to form food chain.
• Among various ecosystems, each one is having definite food chain.
• But single organism is never dependent only on one organism for food.
• So trophic relationships for food can never be explained as straight chain.
• The individuals involved in food chain of one ecosystem are also linked with food chains of other ecosystems.
• So, trophic relations for food do not operate in isolation but interlinked to form complex net called food web.
• Thus, the trophic relationships of organisms occur in form of food web.

• The solar energy enters in an ecosystem through the process of photosynthesis performed by green plants.
• The energy that is captured by green plants does not revert back to the sun.
• From green plants energy passes to upper trophic levels of consumers.
• Energy obtained by herbivores does not come back to the green plants.
• As it moves progressively through the various trophic levels it is no longer available to the previous level.
• Thus, energy flow is always unidirectional in an ecosystem.

• In ecosystem, green plants absorb solar energy and transform it in chemical energy.
• Thus at first trophic level green plants produce food by transforming chemical energy from available solar energy.
• Consumers consume other organisms or their products as food for their energy requirement.
• Flow of energy occurs in form of food from green plants to herbivores and from it to carnivores.
• Consumers are heterotrophic so their energy requirement is satisfied from lower trophic level.
• Thus, consumers are directly or indirectly dependent on green plants for energy.

• If all the waste we generate is biodegradable and if properly allowed it to decompose, then it will have no impact on the environment.
• They should be properly managed

• The impact of removing all the organisms in a trophic level will be different for different trophic levels.
• Removal of producers will affect all the organisms of successive trophic levels.
• It will be a threat the survival.
• The removal of organisms at higher trophic level will lead to increase in organisms of lower trophic level.
• Removal of organisms of any trophic level will cause the damage to the ecosystem.

• If we kill all the organisms in one trophic level then organisms of ext trophic level will not get food (chemical energy) and the entire food chain gets disturbed.
• All the organisms which are dependent on these are died.
• On the other hand, the organisms at the lower trophic level will increase in abundance.
• Due to this, ecosystem will be in imbalance.

• All the interacting organisms in an area together with the abiotic constituents of the environment form an ecosystem.
• Various kinds of plants such as grasses, trees, shrubs and many flower bearing plants and animals like frogs, squirrels, calotes, insects, birds, etc., are found in garden.
• All these organisms interact with each other.
• Their growth, reproduction and other activities are affected by the abiotic components such as light, wind, water, minerals, soil, etc.
• So, a garden is considered as an ecosystem.

• Decomposers feed on the excretory substances as well as dead bodies of plants and animals.
• Bacteria and fungi are decomposers.
• They breakdown the complex organic substances into simple inorganic substances.
• Such simple inorganic substances are used up by the plants again.
• So, they play an important role in cyclic pathway of the elements.

• All organisms including plants, animals and microorganisms and their physical surrounding with which they interact is called environment.
• All biotic and abiotic components of the environment are dependent on each other for maintaining balance.
• Therefore, the different components of the environment are interlinked and interdependent.
• The environment varies from place to place due to variation in climate, soil-type and topography.
• All plants and animals adapted to the environment in which they are born and live.
• A change in any component of environment may cause discomfort and affect normal life of living organisms.

• (1) Biodegradable substances get degraded by microbial activity releasing simple component back to nature.
• These components help to sustain the life of other organisms.
• (2) During the biodegradation certain gases may be released in atmosphere causing pollution.

• Some substances such as paper, vegetables, peels peels, etc. are acted upon by decomposers and get converted into simple form are called biodegradable.
• Biodegradable substances are natural substances.
• Some synthetic substances such as plastic, polythene, etc. cannot be degraded by microbial activity are called non-biodegradable.

(1) Biodegradable waste: The waste, which can be degraded / decomposed by biological process, is called biodegradable waste eg. Vegetables fruits peels etc.
(2) Non-biodegradable Waste: The waste, which can not be degraded / decomposed by any biodegradable waste. eg. Glass, plastic, polythene etc.

→ There are grass, trees, ornamental plants like rose, mogra, sunflower in the garden. They are producers. There are also animals and consumers like insects, frogs, birds, rabbits, squirrel etc.
→ Garden ecosystem is an example of artificial or man-made ecosystem.

Biodegradable wastes are decomposed by bacteria and fungi into simpler form which can be used by producers as raw materials. But all the waste becomes biodedgrable then following problem can arise.
(1) Decomposition process is slow process, so accumalation of waste for too long will produce bad smell which can be harmful to man.
(2) Dumping of this waste can be breeding source of so many harmful microbes or insects.

There are two major types of an ecosystem.
(1) Natural ecosystem
(2) Artificial or man-made ecosystem.

(1) Producers : Green plants, cyanobacteria (Bluegreen algae) contain chlorophyll. They perform photosynthesis using the sun-light. They produce food (organic compounds). So they are called autotrophs. They store extra organic compounds.
(2) Consumers : They are dependent on stored food of producers. So they are called consumers. They are directly or indirectly dependent on food produced by producers.
→ Consumers are mainly classified into herbivores, carnivores, omnivores and parasites.

(b) Ecosystem : The system formed of both biotic and abiotic components.

(A) Environment
(B) Trophic level
(C) Abiotic factors
(D) Consumers

→ Uncontrolled use of pesticides and other chemicals to protect crops from diseases or pests increases the concentration of there chemicals in soil and water.
→ From the soil or water, they enter into the plant bodies and then into the herbivores and carnivores.
→ These chemicals do not degrade, they accumulate progressively at each trophic level. The phenomenon is known as biological magnification.

Yes, the impact of removing all the organisms in a trophic level will be different for different trophic levels. For example, if we remove the producers, there will be no food for the consumers so all the consumers of different trophic levels also die,