CBSE Class 10 Science HOTs Our Environment

Question. The depletion of the ozone layer causes
(a) global wanning
(b) earthquakes
(c) increased UV radiations
(d) acid rain

Answer : C

Question. Which of the following is biodegradable?
(a) Plastic mugs
(b) Leather belts
(c) Silver foil
(d) Iron nails

Answer : B

Question. The amount of energy absorbed by the plants in the form of solar energy is ____% and then _____% of this energy is transferred to the next level.
(a) 10%; 10%
(b) 1%; 10%
(c) 10%; 1%
(d) 1%; 1%

Answer: B

Question. Excessive exposure of humans to UV rays results in :
(i) damage to immune system
(ii) damage to lungs
(iii) skin cancer
(iv) peptic ulcers
(a) (i), (ii)
(b) (ii),(iv)
(c) (i), (iii)
(d) (iii), (iv)

Answer: C

Question. Which of the statements given below is correct?
(a) Omnivores are in the middle of the food chain.
(b) Omnivores areeither in the middle or at the top of the food chain.
(c) Omnivores are at the top of the food chain.
(d) Omnivores are capable of modifying the natural food chain.

Answer: B

Question. A _________ is considered a terrestrial ecosystem.
(a) ocean
(b) pond
(c) underground caves
(d) forest

Answer: D

Question. Which of the following constitute a food chain ?
(a) Grass, wheat and mango
(b) Grass, goat and human
(c) Goat, cow and elephant
(d) Grass, fish and goat

Answer: B

Question. In an area, the frog population decreased due to the spread of some diseases. Frogs are prey for snakes, but no major effect was seen in the population of snakes. Instead, there was a decline in the pesticide sale. What could be the possible reason?
(a) Frogs stopped eating grains due to their infection.
(b) There is no relation between the decrease in frog population and pesticide sales.
(c) Both frog and snake migrated to some other are.
(d) Snakes now depended on other organisms that must be the pests for the crops grown.

Answer: D

Question. Which of the following is an eco-friendly activity?
(a) Use of fertilizers
(b) Use of paper bags
(c) Use of styrofoam cups
(d) Use of insecticides and pesticides

Answer: B

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

Answer: C

Question. The most important trophic level in a terrestrial food chain is
(a) the one with the highest energy requirement per individual
(b) the one withthe least energy requirement per individual
(c) the one with moderate energy requirement per individual
(d) not dependent on the energy requirement per individual, thus, all are equally important

Answer: B

Question. The decomposers in an ecosystem:
(a) convert inorganic material to simpler forms.
(b) convert organic material to inorganic forms.
(c) convert inorganic materials into organic compounds.
(d) do not break down organic compounds.

Answer: B

Question. Refrigerators have led to an environmental imbalance and destroyed ecosystems. How?
(a) Refrigerators emit CFCs that are harmful to only plant species.
(b) Storing food in refrigerators makes them environmentally unhealthy.
(c) Refrigerators use CFCs that are harmful to the ozone layer which forms a blanket around the earth.
(d) Refrigerators emit greenhouse gases.

Answer: C

Question. The depletion of ozone layer is caused by
(a) carbon dioxide and methane
(b) burning of fossil fuels
(c) sulphur dioxide and cabon monoxide
(d) chlorofluorocarbons and other halons

Answer: D

Question. Which of the following statements is incorrect ?
(a) 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: B

Question. UV rays are harmful to the life on earth. However, they play an important role in the upper atmosphere. Which of the following statements holds for this fact?
(i) UV rays are needed for the formation of the ozone layer in the upper atmosphere.
(ii) UV rays are less active and inside the atmosphere, they become activated due to the other atmospheric contents.
(iii) In the upper atmosphere, UV rays have less energy and are not harmful and form the part of the atmosphere.
(a) Only (i)
(b) Only (ii)
(c) Only (iii)
(d) Both (i) and (iii)

Answer: A

Question. Which of the following statements is correct?
(a) It is important to segregate biodegradable and nonbiodegradable wastes.
(b) Non-biodegradable substances cannot be buried in landfills.
(c) We cannot dispose off non-biodegradable waste.
(d) We can use the inorganic waste for vermi-composting.

Answer: A

Question. In a food chain, the third trophic level is always occupied by
(a) herbivore
(b) carnivore
(c) decomposer
(d) producer

Answer : B

Question. First link in any food chain is usually green plants because
(a) they are widely distributed
(b) they are fixed at one place in the soil
(c) they alone have the capacity to synthesise food using sunlight
(d) there are more herbivores than carnivores

Answer : C

Question. Which of the following is a logical sequence of food chain
(a) producer → consumer → decomposer
(b) producer → decomposer → consumer
(c) consumer → producer → decomposer
(d) decomposerproducer → consumer

Answer : A

Question. Which of the two in the following sets belong to the same trophic level?
(a) Grass; Grasshopper
(b) Goat; Spider
(c) Hawk ; Rat
(d) Frog ; Lizard

Answer : D

Question. A food chain comprising birds, green plants, fish and man.
The concentration of harmful chemical entering the food chain will be maximum in
(a) green plants
(b) man
(c) birds
(d) fish

Answer : B

Question. Which of the following is an autotroph?
(a) Lion
(b) Insect
(c) Tree
(d) Mushroom

