CBSE Class 9 Science Natural Resources assignment Set C

1. The” Biosphere” is the life supporting zone of the earthwith three sub-zones called as lithosphere (rock part), atmosphere (air part)and hydrosphere (water part)

Breath of air
2. Composition of Air

3.The interactions between different components of the Biosphere to maintain the balance between the biotic and a biotic component makes “Biogeochemical cycle”. Ex. Water
Cycle, Nitrogen Cycle, Carbon cycle, Oxygen Cycle,

4. Role of atmosphere in climate control : atmosphere act as protective blanket for the earth. Since atmosphere is a bad conductor of heat, it keeps the average temperature of the
earth constant. At night, it slows down the escape of heat into outer space.

5. The movement of air : the atmosphere gets heated from the radiation that is reflected back by the land or water bodies. As a result of heating, convection currents are set up in
the air. Since land gets heated faster than water, the air over land gets heated faster than air above water bodies.

6. In coastal regions, during the day, the air above the land gets heated faster and starts rising. So a region of low pressure is created and air over sea moves into this area of low
pressure. The movement of air from one region to the other region causes Wind.

7. During the day, the direction of wind would be from the sea to the land and at night, both land and sea starts to cool. Since water cools down slower than the land, the air above
water would be warmer than air above land, thus the direction of wind would be from the land to the sea.

8. Air pollution : it is an undesirable change in the physical, chemical or biological characteristics. It is caused due to an increase in the content of harmful substances (pollutant) such as oxides of nitrogen and sulphur, etc.

9. Harmful effect of air pollution :

• It affects the respiratory system causing breathing difficulties eg; bronchitis, asthma, lung cancer, tuberculosis, etc.
• Burning of fossil fuels like coal and petroleum releases oxides of nitrogen and sulphur. Inhalation of these gases is dangerous.
• Combustion of fossil fuel also increases the amount of suspended particles in air. The presence of high levels of all these pollutants, reduce visibility in cold weather where water also condenses out of air forming smog.
• Acid rain formed from the gases like sulphur dioxide and nitrogen oxides present in polluted air. It causes damage to living and non- living thing.

3. The Water Cycle:

a) The process in which water evaporates and falls on the land as rain and later flows back into the sea via rivers is known as the “Water Cycle”. Water flows through rocks containing soluble minerals, some of them get dissolved in the water. Thus the rivers carry many nutrients from the land to sea and these are used by the marine organisms.

b) When the water vapors condense as water droplets and grow big and heavy, they fall down in the form of “rain”. It ranges from 5 cm to 200 cm of rain fall in a year in our country. In large parts of India, rains are mostly brought by the south-west or north-east monsoons. Depressions in the Bay of Bengal may also cause rains in some areas.

c) Water is a wonder liquid because all cellular processes take place in a water medium; substances are transported in a dissolved form; terrestrial forms require fresh water to maintain the equilibrium of salts; major resource to determine the life on the earth.

d) The dissolved fertilizers (NPK fertilizers), pesticides (DDT), sewage (Disease causing Organisms), waste from factories (Mercury) and water released from the dams can affect the life forms on the earth. The dissolved Oxygen is being used by the animals and plants that live in water, would adversely affect the aquatic organisms. The change in temperature
would be dangerous for the eggs and larvae of the various animals particularly susceptible to temperature changes. It leads to “water pollution”.

4. Nitrogen Cycle:

a) The nitrogen gas makes up 78% of our atmosphere. It is essential for the synthesis of proteins, DNA, RNA, urea, alkaloids and Vitamins.

b) The simple molecular nitrogen from the atmosphere is converted into more complexmolecules in the living beings and back again to atmosphere is called “Nitrogen Cycle”.

i) Nitrogen fixation by Lightening: During lightning, the molecular nitrogen is converted into oxides of nitrogen and dissolves in water to give nitric and nitrous acids and fall on lands along with rains. These are then utilized by various life forms.

ii) Nitrogen fixation by Bacteria: The molecular nitrogen is converted into nitrates and nitrites, by free living bacteria or the bacteria present in the root nodules of legumes.

iii) The conversion of molecular nitrogen into nitrates and nitrites is called as” Nitrification”.
Plants generally covert them into amino acids. The conversion of nitrates and nitrates into Ammonia is called as” Ammonification”. The conversion of Ammonia into molecular Nitrogen is called as” Denitrification”. Thereby nitrates and nitrites are converted into molecular or elemental nitrogen in the nature.

