Gujarat Board Textbook Solutions Class 10 Science Chapter 15 Our Environment

Gujarat Board Textbook Solutions Class 10 Science Chapter 15 Our Environment

GSEB Solutions Class 10 Science Chapter 15 Our Environment

Gujarat Board Class 10 Science Our Environment Textbook Questions and Answers

Question 1. Which of the following groups contain only biodegradable items?
(a) Grass, flowers and leather
(b) Grass, wood and plastic
(c) Fruit-peels, cake and lime-juice
(d) Cake, wood and grass
(a), (c) and (d).

Question 2.  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
(b) Grass, goat and human

Question 3. Which of the following are environment-friendly practices?
(a) Carrying cloth-bags to put purchases in while shopping
(b) Switching off unnecessary lights and fans
(c) Walking to school instead of getting your mother to drop you on her scooter
(d) All of the above
(d) All of the above

Question 4. What will happen if we kill all the organisms in one trophic level?
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 thereby disturbing the ecosystem.

Question 5. 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?
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 → Grasshopper → Frog → Snake → Peacock
In this if all grasshoppers are killed/removed, frogs will starve and grass will reproduce in abundance. If snakes are removed, then the number of frogs will increase which will disturb the entire ecosystem.

Question 6. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
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 7. What are the problems caused by the non-biodegradable waste that we generate?

  1. As the non-biodegradable waste cannot be broken down into simpler forms hence they keep on accumulating in nature causing pollution.
  2. They cause diseases.
  3. It also causes biological magnification.

Question 8. If all the waste we generate is bio-degradable, will this have no impact on the environment?
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 9. Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
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 CFC production in 1986.

CFC – Chlorofluorocarbons used as refrigerants and in fire extinguishers.

Gujarat Board Class 10 Science Our Environment Additional Important Questions and Answers

Very Short Answer Type Questions

Question 1. Name any two groups of producers.
Plants and blue-green algae.

Question 2. Name two decomposers.
Bacteria and fungi

Question 3. Write the two raw materials for making food, used by living organisms of first tropic level.
CO2 and Water

Question 4. Which component of sunlight is used for the formation of ozone?
Ultraviolet radiation.

Question 5. Name 4 abiotic components of any ecosystem.
Temperature, rainfall, wind, soil.

Question 6.
Name two natural ecosystem.
Pond ecosystem and forest ecosystem.

Question 7.
Name two artificial ecosystem.
Garden and crop-field.

Question 8.
What are consumers in the food chain?
Those organisms which consume the food produced either directly from producers or indirectly by feeding on other organisms are called consumers.

Question 9.
Name the natural cleansing agent in an ecosystem.
Decomposers, scavengers

Question 10.
Expand UNEP
United Nations Environment Programme.

Question 11.
Define biological magnification.
The accumulation of chemicals in the bodies of the organism that belongs to the top most tropic level is called biological magnification.

Question 12.
What is bad Ozone?
Ozone at ground level is deadly poisonous and is called as bad Ozone.

Short Answer Type Questions

Question 1.
Why is plastic bag called non-biodegradable while paper is not?
Plastic bag is not acted upon by decomposers as it cannot be broken down into simple components, so it is called non-biodegradable while paper gets decomposed.

Question 2.
Differentiate between natural and artificial ecosystem.
Natural ecosystem:

  • Naturally occurring ecosystem.
  • Example: pond, grassland, forest

Artificial ecosystem:

  • These are man-made ecosystem.
  • Example: garden, aquarium, crop-field.

Question 3.
Pesticides are useful to farmers yet considered as pollutants. Give reasons.
Pesticides kill insects and pests thereby protecting the crops but these pesticides remain on the crops which enter the food chain and gets accumulated in the organisms and reaches the topmost trophic level that causes diseases. When washed away by rain, it causes pollution of water.