Answer : C

Question. An ecosystem includes 
(a) all living organisms
(b) non-living objects
(c) both living organisms and non-living objects
(d) sometimes living organisms and sometimes nonliving objects

Answer : C

Question. Excessive exposure of humans to UV-ray s results in 
(i) damage to immune system
(ii) damage to lungs
(iii) skin cancer
(iv) peptic ulcer
(a) (i) and (ii)
(b) (ii) and (iv)
(c) (i) and (iii)
(d) (iii) and (iv)

Answer : C

Question. Which group of organisms are not constituents of a food chain? 
(a) Grass, lion, rabbit
(b) Plankton, man, fish, grasshopper
(c) Wolf, grass, snake, tiger
(d) Frog, snake, eagle, grass, grasshopper

Answer : C

Question. In an ecosystem, herbivores represent
(a) producers
(b) primary consumers
(c) secondary consumers
(d) decomposers

Answer : B

Question. An ecosystem is represented in the figure given above. This ecosystem will be self- sustaining if
(a) the type of organisms represented by B are eliminated.
(b) materials cycle between the organisms labelled A and the organisms labelled B.
(c) the organisms labelled A outnumber the organisms labelled B.
(d) the organisms labelled A are equal in number to the organisms labelled B.

Answer : B

Question. What will happen if all the deer are killed in the given food chain?
Grass → Deer → Lion
(a) The population of grass decreases.
(b) The population of lions increases.
(c) The population of lions remains unchanged.
(d) The population of lions decreases and grass increases.

Answer : D

Question. Which of the following statements about food chain and energy flow through ecosystem is false?
(a) Food webs include two or more food chains.
(b) All organisms that are not producers are consumers.
(c) A single organism can feed at several trophic levels.
(d) Detritivores feed at all trophic levels except the producer level.
(e) The lower the trophic level at which an organism feeds, the more energy available.

Answer : D

True and False :

Question. Factors such as light, temperature, pressure and humidity are considered as biotic components. 
Answer: False

Question. The disposal of wastes by putting it in low-lying areas of ground and covering it with earth is called landfill. 
Answer: True

Question. Decomposers get their energy directly from autotrophs. 
Answer: False

Question. Disposal of waste means recycling of wastes. 
Answer: False

Question. Ozone layer presents harmful infrared radiation. 
Answer: False

Question. Food chains generally consist of three or four organisms.
Answer: True

Fill in the Blanks :

Question. …….. is the ultimate source of energy.
Answer: Sun

Question. A food chain comprises of frog, snake, grass and grasshopper. The organisms at third trophic level is ___________ .
Answer: frog

Question. In 1987 …….. succeeded in forging an agreement to freeze CFC production at 1986 levels.
Answer: United Nations Environment Programme (UNEP)

Question. Ultraviolet radiation from sunlight causes a reaction which produces ___________ .
Answer: O₃

Question. Accumulation of non-biodegradable pesticides in the food chain in increasing amount at each higher trophic level is known as ___________ .
Answer: biomagnification

Question. Those waste materials which can be broken down to non-poisonous susbtances in nature in due course of time by the action of micro-organisms are called …….. wastes.
Answer: biodegradable

Question. Organisms which synthesise carbohydrates from inorganic compounds using radiant energy are called ___________ .
Answer: producers

Question. Ozone at the higher levels of atmosphere is a product of UV radiation acting on …….. molecule.
Answer: oxygen (O₂)

MCQ Questions for NCERT Class 10 Science Our Environment

Very Short Answer Type Questions :

Question. Name any two man-made ecosystems. 
Answer: Agricultural/crop fields, aquaria, gardens. 

Question. What is biodegradable plastic?
Answer: Plastics that are decomposed by the action of living organisms such as bacteria are called biodegradable plastic.

Question. Name few biodegradable substances you generate.
Answer: Waste food, paper, cloth, etc.

Question. List two natural ecosystems. 
Answer: Two natural ecosystems are forest and river.

Question. List two biotic components of a biosphere. 
Answer: Two biotic components of a biosphere are plants and animals.

Question. What happens when a harmful chemical enters a food chain?
Answer: Its concentration increases with increase in trophic level.

Question. Which of the following belong to the first trophic level of a food chain?
Grass, Grasshopper, Plants, Rat, Tiger 
Answer: Grass and plants belong to the 1st trophic level of a food chain.

Question. Write the name and formula of a molecule made up of three atoms of oxygen. 
Answer: Ozone and its chemical formula is O3.

Question. What is a consumer?
Answer: Organisms which depend upon producers for food.

Question. What will be the amount of energy available to the organism of the 2nd trophic level of a food chain, if the energy available at the first trophic level is 10,000 joules? 
Answer: 100 Joules of energy will be available to the organism of the 2nd trophic level.

Question. Why does energy available at each trophic level diminish progressively?
Answer: Energy available at each trophic level diminishes progressively due to loss of energy at each level.
 

