Our Environment : Complete Set of Questions

This set of questions contains all the possible concepts
which could be asked in the examination


What Happens When We Add Our Wastes to the Environment


Q.1  Define environment?

The biotic and abiotic factors which surrounds any living organism is considered as its environment. It can be generally defined as a community of organisms living in a particular environment with which they interact.

Q.2  Differentiate biodegradable and non-biodegradable substances with examples.

Q.3  Why are some wastes broken down by microorganisms while others remain unaffected?

The waste materials that we generate in our daily life are biodegradable or non- biodegradable. In our environment, microorganisms such as bacteria and fungi secrete enzymes. The enzymes are specific in their actions; specific enzymes are needed for the break-down of a particular substance. Because of this, many human- made substances like plastics, glass etc will not be broken down by the action of bacteria and other saprophytes. These materials will be acted upon by physical processes like heat and pressure, but under the ambient conditions found in our environment; these persist for a long time.

Q.4  Will the generation of only biodegradable wastes have any impact on the environment?

If all the waste we generate is biodegradable, this would also have an impact on the environment but most of the impacts would be positive. After decomposition, the biodegradable substance produces different raw materials which are sent back to the ecosystem. The solid remains would add to the humus content of soil.

There can be some negative impacts; like obnoxious smell which is created during the process of decomposition. There can also be a possibility of sparking an epidemic if the waste is dumped near a residential area or is allowed to contaminate the water bodies. So, it is not the biodegradable waste which is going to create the problem, rather the way we dispose it.


Ecosystem - What are its Components ? 


Q.5  Define ecosystem and what are the components of ecosystem?

An ecosystem is a natural system consisting of all plants, animals and microorganisms (biotic factors) in an area functioning together with all the non-living physical (abiotic) factors of the environment.

Two main components exist in an ecosystem: abiotic and biotic.

i) Abiotic components of an ecosystem consist of the nonorganic aspects of the environment that determine what life forms can thrive. Examples of abiotic components are temperature, average humidity, topography and natural disturbances.

ii) The biotic components of an ecosystem are the life forms that inhabit it. The populations are that of animal community, plant community and microbial community.

Q.6  What are the two types of ecosystem?


The two types of ecosystem are-

i)Natural ecosystems: Natural ecosystems may be terrestrial (meaning desert, forest, or meadow) or aquatic, (pond, river, or lake). A natural ecosystem is a biological environment that is found in nature (e.g. a forest) rather than created or altered by man (a farm).

ii)Artificial ecosystems: Humans have modified some ecosystems for their own benefit. These are artificial ecosystems. They can be terrestrial (crop fields and gardens) or aquatic (aquariums, dams, and manmade ponds).

Q.7  According to the sustenance from the environment, organisms can be grouped into which three categories, what are they?

According to the sustenance from the environment, organisms can be grouped into which three categories namely - Producers, Consumers and decomposers.

i)Producers– All green plants, blue green algae can produce their food (Sugar & starch) from in organic substance using light energy (Photosynthesis).

ii) Consumers– Include organisms which depend on the producers either directly or indirectly for their sustenance. In other words, consumers consume the food produced by producers


iii)Decomposers– A decomposer is an organism of decay. These are also called saprobes.
Decomposers are nature's recyclers as they break down the organic matter found in the dead bodies of plants and animals. Decomposers are chiefly the micro-organisms such as bacteria and fungi in the form or yeasts and moulds that break down bodies of dead organisms and release compounds that can be used by producers.

Q.8  What is a food chain?

Food chain is the flow of energy in a sequential process of one organism eating the other and itself being eaten by another in turn. Thus, it is a series of organisms taking part at various biotic levels from the producer and ends in consumer.

Example- Producer → Primary Consumer → Secondary Consumer → Tertiary Consumer

Examples of food chains:

(i) Food chain in forest or grassland ecosystems:- 

Grass → Grasshopper → Frog  → Snake →  Eagle

(Producer) → (Herbivore)  →  (Carnivore) → (Carnivore) → (Top Carnivore) 

(ii) Food chain in aquatic ecosystems:-

red and green algae → jellyfish  → crabs → fish → crane

Phytoplankton → Zooplankton → Crustacean → Fish  → Crane

Producer)             (Herbivore)     (Carnivore) (Carnivore)  (Top Carnivore)

Q.9  What are trophic levels? State the different trophic levels through an example:

Each step or level of the food chain where transfer of food or energy takes place forms a trophic level.

For example- Grass → Grasshopper → Frog → Snake→ Peacock


(a) First trophic level- Autotrophs.i.e., plants like grasses are producers in the ecosystem.

(b) Second trophic level- Herbivores(plant eating animals or heterotrophs) like grasshopper, deer, rabbit are primary consumers that eat the grass.

