Microorganisms, Agriculture and Animal Husbandry

What to remember

• Microorganisms are of four main groups: bacteria, fungi, protozoa and algae; viruses are also studied with them. Some are useful (curd, bread, antibiotics, nitrogen fixation) and some cause disease.
• Crop production needs soil preparation, sowing, manure and fertilisers, irrigation, weeding, harvesting and storage. Kharif crops grow in the rainy season and rabi crops in winter.
• Animal husbandry is the care and breeding of animals for milk, meat, eggs, wool and work. Good breed, feed, housing and health care raise the yield.

Microorganisms

Microorganisms are living things too small to see with the eye. They are seen under a microscope. They live in air, water, soil, and inside plants and animals, even in very hot or very cold places.

A virus is non-living outside a host and shows life only when inside a living cell. It has a protein coat and genetic material (DNA or RNA).

Useful roles.

• Lactobacillus turns milk into curd. Warm milk with a little curd (starter) sets quicker.
• Yeast is used for bread, idli and dosa batter, and for making alcohol by fermentation. Yeast respires without oxygen, produces carbon dioxide (which makes dough rise) and alcohol. Sugar to alcohol conversion is fermentation (Pasteur explained it).
• Antibiotics are made from microbes. Alexander Fleming discovered penicillin from the mould Penicillium. Antibiotics do not work against viruses. A full course must be completed.
• Vaccines train the body to fight disease. Edward Jenner made the first vaccine, for smallpox, using cowpox material. Vaccination has removed smallpox from the world.
• Rhizobium bacteria live in root nodules of legumes (pulse plants such as gram, pea and groundnut) and fix atmospheric nitrogen. Blue-green algae also fix nitrogen in rice fields.
• Bacteria and fungi are decomposers: they break dead plants and animals and help to recycle nutrients. They are used in making compost and biogas, and in sewage treatment.

Harmful roles. Microbes cause disease in humans, animals and plants and spoil food.

A carrier is a living thing that carries and spreads a disease-causing microbe; the housefly and the mosquito are examples. Malaria needs a vector, so removing standing water breaks the cycle.

Food preservation. Methods slow microbial growth: heating, cooling and refrigeration, drying, salting (pickles, fish), sugar (jams), oil and vinegar, and sealed packing. Pasteurisation heats milk to about 70°C for 15 to 30 seconds and cools it quickly; it was developed by Louis Pasteur.

Agriculture: crop production

Crop seasons. Kharif crops are sown with the rains in June–July and harvested in October–November: paddy, maize, cotton, soyabean, groundnut, jowar. Rabi crops are sown in winter in October–November and harvested in March–April: wheat, gram, pea, mustard, barley.

Steps in crop production.

• 1. Preparing the soil: ploughing (tilling), levelling and adding manure. Ploughing loosens the soil, brings nutrients up and helps earthworms and microbes. Tools: plough, hoe, cultivator.
• 2. Sowing: good-quality, healthy seeds are chosen. Seed drill is a tractor-driven tool that sows evenly at the correct depth. Seeds sown by hand are broadcast. Transplanting is moving small seedlings (as in paddy).
• 3. Adding manure and fertilisers: Nutrients are replaced in the soil. Manure is made from decomposed plant and animal waste; it improves soil texture and is rich in humus. Fertilisers are made in factories (urea, ammonium sulphate, NPK). Over-use of fertilisers harms soil and water. Crop rotation (growing legumes between cereals) restores nitrogen.
• 4. Irrigation: Giving water at proper intervals. Sources are wells, tube wells, canals, tanks, rivers and rain. Traditional methods are moat (pulley-system), chain pump, dhekli and rahat. Modern methods that save water are the sprinkler system and drip irrigation.
• 5. Protecting from weeds: Weeds are unwanted plants. They are removed by weeding (manually by khurpi, or by weedicides such as 2,4-D). Pesticides control insects.
• 6. Harvesting: cutting the mature crop with a sickle or a combine harvester.
• 7. Threshing and winnowing: Threshing separates the grain from the chaff. Winnowing separates grain from husk using wind.
• 8. Storage: Grains must be dry to prevent attack by pests, rodents and microbes. Drying, neem leaves and chemical treatment are used. Silos and granaries are used for storage.

Organic and modern farming. Organic farming uses manure, compost and biological pest control and avoids chemicals. Vermicompost is made by earthworms. Green revolution brought high-yielding seeds, fertilisers and irrigation and raised grain production. Hybrid seeds come from crossing two varieties. Mixed cropping (two or more crops on one field) and crop rotation reduce risk.