Long Answer Type Questions :

Question. Given below is a reaction which occurs in the stratosphere.
O₃ ↔ O₂ + [O]
(i) Name the two reactions which are in equilibrium thereby maintaining steady concentration of ozone in the ozonosphere.
(ii) What is being absorbed by the ozone for the occurrence of above two reactions ?
Answer: (i) Photodissociation of ozone and generation of ozone are the two reactions which are in equilibrium thereby maintaining steady concentration of ozone in the ozonosphere.
(ii) Ultraviolet radiations from sun are being absorbed by the ozone for the occurrence of above two reactions.

Question. Answer the following questions:
(i) If Sita is consuming curd/yogurt for lunch, which trophic level in a food chain should she be considered as occupying?
(ii) Aquarium needs to be cleaned once in a while whereas ponds or lakes do not require any cleaning. Explain.
(iii) To protect the food plants from insects, an insecticide was sprayed in small amounts but it was detected in high concentration in human beings. How did it happen?
Answer: (i) In the predatory food chain, it consists of first, second, and third to fifth trophic levels where the first trophic level is occupied by producer’s i.e, plants. The animals which consume plants are placed in the second trophic level. They are primary consumers.
Herbivores are included in this trophic level. The organisms that depend on the organisms in the second trophic level are called secondary consumers; they are categorized under the third trophic level. Curd and yogurt are the products of cow or buffalo that belong to the second trophic level. So, Sita who is eating either curd or yogurt belongs to the third trophic level.
(ii) Aquariums are artificially built ecosystems which generally do not contain every aspect of a natural ecosystem. These artificial systems do not contain any form of natural decomposers and cleaners in the ecosystem as a result, food and waste generated by the organisms living in the aquarium accumulate and contaminate the water in the tank making it toxic. Hence, they have to be cleaned manually.
Ponds and lakes being natural ecosystems have natural decomposers and cleaners embedded as an integral part of the ecosystem, hence we do not have to clean them.
(iii) Insecticide are chemicals that are either washed down into the soil or into the water bodies. From the soil, these are absorbed by the plants along with water and minerals, and from the water bodies these are taken up by aquatic plants and animals. This is one of the ways in which they enter the food chain. As these chemicals are not degradable, these get accumulated progressively at each trophic level. As human beings occupy the top level in any food chain, the maximum concentration of these chemicals get accumulated in our
bodies. This phenomenon is known as biological magnification.
This is the reason why our food grains such as wheat and rice, vegetables and fruits, and even meat, contain varying amounts of pesticide residues. They cannot always be removed by washing or other means.

Question. Study the given flow chart and answer the below given questions. 

(i) Which form of the Sun’s energy is trapped by the producer?
(ii) Into which energy form is the Sun’s energy converted when it is trapped by the producer?
(iii) What does D refer to in the box?
Answer: (i) Sun’s energy is trapped by the producer in the form of Light (or solar) energy.
(ii) Sun energy trapped by producer is converted into Chemical energy.
(iii) D refer to Decomposers like bacteria or fungi.

Question. A team of Indian researchers went to Antarctica to study the ozone layer. They confirmed the presence of largest ozone hole over Antarctica and was just short of 27 million sq. km. After few days of their return, one of the scientists developed rashes, burning sensation and other skin problems which the doctors have confirmed as skin cancer.
(i) What may be the cause of cancer just after return from Antarctica?
(ii) What do we learn from this incident?
Answer: (i) The scientists were exposed to harmful UV-radiations of the sunlight as there was a big hole over Antarctica and this might be the cause of skin cancer. The ozone layer acts as an ozone shield and absorbs the harmful UV-radiations. The UV-radiations have extremely harmful effects on human beings, animals as well as plants.
(ii) We learn that the ozone layer is very important for the existence and survival of life on earth. Ozone layer absorbs high energy UV-radiations causing a rise in temperature of the
stratosphere. The use of chemicals like CFCs has endangered the ozone layer. CFCs used as refrigerator coolants rise to the stratosphere where these molecules are broken down by UVrays resulting in attack on the ozone molecules damaging the ozone umbrella of earth. Due to ozone layer depletion UV-rays reaching the earth cause skin cancer, cataracts, damage
immune system, etc. UV-rays also decreases crop yield and certain fish larvae which are important constituents of aquatic food chains. It may also disturb global rainfall causing
ecological disturbance. In this way all on the earth would be destroyed gradually.

Question. Suggest one word for each of the following statements or definitions.
(i) The physical and biological world where we live in.
(ii) Each level of food chain where transfer of energy takes place.
(iii) The physical factors like temperature, rainfall, wind and soil of an ecosystem.
(iv) Organisms which depend on the producers either directly or indirectly for food.
Answer: (i) Environment
(ii) Trophic level
(iii) Abiotic factors
(iv) Heterotrophs

Question. What is an ecosystem? What are the components of an ecosystem? Also discuss the types of ecosystem? Draw a block diagram to show the flow of energy in an ecosystem?
Answer: An ecosystem is the structural and functional unit of biosphere where there is an interaction between living and non-living components to maintain balance between them.
The components of ecosystem are:
(a) Biotic components: They are the living organisms like plants, animals, human beings etc. Basing on the mode of obtaining food they are classified as producers, consumers and decomposers.
1. Producers: They are autotrophs which have the capacity to prepare their own food by trapping solar energy and converting them to chemical energy in the form of carbohydrates by the process of photosynthesis.
2. Consumers: They depend upon producers for food either directly or indirectly. They can be primary, secondary, tertiary or quaternary consumers.
3. Decomposers: They obtain food from dead and decayed organisms by breaking them down into simpler forms.
(b) Abiotic components: They are the non-living components i.e., the physical factors like temperature, light, wind, water, humidity and edaphic factors like soil, minerals etc.
The two types of ecosystem are:
1. Natural ecosystem: They are made by nature themselves without human interference. They can be terrestrial like forest, grassland and desert ecosystem and aquatic like freshwater
and marine ecosystem.
2. Artificial ecosystem: They are made and maintained by human beings. Examples–Gardens, parks, croplands etc.

