CBSE Class 8 Science Advanced Biology Crop Production and Management MCQs Set 01

Answer: (c) transplantation

Explanation:
1. Some crops, such as paddy, are first sown in a nursery bed.
2. When the seedlings are big enough they are lifted and planted in the main field.
3. This shifting of seedlings is called transplantation.

Teacher's Note:
1. Weeding removes unwanted plants, and sowing means putting seeds into the soil.
2. Paddy is the standard example of a transplanted crop.

Answer: (a) weeds

Explanation:
1. Any plant that grows in a field along with the crop and is not wanted there is a weed.
2. Weeds compete with the crop for water, nutrients, space and light.
3. So the answer is weeds.

Teacher's Note:
1. Seedlings are young crop plants, so they are wanted.
2. Removing weeds is called weeding.

Answer: (c) Protozoa

Explanation:
1. Crop diseases are caused mainly by fungi (rust, smut), bacteria (bacterial blight) and viruses.
2. Protozoa are not the usual cause of crop diseases.
3. So the one that does not cause plant diseases among the options is protozoa.

Teacher's Note:
1. Fungi cause most of the common crop diseases listed in this chapter.
2. Answer by elimination: three of the four are well-known plant pathogens.

Answer: (d) All of these

Explanation:
1. Traditional methods lift water from wells, lakes or canals with human or cattle power.
2. The moat (pulley), chain pump and the rahat (lever) are all traditional systems.
3. So the answer is all of these.

Teacher's Note:
1. Modern methods are the sprinkler and drip systems.
2. Learn the three traditional ones: moat, chain pump, dhekli and rahat.

Answer: (c) Weedicides

Explanation:
1. Insecticides kill insects and pesticides is a general word for pest killers.
2. Chemicals sprayed to kill weeds are called weedicides (herbicides).
3. So the answer is weedicides.

Teacher's Note:
1. Examples of weedicides are 2,4-D and atrazine.
2. Pesticide is a wide term, so choose the one specific to weeds.

Answer: (d) All of the these

Explanation:
1. Farmers store grain in granaries, traders use gunny (jute) bags, and the FCI uses silos.
2. All three are used for storing grain.
3. So the answer is all of these.

Teacher's Note:
1. Remember the three levels: producer, trader and FCI.
2. Silos are large storage structures used on a big scale.

Answer: (b) they cause the soil pollution

Explanation:
1. Increasing fertility and providing nutrients are benefits, not harms.
2. Being an inorganic salt is only a description of what a fertiliser is.
3. The real harm is that excess fertiliser pollutes the soil (and water), so the answer is they cause the soil pollution.

Teacher's Note:
1. Fertilisers also cause eutrophication in nearby water bodies.
2. Read options (a) and (c): they are advantages, not harms.

Answer: (c) Rice

Explanation:
1. Kharif crops are grown in the rainy season, sown in June-July.
2. Wheat, barley and mustard are rabi (winter) crops.
3. Rice is sown with the monsoon, so it is a kharif crop: rice.

Teacher's Note:
1. Kharif crops: rice, jowar, bajra, cotton, groundnut, urad, moong.
2. Rabi crops: wheat, barley, gram, mustard, potato.

Answer: (d) All of these are correct

Explanation:
1. Turning the soil brings the nutrient-rich crumbs within reach of the roots, so fertility is better used (a).
2. Loose soil holds air, so roots breathe easily (b).
3. Loose soil lets roots go deep (c).
4. All three are advantages, so the answer is all of these are correct.

Teacher's Note:
1. Ploughing loosens the soil; it never makes it compact.
2. When every option is a true advantage, choose 'all of these'.

Answer: (d) Both (B) & (C)

Explanation:
1. Fertigation means giving fertiliser through the drip irrigation water.
2. So it applies both fertiliser and water together.
3. The answer is both (B) and (C).

Teacher's Note:
1. The word joins fertiliser and irrigation.
2. Its aim is the maximum yield from the water available.