5. The Carbon cycle:

i) The Carbon dioxide gas makes up 0.039 % of our atmosphere. Carbon occurs in the elemental form as diamonds and graphite in earth. Carbon is essential for the synthesis of proteins, carbohydrates, fats, nucleic acids and Vitamins in living organisms.

ii) The Carbon dioxide Fixation: Green plants convert Carbon dioxide into glucose in the presence of sunlight through Photosynthesis. The glucose molecules are converted into other biologically important molecules. And many marine animals use carbonates dissolved in sea water to make shells, exoskeletons.

iii) The combustion: The Carbon dioxide in the atmosphere is added by the process of combustion, where fuels are burnt to provide energy for various needs like heating, cooking, transportation, and industrial process.

iv) The Greenhouse Effect: The percentage of Carbon dioxide in the atmosphere is said to have doubled since the industrial revolution when human beings stated burning fossil fuels on a very large scale. The Carbon dioxide is a greenhouse gas. The increase in the Carbon dioxide content would cause more heat to be retained by the atmosphere and lead to Global Warming. It is called” Greenhouse Effect”

v) The carbon cycle is repeated through different physical and biological activities.

6 .Oxygen Cycle:

i) The Oxygen gas makes up 21 % of our atmosphere. Oxygen is essential component of proteins, carbohydrates, fats, nucleic acids in living organisms.

ii) Oxygen from our atmosphere is used up in three processes, namely combustion, respiration and in the formation of oxides of nitrogen. Oxygen is returned to the
atmosphere in only one major process, that is, Photosynthesis, it is called as Oxygen Cycle.

iii) The air is heated faster than water; the air over land would also be heated faster than the air over water bodies. The movement of air from one region to the other creates winds, during the day the direction of the wind would be from the sea to land. At night, both land and sea start to cool.

iv) The oxides of nitrogen and sulphur gases dissolve in rain to gives rise to “Acid rains”. The smog is a visible indication of Air Pollution. The pollutants bring respiratory, cardiac problems and allergies. The organisms called Lichens are found on the bark of trees, they are indicators of pollution free environment. Three atoms of Oxygen ( O3) is called as Ozone.
The Ozone is poisonous but absorbs harmful radiations from the Sun. The Ozone layer around the earth, if, dwindles further may cause Health hazards including Cancers . Recently discovered the Ozone hole; in the region of Antarctica.

QUESTION BANK

1. What are the three sub-zones in the Biosphere? {Lithosphere (rock part),atmosphere (air part)and hydrosphere (water part)}.

2. The process in which water evaporates and falls on the land as rain and later flows back into the sea via rivers is known ……………..(Water Cycle).

3. In large parts of India, rains are mostly brought by………………… monsoons.( the southwest or north-east monsoons).

4. Why water is a wonder liquid? Justify ( A major resource to determine life on the earth)

5. What are the four major water Pollutants?{ (NPK fertilizers, pesticides (DDT), sewage (Disease causing Organisms), waste from factories (Mercury)}

6. Write a short notes on Nitrogen fixation by Bacteria.{The molecular nitrogen is converted into nitrates and nitrites, by free living bacteria or the bacteria present in the root nodules of legumes}.

7. What is Greenhouse Effect? {The Carbon dioxide is a greenhouse gas. The increase in the Carbon dioxide content would cause more heat to be retained by the
atmosphere and lead to Global Warming. It is called” Greenhouse Effect”} 

8. What is the percentage of Oxygen gas in our atmosphere? {21 %}

9. Which organisms are found on the bark of trees as indicators of pollution free environment? { Lichens}

10. Write about the Ozone hole in the Antarctica. {The Ozone layer around the earth is dwindling further to damage and cause Health hazards including Cancers. Recently discovered Ozone hole in the Antarctica.}

Very Short answer Type Question

Question. Name any two weeds.
Answer: Parthenium and Xanthium.

