Haryana State Board HBSE 10th Class Science Solutions Chapter 15 Our Environment Textbook Exercise Questions and Answers.
Haryana Board 10th Class Science Solutions Chapter 15 Our Environment
HBSE 10th Class 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
Answer:
(a) (c) and (d) are all biodegradable items.
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
Answer:
(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
Answer:
(d) All of the above
Question 4.
What will happen if we kill all the organisms in one trophic level?
Answer:
Nature has created a finely balanced ecosystem with right proportion of individuals at each trophic level.
1. If all the organisms of one trophic level are killed the organisms in the next level would also die out of starving. This will in turn affect other levels too.
2. The number of individuals in the lower trophic level will rise drastically because there would be no one to feed on them.
3. Thus, by killing all the organisms in any one trophic level would imbalance the entire 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?
Answer:
1. Removing all the organisms of a trophic level will have the same impact as removing any other organism completely from any other trophic level.
Example: Grass → Grasshopper → Frog → Snake
2. In the above example, whether you remove grasshopper or remove frog completely, both will have same impact on the balance of ecosystem because the next level individuals will starve to death.
Question 6.
What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Answer:
1. Pesticides and other chemicals are sprinkled on crops to protect them from diseases or pests.
2. There is no control over the amount of pesticides used. Hence, gradually, with the passage of time, the amount of these chemicals increase in the soil and water bodies.
3. The pesticides then enter the body of plants through soil or water.
4. Later, when herbivores consume these plants, pesticides enter their bodies too; and when carnivores eat affected herbivores, the pesticides enter the bodies of carnivores too.
5. These pesticides and other harmful chemicals are not degradable. So they get accumulated at each trophic level of a food chain.
6. This phenomenon of progressive accumulation of pesticides at each level in a food chain is called biological magnification.
7. Humans occupy the top level of any food chain. Hence, the maximum concentration of these chemicals get accumulated in human bodies.
Question 7.
What are the problems caused by the non-biodegradable wastes that we generate?
Answer:
- The non-biodegradable waste is inert and so it does not break down into simpler forms. Hence, such waste keeps on accumulating in the nature.
- Accumulation of such wastes pollutes soil, air and water.
- It also leads to increased level of bio-magnification.
Question 8.
If all the waste we generate is biodegradable, will this have no impact on the environment?
Answer:
If all the generated waste is biodegradable and if the authorities properly manage for its disposal or recycle, it will not cause any harmful 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?
Answer:
1. Ozone layer protects us from harmful UV rays.
2. If the ozone layer gets damaged, the UV radiations will fall directly on the earth and cause several diseases.
3. Diseases such as skin cancer, cataract, etc. would be rampant.
4. To reduce the damage to the ozone layer, use of CFC has been minimized.
5. In this regard, In 1987, the United Nations Environment Programme (UNEP) successfully got an agreement done to freeze CFC production at the base year level of 1986.
HBSE 10th Class Science Our Environment InText Activity Questions and Answers
Textbook Page no – 257
Question 1.
Why are some substances biodegradable and some non-biodegradable?
Answer:
Many substances are such that they get broken down into simpler substances by decomposers like bacteria and fungi present in the environment. Hence they get classified as biodegradable substances. However, several substances are such which the decomposers cannot convert into simpler substances. As a result, such substances remain in the environment and get termed as non-biodegradable substances.
Question 2.
Give any two ways in which biodegradable substances would affect the environment.
Answer:
(i) Presence of biodegradable substances would pollute the environment and also cause foul smell.
(ii) The location where biodegradable substances are present becomes breeding centre for insects, flies, mosquitoes, etc.
Question 3.
Give any two rays in which non-biodegradable substances would affect the environment.
Answer:
(i) The non-biodegradable substances remain present in the environment and cause pollution.
(ii) These substances remain in the environment and so enters into the ecosystem leading to death and diseases in plants, animals and humans.
Textbook Page no – 261
Question 1.
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
Answer:
1. No living organism is independent.
2. Each organism has to depend on other for its food requirement. Thus, organisms form a chain in which they depend on other for their food. This is termed as food chain.
3. Each step or level of a food chain forms a trophic leveL
4. The producers form the first trophic level, the herbivores form the second and the carnivores form the third level.
An example of food chain has been given below:
Grass → Insects → Grasshopper → Rats → Snakes → Hawks
5. A food chain generally starts with primary producers and ends with carnivores.
6. The autotrophs or the producers are at the first trophic level. They produce energy for themselves.
7. The autotrophs are consumed by herbivores i.e. the primary consumers. The carnivores (the secondary consumers) consume herbivores.