(c) Third trophic level- The insect(grasshopper) is turn, is eaten by the frog(carnivore I). Thus, frog is at the third trophic level. Small carnivores like frog are secondary consumers.

(d) Fourth trophic level- The frog in turn is eaten by the snake(carnivore II). Thus, the snake is at fourth trophic level.

(e) Fifth trophic level- Snake is turn, eaten by the peacock(carnivore III). Thus, the peacock is at fifth trophic level. Larger carnivores like snake and peacocks are tertiary consumers.

Q.10  Define and give examples of each of these heterotrophic types: herbivores, carnivores, omnivores, and parasites.

There are several groups of heterotrophs. Heterotrophs are all organisms that obtain their food from the environment. All animals and certain types of micro-organisms are heterotrophs. Heterotrophs or consumers include herbivores, carnivores, omnivores and parasites.

i)Herbivores are animals that feed only on plants. Rabbits, cattle, horses, sheep and deer are all herbivores.

ii)Carnivores are animals that feed on other animals. Some carnivores may be predators (such as lions, hawks, and wolves who attack and kill their prey and feed on their bodies) and some may be scavengers (they feed on dead animals that they find like vulture, crow).

iii)Omnivores are animals that feed on both plants and animals. Examples of omnivores are humans and bears.

iv) Parasites are those organisms that live on (ectoparasites) or in (endoparasites) the body of another organism, i.e., host from which it obtains its nutrients, e.g., parasites of man includes fleas and lice (ectoparasites) various protozoans (endoparasites) and tapeworms

Q.11  What is the role of decomposers in an ecosystem?

Decomposers are an essential component of any ecosystem. Their main role is to recycle nutrients in dead organisms and their wastes. By doing so, they serve two purposes.

1.  They reduce the burden on the environment by clearing dead remains.

2.  They channelize the raw materials back to the environment.

Most decomposers are bacteria and fungi.

Q.12  What are the characteristics of a food chain?

Characteristics of a food chain:

(i) A food chain is always straight and proceeds in a progressive straight line (unidirectional).

(ii) A food chain helps in understanding the food relationship and interactions among various organisms in an ecosystem

(iii) With such studies one can follow the basic mechanism of transfer of food energy and nutrients through various components of nature

(iv) One can also understand the movement of the toxic substances in an ecosystem and the problem of their biological magnification.

Q.13  Explain the flow of energy through various components of an ecosystem:

Energy is used and some of it is transferred from one trophic level to another in a food chain. This is called flow of energy. The green plants (primary producers) absorb 1% of the sunlight that reaches the earth, convert it into chemical energy and store it as food energy.

Herbivores(primary consumers) eat plants. A major part of the absorbed energy is lost as heat to the environment, some amount goes into digestion and in doing work and the rest of the energy goes towards growth and reproduction.

An average of 10% of the food eaten is turned into its own body and made available for the primary consumers. Similarly, 10% of energy is conserved at each of the trophic level of the secondary and tertiary consumers.

Therefore, 10% of the energy can be taken as the average value for the amount of organic matter that is present at each step and reaches the next level of consumers.

Since, so little energy is available for the next level of consumers, food chains, generally consists of only 3-4 steps. The loss of energy at each step is so great that very little usable energy remains after 4 trophic levels.

Q.14  Explicate the principle of food web:

Each organism is generally eaten by 2 or more other kinds of organisms which in turn are eaten by several other organisms. So, instead of a straight line food chain, the relationship can be shown as a series of branching lines. Thus, the network of interconnected food chains is called as a food web.


Q.15  What are the characteristics of energy transfer in the biosphere?

(i) Energy is supplied by the sun and it is not created in the biosphere. Energy is only converted from one form to another in the biosphere.

(ii) There is a continuous transfer of energy from one trophic level to the next in a food chain.

(iii)At each trophic level, some of the energy is utilized by the organisms for their metabolic activities.

(iv) At each trophic level, some amount of energy is utilized for the composition of decomposers.

(v) At each trophic level, there is loss of energy, which goes into the environment and remains un-utilized.

(vi) At each trophic level, the amount of energy available is less than that available at the previous level.

Q.16  Why is energy flow considered as unidirectional?

The flow of energy is unidirectional and non cyclic. The energy captured by the autotrophs does not return to the sun, and the energy which passes to the subsequent levels does not come back to autotrophs. The amount of energy goes on successively decreasing from the producers to the carnivores making it impossible for the energy to flow in the reverse direction.

Q.17  What is biomass?

The amount of organic matter present in an organism is called biomass.

Q.18  What is biological magnification? Will the level of magnification increase or decrease as we move to higher trophic levels?

The increase in the concentration of harmful chemical substances (pesticides) in the body of living organisms at each trophic level of a food chain is called biological magnification.

