CBSE Class 10 Biology Our Environment Worksheet Set A

Question. In a given food chain if the amount of energy at the fourth trophic level is 6 kJ, what will be the energy available at the producer level?
(a) 6000 kJ
(b) 20 kJ
(c) 60 kJ
(d) 600 kJ
Answer: A

Question. Which of the following is a biodegradable waste ?
(a) DDT
(b) Aluminium can
(c) Plastic bag
(d) Cow dung
Answer: D

Question. Which of the following is the best way for disposal of vegetable and fruit peels?
(a) Landfill
(b) Recycling
(c) Composting
(d) Burning
Answer: C

Question. Accumulation of non-biodegradable pesticides in the food chain in increasing amount at each higher trophic level is known as:
(a) Eutrophication
(b) Pollution
(c) Biomagnification
(d) Accumulation
Answer: C

Question. In an ecosystem, the 10% of energy available for transfer from one trophic level to the next is in the form of :
(a) heat energy
(b) light energy
(c) chemical energy
(d) mechanical energy
Answer: C

Question. Which of the statements is incorrect?
(а) All green plants and blue green algae are producers
(b) Green plants get their food from organic compounds
(c) Producers prepare their own food from inorganic compounds
(d) Plants convert solar energy into chemical energy
Answer: C

Question. What will happen if Deer is missing in the food chain given below?
Grass → Deer → Tiger
(а) The population of tiger increases
(b) The population of grass decreases
(c) Tiger will start eating grass
(d) The population of tiger decreases and the population of grass increases
Answer: D

Question. When is the World Environment Day celebrated?
(a) 16 June
(b) 5 December
(c) 5 June
(d) 5 July
Answer: C

Question. Which of these is a greenhouse gas?
(a) Hydrogen Sulphide
(b) Methane
(c) Ozone
(d) Carbon monoxide
Answer: B

Question. The transfer of Energy in a food chain is always:
(a) Unidirectional
(b) Methane
(c) Bi-directional
(d) Random
Answer: A

Question. If a grasshopper is eaten by frog, then the energy transfer will be from:
(a) producers to decomposers
(b) producer to primary consumer
(c) primary consumer to secondary consumer
(d) secondary consumer to primary consumer
Answer: C

Question. The % of solar radiation absorbed by all green plants for photosynthesis is about ———–.
(a) 1%
(b) 5%
(c) 8%
(d) 10%
Answer: A

Question. In 1987 the -------------------- Succeeded in forging an agreement to freeze CFC Production
(a) UNESCO
(b) UNEP
(c) UNCTED
(d) UNICEF
Answer: B

Question. O2 ----UV → O + O ; O + O2 →O3 (Ozone)
The role of UV rays in this reaction is -------
(a) To Split Oxygen molecule
(b) To unite oxygen molecule
(c) To Destroy Ozone
(d) None
Answer: A

Question. O3---------???---------→ O2 + (O+O)
Which substance catalyzes the reaction?
(a) Chlorine
(b) Sulphur dioxide
(c) Hydrogen sulphide
(d) Neon
Answer: A

Question. Which group of waste materials can be classified as Non biodegradable ?
(a) Plant waste, used tea bags
(b) Polyethene bags, plastic toys
(c) Used tea bags, paper straw
(d) Old clothes, broken footwear
Answer: B

Question. Environment includes:
(a) Land, air, water
(b) Light, temperature, rainfall
(c) Plants, animals, microbes
(d) All of these
Answer: D

Question. Which of the following wastesis NOT broken down by decomposers?
(a) Glass
(b) Dead leaves
(c) Wood
(d) Carcass
Answer: A

Question. Identify A, B and C in the given food chain.
Sunlight → A → B → C→Large fish
(a) A: Phytoplanktons; B: Zooplanktons; C: Small fish
(b) A: Zooplanktons; B: Phytoplanktons; C: Small fish
(c) A: Zooplanktons; B: Small fish; C: Phytoplanktons
(d) A: Phytoplanktons; B: Small fish; C: Zooplanktons
Answer: B

Question. What will happen if deer is missing in the food chain given below ?
Grass → Deer → Tiger
(a) The population of tiger increases.
(b) Tiger will start eating grass.
(c) The population of grass decreases.
(d) The population of tiger decreases and the population of grass increases.
Answer: D

Question. __________ is not an abiotic factor.
(a) Humidity
(b) Animals
(c) Temperature
(d) Altitude
Answer: B

Question. The direction of energy flow in an ecosystem is
(a) unidirectional but in any direction
(b) multidirectional
(c) unidirectional but from lower trophic level towards the higher trophic level
(d) bidirectional
Answer: C

