Class 10 Science Chapter 15 Our Environment The answer to each chapter is provided in the list so that you can easily browse throughout different chapters NCERT Class 10 Science Chapter 15 Our Environment and select need one.
Class 10 Science Chapter 15 Our Environment
Also, you can read the SCERT book online in these sections Solutions by Expert Teachers as per SCERT (CBSE) Book guidelines. These solutions are part of SCERT All Subject Solutions. Here we have given Assam Board Class 10 Science Chapter 15 Our Environment Solutions for All Subjects, You can practice these here…
Our Environment
Chapter – 15
GENERAL SCIENCE
TEXTUAL QUESTIONS AND ANSWERS
Page no – 257
Q.1. Why are some substances biodegradable and some non- biodegradable?
Ans :- Many human made materials like plastics will not be broken down by the action of bacteria or other saprophytes. These materials will be acted upon by physical process like heat and pressure, but under the ambient conditions found in our environment, these persist for a long time. Substances that are broken down by biological 1. processes are said to be biodegradable substances that are not broken down in this manner are said to be non-biodegradable.
Q.2. Give any two ways in which biodegradable substances would affect the environment.
Ans :- ( i ) The biodegradable substances become pollutants when that are present in large quantities and are not degraded at right time due to any reason.
( ii ) Biodegradable substances carries many diseases such as cholera.
Q.3. Give any two ways in which non-biodegradable substances would affect the environment.
Ans :- ( i ) Non-biodegradable substances can not degrade and return the minerals to the environment. They pile up and cause harm to the various members of the ecosystem.
( ii ) They may cause biomagnification in the food chain and end up in humans.
Page – 261
Q.1. What are trophic levels? Give an example of a good chain and state the different trophic levels in it.
Ans :- Trophic level is the fundamental level occupied by an organism in food chain. Trophic literally means feeding, so trophic levels are the levels or positions at which species feed. Examples of trophic Levels include ‘herbivores’ and ‘decomposers’
An example of a food chain depicting various trophic levels is as follows :-
3rd level carnivore Eagle
↑ ↑
2nd level carnivore Snake
↑ ↑
1st level carnivore Frog
↑ ↑
Herbivore Grasshopper
↑ ↑
Producers Grass
Q.2. What is the role of decomposers in an ecosystem?
Ans :- Decomposers are microorganisms comprising of bacteria and fungi that breakdown the dead remains and waste products of organisms. They break down the complex organic substances into simple inorganic substances that go into the soil and are used up once mor by the plants.
Page – 264
Q.1. What is ozone and how does it affect any ecosystem?
Ans :- Ozone is a molecule formed by three atoms of oxygen. Ozone is a deadly poison. However, at the higher levels of the atmosphere, ozone performs an essential function. It shields the sunface of the earth from ultraviolet radiation from the sun. This radiation is highly damaging to organisms, for example, it is known to cause skin cancer in human beings.
Q.2. How can you help in reducing the problem of waste disposal? Give any two methods.
Ans :- ( i ) Minimizing the use of non-biodegradable wastes.
( ii ) Production of compost, bio gas from biodegradable wastes.
EXERCISES
Q.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.
Ans :- ( c ) fruit-peels, cake and lime-juice.
Q.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.
Ans :- ( b ) Grass, goat and human.
Q.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.
Ans :- ( d ) All of the above.
Q.4. What will happen if we kill all the organisms in one trophic level?
Ans :- If we kill all the organisms in one trophic level then transfer of food to the next trophic level will stop due to which the organisms of next trophic level will starve and die or migrate to other areas. The killing of all the organisms in one trophic level will also lead to the overpopulation of organisms in the previous trophic level. These effects will cause an imbalance in the ecosystem.
Q.5. Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can the Jun organisms of any trophic level be removed without causing any damage to the ecosystem?
Ans :- Yes, the impact of removing all the organisms in a trophic level will be different for different trophic levels. For example in the food chain : Grass → Deer → Lion :
If we remove all the Lion at the third trophic level, then the number of deer will increase too much. All these deer will eat up all the grass and other plants turning the forest into a desert.
If we remove all the deer at the second trophic level, then lions will not get sufficient food, they will starve and die. Deer eat grass and other green plants, so the amount of grass and other green plants will increase too much.
All the organisms of my trophic level cannot be removed without causing any damage to the ecosystem.
Q.6. What is biological magnification? Will the level of this magnification be different at different levels of the y ecosystem?
Ans :- Biological Magnification is a phenomenon which explains the increasing concentration of harmful chemicals like DDT with each increase in trophic level. From the soil the chemicals are absorbed by the plants. The primary consumers eat these plants and the harmful chemicals come to reside in their bodies. As these chemicals are not degradable, they accumulate in the bodies of the organisms and the top level of the food chain gets the highest concentration of these harmful chemicals.