Question. Distinguish between producers and consumers.

Answer:

Question. Explain energy relationships with trophic levels? 
Answer: Each step or level of the food chain where transfer of food or energy takes place is referred to as a trophic level. The energy relationship within trophic levels is shown in a form of pyramid.
Consider a food chain Grass → Grasshopper → Frog → Snake → Hawk. This food chain can also be considered as energy chain. We can place these animals in different trophic levels, for
example:
Grass: They are the producers so are placed in first trophic level.
They utilize solar energy to prepare food. They transfer this energy to grasshopper, but only 10% of the energy is available to grasshopper according to Lindeman’s 10% Law. If grass has 10,000 kcal of energy only 1000 kcal will be transferred to grasshopper. So energy at next trophic level is reduced.
Similarly grasshopper is placed at second trophic level; frog in third, snake in fourth and fifth trophic level is occupied by hawk. At each trophic level the energy goes on decreasing i.e., frog will receive 100 kcal of energy, snake 10 kcal and finally hawk only 1 kcal. Thus energy at each trophic level goes on decreasing and the animal placed at apex will receive lowest energy. Thus a food chain can be only up to maximum 5 trophic levels. In this way there exists a relationship between trophic levels and energy.

Question. Why are crop fields known as artificial ecosystems?
Answer: Crop fields are made by man, most of the factors like sowing of seeds, watering etc., are done by man. Various types of crops are grown depending upon the type of soil and climatic conditions. Hence crop fields are known as artificial ecosystems.

Question. Differentiate between food chain and food web? 
Answer:

Reasoning Based Questions :

Question. The first trophic level in a food chain is always a green plant. Why?
Answer: Green plants are the producers which prepare their own food by utilizing solar energy from inorganic sources and all other living organisms depends on them for food. Herbivores and carnivores depend upon green plants either directly or indirectly for food. Hence the first trophic level in a food chain is always a green plant.

Question. We do not clean ponds or lakes, but an aquarium needs to be cleaned. Why?
Answer: Ponds or lakes are natural, self-sustaining and complete ecosystem. They have decomposers like bacteria or fungi which break down the waste material and hence they remain clean. But an aquarium is a man-made, incomplete ecosystem and they do not have decomposers to clean the waste material. So an aquarium needs to be cleaned but we do not clean ponds or lakes.

Question. Why is damage to the ozone layer a cause of concern? What steps are being taken to limit this damage? 
Answer: Ozone layer is found in stratosphere which prevents the harmful UV rays of sun from entering earth’s surface. Various ozone depleting substances like CFCs cause a great damage to ozone layer thus leading to its depletion. So harmful UV rays from sun can easily pass through this layer and cause various genetic disorders, mutations, cancer, eye diseases etc., in humans. UV rays also affect plants and animals. In 1987, UNEP [United Nations Environment Programme] succeeded in forging an agreement called Montreal Protocol which states that to reduce the use of CFCs and replace CFCs with other alternatives.

Question. Why is food chain having two trophic levels most advantageous in terms of energy?
Answer: A food chain having two trophic levels only would minimise the energy lost as heat which is an advantage in terms of energy.

Question. Why is lake considered to be a natural ecosystem?
Answer: A lake is considered as a natural ecosystem as it consists of both biotic and abiotic components and these components are interdependent on each other and do not require any human interference for their sustenance.

Question. Why should biodegradable and non-biodegradable wastes be discarded in two separate dustbins?
Answer: Biodegradable wastes can be easily degraded by natural organisms like bacteria and fungi but non-biodegradable wastes cannot be degraded in a natural way by the action of microbes, they stay in environment as such. There are various techniques like recycling to degrade these non-biodegradable substances.
Hence both biodegradable and non-biodegradable wastes should be discarded in two separate dustbins.

Question. Why is it necessary to conserve the environment?
Answer: It is necessary to conserve the environment to prevent the damage to the environment and to protect the endangered species.

 Creating Based Questions :

Question. Rita wants to have an aquarium at home. What are the things that she needs to keep in mind in designing an aquarium?
Answer: The fish would need a free space for swimming, water, oxygen and food. Thus, she needs a good aquarium tank, oxygen can be provided through an oxygen pump (aerator) and fish food is available in the market.
Water parameters for nitrate, nitrite, ammonia and pH levels are to be maintained. To condition water properly, use a de-chlorinating and biological aquarium supplement. It is recommended to change 25 percent of the aquarium water at least once a month. This will help maintain a clean and healthy tank, plus it keeps nitrate concentrations at a safe level. Overcrowding can lead to low oxygen levels in the water. Another crisis of overcrowding includes excess waste, which clogs the filter and degrades the aquarium water.