Question. _________ is a non-biodegradable substance.
(a) Human/ animal waste
(b) Newspaper
(c) Aluminium
(d) Plant products
Answer: C

Question. Ozone prevents the entry of
(a) UV radiations from the sun
(b) IR radiations
(c) all solar radiations
(d) all radiations with the large wavelength
Answer: A

Question. If UNEP had not passed any regulation to control the CFC levels, then what could have been the possible consequences after a few years?
(a) Increase in CFC levels and thus increase in global warming.
(b) Major amount of UV radiations reaching the earth, therefore, multifold increase in problems like cancer.
(c) Increase in natural calamities like Tsunamis and cyclones.
(d) Lowering of the temperature of the earth.
Answer: B

Question. Which of the following cannot be called a biodegradable substance?
(a) Dead leaves
(b) Cotton balls
(c) Plastic coverings
(d) Food wastes
Answer: C

Question. Which of the following options complete the statementgiven below?
Ozone is both harmful and beneficial because it is ___________.
(a) not poisonous to the ecosystem
(b) poisonous but not for humans
(c) poisonous in very high amounts, and its concentration is very low in the atmosphere
(d) poisonous to humans but it also prevents UV rays from entering into the earth’s atmosphere
Answer: D

Question. The accumulation of the heavy metals in birds have caused a decline in their population. This is because
(a) the eggs produced by these birds have very thin and brittle shells
(b) heavy metals damage the eyesight of these birds
(c) heavy metals kill the fish that is the major diet of these birds
(d) heavy metals damage the feathers of these birds
Answer: A

Question. Which of the following statements is correct?
(a) All plants and bacteria are producers.
(b) All green plants and certain bacteria are producers.
(c) Only some species of green plants and all bacteria are producers.
(d) Only green plants are producers.
Answer: B

Question. Ozone formation is possible in the upper layers of atmosphere because of the
(a) presence of active molecules of carbon
(b) presence of high energy UV rays
(c) presence of activated oxides of carbon
(d) presence of longer wavelength radiations
Answer: B

Question. What is an ecosystem?
Answer: An ecosystem is a self-sustaining system where biotic and abiotic organisms of various communities interact with each other. Ponds, forests, grasslands etc., are the few examples of ecosystem.

Question. In the following food chain plants provide 500 J of energy to rats.
How much energy will be available to hawks from snakes?
Plants → Rats → Snakes → Hawks
Answer: 500 J of energy is available to rats from plants is then according to 10 per cent law 50 J of energy will be available to snakes and only 5 J of energy will be available to hawks.

Question. Write the full name of the group of compounds mainly responsible for the depletion of ozone layer?
Answer: CFCs (Chlorofluorocarbons) are mainly responsible for the depletion of ozone layer.

Question. Mention one negative effect of our affluent lifestyle on the environment?
Answer: The affluent life style of few persons results in overuse of natural resources and in long term effects it can led to scarcity of resources. For example: usage of personal vehicles instead of public transport increases consumption of fuel, pollution, use of air conditioners, refrigerators etc., which contain CFCs when released into atmosphere leads to depletion of ozone layer.

Question. How can you help in reducing the problem of waste disposal? Give any two methods.
Answer: We can help in reducing the problem of waste disposal by the following two methods:
(a) By separating biodegradable substances from nonbiodegradable substances.
(b) By putting the biodegradable organic waste into compost pits dug in the ground and preparing compost.

Question. List two non-biodegradable wastes generated daily in kitchen which can be recycled ?
Answer: Milk bags, tin cans are non-biodegradable wastes generated daily in kitchen which can be recycled.

Question. In the following food chain, 100 J of energy is available to the lion.
How much energy was available to the producer?
Plant → Dear → Lion
Answer: There are three trophic levels the producer, the consumer and the secondary consumer according to 10 per cent law of energy transfer in trophic level, If the lion has 100 J of energy then, deer will have:
According to 10% law 100 J of energy is available to lion, so dear will get:
10% of x = 100 J
x = 1000 J
Plant is the producer, it will have:
10% of y = 1000
y = 10000 J

Short Answers :

Question : How can you help in reducing the problem of waste disposal? Give any two methods.
Answer : To reduce the problem of waste disposal we can
(i) Segregate the bio-degradable waste from non-biodegradable waste before dumping it.
(ii) Remove all materials which can be recycled and send it for recycling. e.g., paper, glass, metal, rubber.

