10th Class Biology 9th Lesson Our Environment Textbook Questions and Answers

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Question 1. What happens to the amount of energy transferred from one step to the next in a food chain?


  • Energy is transferred along food chains from one trophic level to the next
  • The amount of available energy decreases from one stage to the next
  • This is because not all the food can be fully digested and assimilate
  • Hair, feathers, insect exoskeletons, cartilage and bone in animal foods, cellulose and lignin in plant foods cannot be digested by most animals
  • These materials are excreted or made into pellets of indigested remains
  • Assimilated energy is available for the synthesis of new biomass through growth and reproduction
  • Organisms also lose some biomass by death disease or annual leaf-drop
  • Moreover at each tropic level, organisms use the most of the assimilated energy to fulfill their metabolic requirements - performance of work, growth and reproduction
  • Most of the energy is lost in the form of heat during biological processes
  • Only a small fraction goes to the consumer at next tropic level
Question 2. What do pyramids and food chain indicate in an ecosystem?


  • The ecologists used the idea of pyramid to show relationship among organisms in an existing food chain
  • Ecological pyramids are of three types. They are pyramid of biomass, pyramid of number, pyramid of energy
  • Pyramid of biomass indicates the available biomass in an ecosystem; pyramid of number indicates the organisms present and pyramid of energy indicates the available energy in an ecosystem
  • The food chain in an ecosystem indicates how energy is transferred from one organism to another
  • The starting point of a food chain are producers and it ends with top carnivores
  • A food chain represents a single directional transfer of energy
Question 3. Write a short note on pyramid of number for any food chain. What can we conclude from this pyramid of numbers?
i) tree ii) insect iii) woodpecker (OR) What is a pyramid of numbers? Write a brief note on the pyramid of numbers with the help of a block diagram.


  • The number of organisms in a food chain can be represented graphically in a pyramid of number
  • Each bar represents the number of individuals at each tropic level in a food chain
  • In the pyramid of numbers, from the first - order consumers to the large carnivores, there is normally an increase in size, but decrease in number
  • For example, in a wood, the aphids are very small and occur in astronomical numbers
  • The ladybirds which feed on them are distinctly larger and not so numerous
  • The insectivorous birds which feed on the ladybirds are larger still and are only present in a small numbers, and there may only be a single pair of hawks of much larger size than the insectivorous birds on which they prey
  • b.
  • In the given pyramid, the producer is a large tree, primary consumers are small insects which are numerous in number and secondary consumers are woodpeckers which are comparatively less in number than insects
  • From this pyramid of number, we can conclude that sometimes the pyramid of numbers does not look like a pyramid a all
  • This could happen if the producer is a large plant or if one of the organisms at any tropic level is very small
  • Whatever the situation, the producer still goes at the bottom of the pyramid
Question 4. What is biomass? Draw a pyramid of biomass for the given food chain. i) grass leaves ii) herbivores iii) predators iv) hawk?


  • Biomass is organic material of biological origin that has ultimately derived from the fixation of carbon dioxide and the trapping of solar energy
  • This includes trees, shrubs, crops, grasses, algae, aquatic plants* agricultural and forest residues and all forms of human, animal and plant waste
  • Any type of plant or animal material that can be converted into energy is called "Biomass"
  • Question 5. How is using of toxic material affecting the ecosystem? Write a short note on bioaccumulation and biomagnifications?


    • Use of toxic materials such as pesticides, herbicides and fungicides creates new problems in the ecosystem
    • As these toxic materials are often indiscriminate in their action and vast numbers of other animals may be destroyed
    • Some of them may be predators which naturally feed on these pests, others may be the food for other animals
    • Thus causing unpredictable changes in food chains and upsetting the balance within the ecosystem
    • Some toxic substances have a cumulative effect
    • Some of them are degradable, can be broken down into harmless substances in a comparatively short time usually a year
    • Others are non-degradable which are potentially dangerous as they accumulate in the bodies of animals and pass right through food web
    • This process of entering of pollutants in a food chain is known as "Bioaccumulation"
    • The tendency of pollutants to concentrate as they move from one tropic level to the next is known as "Biomagnifications"
    Question 6. Should we use pesticides as they prevent our crop and food from pests or we should think of alternatives? Write your view about this issue and give sound reason for your answer?
    (OR) Why should we think of alternatives to pesticides? Give reasons.