Animal husbandry

Animal husbandry is the branch of agriculture that deals with feeding, housing, breeding and caring for livestock.

Cattle. Indigenous milk breeds include Gir, Sahiwal and Red Sindhi. Jersey and Holstein-Friesian are exotic milk breeds. Murrah is a famous buffalo breed. Cross-breeding of local and exotic breeds gives hardy animals with high milk yield. In Andhra Pradesh, Ongole cattle is a well-known indigenous breed, valued for draught work and for improving other breeds, and Nellore sheep is a local breed.

Poultry. Layers are reared for eggs and broilers for meat. Good breeds, clean housing, balanced feed and vaccines (for diseases such as Ranikhet disease and bird flu) are needed.

Fish farming. Composite fish culture rears several species that eat at different levels of a pond. Fish are rich in protein. Prawn culture and sea fishing are important on the Andhra coast.

Apiculture. Honey bees live in colonies with a queen, drones and workers. Beehives are kept in boxes. Honey is used as food and medicine; beeswax has uses in cosmetics and candles.

Sericulture. Silkworm eggs hatch into larvae that feed on mulberry leaves, then spin a cocoon made of silk fibre. The cocoons are boiled to unwind the silk thread (reeling).

Care of animals. Clean shelter, clean water, balanced feed, regular vaccination, deworming and a veterinary check are the basic needs. Foot and mouth disease affects cattle; anthrax affects cattle and sometimes humans.

Teaching angle

These units suit field visits to a farm, a dairy or a compost pit. A teacher can ask learners to prepare curd, grow seeds in pots and keep a record chart. Link the content to the local crops and animals so that the learner can relate to it.

Exam traps

• Microbes in curd are bacteria; in bread they are yeast (a fungus).
• Penicillin was found by Fleming; the first vaccine was by Jenner.
• Antibiotics fight bacteria but not viruses.
• Rhizobium fixes nitrogen in root nodules of legumes; it is not found in cereals.
• Malaria is by a protozoan; dengue is by a virus. Both are carried by mosquitoes (Anopheles and Aedes).
• Kharif is the rainy season; rabi is the winter season.
• Threshing separates grain from stalk; winnowing separates grain from husk.
• Manure is natural; fertiliser is made in factory.

One-liners

• 1. Lactobacillus converts milk to curd.
• 2. Yeast makes bread dough rise by releasing carbon dioxide.
• 3. Fleming discovered penicillin from Penicillium.
• 4. Jenner developed the smallpox vaccine.
• 5. Rhizobium fixes nitrogen in root nodules of pulses.
• 6. Female Anopheles spreads malaria.
• 7. Pasteurisation was developed by Louis Pasteur.
• 8. Paddy, maize and cotton are kharif crops.
• 9. Wheat, gram and mustard are rabi crops.
• 10. Drip irrigation saves water.
• 11. Sericulture means rearing silkworms for silk.
• 12. Ongole is a well-known Andhra cattle breed.

Practice questions

1. Which bacterium helps to convert milk into curd?

   1. Streptococcus pneumoniae
   2. Vibrio
   3. Rhizobium
   4. Lactobacillus
   Answer

   D. Lactobacillus

   Lactobacillus ferments lactose to lactic acid and sets curd.

2. Who discovered penicillin?

   1. Edward Jenner
   2. Alexander Fleming
   3. Robert Koch
   4. Louis Pasteur
   Answer

   B. Alexander Fleming

   Fleming found penicillin from the mould Penicillium.

3. The first vaccine, against smallpox, was developed by

   1. Alexander Fleming
   2. Louis Pasteur
   3. Edward Jenner
   4. Ronald Ross
   Answer

   C. Edward Jenner

   Jenner used cowpox material.

4. Which microorganism makes bread dough rise?

   1. Spirogyra
   2. Yeast
   3. Rhizobium
   4. Amoeba
   Answer

   B. Yeast

   Yeast releases carbon dioxide during fermentation.

5. Malaria is caused by a

   1. virus
   2. bacterium
   3. fungus
   4. protozoan
   Answer

   D. protozoan

   Plasmodium is a protozoan.

6. Malaria is spread by the

   1. housefly
   2. male Culex mosquito
   3. female Anopheles mosquito
   4. Aedes mosquito
   Answer

   C. female Anopheles mosquito

   Female Anopheles is the vector.

7. Which of these is a rabi crop?

   1. Wheat
   2. Paddy
   3. Maize
   4. Cotton
   Answer

   A. Wheat

   Wheat is sown in winter.