Question : Give any two ways in which non-biodegradable substances would affect the environment.
Answer : (i) The non-biodegradable substances get accumulated and doesn’t get decomposed hence it remains in the ecosystem and causes pollution, chokes the system of many animals and kill them.
(ii) These substances due to accumulation cause water and soil pollution e.g., pesticides, detergents, polythene.

Question : Give any two ways in which bio-degradable substances would affect the environment.
Answer : Two ways in which bio-degradable substances would affect the environment are:
(i) During decomposition of the substances lot of foul smell spreads in the surrounding areas.
(ii) The place where these bio-degradable substance are present with some moisture becomes breeding ground for insects like mosquitoes, housefly which are vectors in carrying parasites that cause different diseases.

Question : What is the role of decomposers in the ecosystem?
Answer : Decomposers breakdown the complex organic substances like plant’s and animal’s dead body and convert them into simpler inorganic substances.
All the elements that are present in the body on which decomposers act is released back to the nature. Decomposers maintain balance in the nature and plays an important role in the environment.

Question : What are the problems caused by the non-biodegradable waste that we generate?
Answer : (i) As the non-biodegradable waste cannot be broken down into simpler forms hence they keep on accumulating in nature causing pollution.
(ii) They cause diseases.
(iii) It also causes biological magnification.

Question : What will happen if we kill all the organisms in one trophic level?
Answer : If all the organisms in one trophic level are killed then all the organisms of next trophic level which are dependent on these are killed. Next trophic levels will not get food to eat and the entire food chain gets disturbed. At the same time the organisms at the lower trophic level will reproduce and the population will increase in abundance there by disturbing the ecosystem.

Question : What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
Answer : The various levels or stages in a food chain at which the transfer of food takes place is called trophic level, e.g., food chain.
Grass → Grasshopper → frog → snake → peacock
Grass — Producer — I trophic level.
Grasshopper — I Consumer (Herbivores) — II trophic level.
Frog — II Consumer (Carnivores) — III trophic level
Snake — III Consumer (Carnivores) — IV trophic level
Peacock — IV Consumer (Carnivores) — V trophic level.

Question : Why are some substances biodegradable and some non-biodegradable?
Answer : Substances which can be decomposed and broken down to simpler substances by micro-organisms acting on it is called bio-degradable and those substances which cannot be acted upon by micro-organisms and are not broken down into simpler substances are called non-biodegradable substances.

Question : If all the waste we generate is bio-degradable, will this have no impact on the environment?
Answer : If all the waste we generate is bio-degradable and is managed in such a way that it is allowed to decompose then it will have no impact on the environment.

Question : Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can the organisms of any trophic level be removed without causing any damage to the ecosystem?
Answer : The impact of removing all the organisms in a trophic level will be same. If the organisms of any trophic level be removed it will certainly damage the ecosystem. 
For example,
Grass → Grass hopper → Frog → Snake → Peacock
In this if all grasshoppers are killed/removed frogs will strive and grass will reproduce in abundance.
If snakes are removed then the number of frogs will increase which will disturb the entire ecosystem.

Question : What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Answer : The pesticides and chemicals are absorbed by plants from the soil and enter the food chain. Being non-biodegradable they accumulate progressively at each trophic level. As human occupy the top level of any food chain, the maximum concentration of chemicals is found in our bodies. This is called biological magnification.
The level of magnification will be different at different trophic levels, the maximum concentrations will be at the highest trophic level and the chemical will be less at lower trophic levels.

Question : Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Answer : Ozone layer in the strastosphere is very helpful in shielding harmful UV rays. In absence of ozone layer heavy damage to organism may occur. It may cause diseases like skin cancer, cataract, reduced crop production etc.
The damage is limited by UNEP (United Nations Environment Programme), it has
forged an agreement to freeze for CFC production in 1986.
CFC– Chlorofluorocarbons used as refrigerants and in fire extinguishers.

Question : State two problems caused by the non- biodegradable waste that we generate in our daily life.
Answer : Two problems caused by non-biodegradable waste that we generate in our daily life are:
• It clogs drains.
• It causes water and soil pollution.

Question : Construct an aquatic food chain showing four trophic levels.
Answer : Food chain in aquatic ecosystem:
Phytoplankton → Zoopiankton → Custacean → Fish → Crane
(Producer) (Herbivore) (Carnivore) (Carnivore) (Top Carnivore)

Question : What is biodiversity? What will happen if biodiversity of an area is not preserved? Mention one effect of it.
Answer : Biodiversity is the existence of a wide variety of species of plants, animals and microorganisms in a natural habitat within a particular environment or existence of genetic variation within a species. Biodiversity of an area is the number of species or range of different life forms found there. Forests are ‘biodiversity hotspots’.
Every living being is dependent on another living being. It is a chain. If biodiversity is not maintained, the links of the chain go missing. If one organism goes missing, this will affect all the living beings who are dependent on it.