Question. Shyam was very upset after reading the news of a whale shark that was found dead in waters off the Tanjung Aru beach in Menumbok. Postmortem results showed the shark had died of starvation and indigestion as it had a huge plastic bag stuck in its stomach. Suggest some measures that can be taken to reduce plastic waste.
Answer: Cloth bags can be used instead of using plastic bags as they are washable, strong and more durable than plastic bags. They are made of biodegradable material and do not pollute the environment. They can be recycled and reused and are capable of carrying more things. These days, new types of plastics which are said to be biodegradable, are available.

Question. Using the following information form a pathway showing the formation of ozone at higher levels. And also include information that is not mentioned below to complete it. Ozone, UV, Molecular oxygen.
Answer: Ozone production → UV radiation acting on oxygen (O2) molecule → the higher energy UV radiations split apart some molecular oxygen (O2) → O2 O + O →free oxygen (O) atoms then → combine with molecular oxygen ozone O + O2 → O3
(Ozone)

Question. Why energy transfer is said to be unidirectional whereas biochemical transfer is said to be cyclic?
Answer: Energy transfer is said to be unidirectional because when the energy is absorbed by autotrophs from the sun, it is never reabsorbed by it. Similarly, when consumers eat up the producers directly or indirectly the energy transferred in this process can never be reversed in the food chain. In biogeochemical cycles chemical elements move from environment to organism and back to the environment.

Question. Study the table and complete the missing terms. 

Answer: (a) Tiger
(b) Grass
(c) Snake
(d) Shark

Question. Using the following information, form a pathway which shows the flow of energy at each trophic level. And also include information that is not mentioned below to complete it.light energy, organic products, first trophic level, herbivores, second trophic level, energy.
Answer: Light energy green surfaces of plants → chemical energy stored in various → organic products in the plants first trophic level herbivores consume → plants as food second trophic level convert chemical energy into kinetic energy herbivores → are consumed by carnivores of the first order → (secondary consumers) third trophic level → primary carnivores are consumed by → top carnivores (last level) energy will be degraded.

Question. Which of the labelled arrows in the below diagram represents the smallest amount of energy transferred between organisms and the largest amount of energy lost to ecosystem?186
Answer: The arrow which represents the smallest amount of energy transferred between organisms is Q and the largest amount of energy lost to ecosystem is R.

Question. Write the appropriate names of the trophic levels Z and X in the figure given below: 

Answer: X –Primary consumers; Z – Tertiary consumers

Question. Complete the below diagram by filling spaces marked as A, B, C and D: 

Answer: A – Phytoplankton; B – Herbivores
C – Small fish; D – Secondary carnivores

Question. In which form is the 10% energy available for transfer from one trophic level to the next in an ecosystem?
(a) Light energy
(b) Mechanical energy
(c) Heat energy
(d) Chemical energy
Answer : D

Question. Why is the number of trophic levels limited in afood  chain?
(a) Because there is increase in energy at each level.
(b) Because there is succesive decrease in energy at higher trophic levels.
(c) Because trophic levels are connected.
(d) Because producers constitute first trophic level.
Answer : B

Question. Which trophic level is occupied by carnivores in a food chain?
(a) First
(b) Second
(c) Third
(d) Fourth
Answer : C

Question. What percentage of solar radiation is absorbed by all the green plants for photosynthesis?
(a) 0.1%
(b) 1%
(c) 10%
(d) 100%
Answer : B

Question. Chlorofluorocarbons (CFCs) are mainly responsible for
(a) global warming
(b) acid rain
(c) biomagnification
(d) ozone-layer depletion
Answer : D

Question. In the following diagram which trophic level will have the maximum energy?
(a) T1
(b) T2
(c) T3
(d) T4   

Answer : A

Question. Omnivores are one type of
(a) producers
(b) consumers
(c) decomposers
(d) abiotic component
Answer : B

Question. A network of interconnected food chains is called
(a) ecological pyramid
(b) food web
(c) ecosystem
(d) trophic level
Answer : B

Question. The herbivores are not
(a) consumers
(b) decomposers
(c) producers
(d) autotrophs
Answer : B , C

Question. If 10 kilocalories of energy is available to snakes (fourth trophic level), what will be the available energy at producer level in the following food chain?
Grass → Grasshopper → Frog → Snake
(a) 100 kilocalories
(b) 1000 kilocalories
(c) 1 kilocalory
(d) 10,000 kilocalories
Answer : D

Question. What does the following diagram represent?
(a) Pyramid of energy
(b) Pyramid of biomass
(c) Pyramid of number
(d) Biomagnification  

Answer : C

Fill in the blanks.

Question. The ultimate source of energy in an ecosystem is the ...... .
Answer : sun

Question. The ozone at the higher levels of atmosphere is a product of UV radiations acting on ...... molecule.
Answer : oxygen

Question. Substances that are broken down by biologial processes are called ...... .
Answer : biodegradable

Question8. The various components of an ecosystem are ...... .
Answer : interdependent

Question. ...... wastes can be broken down into simpler substances by decomposers.
Answer : Biodegradable

Question. There is ...... of energy when we go from a trophic level to the next trophic level.
Answer : loss

Mark the statements true (T) or false(F).