Question 4.
Describe the ozone layer pressence in stratosphere.
Ozone layer is also known as stratosphere. When ultraviolet radiations act on oxygen, the oxygen gets converted into ozone.

Ozone layer works like a protective shield for living beings. The ozone layers wards off harmful ultraviolet radiations from the sun.

Question 5.
Explain how the energy transfer takes place through a food chain.
Different levels in the food chain are called trophic level. Out of the energy consumed by an organism at a particular trophic level, 90% is utilized by an organism for its own need and rest 10% is left for the organism of the next trophic level. So, very little energy is left for the next level organism. For example : a green plant makes 100% energy in the form of chemical energy. 90% of this energy is utilized for its own purpose and only 10% of energy is left for the primary consumer.

Now, primary consumer shall also utilize 90% of energy which was consumed by it and transfer the 10% to next level, this would leave just 1% energy for the secondary consumer. Hence the tertiary consumer would get just 0.1% of energy which was originally made by the green plant. This is the reason that there can be just one or two organisms at the top of the food pyramid.

Question 6.
Discuss the role of UNEP in controlling the level of CFC release.
In 1987, the UNEP (United Nations Environment Programme) succeeded in forging an agreement among different nations to freeze the CFC production at 1986. Later, an agreement was signed among different nations to phase out CFCs. It is important to note that CFC is used in refrigerators and aerosol spray.

It is due to the efforts by the United Nations and different environmentalists, the CFC emission has been put under some control. To mark the importance of ozone every year, 16th September is celebrated as Ozone Day.

Question 7.
Study the given flow chart and answer the below given questions.

(a) (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?

(b) (i) Calculate X in the flow chart.
(ii) Calculate Y on the flow chart.

(c) Label the above box on flow chart.
(i) Light (or solar) energy
(ii) Chemical energy

(b) (i) 1200 units

(c) Decomposers like bacteria or fungi.

Question 8.
Today it is very important to conserve our environment and the species. Discusss the need for conserving species.
Many species of animals and plants are in danger of extinction, due to factors such as habitat destruction, the introduction of other species, international trade and pollution. Loss of a species also means that its genes are lost which may be important in the future for genetic engineering (e.g. to improve crops) and the production of useful chemicals such as medicines. The species also play an important role in a food chain and its loss could endanger other species.

Question 9.
Discuss the need and ways for conserving the habitat for the organisms.
If habitat is lost the species that live in them also moves towards extinction. The habitat destruction poses the greatest threat to the survival of species. A habitat maybe conserved by:

  1. Using laws to protect the habitat
  2. Stakeholders playing an important role to protect the habitat
  3. Reducing or controlling public access to the habitat
  4. Controlling factors, such as water drainage and grazing, that may otherwise contribute to destruction of the habitat.

Question 10.
Why decomposers are necessary in environment?
Decomposers act on all biodegradable substances and break them into simple inorganic materials and maintain the balance of materials in the ecosystem and cleanse the environment.

Question 11.
Give one advantage and one disadvantage of Ozone.
Advantage of Ozone – When it is in the stratosphere it does not allow the ultraviolet radiations to reach the earth, as UV radiations cause skin cancer and cataract.

Disadvantage of ozone – On ground level ozone is poisonous gas.

Question 12.
Give one example of grassland ecosystem and one example of pond ecosystem.

  • Grass land Ecosystem: Grass → grasshopper → frog → snake → Peacock.
  • Pond Ecosystem : Blue – green algae → small fish → big fish → birds

Question 13.
Energy flow in a food chain is unidirectional. Explain.
The energy from the sun flows into autotrophs and it passes to herbivores and then to carnivores. The energy does not revert from autotrophs to the solar input or from herbivores back to autotrophs. Hence the flow is unidirectional.

Question 14.
State different types of consumers in art ecosystem.
The consumers are herbivores, carnivores, omnivores, parasites, saprophytes and decomposers.