The levels of biomagnifications will be different at different trophic levels. For example, when pesticides are sprayed, it enters the food chain through the producers while they are absorbing nutrients from the soil. Since many types of plants are eaten by the herbivores, their body accumulates more amounts of the pesticides. Similarly, the carnivores that feed on the herbivores accumulate more pesticides in its body as one carnivore eats more than one herbivore. Therefore, the omnivore (man) or the top carnivore has the highest concentration of the pesticide.

Q.19  Difference between food chain and food web:


Q.20  Describe four benefits of a food web.

(i) Starvation: Food web does not allow any population to starve when members of lower trophic level decrease in number.

(ii) Checking Overpopulation: Food web does not allow a species to overgrow as increased availability will increase the chance of higher number of its predations.

(iii) Endangered Population: It allows endangered population to grow in size.

(iv) Stability: Food webs provide stability to ecosystems.

Q.21  Write two information’s obtained from the energy flow diagram


The information’s obtained from the energy flow diagram are

(i) Direction of flow of energy. The dark arrows represent the movement of this energy

(ii) Direction of flow of inorganic The movement of the inorganic nutrients is represented by the open arrows.

Q.22  How do the harmful and toxic chemicals enter the food chain?

Some poisonous chemicals enter our bodies through the food chain.

(i) By the use of several pesticides and other chemicals for crop protection and storage, etc.

(ii)The plants absorb these harmful chemicals from soil along with water and   minerals.

(iii) They enter the food chain in producer level and then transferred to next trophic levels.

(iv)The highest levels get more of these chemicals.

Water → Planktons → Fish

(Aquatic plants and animals)


How do our activities affect the Environment


Q.23  Difference between ozone and oxygen

Q.24  Why is damage to the ozone layer a cause of concern? What steps are being taken to limit this damage?

Ozone layer has become a cause of concern because depletion of ozone layer can cause serious effects on human body and other organisms of the environment like -

(i) Cancer in human beings.

(ii) Loss of immunity in humans.

(iii) Destruction of aquatic life and vegetation.

(iv) Temperature changes and rainfall failures.

Steps being taken to reduce it are:

(i) To protect the ozone layer, the United Nations Environment Programme forged an agreement to freeze CFC production at 1986 levels

(ii)By reducing the use of CFCs — Many countries have already banned the use of CFCs.

(iii) By developing substitutes of CFCs — Scientists have already developed some substitutes which are ozone-friendly.

Q.25  Which compounds are responsible for the depletion of ozone layer?

Ozone depleting substances like chlorofluorocarbons, hydrocarbon, N2O, chlorine, etc. are responsible for the depletion of the ozone layer.

Q.26  Which disease is caused in human being due to depletion of ozone layer in the atmosphere?

Ozone layer is located in the atmosphere as a part of stratosphere. Skin cancer is caused in human being due to depletion of ozone layer in the atmosphere.

Q.27  How is ozone formed in the upper atmosphere?

The ozone layer occurs naturally in the stratosphere. The ozone layer is formed when intense UV radiation from the sun reacts with ordinary molecules of oxygen (O2) in the stratosphere to dissociate into single oxygen atoms (O). Single oxygen atoms are very reactive they combine with O2 to form O3.

O2 +UVradiation→O+O
O + O2 → O3 (ozone)

Q.28  When is World Ozone Layer Preservation Day celebrated?

Wold Ozone Layer Preservation Day is celebrated on September 16.

Q.29  What is green house effect?

The gases like CO2 and methane absorb infra red radiations of the sun and cause heating of the earth. It is known as green house effect.

Q.30  What is the function of the ozone layer?

Function of the ozone layer is to absorb UV radiation from the sun, thus shielding the earth’s surface from the harmful effects of this radiation eg: skin cancer.

Q.31  Explain Ozone depletion and how does Ozone depletion affect our environment?

Life on Earth is protected from the harmful UV rays by a layer of ozone molecules. The amount of Ozone began to drop sharply in 1980’s. This decrease has been linked to the synthetic chemicals like Chloro-Fluorocarbons(CFC’s) which are used as refrigerants and fire extinguishers.

CFC’s contain both Bromine and Chlorine. CFC’s are very stable and are not degraded by any natural process near the Earth. 

  • UV radiations cause a chlorine atom to break away from the CFC molecule.
  • These free chlorine and bromine atom are responsible for the breaking down of ozone.
  • These free atoms remain in the stratosphere for a long time , destroying ozone molecules.
  • These chlorine and bromine atoms catalyse the breakdown of ozone molecule

Step 1- Chlorine atom reacts with a molecule of ozone to form chlorine monoxide and oxygen.