    • We should think of alternatives. This is because these pesticides are toxic chemical whose usage leads to Bioaccumulation and Biomagnifications
    • When we use pesticides, they prevent our crop and food from pests effectively but indiscriminately destroys a vast number of other animals
    • This is causing unpredictable changes in food chains and upsetting the balance within the ecosystem
    • Most of the chemical pesticides that contain mercury, arsenic or lead are non -degradable
    • They enter into food chain, accumulate in the bodies of animals and pass right through food web
    • Being further concentrated at each step until animals at the top of the pyramid may receive enough to do considerable harm
    • This is one of the reasons for ever decreasing number of butterflies, bees, small and large birds
    • Some of the pesticides are nerve poisons and might bring about changes in behaviour
    • As the human beings are at the end of the food chain, these pesticides may get accumulated in our bodies also. This shows some adverse effects on us, when their concentration becomes sufficiently high
    Question 7. What is a tropic level? What does it represent in an ecological pyramid?


    • The various steps in a food chain at which the transfer of food takes place is called tropic level
    • Tropic level means the feeding level of the organism
    • In an ecological pyramid, the first tropic level represents the primary producers, and their number, biomass or energy
    • Second tropic level represents the herbivores or primary consumers and their number, biomass or energy
    • The tropic level represents the lower carnivores or secondary consumers and their number, biomass or energy
    • The fourth tropic level represents the higher carnivores or tertiary consumers and their number, biomass or energy
    Question 8. If you want to know more about the flow of energy in an ecosystem, what questions do you ask?

    Answer: I will ask the following questions to know more about flow of energy in an ecosystem

    • How does the energy flow in an ecosystem from one organism to other
    • Is the energy transformation from one level to other 100% efficient
    • What per cent of energy transfers from one level to other
    • What happens to the remaining energy
    • How does the ecosystem lose its energy during energy transformation
    • Which tropic level in an ecosystem has more energy and which has less
    • What is the ultimate source of energy in an ecosystem
    Question 9. What will happen if we remove predators from food web?


    • Removal of organisms from any tropic level of a food chain or food web disturbs the ecosystem and leads to ecological imbalance
    • If we remove predators from food web, the prey population will increase enormously as there is no natural control over them
    • The producers population will decrease rapidly as the organisms feeding on them increase
    • After few generations the prey population also begins to decrease as some of the preys begin to die due to starvation
    • Some adaptations may also be developed by the organisms to bring the ecological balance
    • But it may take some generations, till that the ecosystem will be disturbed and imbalanced
    • For example, if we remove all the predators (carnivorous) from a forest ecosystem, the herbivorous animal population will increase as there are no carnivores to hunt them
    • As a result plant population will decrease as the ever increasing herbivores feed more and more on plants
    • After some generations the herbivore population begins to decrease as the decreasing number of plants are not sufficient to feed
    • Then some herbivorous animals may adapt to feed on other herbivores to increase their survival
    • Then scope for survival will increase for plants again which leads to ecological balance
    • But this may take lot of time to evolve new predators and to form ecological balance
    Question 10. Observe a plant in your kitchen garden, and write a note on producer-consumer relationship?

    Answer: When I observe a plant in kitchen garden, I came to know the following things

    • Though it may be relatively small, a garden is a complete ecosystem
    • It has the same components as any other large and elaborate ecosystems had
    • The plant in a kitchen garden is a producer as it produces their own food from sunlight
    • There are two types of consumers in this ecosystem, a) Primary consumers and b) Secondary consumers
    • Primary consumers feed on plants. This tropic level consists of caterpillars, bees and butterflies
    • Secondary consumers feed on primary consumers. This tropic level consists of birds, garden lizards and spiders
    • Fungi, bacteria, insects and worms make up decomposers
    • The producer and consumer relationship can be shown in the following food chain. Plant ? Plant eaters such as caterpillars, bees, butterflies ? Meat-eaters such as birds, garden lizards, spiders Producers ? Primary consumers ? Secondary consumers
    • The pyramid of number appears like this
    • The pyramid of Biomass appears like this
    • The pyramid of energy appears like this
    Question 11. What type of information do you require to explain the pyramid of biomass?

    Answer: To explain the pyramid of biomass, we require the following information

    • The type of ecosystem
    • Producers in the ecosystem
    • Primary consumers in the ecosystem
    • Secondary consumers in the ecosystem
    • Tertiary consumers in the ecosystem
    • Number of organisms at each tropic level
    • Size of organisms at each tropic level
    • Weight of organisms at each tropic level
    • All forms of waste produced at each tropic level and
    • In total, total amount of biomass produced at each tropic level
    Question 12. Draw a pyramid of numbers considering yourself sis top level consumer. Pyramid of numbers?