Question 15.
Differentiate between biodegradable and non biodegradable substances.
Biodegradable -These substances can be broken down by the action of saprotrophs and other agents, example : paper, cloth.

Non-biodegradable – These substances cannot be broken down by the action of saprotrophs, example : glass, plastics.

Question 16.
Define an ecosystem. Explain in detail about its various components.
Ecosystem is defined as a well defined unit or area in an environment where biotic and abiotic components interact with each other to maintain balance in nature.

  • Biotic components – producers, consumers, saprotrophs.
  • Abiotic components – air, water, sunlight.

Question 17.
What is a food chain? List its characteristic features.
Food chain is defined as the phenomenon of transfer of energy through series of organisms falling on successive trophic levels.
Example: Sun is the ultimate source of energy. Producers or green plants photosynthesize and utilize solar energy. Thereafter, the energy is transferred to other successive levels. Food chain can be depicted as follows:

Plants → grasshopper → frog → snake → decomposers

Question 18.
What is biological magnification?
The accumulation of chemicals in the bodies of the organism that belongs to the top most tropic level is called biological magnification. As human beings occupy highest trophic level its maximum concentration was found in human beings only, which resulted in neurological disorders due to damaging of CNS (Central Nervous System).

Question 19.
How is ozone layer important to us?
Ozone is a pollutant at lower level of atmosphere but is very useful in shielding harmful UV rays. This layer is present in the stratosphere. In absence of ozone layer heavy damage to organism may occur example : skin cancer, cataract etc.

Question 20.
What is causing the damage to ozone layer?
The CFC emission due to various industrial activities has caused damage to the Ozone layer and has contributed to global warming by allowing a major portion of UV rays to reach the earth’s atmosphere through ozone holes.

Question 21.
What are the problems caused by the non-biodegradable waste that we generate?
Non-biodegradable waste doesn’t decompose under the action of bacteria and other microorganisms.

  1. When these substances, example : polythene, plastics are buried under soil render that area barren and leads to soil pollution.
  2. These wastes don’t bum completely in presence of oxygen and release toxic gases which causes air pollution.
  3. The substances may be harmful on accumulating in food chain like DDT due to biomagnification.

Question 22.
Why is damage to ozone layer a cause for concern? What steps are being taken to limit this damage?
Ozone layer doesn’t allow harmful ultraviolet rays of the sun to reach the earth’s surface. In order to stop further depletion of ozone layer we must scale down the use of CFC’s in form of aerosols, refrigerants etc and check their release in the atmosphere. Moreover, stress should be laid on using eco-friendly techniques and proper disposal of toxic material.

Long Answer Type Questions

Question 1.
Enlist various categories of consumers giving examples of each.
The various categories of consumers are:

  • Herbivores – Grass eating animals, example : deer, rabbit.
  • Carnivores – Flesh eating animals, example : tiger, lion.
  • Omnivores – Animals that eat both plants and other small animals i.e., flesh example : crow, human being.
  • Parasites – Those organisms which depend on other living organisms and harm them for food, example : lice, tapeworm.
  • Saprophytes – Organisms that depend on dead and decaying matter for their food, example : fungi, bacteria.

Question 2.
What three informations are obtained from the energy flow diagrams?
The information we get are:
(i) The energy flow is unidirectional, it flows from Sun → autotrophs → herbivores → carnivores → decomposers

(ii) The flow of energy is 10% i.e., 90% of the energy is used by a given level of food chain for metabolic activities.

(iii) The unwanted chemicals like pesticides gets accumulated in the highest organism in the food chain.

  1. Why is it necessary to conserve our environment?
  2. State the importance of green and blue dustbins in the safe disposal of the household waste.
  3. List two values exhibited by your classmate who is an active member of Eco¬club of your school.

Question 3.
Explain the interlink of biotic and abiotic factors in any ecosystem.
In an ecosystem biotic and abiotic factors are interdependent and interlinked.