Answer: (a) Sandy

Explanation:
1. Sandy soil lets water drain away quickly and holds little.
2. Clay soil holds water for a long time.
3. So frequent irrigation is needed in sandy soil.

Teacher's Note:
1. Match the soil to its water-holding power.
2. Wheat in sandy soil needs more frequent watering than wheat in clay soil.

Answer: (a) Sprinkler system

Explanation:
1. The chapter lists sprinkler and drip systems for the southern states such as Karnataka, Andhra Pradesh and Tamil Nadu.
2. Of the given options, the sprinkler system is the one named.
3. So the answer given in the source is sprinkler system.

Teacher's Note:
1. Fertigation is a method of applying fertiliser, not a type of irrigation system.
2. Learn the states along with the systems.

Answer: (b) Wax

Explanation:
1. Honey is the main product of bee keeping.
2. Bees build the honeycomb from wax, which is collected as a by-product.
3. So the answer is wax.

Teacher's Note:
1. Bee keeping is called apiculture.
2. Beeswax is used in candles and polishes.

Answer: (b) straw

Explanation:
1. Grass is a green fodder and horse gram is a pulse fed as a concentrate.
2. Straw is the dry stalk left after threshing and is fed as dry roughage.
3. So the answer is straw.

Teacher's Note:
1. Milch animals are given green fodder, dry fodder and concentrates.
2. Fodder crops include berseem, oat and sorghum.

Answer: (c) Storage of Grains

Explanation:
1. Silos are tall tower-like structures.
2. The Food Corporation of India stores large amounts of grain in them.
3. So silos are used for storage of grains.

Teacher's Note:
1. Silos protect grain from rain, rodents and birds.
2. Do not confuse silos with water tanks.

Answer: (a) Presence of Nitrogen in the soil

Explanation:
1. Carbon comes to the plant from the air as carbon dioxide, not from the soil.
2. Nitrogen is a soil nutrient that crops use in large amounts, so it is the key to soil fertility.
3. Of the options, the answer is presence of nitrogen in the soil.

Teacher's Note:
1. Leguminous crops with Rhizobium add nitrogen to the soil.
2. Eliminate the options that mention carbon.

Answer: (b) b and c

Explanation:
1. Statement (a) is wrong: earthworms improve the soil and do not damage roots.
2. Statement (b) is right: they carry organic matter down into the soil.
3. Statement (c) is right: their castings are rich in organic matter.
4. Statement (d) is not an ecological importance given here, so the answer is b and c.

Teacher's Note:
1. Earthworms aerate the soil and are used in vermicomposting.
2. Cross out (a) first and only (b)-(c) remains.

Answer: (c) Low temperature

Explanation:
1. Maize is a warm-season crop that needs high temperature, humidity and rain.
2. Low temperature is not needed by it.
3. So the condition that is not essential is low temperature.

Teacher's Note:
1. Cold, dry weather suits rabi crops, not maize.
2. Remember: maize is sown with the monsoon.

Answer: (b) stem (rhizome)

Explanation:
1. Ginger is an underground modified stem.
2. A piece of this rhizome with a bud is planted to grow a new plant.
3. So ginger is propagated by stem (rhizome).

Teacher's Note:
1. Potato, onion, garlic and ginger are modified underground stems.
2. Propagation by a part other than seed is called vegetative propagation.

Answer: (b) It has a balance of all plant nutrients.

Explanation:
1. Organic manure does improve water holding capacity, add humus and improve texture.
2. But it holds only small amounts of nutrients and is not a balanced supply of all nutrients.
3. So the untrue statement is (b).

Teacher's Note:
1. A manure is not nutrient specific, and it is poor in nutrients.
2. Three of the four are listed advantages of manure.

Answer: (c) winnowing

Explanation:
1. Threshing separates the grain from the plant (stalk and ears) by beating or by a machine.
2. Separating light chaff from the grain by blowing air is winnowing.
3. So the answer is winnowing.

Teacher's Note:
1. The words 'by blowing air' decide between threshing and winnowing.
2. Small farmers winnow by hand or with a winnowing machine.