Question : (a) What is ‘environmental pollution’?
(b) Distinguish between biodegradable and non-biodegradable pollutants.
(c) Choose the biodegradable pollutants from the list given below:
Sewage, DDT, radioactive waste, agricultural waste.
Answer : (a) Environmental pollution is an undesirable change in the physical, chemical or biological characteristics of the natural environment, brought about by man’s activities. This pollution may  affect the soil, rivers, seas or the atmosphere.
(b)

Question : How is ozone formed in the upper atmosphere? Why is the damage of ozone layer a cause of concern to us? State a cause of this damage.
Answer : Ozone is formed in upper atmosphere by the reaction of ultraviolet (UV) radiations on oxygen (0₂) molecule.
The damage to ozone layer is a cause of concern to us as due to its damage, more ultraviolet rays reach the earth’s surface causing various health hazards.

Question : Explain ‘biological magnification’ with the help of an example.
Answer : Pesticides used in crops are washed down .into the soil. From soil these are absorbed by plants along with water and minerals and thus, they enter the food chain. While consuming the crops, human beings also consume these pesticides which get accumulated in our bodies. This phenomenon is known as biological magnification.

Question : What is meant by biodiversity? List two advantages of conserving forests and wildlife.
Answer : Biodiversity is the existence of a wide variety of species of plants, animals and microorganisms in a natural habitat within a particular environment.
Two reasons each of conserving:
(a) Forest
(i) It helps in retaining the sub-soil water.
(ii) It checks flood.
(b) Wildlife
(i) To maintain ecological equilibrium.
(ii) To protect the nature.

Question : A non-biodegradable toxic chemical has entered into the food chain. Which type of food habit will you suggest to a man, vegetarian or non-vegetarian? Explain with the help of a food chain. The food chain which you would suggest, is advantageous in an another aspect.  How?
Answer : Vegetarian food chain will be suggested in case of entry of non-biodegradable toxic chemical into the food chain.
Non-biodegradable chemical gets concentrated at every trophic level by the process of biological magnification. As the concentration increases with the number of trophic level in a food chain, man will get high concentration of the chemical in a non-vegetarian food chain than in a vegetarian food chain, e.g.
Vegetarian food chain:

Vegetarian food chain is advantageous in terms of energy available to man because it has less number of trophic levels. As 90% of energy is lost to the enviornment, at every trophic level, lesser number of trophic levels will result in lesser energy loss.

Question : What are biodegradable and non- biodegradable substances? Select two biodegradable pollutants from the following: Agricultural waste, glass, plastic, sewage, DDT.
Answer : 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 micro organisms like certain bacteria.
Non-biodegradable substances are those substances which cannot be broken down into simpler, harmless substances in nature.
Two biodegradable pollutants are agricultural waste and sewage.

Question : Why are bacteria and fungi called decomposers? List any two advantages of decomposers to the environment.
Answer : Bacteria and fungi breakdown the dead remains and waste products of organisms. These micro organisms are called the decomposers as they breakdown the complex organic substances into simple inorganic substances that go into the soil and are used up once more by the plants.
Two advantages of decomposers to the environment are as follows:
• Decomposers feed, on the dead bodies of plants and animals. They return the simple components to soil and help in making the steady state of ecosystem by recycling of nutrients. They, therefore, create a balance in the environment.
• They also act as scavengers or cleansing agents of the atmosphere.

Question : Why we say energy flow in the biosphere is unidirectional?
Answer : The energy flow 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, i.e. it moves progressively through various trophic levels. Thus, energy flow from the sun through producers to consumers is in single direction only.

Question : Describe how decomposers facilitate recycling of matter in order to maintain balance in the ecosystem.
Answer : Decomposers are micro organisms that obtain energy from the chemical breakdown of dead organisms of animals or plants. These micro organisms breakdown the complex organic substances of dead organisms into simple inorganic substances that go into the soil and are used up once more by the plants. Decomposers thus, help in recycling of matter.

Question : How can we help in reducing the problem of waste disposal? Give any two methods.
Answer : Problem of waste disposal can be solved by following methods:
(i) by disposing biodegradable and non-biodegradable waster separately.
(ii) by reusing materials as much as possible.