Most of the plants products which we eat are grown in fields in which pesticides and fertilisers have been used. These are absorbed by the plants and cannot be removed by washing or other means. As humans are at the top level of the food chain these chemicals get accumulated in our bodies and cause various disorders.
The level of biological magnification is different for different trophic levels of an eco system.
Q.7. What are the problems caused by the non-biodegradable wastes that we generate?
Ans :- The non-biodegradable wastes cannot be made less toxic easily, so they cause a lot of problems for us as well as environment. For example some of the non-biodegradable wastes enter the food chain of humans. These non-biodegradable wastes get concentrated in human beings and damage their health in the long run.
The excessive use of non-biodegradable fertilisers in agriculture makes the soil either too much acidic or too much alkaline. When the soil becomes too acidic or too alkaline the crop yields is reduced.
Q.8. If all the waste we generate is biodegradable, will this have no impact on the environment?
Ans :- Even if all the waste we generate is biodegradable, it will have an impact on the environment. This is because too much biodegradable waste can not be broken down into harmless simpler substances by the decomposes like micro-organisms at the right time.
Q.9. Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Ans :- Ozone layer is very important for the existence of life an earth because it absorbs most of the harmful ultraviolet radiations coming from the sun and prevents them from reaching the earth. The ultraviolet radiations have extremely harmful effects on human beings, Other animals as well as plants. Ultraviolet rays can cause skin cancer. Ultraviolet rays damage immune system by lowering the body’s resistance to diseases. Thus, it is the ozone layer in the upper atmosphere which protects us from these diseases by absorbing ultraviolet rays coming from the sun.
Main pollutants responsible for the threat to ozone layer are CFCS which are found in air conditioners and refrigeration, as clearing solvents, aerosol propellants, ion foam insulation and in certain fire extinguishers. In 1987, the United Nations Environment Program succeeded in forgoing and agreement to freeze CFC production at 1986 level.
Additional Questions
Very short answers type questions
Q.1. What is the functional unit of the environment comprising of the living and nonliving components called?
Ans :- Ecosystem.
Q.2. Name two biodegradable waste.
Ans :- ( i ) Cattle dung.
( ii ) Compost.
Q.3. Name two non-biodegradable waste.
Ans :- ( i ) D.D.T.
( ii ) Plastics.
Q.4. Write four examples of ecosystem.
Ans :- ( i ) A grassland.
( ii ) A forest.
( iii ) A desert.
( iv ) A river.
Q.5. Write two examples of artificial ecosystem.
Ans :- ( i ) Crop-fields.
( ii ) Aquarium.
Q.6. Name two natural ecosystem.
Ans :- ( i ) A forest.
( ii ) A river.
Q.7. Which one of the following is not a terrestrial ecosystem?
( a ) Forest.
( b ) Grassland.
( c ) Aquarium.
( d ) Desert.
Ans :- ( c ) Aquarium.
Q.8. State whether the following statements are true or false :
( a ) In biology, human beings are called producers.
( b ) Secondary consumers and tertiary consumers, both are carnivores.
Ans :- ( a ) False.
( b ) True.
Q.9. Which of the following belong to the same trophic level?
( a ) Goat.
( b ) Spider.
( c ) Plants.
( d ) Hawk.
( e ) Rat.
Ans :- ( a ) Goat and ( e ) Rat.
Q.10. Which of the following belong to the same trophic level?
( a ) Tree.
( b ) Frog.
( c ) Snake.
( d ) Grass.
( e ) Lizard.
Ans :- ( a ) Tree and ( d ) Grass.
Q.11. Name the organisms belonging to the second and the fourth trophic levels in the food chain comprising the following :
( a ) Frogs.
( b ) Plants.
( c ) Snakes.
( d ) Hawks.
( e ) Insects.
Ans :- Second trophic level :- Insects
Fourth trophic level : -Snakes.
Q.12. In a food chain consisting of grass, frog, bird and insects, where will the concentration of the harmful chemicals be maximum?
Ans :- Bird.
Q.13. If a harmful chemical enters a food chain comprising cat, mice and plants, which one of these organisms is likely to have the maximum concentration of the harmful chemical in its body?
Ans :- Cat.
Q.14. Name two waste materials which can be recycled.
Ans :- Paper and plastics.
Q.15. If 5 joules of energy is available at producer level (plants) then how much energy will be transferred to the lion in the following food chain? Plants → Goat → Lion
Ans :- 0.05J
Q.16. Where does all the energy in living organisms originate from?
Ans :- Sun.
Q.17. Name two predators of snakes in a food web operating in a forest ecosystem?
Ans :- Peacock and Hawk.
Q.18. Which one term in the following includes the others? air, flora, fauna, environment, water, sunlight, soil.
Ans :- Environment.
Q.19. A food chain represents a unidirectional flow of X. What is X?
Ans :- Energy.
Q.20. Name the pigment which is essential for trapping of solar energy.
Ans :- Chlorophyll.
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