8. Which of these is a kharif crop?

   1. Paddy
   2. Wheat
   3. Gram
   4. Mustard
   Answer

   A. Paddy

   Paddy is sown with the rains.

9. Separating grain from the chaff is called

   1. winnowing
   2. weeding
   3. ploughing
   4. threshing
   Answer

   D. threshing

   Threshing separates grain from stalks and chaff.

10. Which irrigation method saves the most water?

    1. Chain pump
    2. Moat
    3. Drip irrigation
    4. Canal flooding
    Answer

    C. Drip irrigation

    Drip irrigation gives water drop by drop at roots.

11. Rearing of honey bees for honey is called

    1. sericulture
    2. apiculture
    3. pisciculture
    4. poultry
    Answer

    B. apiculture

    Apiculture is bee keeping.

12. Rearing of silkworms for silk is called

    1. apiculture
    2. viticulture
    3. sericulture
    4. aquaculture
    Answer

    C. sericulture

    Sericulture produces silk.

13. Which of the following is an exotic milk breed of cattle?

    1. Sahiwal
    2. Jersey
    3. Ongole
    4. Gir
    Answer

    B. Jersey

    Jersey and Holstein-Friesian are exotic breeds.

14. Which is a well-known Andhra indigenous cattle breed?

    1. Jersey
    2. Holstein-Friesian
    3. Murrah
    4. Ongole
    Answer

    D. Ongole

    Ongole cattle is from the Andhra region; Murrah is a buffalo breed.

15. Rhizobium bacteria are found in root nodules of

    1. pea plant
    2. rice plant
    3. wheat plant
    4. maize plant
    Answer

    A. pea plant

    Rhizobium lives in legume roots.

16. Pasteurisation of milk was developed by

    1. Edward Jenner
    2. Louis Pasteur
    3. Alexander Fleming
    4. Joseph Lister
    Answer

    B. Louis Pasteur

    It is named after Pasteur.

17. The tool used for even sowing of seeds at the correct depth is

    1. seed drill
    2. sickle
    3. khurpi
    4. plough
    Answer

    A. seed drill

    A seed drill sows seeds in rows at uniform depth.

18. Antibiotics are NOT effective against

    1. bacterial wound infections
    2. cholera germs
    3. bacteria
    4. viruses
    Answer

    D. viruses

    Antibiotics act on bacteria, not on viruses.

19. Growing a legume crop between two cereal crops helps because it

    1. adds more weeds
    2. kills the earthworms
    3. restores nitrogen to the soil
    4. removes all water
    Answer

    C. restores nitrogen to the soil

    Legume root nodules fix nitrogen.

20. A single bacterium divides every 20 minutes. Starting from one bacterium, how many will be present after 1 hour?

    1. 6
    2. 3
    3. 16
    4. 8
    Answer

    D. 8

    One hour has 3 divisions: 1, 2, 4, 8.

21. A farmer has 2.5 hectares of land and uses 40 kg of seed per hectare. The total seed needed is

    1. 160 kg
    2. 100 kg
    3. 62.5 kg
    4. 80 kg
    Answer

    B. 100 kg

    2.5 x 40 = 100 kg.

22. Milk is pasteurised at about 70°C and cooled quickly. The aim is to

    1. kill harmful microbes without spoiling the milk
    2. turn it into curd
    3. add nutrients
    4. make the milk thicker
    Answer

    A. kill harmful microbes without spoiling the milk

    Pasteurisation kills harmful microbes.

23. Which of these diseases is caused by a virus?

    1. Typhoid
    2. Tuberculosis
    3. Polio
    4. Cholera
    Answer

    C. Polio

    Polio is viral; the others are bacterial.

24. Which of these plant diseases is caused by a fungus?

    1. Crown gall
    2. Rust of wheat
    3. Citrus canker
    4. Bacterial blight of rice
    Answer

    B. Rust of wheat

    Wheat rust is fungal; citrus canker is bacterial.

25. The main advantage of composite fish culture is that

    1. Several fish species use food at different levels of the same pond
    2. Only one species is kept
    3. Only surface feeders are kept
    4. Fish are kept without water
    Answer

    A. Several fish species use food at different levels of the same pond

    Composite culture raises many species together.

26. Which of the following is a fertiliser?

    1. Vermicompost
    2. Farmyard manure
    3. Compost
    4. Urea
    Answer

    D. Urea

    Urea is factory made; others are manures.

27. Weedicide commonly used for removing weeds is

    1. Penicillin
    2. Urea
    3. 2,4-D
    4. DDT
    Answer

    C. 2,4-D

    2,4-D is a weedicide.