Question. What causes disease in plants?
Answer: It is caused by pathogens such as bacteria, fungi and viruses.

Question. Name two Indian cattle.
Answer: Bos indicus – cows
Bos bubalis – buffaloes

Question. Define animal husbandry.
Answer: Animal husbandry is the management and care of farm animals by humans for profit.

Question. Name two factors responsible for wastage of grains during storage.
Answer: Factors responsible for such losses are :
Biotic : insects, rodents, fungi, mites and bacteria,
Abiotic : inappropriate moisture and temperatures in the place of storage.

Question. (i) Name an exotic variety of honey bee grown in India.
(ii) What is called the rearing of fish on a large scale?
Answer: (i) Apis cerana indica
(ii) Pisciculture

Question. State the difference between compost and vermicompost.
Answer: The compost is obtained by decomposition of organic waste like animal excreta, plant waste, etc. naturally due to decomposition by bacteria. Vermi-compost : Red-worms are added to organic matter in the process of decomposition to obtain compost to fasten. This will fasten the process.

Question. What is the advantage of crop rotation?
Answer: Rotation of crops helps in saving on nitrogenous fertilizers, because leguminous plants grown during the rotation of crops can fix atmospheric nitrogen in the soil with the help of itrogen fixing bacteria.

Question. What are the types of food requirements of dairy animals? Why external and internal parasites live on and in the cattle can be fatal.
Answer: Roughage and concentrates are the types of food requirements of dairy animals. The external parasites live on the skin and mainly cause skin diseases. The internal parasites like worms, affect stomach and intestine while flukes damage the liver.

Question. What do you understand by photoperiod of sunlight?
Answer: Photoperiod are related to the duration of sunlight required for plant growth.

Question. Define hybridisation.
Answer: Hybridisation refers to crossing between genetically dissimilar plants, to obtain better variety of crops.

Question. What are genetically modified crops?
Answer: A gene with required characters can introduce into a crop for its improvement is called genetically modified crop.

Question. State one importance of photoperiod in agriculture.
Answer: Photoperiod in agriculture provide adequate light for flowering.

Question. Name one micronutrient and one macronutrient which plants take from the soil.
Answer: Macronutrients are : Calcium (Ca), Magnesium (Mg) and Micronutrients are : Boron (B), Chlorine (Cl).

Question. From where do plants acquire the following nutrients?
(a) Nitrogen, (b) Hydrogen.
Answer: (a) Nitrogen from soil,
(b) Hydrogen from waste.

Question. Name different types of crop production practices involved in India.
Answer: They are (a) no cost production, (b) low cost production and (c) high cost production.

Question. Name the nutrients that plant obtains from air and water.
Answer: Air – Carbon and oxygen
\Water – Hydrogen and oxygen

Question. Name the products obtained from apiculture.
Answer: Honey and wax both are obtained from apiculture.

Question. State the meaning of capture fishing and culture fishing.
Answer: Capture fishing : It is done from natural resources. Culture fishing : It is done by fish farming.

Question. Why should weeds be constantly removed from cultivated fields?
Answer: Weeds take up nutrients and reduce the growth of the crop.

Question. What are weeds? Give example.
Answer: Unwanted plants growing with main crops are called weeds. Example : Xanthium, Parthenium, Cyperinus Rotundus.

Question. Explain how fertilisers are different from manure.
Answer: Fertilisers are synthesized in factories from inorganic materials. On the other hand, manure is made from organic materials; through the process of decomposition. Excessive use of fertilisers is not good for soil and may lead to soil pollution. Use of manure is beneficial for soil.

Question. What is Pisciculture?
Answer: The production and management of fish is called Pisciculture.

Question. What are the harmful effects of fertilizer?
Answer: Continuous use of fertilizer can cause of soil and water pollution and also destroy soil fertility.

Question. What are the three advantages of shorter duration of the crop in between sowing and harvesting?
Answer: Short durations allow farmers to grow multiple rounds of crops in a year. Short duration also reduces the cost of crop production. Uniform maturity makes the harvesting process easy and reduces losses during harvesting.