Question. Energy and materials are not transferred from one trophic level to another.
Answer : false

Question. CFCs are used as refrigerants and in fire extinguishers.
Answer : true 

Question. DDT is a nonbiodegradable substance.
Answer : true 

Question. Solar energy is converted into chemical energy by heterotrophs.
Answer : false

Write Yes/No.

Question. Can we say that there is progressive increase in energy level in successive trophic levels?
Answer : No

Question. Do autotrophs constitute the first trophic level in an ecosystem?
Answer : Yes

Question. Does an ecosystem consist of both biotic and abiotic components?
Answer : Yes

Question. Can the flow of energy be bidirectional?
Answer : No

Question. Why some substances are degraded and others not?
Answer : Different components of food are changed to simpler substances by digestive enzymes and these enzymes are very much specific in nature and action. Similarly, substances are broken down by bacteria and saprophytes. They are also very specificin action and break down of the particular substance. Therefore, some substances are biodegradable and other are non-biodegradable.

Question. What limits the number of trophic levels in a food chain.
Answer : There is a loss of energy as we go from one trophic level to the next, this limits the number of trophic levels in a food chain.

Question. What will happen if decomposers are not there in the environment?
Answer : If decomposers are not there in the environment, the breakdown of the complex organic substances into simple substances will not take place and natural replenishment of the soil will not take place. So, presence of decomposers is essential for the replenishment of soil and biogeochemical cycle of elements or substances.

Question. What is the harm of clay cups?
Answer : Clay cups cause depletion of top fertile soil as they are formed from the same.

Question. What will happen if all the carnivores are removed from the earth?
Answer : If all the carnivores are removed from the earth, the population of herbivores.will increase. Large population of herbivores will overgraze. As a result, all plants will disappear from the earth surface and ultimately the earth may become a desert. The biosphere will get disturbed which will lead to end of life on earth.

Question. What will happen to grasslands if all the grazers are removed from there?
Answer :. If all the grazers are removed from grassland, grass will grow unchecked. It may help the growth of some organisms harmful to the animals and the animals which feed on the grazers will die of starvation. The biogeochemical cycle will stop and the whole biosphere will get disturbed.

Question. The number of malarial patients in a village increase tremendously, when a large number of frogs were exported from the village. What could be the cause for it? Explain the help of food chain?
Answer : Phytoplankton Zooplankton Mosquito larva Frog In the absence of frog, more mosquito larva survive, giving rise to large number of mosquitoes which cause increase incidence of malaria.

Question. State one reason to justify the position of man at the apex of most food chains?
Answer : The position of man is at the apex of most food chains as he is an intelligent organism and can take any advantageous position by manipulation.

Question. Which food chains are advantageous in terms of energy?
Answer : The two step chains in which man is close to producer are advantageous. For example, Producer  → Man

Question. Construct a food chain composing the following Snake, Hawk, Rats, Plants.
Answer : Plants  → Rats   → Snake   → Hawks

Question. Name the process that is a direct outcome of excessive burning of fossil fuels?
Answer : Global warming is a direct outcome of excessive burning of fossil fuels.

Question. If all the wastes we generate is bio-degradable what impact may this have on the environment?
Answer : Cleaner environment without any pollution, more nutrients will be released into the nutrient pool, will help to maintain ecological balance.

Question. Write the harmful effect of ozone depletion.
Answer : 1. Cause the skin cancer

2. Damage to eyes 

3. Immune system

Question. Why food chains consists of three or four steps only?
Answer : Since so little energy is available for the next level of consumers and for this reason food generally consists of three or four steps. The loss of energy at the each step is so great that very little usable energy remains after four tropic levels.

Question. Which of the following will have the maximum concentration of harmful chemicals in its body? Peacock, Frog, Grass, Snake, Grasshopper.
Answer : Grass Grasshopper Frog Peacock . Peacock will have maximum conc.

Question. Why energy of herbivores never come back to the autotrophs?
Answer : Energy of herbivorous never comes back to autotrophs as flow of energy is always unidirectional. So once it passes the trophic level it is no longer available to the previous level.

Question. What are decomposers and what is the importance of them in the ecosystem?
Answer : The micro-organisms which break down the complex organic substances into simple inorganic substances e.g. bacteria, fungi. Decomposers decompose the complex substances into simple ones so that plants can use it again. 

Question. What is biological magnification and give its causes?
Answer : The increased concentration of chemicals at any trophic level is called biological magnification. It occurs due to the excessive use of pesticides which enter our food chain. 

Question. Are plants actually producers of energy?
Answer : No, plants are not actually producers of energy, they can trap the energy of sun and can convert solar energy into chemical energy in the form of carbohydrates and other food materials so they are called transducers.

