BASIC SCIENCE SOLUTION CLASS 8 CHAPTER 1 Food Production

              

Exercise 

Question

A. Answer the following in not more than 20 words.

1. What is agriculture?

2. Name two plantation crops.

3. Mention the major activities involved in growing a crop.

4. What are weeds?

5. Mention three ways of removing weeds from the crop field.

6. What are pests?

7. Why are animal proteins considered to be better than plant proteins?

8. When are kharif crops sown?

9. What is animal husbandry?

10. What are the two things that have to be controlled in a cold storage?

Answers

1. Agriculture is the cultivation of crops, livestock, and other food products through various techniques and methods.

2. Tea and coffee are two common plantation crops.

3. Preparing the soil, sowing the seeds, irrigating, applying fertilizers and pesticides, and harvesting are major activities involved in growing a crop.

4. Weeds are unwanted plants that compete with crops for nutrients, sunlight, and space.

5. Manual weeding, chemical weeding, and mechanical weeding are three common ways of removing weeds from the crop field.

6. Pests are insects or animals that damage crops and reduce yield.

7. Animal proteins contain all essential amino acids, whereas most plant proteins lack one or more of these amino acids.

8. Kharif crops are sown in the rainy season, typically between June and July in India.

9. Animal husbandry refers to the care, breeding, and management of domestic animals such as cattle, poultry, and fish for various purposes.

10. Temperature and humidity are two things that must be controlled in a cold storage to preserve perishable goods. 

Question 

B. Answer the following in not more than 40 words.

1. (a) Why is crop rotation considered a good agricultural practice? (b) Why are pulses alternated with crops like wheat or paddy?

2. (a) What is green manure?

(b) How is compost prepared?

3. (a) What do you understand by biological control of weeds and pests? (b) In what way is biological control better than using weedicides and pesticides?

4. What are root nodules? How are they helpful?

5. What is surface irrigation? Mention two modes of irrigation under this category. 

Answer 

1. (a) Crop rotation is a good agricultural practice as it helps maintain soil fertility, reduces soil erosion, controls pests and diseases, and improves crop yield. (b) Pulses are alternated with crops like wheat or paddy as they fix nitrogen in the soil, which is beneficial for the following crop.

2. (a) Green manure is a practice of growing specific crops and then plowing them into the soil to improve soil fertility. (b) Compost is prepared by decomposing organic waste such as leaves, kitchen waste, and animal manure, which is then used as a natural fertilizer for plants.

3. (a) Biological control of weeds and pests is the use of natural enemies such as predators, parasites, and pathogens to control pests and weeds. (b) Biological control is better than using weedicides and pesticides as it is environmentally friendly, sustainable, and does not harm non-target organisms.

4. Root nodules are small swellings on the roots of leguminous plants that contain nitrogen-fixing bacteria. They help in converting atmospheric nitrogen into a form that is usable by plants, thus increasing soil fertility.

5. Surface irrigation is a method of irrigation where water is applied to the soil surface and then infiltrates into the soil. Two modes of irrigation under this category are flood irrigation, where water is applied to the entire field, and furrow irrigation, where water is applied to trenches or furrows between rows of crops.

 Question

C. Answer the following in not more than 100 words.

1. Write briefly about the advantages and disadvantages of using chemical fertilisers.

2. What is the nitrogen cycle? 

3. Write briefly about the sources of irrigation in India. 

Answer 

1. Chemical fertilizers have advantages and disadvantages. Advantages include increased crop yield, improved plant growth, and nutrient availability. Disadvantages include soil degradation, groundwater pollution, and harm to non-target organisms such as beneficial insects and microorganisms. Chemical fertilizers can also contribute to global warming and climate change through greenhouse gas emissions during production and use. Overuse of chemical fertilizers can also lead to nutrient imbalances and reduce soil fertility over time.

2. The nitrogen cycle is a process where nitrogen is converted into various forms that can be used by living organisms. Nitrogen is taken up from the atmosphere by plants in the form of nitrogen gas (N2) and converted into ammonia (NH3) by nitrogen-fixing bacteria. Ammonia is then converted into nitrite (NO2) and nitrate (NO3) by nitrifying bacteria. Plants absorb nitrate and incorporate it into their tissues, and when they die, decomposers break down the nitrogen compounds back into ammonia, which can then be reused by plants or converted back into nitrogen gas.