Question. Which method is commonly used for improving cattle breeds and why?
Answer: Cross breeding between a two good variety crops is called hybridization that also results in a new improved variety. Another way of improving the crop is by introducing a gene that would provide the desired characteristic. This results in genetically modified crops.

Question. “Shorter the duration of the crop from sowing to harvesting, the more economical is the variety.” Give reason for this.
Answer: Farmers can grow more crops in a year due to short duration of crop growth, and reduce the cost of crop production.

Question. What is mariculture?
Answer: The culture of marine fish in sea water is called mariculture.

Question. What are macro-nutrients?
Answer: The nutrients required by plants in larger quantity is called macro-nutrients. They are nitrogen, phosphorus, potassium, calcium, magnesium and sulphur.

Question. State one demerit with composite fish culture system.
Answer: Fish breed only during monsoon and lack of availability of good quality seeds.

Question. Mention two examples of mixed cropping.
Answer: Some combinations of mixed cropping are : wheat and mustard, groundnut and sunflower.

Question. Write four methods of weed control.
Answer: Spraying weedicide, mechanical removal, sowing of crops, intercropping and crop rotation also help in weed-control.

Question. Is breeding and rearing of Bombay duck part of poultry farming or a part of pisciculture?
Answer: It is a part of pisciculture as Bombay duck is fish not a duck.

Question. How does Bombay duck differ from common carp?
Answer: Bombay duck is a marine fish, while common carp is a freshwater fish.

Question. What is apiculture?
Answer: Keeping bee for obtaining honey commercially is called apiculture.

Question. Mention any two advantages of using Italian bee variety in honey production.
Answer: The Italian bees have high honey collection capacity. They sting somewhat less. They stay in a given beehive for long periods and breed very well.

Short answer Type Question

Question. What are the main characters required in a crop during its improvement practices?
Answer: The useful characters that are required in a crop during its improvement :
(i) Disease resistance
(ii) Response to fertilizer
(iii) Product quality
(iv) High yield

Question. What are fertilizers? Excess use of fertilizers is not advisable, explain.
Answer: Fertilizers are commercially produced plant nutrients. They supply nitrogen, phosphorus and potassium. hey are used to ensure good vegetative growth, giving rise to healthy plants.
Excessive use of fertilizers are not advisable as:
(a) It leads to soil and water pollution.
(b) It can destroy the fertility of soil.

Question. What factors may be responsible for losses of grains during storage?
Ans : During the storage of grains, various biotic factors such as insects, rodents, mites, fungi, bacteria, etc. and various abiotic factors such as inappropriate moisture, temperature, lack of sunlight, etc. are responsible for losses of grains. These factors act on stored grains and result in degradation, poor germ inability, discolouration, etc.

Question. List any six factors for which variety improvement in crops is done.
Answer: (i) Higher yield,
(ii) Improved quality,
(iii) Biotic and abiotic resistance,
(iv) Change in maturity duration,
(v) Wider adaptability,
(vi) Desirable characteristics.

Question. What is composite fish culture system? Mention one merit and one demerit of this system.
Answer: The composite fish culture system is a technology to grow both local and imported fish species in the water in the paddy field. One problem with such composite fish culture is that many of these fish breed only during monsoon mixed with other species, one of the advantages is that fish do not compete for food.

Question. How do insect pests attack the plant and affect it?
Answer: Insect pests attack the plants and reduces yield in three ways :
(i) They cut the root, stem and leaf.
(ii) They suck the cell sap from various parts of the plant.
(iii) They bore into stem and fruits.

Question. Write a paragraph in your own words on each of the following.
(a) Preparation of soil,
(b) Sowing,
(c) Weeding,
(d) Threshing
Answer: (a) Preparation of soil : Preparation of soil is the first step of farming. Soil is loosened and turned over. This helps in making the soil more airy so that roots can breathe in air. Moreover, loosening of soil also facilitates better penetration of roots into the soil. Seeds can be easily sown in loosened soil.
(b) Sowing : The method of putting the seeds into soil is called sowing. Traditionally, seed is sown manually by spreading the seeds by hands. This process is called broadcasting. Seed drills are used when sowing needs to be done on a large scale.
(c) Weeding : Removal of weeds is called weeding. Unwanted plants which grow along with the crop are called weeds. They compete for resources; like sunlight, water and air; with the main crop. So, it is necessary to remove weeds for proper growth ofcrops. Weeding is usually done manually by using  hands and sickles. Sometimes weedicides are also sprayed.
(d) Threshing : Separation of grains from harvested stems is called threshing. For smaller quantity, threshing is done by hands. For somewhat bigger quantity, threshing is done using animal; especially bullocks. Animals are made to trample over the harvested stock which helps in separation of grains. Threshing machines are used for bigger  quantities.