Question. Which one of the following is an artificial ecosystem? 
(a) Pond
(b) Crop field
(c) Lake
(d) Forest

Answer : B

Question. Which one of the following will undergo fastest bio-degradation?
(a) Mango seed
(b) Wood
(c) Mango peel
(d) Mango pulp

Answer : D

Question. Excessive exposure to ultraviolet radiation causes
(a) inflammation of liver
(b) cancer of skin
(c) damage to the lungs
(d) jaundice

Answer : B

Question. Which of the following is an abiotic component of an ecosystem?
(a) Humus
(b) Bacteria
(c) Plants
(d) Fungi

Answer : A

Question. Which of the following is non- biodegradable?
(a) Wool
(b) Nylon
(c) Animal bones
(d) Tea leaves

Answer : B

Question. In the garden ecosystem, which of the following are producers?
(a) Insects
(b) Snakes
(c) Grasses
(d) Rabbits

Answer : C

Question. Acid rain is caused by the oxides of
(a) carbon
(b) nitrogen only
(c) sulphur only
(d) sulphur and nitrogen

Answer : D

Question. Which one of the following pairs belong to the category of primary consumers?
(a) Eagle and snake
(b) Grasshoppers & cattle
(c) Snake and frog
(d) Water beetles & fish

Answer : B

Question. Trophic level in an ecosystem represents
(a) oxygen level
(b) water level
(c) energy level
(d) salt level

Answer : C

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

Answer : C

Question. Which one of the following is an artificial ecosystem?
(a) Lake
(b) Forest
(c) Pond
(d) Crop field

Answer : D

Question. Which of the following chemicals causes depletion of the ozone layer?
(a) Carbon tetrachloride
(b) Methane
(c) Chloro fluoro carbon
(d) Carbon monoxide

Answer : C

Question. In the given foodchain if the amount of energy at the fourth trophic level is 4 kJ, what will be the energy available at the producer level?
Grass → Grasshopper → Frog → Snake
(a) 4 kJ
(b) 40 kJ
(c) 400 kJ
(d) 4000 kJ

Answer : D

Question. Which of the following is biodegradable?
(a) Aluminium can
(b) Polythene bag
(c) Cowdung
(d) DDT

Answer : C

(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.

Question. Assertion: Ozone layer is getting depleted at upper atmosphere which is a cause of concern.
Reason: CFC reacts with ozone and breaks it.

Answer : A

Question. Assertion: Autotrophs can produce food on its own.
Reason: Green plants can absorb 1% energy of sunlight that fall on the leaves.

Answer : B

Question. Assertion: Vegetarian food habit is more beneficial to organisms.
Reason: Only 10% energy is available as food from one trophic level to next.

Answer : A

Question. Assertion: Biodegradable waste and non biodegradable waste should be discarded separately,
Reason: Biodegradable waste are not harmful.

Answer : C

Question. Assertion: Accumulation of harmful chemicals is maximum in case of organisms at higher trophic level.
Reason: Food chain normally do not go beyond 3 or 4 trophic level.

Answer : B

Fill in the Blanks :

Question. In an ecosystem, various organisms are linked forming interconnections such a condition is termed as ___________ .
Answer: Food web

Question. Flow of energy in an ecosystem is always ___________ .
Answer: unidirectional

Question. Burning of waste substances usually at high temperature of over 1000° C to convert them into ashes is called ___________ .
Answer: Incineration

Question. The waste materials which can not be broken down into harmless substances in nature are called …….. .
Answer: non-biodegradable wastes

Question. Depletion of ozone is mainly due to ___________ .
Answer: chlorofluorocarbon compounds

Question. …….. can be classified as herbivores, carnivores, omnivores and parasites.
Answer: Consumers

Question. Animal dung is ___________ waste.
Answer: Biodegradable

Very Short Answer Type Questions :

Question. What are the various steps in a food chain called?
Answer: The various steps in a food chain are called trophic levels.

Question. Which of the following are always at the second trophic level of the food chains? 
Carnivores, Autotrophs, Herbivores
Answer: Herbivores are always at the 2nd trophic level.

Question. What happens to Sun’s energy that fall on green plants?
Answer: Green plants absorb 1% of Sun’s energy that falls on their leaves.

Question. Which disease is caused in human beings due to depletion of ozone layer in the atmosphere? 
Answer: Skin cancer is caused in human beings due to a depletion of ozone layer in the atmosphere.

Question. In a food chain, 10,000 joules of energy is available to the producer. How much energy will be available to the secondary consumer to transfer it to the tertiary consumer?
Answer: 10J of energy will be available to the secondary consumer to transfer to the tertiary consumer.

Question. We often use the word environment. What does it mean? 
Answer: 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.

Question. When plants are eaten by primary consumers, a great deal of energy is lost as heat to the environment and some amount goes in carrying out various life processes. State the average percentage of energy lost in this manner. 
Answer: The average percentage of energy lost when plants are eaten by primary consumers is 90%.

Question. List two criteria of measuring the biodiversity of an area. 
Answer: One measure of the biodiversity of an area is the number of species found there. Secondly, the range of different life forms is also important.

Question. How should we dispose waste?
Answer: By segregating biodegradable and non-biodegradable material.

Question. Consider the following food chain which occurs in a forest:
Grass → Deer → Lion
If 10000 J of solar energy is available to the grass, how much energy would be available to the deer to transfer it to the lion?
Answer: 1 J energy will be available to deer to transfer it to lion.

Question. What is the full form of CFC and UNEP? 
Answer: CFC: Chlorofloro carbon.
UNEP: United Nation Environmental Programmes.

Question. Write the full name of the group of compounds mainly responsible for the depletion of ozone layer.
Answer: CFC → Chlorofluorocarbon

Question. Why is it necessary to conserve our environment? 
Answer: It is necessary to conserve our environment to prevent depletion of natural resources and environmental damage, thereby sustaining life.