For example : The grass in grassland will grow only if it gets soil which can hold water and gets sunlight with proper temperature hence the grass grows in a place which has all abiotic factors responsible for its growth but in desert these abiotic factors are not available for the growth of grass.

Question 4.
Explain the formation of ozone layer and its importance.
Ozone is formed when high energy ultraviolet radiations split oxygen molecule into oxygen atoms. The oxygen atom combines with oxygen molecules to form a new molecules with three oxygen atoms named ozone.

Importance of Ozone: It is very protective when present in stratosphere it does not allow the harmful ultraviolet radiations to enter the earth’s surface which can cause skin cancer in human beings.

Question 5.
What is biological magnification? Explain giving one example.
The accumulation of chemicals in the top most organism of the trophic level or food chain is called biological magnification.

Example : Farmer sprays pesticides on. the crops which enters the food chain, from crops these pesticides enter into the organisms that feed on it.
grass → grasshopper → frog → snake → hawk
In this food chain the maximum amount of pesticide will be found in the top most organism i.e., in hawk the chemical keeps accumulating.

Question 6.
What are decomposers? How are they important for the ecosystem?
Decomposers are the organisms which act on dead organisms to decompose the body so as to release all the elements back to nature. They act as cleansing agents, hence they are important in the ecosystem.

Question 7.
What is the importance of ozone in the environment? Why is it depleting? What precautions are taken to preserve it?
Ozone is present in the stratosphere. It protects the earth from harmful ultraviolet radiations. UV ray causes various diseases to organisms e.g. skin cancer, cataract in human beings.

Ozone layer is depleting because of chlorides and fluorides. They act on ozone molecules and deplete it. Chlorides, fluorides are present in CFC’s which are used in refrigerants and fire extinguishers.
CFC → Chlorofluorocarbon
The precautions taken to preserve the ozone layer is to ban the use of CFC’s.

Question 8.
What are food-chains and food webs? Why are smaller food chains better? What is 10% flow?
Food chain – The flow of food from sun to autotrophs, from autotrophs to herbivores and from herbivores to carnivores is called food chain. A food chain can have two levels or five to six levels also.

Food web – When an organism is eaten by two or more other kinds of organisms, instead of straight chain an interlinked chain is formed, is termed as food web.

Smaller the food chain, the energy available for the next level of consumer in such a chain is more. As the loss of energy at each step takes place and very little energy is left after four trophic levels.

The green plants in terrestrial ecosystem capture about 1% of the sun’s energy and convert it into food energy. When green plants are eaten by primary consumers a great deal of energy is lost for the life processes and only 10% of the energy is available for the next level of consumers.

Gujarat Board Class 10 Science Our Environment InText Questions and Answers

Question 1. What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
The various levels or stages in a food chain at which the transfer of food takes place is called trophic level, example food chain.
Grass → Grasshopper → frog → snake → peacock
Grass → Producer → 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 2. What is the role of decomposers in the ecosystem?
Decomposers break down 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 3. Why are some substances biodegradable and some non-biodegradable?
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 4. Give any two ways in which bio-degradable substances would affect the environment.
Two ways in which bio-degradable substances would affect the environment are:

  • During decomposition of the substances lot of foul smell spreads in the surrounding areas.
  • 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 5. Give any two ways in which non-biodegradable substances would affect the environment.

  • 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.
  • These substances due to accumulation cause water and soil pollution. example pesticides, detergents, polythene.

Question 6. What is ozone and how does it affect any ecosystem?
Ozone is a molecule of oxygen with 3 atoms. Its formula is 03. The ultraviolet radiations split oxygen into free oxygen atoms. These atoms combine with oxygen molecules to form ozone.

Ozone in Ecosystem:
At ground level, ozone is poisonous but at higher level it is very useful as it protects all living organisms from harmful UV radiations of the sun. It doesn’t allow the ultra violet radiations to enter the surface of earth. The UV radiations cause ionizing effect that leads to skin cancer in human beings.