Question. What are the practices used for dairy industry?
Answer: The practices used for dairy industry to get the optimum yield are :
(i) Shelter : The shelter should be clean, spacious and airy.
(ii) Feeding : Proper food at proper time is essential for dairy animals.
(iii) Rearing of animals : Providing them proper health care and protection from pathogens, diseases and proper vaccination.
(iv) Breeding : The crossing of different variety of milch animals to obtain a breed that can produce more yield of milk.

Question. Give brief sketch on advantages and disadvantages on manure and fertilizers.
Answer: Advantages of manure :
(i) It increases the number of friendly microbes.
(ii) It improves the texture of soil by adding organic matter (humus).
(iii) It increases soil fertility, water holding capacity and aeration.
(iv) It reduces soil erosion.
(v) It is cheap.
Disadvantages of manure :
(i) They have fewer amounts of nutrients as compared to fertilizers.
(ii) Manures are bulky and not easy to store and transport.
Fertilizers : These are commercially manufactured inorganic salts containing one or more essential plant nutrients like NPK, which are used to increase soil fertility.
Advantages of fertilizers :
(i) They are nutrient specific and required in small amounts.
(ii) They are water soluble and absorbed by the plant easily.
(iii) They are easy to store and transport. Disadvantages of fertilizers :
(i) Fertilizers can change the soil structure by killing the soil microbes.
(ii) Fertilizers can change the chemical composition of soil.
(iii) Accumulation of fertilizers in water bodies causes eutrophication.

Question. What are the main characters required in a crop during its improvement practices?
Answer: The useful characters that are required in a crop during its improvement :
(i) Disease resistance
(ii) Response to fertilizer
(iii) Product quality
(iv) High yield
(iii) Intergeneric – between two different genera

Question. What are the factors for which variety improvement of crop is done?
Answer: (a) Higher yield : It increases production of crop.
(b) Biotic and abiotic resistance : Crop should be resistant to biotic factors like diseases, insects, pests and abiotic factors like drought, salinity, heat, etc.
(c) Change in maturity duration : Short-duration maturity allows farmer to grow more crops in a year with short duration maturity and reduces the crop production cost.
(d) Wider adaptability : Crop should be able to adapt to changing environmental conditions.
(e) Desirable agronomic characteristics : Crop should have tallness and dwarfness as per need. Dwarfness is required for cereals, so that few nutrients are consumed.

Question. What are the new varieties obtained by cross breeding of Indian and exotic breeds of poultry?
Answer: The new variety/traits obtained by cross breeding of Indian and exotic breeds of poultry are :
(i) Number and quality of chicks
(ii) Dwarf broiler parent for commercial chick production
(iii) Summer adaptation capacity/tolerance to high temperature
(iv) Low maintenance requirements
(v) Reduction in the size of the egg-laying bird with ability to utilise more fibrous and cheaper diet, formulated using agricultural by products.

Question. Large amount of food grains get spoiled every year in India due to improper storage of food grains. How can this be avoided?
Answer: Food grains get spoiled by insects, fungi, rodents, bacteria, moisture at the place of storage. Storage losses can be reduced by taking some preventive and control measures.
(i) The seeds that are to be stored should be dry
(ii) The grains should be cleaned
(iii) The grains should be fumigated using chemicals that kills pest.
(iv) The storage houses should be waterproof.
(v) The grains should be stored in sealed gunny bags.
(vi) The bags should be kept few centimetres away from the wall.
(vii) The walls and the floor should be water-proof with no holes in it, to avoid rodents, pests.