NCERT solution for class 10th //Science //Chapter 15 - Our environment

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NCERT solution for class 10th //Science //Chapter 15 - Our environment 

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Q1. What are trophic levels give an example of a food chain and state the different trophic levels in it ? 

Answer .-The transfer of food or energy takes place through various levels in a food chain . Which are known as trophic level

ex. Plants →  Grasshopper   →    Frog    →     Snake      →     Hawk 

1st Trophic level   → 2nd Trophic level → 3rd  Trophic level →4th  Trophic level  → 5thTrophic level

Q2. What is the role of decomposers in the ecosystem ? 

Answer - Organisms are depend on dead plants and animals for their nutrition is called decomposers Ex . Bacteria , fungi etc. They break down the complex food component into simple one and released into the soil and environment so they are recycling of  the materials . They also clean our surrounding 

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Q3. Why are some substances biodegradable and some non biodegradable ? 

Answer - Some complex substances are easily converted into simple one with the help of micro-organisms found in soil or atmosphere hence are biodegradable substance Ex . paper , wood etc. 

While some substance can not degraded by the action of enzymes and micro- organisms thus are called non biodegradable ex. Plastic , glass etc. 

Q 4  . Give any two ways in which biodegradable substances would affect  the environment ? 

Answer -   The two ways in which biodegradable substances would affect  the environment are 

        1. during the process of degradation some gases are released .It may cause pollution 

        2. In degradation process temperature  of the substance so it is a good condition for breeding moths and mosquitos and they causing diseases 

Q5 . Give any two ways in which non biodegradable substances would affect the environment ? 

Answer - The  two ways in which non biodegradable substances would affect the environment are

• They make environment  unfit to survival of other living beings 
• They create obstacles to transfer of energy and minerals in the ecosystem  

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Q6. What is ozone and how does it affect any ecosystem ? 

Answer - Ozone is the triatomic molecules of oxygen O3 is the chemical formula of ozone . It absorbs the ultraviolet rays comes from the sun  These UV rays are very harmful for living beings and can cause diseases to living beings 

Q7. How can you help in reducing the problem of waste disposal give any two methods? 

Answer -  The methods for waste disposal are as fallows 

• Recycling the all waste substance like  plastic , glass , paper etc. 
• Composting biodegradable waste 
• Incineration  - It is a heating of waste at high temperatures to make ash 
• Landfills - solid waste dump into a low laying area and covered with soil

                     Exercise 

Q1. 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  

Answer - Fruit peels ,Cake ,Lime juice

Q2. Which of the following constitutes a food chain 

a) Grass wheat and mango 

b) Grass goat and human 

c) Goat cow and elephant 

d) Grass fish and goat  

Answer - Grass ,goat , human

Q3. 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  

Answer - All the above 

Q4. What will happen if we kill all the organisms in one trophic level ? 

Answer - If we kill all the organism in one trophic level .then the lower trophic level grow more in number and the energy flow will not takes properly 

Q5 .  a) Will the impact of removing all the organisms in a trophic level be different for different trophic levels 

b) Can the organisms of any trophic level be removed with out causing any damage to the ecosystem? 

Answer - a) Yes the impact of removing all the organisms in a trophic level be different for different trophic levels . Producers are more in number so if we removed it . It affect all successive trophic levels. And if we removed upper layer it may increases the number of lower trophic level 

b) No removal of all organisms in one trophic level will disturb the ecosystem . 

Q6. What is biological magnification?  will the level of this magnification be different at different levels of the ecosystem?  

Answer - Biological magnification is to the increase the concentration  of some toxic materials at each successive  trophic level  yes  this magnification be different at different levels of the ecosystem. but it is more in higher trophic levels   

Q7 . What are the problems caused by the non biodegradable waste is that we generate ? 

Answer - The  two ways in which non biodegradable substances would affect the environment are

• They make environment  unfit to survival of other living beings 
• They create obstacles to transfer of energy and minerals in the ecosystem  

Q 8 . If all the waste we generate is biodegradable will this have no impact on the environment?

Answer -  If all the waste we generate is biodegradable then it is good for environment it not accumulate any type of waste in environment . but its degradation process is slow so it cause little air  pollution in environment .

Q9. Why is damage to the ozone layer a cause for concern what steps are being taken to limit this damage ? 

Answer - Ozone layer is present in stratosphere 

It is thin so it called thinning is of ozone layer or depletion of ozone due to it's depletion the harmful U. V.  Rays comes on the earth surface or it may cause skin disease or cancer . To reduce it we should minimize the use of  CFC .