    Answer: Pyramid of numbers Ex: 1 Ex: 2

    Question 13. Prepare slogans to promote awareness in your classmates about eco-friendly activities. All the living things have the right to live on this earth along with us. Prepare slogans to promote awareness in public about the conservation of biodiversity?
    (OR) Which slogans do you prefer to promote awareness in your locality about eco-friendly activities?


    • Live and let live
    • If we protect the environment, it protects us
    • Conserve nature - Conserve life
    • Save mother earth
    • Earth needs you
    • Go ecofriendly
    • Clean the environment, live happily
    • Heal our planet! Turn it into a better planetv
    • Plant a tree for your environment
    • Think ecofriendly and live ecofriendly
    • Earth enables you to definitely stand. Allow it to stand the actual way it is
    • Youve only got one planet. Dont trash it
    Question 14. Suggest any three programmes on the prevention of soil pollution in view of avoiding pesticides?
    (OR) Suggest any four eco-friendly methods for prevention of soil pollution in view of avoiding pesticides. (OR) In your area, soil is polluted by the enormous usage of pesticides. Suggest any two programmes for the prevention of soil pollution.

    Answer: To prevent the soil pollution caused by pesticides following programmes should be implemented

    • Rotation of crops
    • Same crop should not be grown in the same field in successive seasons
    • Rotation of crops reduce occurance of pests and damage due to pests will be decreased
    • Biological control: Introducing natural predator or parasite of the pest
    • Sterility: Sterilising the males of a pest species reduces the population of pests
    • Genetic strains: The development of genetic strains which are resistant to certain pest
    • Studying the life histories of the pests: When this is done it is sometimes possible to sow the crops at a time when least damage will be caused
    Choose the correct answer. 1.
    What does a food chain always start with?
    • The herbivore
    • The carnivore
    • The producer
    • None of these

    Answer: C

    Which of the following do plants not compete for?
    • Water
    • Food
    • Space
    • All the above

    Answer: B

    Ban all pesticides, this means that?
    • Control on the usage of pesticides
    • Prevention of pesticides
    • Promote eco-friendly agricultural practices
    • Stop biochemical factories

    Answer: C

    According to Charles Elton?
    • Carnivores at the top of the pyramid herbivore
    • Energy trapping is high at the top of the pyramid
    • No producers at the top of the pyramid
    • A and C

    Answer: D

    10th Class Biology 9th Lesson Our Environment InText Questions and Answers

    Question 1. Are all terrestrial ecosystems similar?


    • No. All the terrestrial ecosystems are not similar
    • Basing on variations in climatic conditions such as rainfall, temperature and the availability of light, there are various kinds of ecosystems
    • The major types of terrestrial ecosystem are
    • Tundra
    • Coniferous forest
    • Deciduous forest
    • Savannah
    • Tropical forest and
    • Deserts
    Question 2. If we want to show a food chain consisting of grass, rabbit, snake and hawk then connect the given picture of organisms by putting arrows and make a food chain?
    • Name the producers and consumers in the above food chain
    • Try to guess what does the arrows marked by you are indicate
    • Identify at least four other food chains from your surroundings. Name the producers and different levels of consumers in those food chains

Answer: Grass ? Rabbit ? Snake ? Hawk

  • In the above food chain grass is the primary producer. Rabbit is the primary consumer, snake is the secondary consumer and hawk is the tertiary consumer
  • The arrows indicate the flow of energy from one organism to another. So these are always pointed from the food to the feeder
  • Plant ? insect ? frog ? bird
  • Plant ? insect ? frog ? snake
  • Aquatic plants ? insects ? fish ? crane
  • Plant ? mice ? snake ? vulture
  • Plant ? aphids ? spiders ? birds
Question 3. Why do most of the food chains consists of four steps?


  • Most of the food chains are quite short and mostly consists of four steps
  • This is because only 10% of the energy present in a tropic level transfers to the other tropic level
  • Remaining energy is dissipated as heat produced during the process of respiration and other ways
  • Thus about three steps in a food chain very little energy is still available for use by living organisms
Question 4. Why do the number of organisms get decreased as we move from producer to different level of consumers?