1.  Cl + O3 → ClO + O2

Step 2- Chlorine monoxide reacts with a molecule of ozone to form an atom of chlorine and two atoms of oxygen. This liberates the chlorine atom to destroy another ozone molecule

2.  ClO + O3 → 2O2 + Cl

The above two reactions can be simplified as follows:

O3 + O → O2 + O2

In this way, free chlorine will continue to deplete the ozone in the stratosphere. One chlorine atom can destroy more than 100,000 ozone molecules before it is removed from the stratosphere. 

Decreased ozone levels in the stratosphere increase the intensity of UV radiations. Its consequences can be very harmful and may lead to an increase in skin cancer and cataracts among humans. UV radiations are also harmful to crops and other primary producers and may lead to unpredictable results.

Q.32  Why Kulhads are not being used in trains now? Why are plastic cups being replaced by paper cups?

Kulhads, that is, disposable cups made of clay are not being used in trains nowadays because making these kulhads on a large scale would result in the loss of fertile top soil making the soil unfit for cultivation.

Advantages of using paper cups over plastic cups:

(i) Plastic cups are non- biodegradable and thus cause environmental pollution, thus they were replaced by paper cups as paper is biodegradable and does not pose a threat to the environment.

(ii) Paper cups are cheaper and hygienic and can be recycled and reused.

Q.33  Expand- CFC, UNEP.

CFC- ChloroFluoroCarbon

UNEP-  United Nations Environment Programme.

Q.34  Name the wastes which are generated in our house daily. What measures would you take for its disposal?

(a) Kitchen wastes

(b) Paper wastes like newspaper, bags, envelopes etc

(c) Plastic bags, bottles

(d) Vegetable/fruit waste, rinds etc

Measures for disposal

(a) Segregation of biodegradable and non-biodegradable wastes

(b) Safe disposal of plastic bags

(c) Vegetable and fruit wastes can be used to make compost which can be used to enrich the spoil with nutrients.

Q.35  How is packaging related to increase in non-biodegradable waste?

As we become more technologically advanced, we produce materials that can withstand extreme temperatures, are durable and easy to use. Plastic bags, synthetics, plastic bottles, tin cans, are some of the packing materials used nowadays to protect the product from tampering and to maintain its freshness.
But, these advanced products do not break down naturally. When we dispose them in a garbage pile; the air, moisture, climate, or soil cannot break them down naturally to be dissolved with the surrounding land as they are not biodegradable thereby leading to environmental pollution. Thus, we can say that packaging is related to increase in non-biodegradable waste.

For example, the potato chips wrappers used to pack the chips can be cited as one of the packing material that adds to the increase in the amount of non-biodegradable wastes.

Q.36  Suggest ways in reducing the problem of waste disposal:

To reduce the problem of waste disposal, we can-

(a) Avoid use of packing materials particularly non-biodegradable materials like polythene and plastics. Instead, we can use cloth or paper bags or carry our own bags.

(b) Dispose the waste after segregating biodegradable and non-biodegradable wastes. Reuse and recycle non-biodegradable materials like empty bottles, metals and plastics.

(c) Convert biodegradable wastes into manure by vermi-composting or simple composting.


Value Based Qustions 


Q.1  In a colony, it was decided to remove a green park and construct an air conditioned shopping mall. Children of the colony took out a march against this decision with several placards to make the colony people aware of the importance of green plants

(a) What are the ill effects of air conditioners?

(b) Is the action taken by the children justified?

(c) How does the ecosystem get affected when plants are removed?

(d) What values do you think are depicted bychildren?

(a) Air conditioners release CFC’s into the atmosphere which will eventually lead to ozone depletion. 

(b) Yes. The action of the children is justified because felling of trees will affect the ecological balance, increase in temperature etc. Moreover, the construction of an AC shopping mall will cause the release of harmful gases like CFC which causes ozone depletion. This will cause serious health hazards like skin cancer etc. 

(c) Every living thing plays a part in an ecosystem, Trees give out oxygen. They also play a vital role in bringing rain.  In short, they assert the ecological balance. If trees are felled, then there will be less of oxygen and moreover, it will affect the habitat of many animals who live and feed on them. There will also be dearth of rains and eventually leading to global warming. Floods and soil erosion will also happen.

(d) The values depicted by children -

Environmentally sensitive

Participatory citizenship


Q.2  Naveen always makes it a point to throw paper bits in green bin and also encourages his friends to do so. Lalit  ignores it and throws it in black bin.

(a) Why there is a need to segregate wastes?

(b) What concern Naveen is showing towards the environment.

(a) Only a segregation system can ensure that the waste will be treated according to the hazards of the waste and that the correct disposal routes are taken and that the correct transportation equipment will be used

(b) Naveen shows-

i) Displays a sense of responsibility that each citizen has towards the society and the environment in which he lives.

ii)Awareness about the damages caused by wastes to both society and humans.


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