Question 7. How can you help in reducing the problem of waste disposal? Give any two methods.
To reduce the problem of waste disposal we can –

  1. Segregate the bio-degradable waste from non-biodegradable waste before dumping it.
  2. Remove all materials which can be recycled and send it for recycling, example paper, glass, metal, rubber.

In-Text Activities Solved

Activity 15.1
Design aquarium:

  1. Things required for making an aquarium are a big jar of glass, water, oxygen, food, algae.
  2. We can provide oxygen through an oxygen pump (aerator) and fish food from market.
  3. On adding a few aquatic plants and animals it can become a self-sustaining system.
  4. Aquarium is a self-sustaining man-made ecosystem.
  5. The aquarium cannot be left as it is. It needs to be cleaned once in a while.

We need not clean the ponds or lakes in the same manner because it contains decomposers, as they break down the complex organic substances into
simple inorganic substance.

Activity 15.2
While creating an aquarium, care need to be taken not to put any aquatic animal which would eat others. If kept, all small animals would be eaten by big animals
In Pond/Lakes/River.

Yes, the group producers are of primary importance as they are the ultimate producers for all trophic level.

Activity 15.3

  1. Pesticides sprayed on farms to protect the crops from pests enter the grains and when consumed by consumers from one tropic level to the other. It gets accumulated in the highest organism.
  2. To reduce the intake of pesticide we must use the pesticides judiciously on crop plants. We should use alternate biological method to control pests.

Activity 15.4
Chemicals responsible for depletion of ozone layer is CFC (Chlorofluorocarbons). The regulations put in place to control the emission of these chemicals have succeeded in reducing the damage to the ozone layer. The size of the ozone layer has become smaller in the recent years.

Activity 15.5
1. Collect waste materials from your homes. This could include all the waste generated during a day, like kitchen waste (spoilt food, vegetable peels, used tea leaves, milk packets and empty cartons) waste paper, empty medicine bottles/strips/bubble packs, old and tom clothes and broken footwear.

2. Bury this material in a pit in the school garden or if there is no space available, you can collect the material in an old bucket/flower pot and cover with at least 15 cm of soil.

3. Keep this material moist and observe after every 15 days.

Question a.
What are the materials that remain unchanged over long periods of time?
The materials that remain unchanged over long periods of time are empty medicine bottles, bubble packs, milk packets, broken footwear.

Question b.
What are the materials which change their form and structure over time?
The materials that change their form are rubber, food, vegetable peels, used tea leaves, empty cartons, waste paper, old and tom clothes, broken footwear if made of leather.

Question c.
Of these materials that are changed, which ones change the fastest?
Out of these the materials that are changed very fast are vegetable peels, used tea leaves and spoilt food.

Activity 15.6

  1. Substances that are broken down by biological processes are said to be biodegradable. For example, kitchen waste, vegetables and fruits waste, etc.
  2. Substances that cannot be broken down by biological processes are said to be non- biodegradable. For example, plastic botdes, polythene bags, etc.
  3. Some of the non-biodegradable substances are expected to last for hundreds of years without undergoing any changes.
  4. Biodegradable plastics made with plant based material is available in market. But these plastics also require specific time and condition to biodegrade properly.
  5. So if it is not used judiciously and properly it can also cause havoc which may be more than the conventional plastics.

Activity 15.7
1. Waste generated at home is collected and thrown in garbage house. Here the segregation of biodegradable and non-biodegradable materials takes place. All substances that can be recycled are segregated and sent for recycling. Those substances Which cannot be recycled are kept in the garbage house.

2. Municipal corporation deals with this waste by collecting it and sending it for recycling and decomposing the bio-degradable waste and by land filling with those waste items which cannot be recycled nor are biodegradable. All research work at class and house level will be conducted by the student to get the answers.

3. 15.8 and 15.9 – All research work at class and house level will be conducted by the student to get the answers.

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