  • As we move from producers to different levels of consumers the energy available will decrease gradually
  • Only ten per cent of the energy present in one tropic level transfer to another tropic level
  • Biomass also decreases gradually as only 10 - 20% of the biomass is transferred from one tropic level to the next in a food chain
  • As there is less energy & less biomass available at top levels, number of organisms also less, generally
  • So, the number of organisms get decreased as we move from producer to different level of consumers
Question 5. Draw the pyramid of number for the following food chains?
  • Banyan ? insects ? woodpecker
  • Grass ? rabbit ? wolf
  • Are the pyramid of number having same structure in both of the above two cases as compare to the example given in the earlier paragraph? B) If there is a difference, then what it is


  • No. The pyramid of number in the above two cases doesnt have the sme structure as compared to the example given in the textbook
  • In the example (given in the textbook), number of organisms at producers level is more. This number gradually decreased in consumers level step by step. So the pyramid of number formed has typical pyramid shape with broad base and the narrow apex
  • But in the first case given here, on a single Banyan tree, a large number of insects live and feed. These insects become food for few Woodpeckers. So producers number is less than primary and secondary consumers, and secondary consumers are less than primary consumers. So the pyramid of number does not look like a pyramid. It consists of narrow base, broad middle part and medium apex
  • In the second case, grass which are large in number become food for few rabbits. Rabbit provides food for several wolves which are comparatively less in number than grass. So primary consumers are less in number than secondary consumers and producers. So the pyramid of number for this food chain also does not look like a pyramid. It consists of broad base, narrow middle part and medium apex. Thus it differs from case (i) also
Question 6. Think why the pyramids are always upright?


  • In ecology not all the pyramids are always upright
  • Pyramid of number may be upright, inverted or partly upright.
  • Pyramid of biomass may be upright or inverted
  • But the pyramid of energy is always upright
  • This is because energy will decrease when we move from producers to the high level consumers
  • Only 10% of the energy from one tropic level transfers to the other through food chain
  • So the energy at base is more, gradually decreases, and very less at the top
  • As a result the energy pyramid is always upright
Question 7. Observe the data given in the following table?
Classes Area in 1967(Km2) Area in 1967(Km2)
Lake - water spread area 70.70 62.65
Lake with sparse weed 0 47.45
Lake with dense weed 0 15.20
Lake-liable to flood in rainy season 100.97 0
Aquaculture ponds 0 99.74
Rice fields 8.40 16.62
Enchrochment 0.31 1.37
Total 180.38 180.38
i) In which year lake-water spread area is more? Why?

Answer: In the year 1967. Because lake was not brought under cultivation

ii) How do you think weeds are more in the lake?

Answer: Excessive nutrient addition, especially from anthropogenic sources, led to explosive weed growth. Ex: Eichornia, pistia

iii) What are the reasons for decrease in lake area?


  • In 1996, almost entire lake was brought under cultivation
  • Industries came along in ever growing intensity in the catchment area of the lake
iv) How do the above reasons lead to pollution?


  • Consequently, the drains and rivulets carry substantial quantity of various types of pollutants into the lake
  • The major sources of pollution are agricultural runoff containing residues of several agrochemicals, fertilizers, fish tank discharges, industrial effluents containing chemical residues
v) How was the threat to the lake due to pollution discovered?


  • The water of the lake turned alkaline in nature, turbid, nutrient rich, low in dissolved oxygen and high in biochemical oxygen demand
  • Water borne diseases like diarrhoea, typhoid, amoebiasis and others are said to be common among the local inhabitants who are unaware of the state of pollution in the lake water
  • Vector borne diseases were also increased
vi) What could be the reasons for the migration of birds to this lake?

Answer: To avoid extreme cold weather conditions in Northern Asia and Eastern Europe birds migrate to Kolleru lake

Question 8. Observe the following table showing different activities in the lake and their influence?
Legend: (+) means has influence on the mentioned problem (-) means has no influence on the mentioned problem
i) What are the factors that affected the number of migratory birds to decrease?

Answer: Aquaculture practices.

ii) Do you find any relationship between biological and physical problems?

Answer: Yes. Aquaculture practices have influence on these problems

iii) What are the reasons for chemical problems ?

Answer: Agricultural practices, aquaculture practices, industrial activities and human activities are the reasons for chemical problems

iv) What happens if the dissolved oxygen reduce in lake water ?

Answer: If the dissolved oxygen reduces in lake water, sufficient amount of oxygen will not be available to organisms that live in the lake. This leads to the death of organisms in the lake

v) Is BOD of turbid and nutrient rich water high or low? What are its consequences?