8. This way, the producers are at the first trophic level, the primary consumers (herbivores) at second, small carnivores i.e. secondary consumers at the third level and large carnivores or tertiary consumers at the fourth trophic level.
Question 2.
What Is the role of decomposers In the ecosystem?
Answer:
Decomposers and transformers:
- Decomposers are the last type of consumers.
- The decomposers obtain their food by decomposing dead bodies of plants and animals.
- The decomposers convert complex organic matter into simple organic constituents and then transform these constituents into inorganic ones and consume them as food.
Textbook Page no – 264
Question 1.
What is ozone and how does it affect any ecosystem?
Answer:
1. Ozone (O3) is a type of gas formed by three oxygen atoms.
2. Ozone is a deadly poisonous gas, however it helps us too.
3. Ozone gas forms a layer of protective shield. This layer prevents the damage to living organisms from the harmful ultraviolet radiations.
Question 2.
How can you help in reducing the problem of waste disposal? Give any two methods.
(1) Minimizing the use of such substances which are not biodegradable.
(2) Avoiding use of disposable items such as disposable crock&y, disposable pen, razors, etc. and produce such products which can be re-used.
Activities
Activity 1.
1. Collect waste material from your homes. This could include all the waste generated during the day, like kitchen waste (spoilt food, vegetables peels, used tea leaves, milk packets and empty cartoons), waste paper, empty medicine bottles/strips/bubble packs, old and torn 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 at 15 days intervals.
Question 1.
What are the materials that remain unchanged over long periods of time?
Answer:
Materials such as plastic bags, broken melamine crockery, empty cartons, etc. are all non-biodegradable and hence remain unchanged for very long period.
Question 2.
What are the materials which change their form and structure over time?
Answer:
Biodegradable material such as left over food, fruit and vegetable peel, used tea leaves, newspaper etc. change their form and structure over time.
Question 3.
Of the materials that are changed, which one changes the tastest?
Answer:
Materials such as fruit and vegetable peel, tea-leaves and rotten food change their form quite fast.
Activity 2.
Use the library or internet to find out more about biodegradable and non-biodegradable substances.
Question 1.
How long are various non-biodegradable substances expected to last in our environment?
Answer:
Non-biodegradable substances remain present en the environment ranging from few to several decades as well as centuries.
Question 2.
These days, new types of plastics which are said to be biodegradable are available. Find out more about such materials and whether they do or do not harm the environment.
Answer:
Students need to find out answer for this question on their own.
Activity 3.
You might have seen an aquarium. Let us try to design one. An aquarium is an example of a human made eco-system.
Question 1.
What are the things that we need to keep in mind when we create an aquarium?
Answer:
An aquarium is a small and artificial ecosystem. So, it does not have sufficient amount of decomposers to clean the waste and dirt created. Hence, we need to clean the aquarium after few days.
Question 2.
If we add a few aquatic plants and animals it can become a self-sustaining system. Can you think how this happens?
Answer:
Aquatic plants are producers. They will make their own food through the available light and grow.
This food will be then available to herbivore fishes. This is how the food chain will be formed.
Question 3.
Can we leave the aquarium as such after we set it up? Why does It have to be cleaned once in a while? Do we have to clean ponds or lakes in the same manner? Why or why not?
Answer:
Ponds and lakes are natural entities. They get sufficient sunlight and atmospheric gases. Also, there are several decomposers and transformers in very large number in waste generated in the water bodies.
Activity 4.
Question 1.
While creating an aquarium did you take care not to put an aquatic animal which would eat others? What would have happened otherwise?
Answer:
If we put a carnivore fish, it would eat other herbivore fish of the aquarium. Since the aquarium is not a natural habitat, new fishes would not generate on their own. This would kill the aquarium ecosystem soon.
Question 2.
Make groups and discuss how each of the above groups of organisms is dependent on each other.
Answer:
In the aquarium, plants produce food which will be eaten by herbivores. The carnivores will eat herbivores. When any of these entities dies or releases waste, the decomposers will convert all such material into simpler substances. This simple substance will again be used by the plants to grow and the cycle will continue.
Question 3.
Write the aquatic organisms in order of who eats whom and form a chain of at least three steps.
Answer:
Question 4.
Would you consider any one group of organisms to be of primary importance? Why or why not?
Answer:
All groups of organisms are almost equally important because each group plays its unique role in maintaining the ecosystem.
Activity 5 to Activity 10.
To be done by students on their own.