Answer: (a) Hoe

Explanation:
1. A plough turns the soil and a cultivator loosens it; an axe cuts wood.
2. A hoe, like the khurpa, is a hand tool for weeding.
3. So the farmer uses a hoe.

Teacher's Note:
1. Khurpa is the Indian name for the small weeding tool.
2. Ploughing also uproots weeds, but it is not a tool for removing them one by one.

Answer: (d) They are environment friendly.

Explanation:
1. Fertilisers do raise the yield and are needed in small quantities.
2. Too much of them upsets the nutrient balance of the soil.
3. They also pollute soil and water, so they are not environment friendly; the untrue statement is (d).

Teacher's Note:
1. Biofertilisers and manures are the environment friendly choices.
2. Fertilisers cause eutrophication in water bodies.

Answer: (a) i, iii, iv

Explanation:
1. Statement (ii) is false: weeds do not help the crop, they harm it.
2. Statements (i), (iii) and (iv) describe real harm: they get in the way of harvesting, compete for resources and stunt growth.
3. So the correct combination is i, iii, iv.

Teacher's Note:
1. First find the false statement and remove every option that includes it.
2. Option (d) includes (ii), so it fails.

Answer: (c) tilling and ploughing

Explanation:
1. Loosening and turning the soil is the first step in preparing a field.
2. It is done by a plough and is called ploughing or tilling.
3. So the answer is tilling and ploughing.

Teacher's Note:
1. Winnowing is a harvest-time process, not a soil preparation step.
2. Ploughing is done with wooden or iron ploughs.

Answer: (b) June to September

Explanation:
1. The monsoon rains in India arrive in June and last till about September.
2. Kharif crops are sown in June-July with the first rains.
3. So the monsoon months are June to September.

Teacher's Note:
1. Winter is roughly November to March, which is the rabi season.
2. Link the months to the kharif crops.

Answer: (b) drip system

Explanation:
1. The pulley and lever systems are traditional methods of lifting water.
2. A sprinkler sprays water like rain.
3. Water falling drop by drop at the roots is the drip system.

Teacher's Note:
1. Drip irrigation saves water because none is wasted.
2. Fertigation is done through drip irrigation.

Answer: (b) i, ii, iii

Explanation:
1. Seeds need moisture to germinate, so irrigation is needed (i).
2. Roots take up nutrients only when they are dissolved in water (ii).
3. Water also protects the crop from frost and from hot air currents (iii).
4. Irrigation does not improve soil texture; manure does that (iv).
5. So the reasons for irrigating are i, ii and iii.

Teacher's Note:
1. Frost protection is a recognised purpose of irrigation, so statement (iii) belongs in the answer.
2. Statement (iv) is the odd one out, as manure improves texture.

Answer: (b) Rhizobium.

Explanation:
1. Rhizobium lives in the root nodules of leguminous plants.
2. It fixes atmospheric nitrogen and gives it to the plant in a usable form.
3. So the answer is Rhizobium.

Teacher's Note:
1. Azotobacter fixes nitrogen too, but it lives free in the soil.
2. Rhizobium cultures are used as biofertilisers.

Answer: (d) Examples of leguminous plants are maize, rice, cotton, peas, beans etc.

Explanation:
1. Statements (a), (b) and (c) are correct: Rhizobium in the nodules fixes nitrogen, the partnership is symbiosis and the nitrogen is made available as nitrogen compounds.
2. Maize, rice and cotton are not leguminous plants; only peas, beans, gram and similar pulses are.
3. So the incorrect statement is (d).

Teacher's Note:
1. Leguminous plants are the pulse plants that bear pods.
2. The figure shows a legume root with swellings (nodules) that hold the bacteria.

Answer: (b) Both statements 1 and 2 are true but statement 2 is not the correct explanation of statement 1.

Explanation:
1. Fertilisers are made in factories from chemicals, so statement 1 is true.
2. Manures come from decayed plant and animal matter, so statement 2 is true.
3. But being natural does not explain why fertilisers are chemical, so statement 2 is not the explanation of statement 1.
4. The answer is (b).