Question. Despite the presence of an adequate amount of decomposers, a lot of waste is accumulating in the ecosystem because
(a) decomposers keep mutating
(b) there is a high amount of non-biodegradable wastes being generated in that ecosystem
(c) decomposers are unable to survive in this ecosystem
(d) the rate at which waste is generated is higher than the rate of decomposition

Answer: B

Question. _________ is an omnivore.
(a) Panther
(b) Bear
(c) Wolf
(d) Lion

Answer: B

Question. zone has the chemical formula ___________.
(a) O₅
(b) O₄
(c) O₃
(d) O₂

Answer: C

Question. Which of the following is an abiotic component of the ecosystem?
(a) Lichens on a bare rock
(b) Weathered rock
(c) Planktons in a pond
(d) Sea-weed

Answer: B

Question. Disposable plastic plates should not be used because :
(a) They are made of materials with light weight.
(b) They are made of toxic materials.
(c) They are made of biodegradable materials.
(d) They are made of non-biodegradable materials.

Answer: D

Question. Which of the following occupies the first trophic level in the food chain they form together?
(a) Apple tree
(b) Honey bee
(c) Grasshopper
(d) Mouse

Answer: A

Question. Cutting of forests for growing crops would
(a) reduce the stability of the ecosystem
(b) enhance the stability of the ecosystem
(c) not affect the stability of the ecosystem
(d) first increase and then decrease the stability of the ecosystem

Answer: A

Question. Which of the following is the set of greenhouse gases in the atmosphere?
(a) Ozone and CFC
(b) Carbon monoxide and sulphur dioxide
(c) Carbon dioxide and methane
(d) Hydrogen sulphide and ozone

Answer: C

Question. The amount of energy that is passed from one trophic level to the next is ______.
(a) 1%
(b) 10%
(c) 11%
(d) 1.1 %

Answer: B

Question. At which trophic level is maximum energy available in the figure given below for the various tropic levels in a food chain ?
(a) T 4
(b) T 2
(c) T 1
(d) T3

Answer: C

Question. _________ are producers.
(a) Amoeba
(b) Mushrooms
(c) Sunlight
(d) Green plants

Answer: D

Question. Which of the following is NOT a type of natural ecosystem?
(a) Sea
(b) Crop field
(c) Lakes and ponds
(d) Estuaries

Answer: B

Question. Fishes living in a crop field with standing water are the part of a/an _____________ ecosystem.
(a) natural
(b) artificial
(c) indigenous
(d) None of these

Answer: B

Question. Classify the given activities under reuse and recycle.
(i) Using plastic bucket for growing plants
(ii) Using old newspaper to make paper bags
(iii) Using broken glass to melt and make a new glass
(iv) Dissolving paper, bleaching and drying it to form a new paper.
(a) (i) and (ii) are examples of reuse and (iii) and (iv) are the examples of recycle.
(b) (ii) and (iii) are the examples of reuse and (i) and (iv) are the examples of recyle.
(c) (i), (ii) and (iii) are the examples of reuse and (iv) is the example of recycle.
(d) (i), (ii) and (iii) are the examples of recycle and (iv) is the example of reuse.

Answer: A

Question. Supriya listed some important points for energy transfer in a food chain. She made an error. Point out that error.
(i) Primary consumers transfer 10% of energy to the next trophic level in the food chain.
(ii) The population at a lower trophic level is greater than the population at a higher trophic level.
(iii) Producers depend entirely on sunlight to make food
(iv) Decomposers work at a double pace to convert complex molecules into simpler forms in case of an epidemi(c)
(a) Only (ii)
(b) Only (iv)
(c) (i) and (iii)
(d) All of the above

Answer: B

Question. Food chain does not comprise of which of the following groups of organisms?
(i) Grass, lion, rabbit, wolf
(ii) Plankton, man, fish, grasshopper
(iii) Wolf, grass, snake, tiger
(iv) Frog, snake, eagle, grass, grasshopper
(a) (i), (iii)
(b) (iii), (iv)
(c) (ii), (iii)
(d) (i), (iv)

Answer: C

Question. Which of the following gets the minimum amount of energy through the food chain in an ecosystem?
(a) Herbivore
(b) Carnivore
(c) Producer
(d) Large carnivore

Answer: D

Question. Which of the following sets represents the substances required for the formation of ozone?
(a) Oxygen and IR radiations
(b) Oxygen and UV radiations
(c) Oxygen and radiations of longer wavelengths
(d) Carbon dioxide, water vapour and UV radiations

Answer: B

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) mechanical energy
(d) chemical energy

Answer: D

Question. The population at each trophic level is less than the previous one. How does this phenomenon help?
(i) It maintains a balance in the energy demand and supply.
(ii) Organisms at lower trophic levels are more complex and organise(d)
(iii) Organisms at higher trophic levels are less complex, and hence, this decreases the population of lower trophic levels.
(iv) Organisms at higher trophic levels have lesser energy demands than the ones at lower levels.
(a) Only (i)
(b) Only (ii)
(c) Only (iv)
(d) (i), (ii) and (iii)

Answer: A