Answer: High. Its consequences are water borne diseases and death of organisms

vi) People living in catchment area of Kolleru faced so many problems. Why?

Answer: Vector borne disease increased. The lands adandoned are useless for agriculture

Question 9. Name any two pesticides / insecticides you have heard about?

Answer: DDT, Aldrin, Malathian, Altrazine, Monocrotophos, Endosulphan etc

Question 10. How are the food grains and cereals being stored in your house and how dojyou protected them from pests and fungus?

Answer: To protect food grains and cereals from pests and fungus, we will follow the following rules in our house

  • First of all we will dry and clean our grain before storing
  • We will avoid moisture in bagged grains by storing them on wooden structures, bamboo mats or polythene covers
  • We use domestic bins or improvised storage structures such as Gaade, Kotlu, Paatara, RCC bins and flat bottom metal bins etc
  • We fumigate the storage room with Ethylene Di-bromide (EDB) ampoules to avoid insect damage
  • We use anticoagulant for rat control in houses
Question 11. Where from pollutants enter to the water sources?

Answer: The used water from industries and run off water containing agricultural effluents bring pollutants into water sources. Municipal and domestic sewage also pollute water sources

Question 12. How can you say fishes living in water having heavy metals in their bodies?

Answer: The bioaccumulation of heavy metals in tissues of fish particularly in liver, kidney and gills were analysed and found their presence

Question 13. Researchers found that pollution levels increase during monsoon season. Why they found so?


  • Pollution levels increase during monsoon season in water bodies.
  • During monsoon season heavy rainfall occurs
  • The rain water brings residues of agrochemicals, fertilizers and different types of organic substances, municipal and domestic sewage
  • Hence pollution levels increase in monsoon season
Question 14. Why did people also suffer from various diseases after consuming fishes living in local water reservoir?


  • The heavy metals could find their way into human beings through food chain
  • This bioaccumulation cause various physiological disorders such as hypertension, sporadic fever, renal damage, nausea etc
Question 15. What is the food chain that has been discussed in the above case?

Answer: The food chain discussed in the above occurrence is Crops ? Locust ? Sparrow ? Hawk

Question 16. How did the campaign disturb the food chain in the fields?


  • Crop yields after the campaign were substantially decreased
  • Though the campaign against sparrows ended it was too late
  • With no sparrows to eat the locust populations, the country was soon swarmed
  • Locust coupled with bad weather led to the great Chinese famine
Question 17. How did these disturbances affect the environment?


  • The number of locust increased
  • Use of pesticides against locust population further degraded the land
Question 18. Is it right to eradicate a living organism in an ecosystem? How is it harmful?


  • No, it is not right to eradicate a living organism in an ecosystem
  • It disturbs the existing food chain
Question 19. Were the sparrows really responsible? What was the reason for the fall in crop production?


  • No, the sparrows were not really responsible for the loss of food grain
  • With no sparrows to eat the locust population crops were damaged and this led to fall in crop production
Question 20. What was the impact of human activities on the environment?


  • The human activities badly affected the environment
  • Use of pesticides against the pest degraded the land
Question 21. What do you suggest for such incidents not to occur?


  • I suggest to use organic manures and organic insecticides to kill the insects
  • Rotation of crops is the best method to protect the crops from pests
  • We should not kill any organism on this earth because every organism has a role to play
  • Think before you start action
10th Class Biology 9th Lesson Our Environment Activities Activity - 1
Observe any water ecosystem in your surroundings and identify the different food chains and food web operating in this ecosystem. Write the following details in your notebook?
  • Names of the students in a group: ------- Date: ----
  • Name of the ecosystem: -------
  • Topography: -------
  • Names / Number of plants (producers) identified: -------
  • Names / Number of animals identified: -------
  • Identify the different types consumers and name them & mention their number below :
  • Herbivores (Primary consumers): ------- Carnivores (Secondary consumers): ------- Top carnivores (Tertiary): -------
  • Food relationships among them: food habits/preferences: -------
  • Show / draw the different food chains: -------
  • Showcase the food web: -------
  • List out all abiotic factors existing in the ecosystem: -------
  • ( A check list can be given, and asked to tick)
  • Is there any threat to the ecosystem ? Yes / No -------
  • If yes, what ? and how ? ------- Suggest few remedial measures -------

Answer: Students Activity

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