Teacher's Note:
1. Both statements are facts but they describe two different things.
2. Ask whether the second statement answers 'why' the first is true.

Answer: (c) (a) - (ii), (b) - (iv), (c) - (i), (d) - (iii)

Explanation:
1. Weeding is removing unwanted plants from the field: (a) - (ii).
2. Winnowing is separating grain from chaff: (b) - (iv).
3. Tilling is loosening and turning the soil: (c) - (i).
4. Harvesting is cutting and gathering the mature crop: (d) - (iii).
5. This is option (c).

Teacher's Note:
1. Match the sure pairs first, such as tilling with loosening soil.
2. Then check each option against them.

Answer: (a) Both statements 1 and 2 are true and statement 2 is the correct explanation of statement 1.

Explanation:
1. Biofertilisers are living organisms that enrich the soil, so statement 1 is true.
2. Nitrogen-fixing bacteria, cyanobacteria and mycorrhizae are the important biofertilisers, so statement 2 is true.
3. Statement 2 names the organisms that do what statement 1 describes, so it supports and explains it.
4. The answer is (a).

Teacher's Note:
1. Statement 2 gives the examples that show how statement 1 works.
2. Statement 2 is not a different idea; it only names the biofertilisers.

Answer: (d) All of these.

Explanation:
1. Loose soil holds air, so roots breathe easily.
2. Air and space help earthworms and friendly microbes to grow.
3. Turning the soil brings nutrients in the crumbs within reach of roots.
4. All three are correct, so the answer is all of these.

Teacher's Note:
1. When all options are true statements, choose 'all of these'.
2. Loose soil also lets roots go deep.

Answer: (d) All of these.

Explanation:
1. Better seeds from plant breeding raise yield.
2. Protecting plants from pests and storing grain well cut losses.
3. Controlling plant diseases keeps the crop healthy.
4. All of them have helped, so the answer is all of these.

Teacher's Note:
1. The Green Revolution used improved wheat varieties.
2. Think of yield as seeds plus protection plus storage.

Answer: (b) Kharif - sowing (June-July), harvesting (September-October)

Explanation:
1. Kharif crops are sown in June-July and harvested in September-October, so (b) is correct.
2. Rabi crops are sown in October-November and harvested in March-April, so (a) and (c) are wrong.
3. Option (d) includes (c), so it is wrong too. The answer is (b).

Teacher's Note:
1. Rabi is winter and kharif is the rainy season.
2. Rabi crops are harvested in March-April, not June.

Answer: (d) All of these.

Explanation:
1. Growing leguminous crops in turn keeps up the nitrogen and so soil fertility.
2. That saves nitrogenous fertiliser.
3. Changing crops also breaks the life cycle of pests and weeds.
4. So the answer is all of these.

Teacher's Note:
1. Remember the two main advantages: pest and weed control, and less need for fertilisers.
2. Rice-wheat is a one-year rotation.

Answer: (d) Fungicides, herbicides, insecticides, rodenticides and nematicides.

Explanation:
1. Pesticide is a wide term for chemicals that kill pests of all kinds.
2. These include fungicides, herbicides, insecticides, rodenticides and nematicides.
3. Options (a) to (c) list only some of them, so the full list in (d) is the answer.

Teacher's Note:
1. Options (a) to (c) are incomplete lists, so choose the fullest one.
2. Fungicides kill fungi, rodenticides kill rodents and nematicides kill nematodes.

Answer: (d) (ii) & (iii)

Explanation:
1. (i) is correct, because manure helps the soil hold water.
2. (ii) is incorrect: manure is not nutrient specific, a fertiliser is.
3. (iii) is incorrect: manure increases the friendly microbes.
4. (iv) and (v) are correct.
5. So the incorrect statements are (ii) and (iii).

Teacher's Note:
1. Read the question carefully: it asks for the incorrect statements.
2. Nutrient specific is a feature of fertilisers.