3. In India, the sources of irrigation include canals, tanks, tube wells, wells, and rivers. Canals are man-made channels that transport water from dams and reservoirs to the fields. Tanks are artificial ponds or lakes that collect and store rainwater. Tube wells and wells are dug wells that tap into groundwater sources. Rivers are also used for irrigation through the construction of dams, barrages, and channels. The government of India has undertaken several initiatives to improve irrigation infrastructure and promote sustainable water use in agriculture, such as the Pradhan Mantri Krishi Sinchai Yojana (PMKSY) and the Atal Bhujal Yojana (ABY).

Question With Answer

 D. Complete the following.

1. The practice of growing fruit, vegetables, flowers and ornamental plants is Horticulture

2. The process of using the vapours of a chemical to disinfect a place and get rid of pests is

called Fumigation

 3. A Buffer stock of grains is maintained to provide food during emergencies.

4. A mutually beneficial association between two organisms is called Syombosis 

5. Seeds have to be sown at the right Depth and with adequate spaces in between.

6. Bilogical control Method is the method of controlling weeds or pests by using their natural enemies.

7. A Fallow field is one that is left uncultivated for one or more seasons

Question 

E. Choose the correct option in each of the following.

1. Removing the chaff from the grain is called

(a) threshing

(b) harvesting 

(c) winnowing
(d) weeding

2. A combine 

(a) cuts the crop

(b) is used for threshing 

(c) is used for winnowing
(d) can harvest, thresh and winnow

3. Which of the following is not a rabi crop?

(a) Rice

(b) Wheat

(c) Mustard

(d) Gram

4. The process of converting atmospheric nitrogen into nitrogenous compounds is called 

(a) nitrogen cycle

(b) nitrogen fixation

(c) denitrification

(d) symbiosis

5. The method of irrigation in which emitters let out a trickle of water near the roots is called

(a) drip irrigation 

(b) sprinkler irrigation

(c) furrow irrigation

(d) basin irrigation

6. In a cold storage, the temperature is maintained

(a) below 0°C

(b) above 0°C 

(c) below 10°C

(d) between 0°C and 4°C

7.Which of the following needs to be transplanted? 

(a) Rice

(b) Wheat

(c) Millets

(d) Mustard 

 Answer                           

1. Removing the chaff from the grain is called

(a) threshing

2. A combine 

(d) can harvest, thresh and winnow

3. Which of the following is not a rabi crop?

(a) Rice

4. The process of converting atmospheric nitrogen into nitrogenous compounds is called 

(b) nitrogen fixation

5. The method of irrigation in which emitters let out a trickle of water near the roots is called

(a) drip irrigation 

6. In a cold storage, the temperature is maintained

(d) between 0°C and 4°C

7.Which of the following needs to be transplanted? 

(a) Rice

Question                 

F. Choose the correct option(s). More than one option might be correct.

1. Nodules with nitrogen-fixing bacteria are found in the roots of

(a) pea

(b) wheat

(c) mustard

(d) kidney bean

2. Which of the following are rabi crops?

(a) Mustard

(b) Wheat

(c) Gram

(d) Jute

3. Which of the following crops require very little water?

(a) Jowar

(b) Rice

(c) Bajra

(d) Wheat

4. Which of these are done after the crops are gathered? 

(a) Irrigation 

(b) Winnowing

(c) Threshing

(d) Transplantation

5. Plants used as green manure include

(a) gram

(b) cauliflower
(c) cowpea
(d) wood sorrel 

                                               Answer

1. Nodules with nitrogen-fixing bacteria are found in the roots of
(a) pea
(c) mustard
(d) kidney bean
2. Which of the following are rabi crops?
(a) Mustard
(b) Wheat
(c) Gram
3. Which of the following crops require very little water?
(a) Jowar
(c) Bajra
4. Which of these are done after the crops are gathered? 
(b) Winnowing
5. Plants used as green manure include

(c) cowpea

 Thanks