Question : Explain the phenomenon of “biological magnification” How does it affect organisms belonging to different trophic levels particularly the tertiary consumers?
Answer : The process in which harmful chemicals enter a food chain and get accumulated progressively at each trophic level is called biological magnification.
Harmful and toxic chemicals enter our bodies when they are added to soil and water. Use of pesticides to protect the food crops from diseases and pests and chemical wastes of factories are dumped in open or disposed off into rivers. These chemicals are washed down into the soil and ultimately to water table or get absorbed or taken up from the soil by the plants along with water and minerals and in this way harmful chemicals enter the food chain. The quantity of these harmful chemicals increase with increase in trophic level of the food chain because these substances are not degradable. Man is at the top of the food chain, so concentration is maximum in human beings.
Thus, accumulation of DDT has been maximum in man as DDT is used to destroy pests. DDT is accumulated in the following way in this food chain:
This is the reason why our food grains such as wheat and rice, vegetables and fruits and even meat contain varying amounts of pesticides residues. So, the highest trophic level at the extreme right of food chain has the maximum concentration of harmful chemicals in a food chain.
Water → Phytoplankton → Fish
0.02 ppm 5.0 ppm 240 ppm
→ Man
1600 ppm

Question : “Damage to the ozone layer is a cause for concern.” Justify this statement. Suggest any two steps to limit this damage. ‘
Answer : Ozone layer prevents the harmful ultraviolet radiation to enter the atmosphere and reach the earth’s surface. Depletion of ozone layer has become a cause for concern because it can cause serious effects on human body and other organisms of the environment like fatal diseases such as skin cancer, changes in genetic material DNA, eye damage, etc.
Two steps to limit this damage are as follows: Judicious use of aerosol spray propellants such as fluorocarbon and chlorofluorocarbons which cause depletion or hole in ozone layer.
• Control over large scale nuclear explosions and limited use of supersonic planes.

Question. Why is it necessary to conserve our environment?
Answer : Human beings are an important part of the environment. But human activities change the environment and the changes in the environment affect life on earth.
For example: An environmental problem caused by human activities is depletion of ozone layer. If the ozone layer in the atmosphere disappears completely, then all the extremely harmful ultraviolet radiations coming from the Sun would reach the earth and would cause skin cancer and other ailments. Therefore it is necessary to conserve our environment

Question. Write one negative effect, on the environment, of affluent lifestyle of few persons of society.
Answer : Excessive use of air conditioners which is a part of affluent lifestyle emits a lot of heat in the atmosphere.
Excessive use of packaging materials which are mostly made up of non-biodegradable material are not environment friendly.
Excessive use of petrol in vehicles also causes pollution.
Thus, affluent lifestyle results in the generation of excessive waste materials

Question. What makes the earth’s atmosphere a heterogeneous mixture?
Answer : Density of various components of the atmosphere is different. Therefore the earth’s atmosphere is a heterogeneous mixture, for example, the heavier gases like CO₂, O₂ and N₂ of the atmosphere occupy the lower level (i.e., near the earth’s surface) of the atmosphere whereas lighter gases like O3 occupy the higher level of the atmosphere. So the components of atmosphere are not equally distributed.

Question. Distinguish between biodegradable and non-biodegradable wastes.
Answer : Difference between biodegradable and non-biodegradable wastes.
Biodegradable waste:
1. Wastes which can be broken down into non-poisonous substances in nature in due course of time by the action of micro-organisms are called bio-degradable wastes.
2. Plastic, glass, etc.
Non-biodegradable waste:
1. Wastes which cannot be broken down into non-poisonous substances in nature are called non-biodegradable wastes.
Sewage, peals of fruits and vegetables, etc

Question. What are the various steps in a food chain called?
Answer : The various steps of a food chain are called trophic levels. These steps are:
• First trophic level consists of producers.
• Second trophic level consists of primary consumers or herbivores.
• Third trophic level consists of secondary consumers or carnivores.
Fourth trophic level consists of tertiary consumers or top carnivores.

Question. Why is the Government of India imposing a ban on the use of polythene bags? Suggest two alternatives to these bags and explain how this ban is likely to improve the environment
Answer : Plastic bags are non-biodegradable which can not be broken down into non-poisonous substances in nature. Plastic bags are the main cause of sewer blockages as plastic bags are not decomposed by micro-organisms. Plastic bags if eaten by stray animals (like cows) can block their alimentary canal.
Two alternatives:
1. We should take our own jute or cloth bags while going for purchasing articles from the market.
2. Disposable paper cups should be used for serving tea in trains instead of plastic cups.
3. Shopkeepers can use paper bags instead of plastic bags.