28. Pulses give a good crop in poor-nitrogen soil because

    1. Rhizobium fixes nitrogen in their roots
    2. they do not need any nutrients
    3. they have no roots
    4. their leaves absorb nitrogen from soil
    Answer

    A. Rhizobium fixes nitrogen in their roots

    Root-nodule bacteria supply nitrogen.

29. Consider the statements. 1. Yeast respires without oxygen during fermentation. 2. Yeast is a bacterium. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Yeast is a unicellular fungus.

30. Consider the statements. 1. Manure improves soil texture. 2. Fertilisers are made from decomposed plant waste. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Fertilisers are made in factories; manures come from decomposed waste.

31. Consider the statements. 1. Kharif crops are sown with the rains. 2. Rabi crops are harvested in March–April. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both are correct.

32. Consider the statements. 1. Winnowing separates grain from husk using wind. 2. Threshing is done to remove weeds. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Threshing separates grain from stalks, not weeds.

33. Consider the statements. 1. Virus can reproduce on its own outside a host. 2. Viruses are cells with a nucleus. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    D. Neither 1 nor 2

    A virus is not a cell and multiplies only inside a host cell.

34. Consider the statements. 1. Silk is spun by the larva of the silkworm in the cocoon. 2. Silkworms feed on mulberry leaves. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both are correct.

35. Consider the statements. 1. Murrah is a buffalo breed. 2. Gir is an exotic breed of cattle. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Gir is an indigenous breed.

36. Consider the statements. 1. Dengue is spread by the Aedes mosquito. 2. Dengue is caused by a bacterium. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Dengue is viral.

37. Match the microbe with its use. (a) Rhizobium (b) Penicillium (c) Lactobacillus (d) Yeast (p) Curd (q) Antibiotic (r) Nitrogen fixation (s) Alcohol making

    1. a-r, b-p, c-q, d-s
    2. a-r, b-q, c-p, d-s
    3. a-q, b-r, c-p, d-s
    4. a-s, b-q, c-p, d-r
    Answer

    B. a-r, b-q, c-p, d-s

    Each pair follows the standard role.

38. Match the disease with its cause. (a) Cholera (b) Malaria (c) Ringworm (d) Measles (p) Fungus (q) Virus (r) Bacterium (s) Protozoan

    1. a-r, b-s, c-q, d-p
    2. a-r, b-s, c-p, d-q
    3. a-p, b-s, c-r, d-q
    4. a-s, b-r, c-p, d-q
    Answer

    B. a-r, b-s, c-p, d-q

    Cholera bacterial; malaria protozoan; ringworm fungal; measles viral.

39. Arrange crop production steps in order.

    1. Sowing, ploughing, harvesting, irrigation
    2. Harvesting, sowing, ploughing, irrigation
    3. Irrigation, harvesting, sowing, ploughing
    4. Ploughing, sowing, irrigation, harvesting
    Answer

    D. Ploughing, sowing, irrigation, harvesting

    Soil is first prepared, then sown, watered and harvested.

40. A compost pit in the school garden is useful in teaching because

    1. It replaces all textbook study
    2. It removes all microbes
    3. It stops plants from growing
    4. It lets learners see decomposition by microbes
    Answer

    D. It lets learners see decomposition by microbes

    Compost pits show decay by bacteria and fungi.

41. The best way to teach the idea of fermentation in a Class VII lesson is to

    1. only dictate the definition
    2. let learners observe dough or batter rising with yeast
    3. ask them to memorise an equation
    4. show a picture without discussion
    Answer

    B. let learners observe dough or batter rising with yeast

    Observation of a real example builds understanding.

42. Which of the following is the livestock product of pisciculture?

    1. Honey
    2. Silk
    3. Fish
    4. Wool
    Answer

    C. Fish

    Pisciculture is fish rearing.

43. Which disease of poultry is caused by a virus?

    1. Cholera
    2. Citrus canker
    3. Ringworm
    4. Ranikhet disease
    Answer

    D. Ranikhet disease

    Ranikhet (Newcastle) disease is viral.

44. Which of these is a decomposer?

    1. Earthworm egg
    2. Green alga
    3. Fungus
    4. Sunflower plant
    Answer

    C. Fungus

    Fungi and bacteria break down dead matter.

45. Winnowing is mostly done when

    1. the grain is wet
    2. the wind is blowing
    3. it rains heavily
    4. the crop is in the field
    Answer

    B. the wind is blowing

    Wind blows lighter husk away.