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Chapter 9b

Economic Importance of Fungi

Class 9 - Concise Biology Selina


Multiple Choice Type

Question 1

Production of ethanol (C2H5OH) occurs in one of the life processes of:

  1. Bread mould
  2. Yeast ✓
  3. Mushroom
  4. Penicillium

Question 2

Which one of the following characteristics is found in all fungi but not in all bacteria?

  1. Aerobic respiration
  2. Cell wall
  3. Spore formation ✓
  4. A long circular DNA lying loose in the cytoplasm.

Question 3

Bacteria are referred to as prokaryotes because:

  1. They have no chlorophyll
  2. They are unicellular
  3. They are free living
  4. They do not have a true nucleus ✓

Question 4

Yeast is used in the production of:

  1. Ethyl alcohol ✓
  2. Acetic acid
  3. Cheese
  4. Curd

Very Short Answer Type

Question 1

Tick mark the correct statement/statements

  1. All mushrooms are poisonous
  2. All toadstools are poisonous
  3. Some toadstools are poisonous
  4. Some mushrooms are edible

Answer

The correct statements are:

  1. All mushrooms are poisonous
  2. All toadstools are poisonous
  3. Some toadstools are poisonous ✓
  4. Some mushrooms are edible ✓

Short Answer Type

Question 1

Where can the mould Rhizopus be most easily found?

Answer

Rhizopus is the common bread mould. It grows not only on bread but also on a variety of other organic matter such as cloth, wood, paper, leather goods, animal dung. In food materials — pickles, bread, fruit, chapatti etc. They specifically occur in humid and warm climatic conditions.

Question 2

Why is it generally advised that every living room in the house should get direct sunlight at least for a short time?

Answer

Direct sunlight contains ultraviolet radiations of the Sun, which help in killing of mould spores present in air. Hence, it is advised that every living room in the house should get direct sunlight at least for a short time.

Question 3

Describe the role of certain fungi in industrial production.

Answer

  1. Used to prepare wine and alcohol
  2. Used in the cultivation of mushroom
  3. Used to prepare enzymes
  4. Used to prepare antibiotics
  5. Used to prepare alcoholic beverages
  6. Used to prepare bakery products and fermented foods
  7. Used to prepare organic acids

Question 4

Mention two useful and two harmful effects of wine.

Answer

When consumed in mild quantities, the useful effects of wine are:

  1. It acts as a stimulant and helps in cough and cold.
  2. It lowers bad cholesterol and helps to keep the heart healthy.

Two harmful effects of wine are:

  1. It effects the functioning of Central Nervous System.
  2. It can cause body ailments particularly liver cirrhosis.

Question 5a

Differentiate between Saprophyte and Parasite

Answer

Saprophyte and Parasite

CharacteristicsParasiteSaprophyte
DefinitionIndividuals of one species that live at the expense of individuals from another species, called hosts.Organisms that feed on decaying dead organic matter and break it down into simple molecules that can be used by the autotrophs.
Food sourceObtained from host without killing it.Obtained from decaying entities.
FeedingFeeds with vital products from the host or parts of its body.Feeds with decaying dead organic matter.

Question 5b

Differentiate between Aerobic and anaerobic respiration with regard to products

Answer

PropertyAerobic respirationAnaerobic respiration
OxygenPresentAbsent
Breakdown of foodcompletePartial
End productsWater and carbon dioxideEthanol and lactic acid
Energy producedSignificant quantity of energyMuch lesser in comparison to aerobic

Question 5c

Differentiate between Decay and Putrefaction.

Answer

DecayPutrefaction
Complete breakdown of organic matter by bacteria.Incomplete breakdown of organic matter by bacteria.
Does not produce a foul smell.Generates a foul smell.

Long Answer Type

Question 1

What are antibiotics? Name any two examples.

Answer

Antibiotics are chemical substances that are produced by living entities which inhibits or kills the growth of micro-organisms that cause the diseases such as fungi and bacteria. Examples of antibiotics are:

  1. Streptomycin
  2. Penicillin

Question 2

Is tinned and sealed food always safe to eat? Give reasons in support of your answer.

Answer

No, tinned and sealed food are not always safe to eat as it may contain harmful bacteria like Clostridium botulinum that causes food poisoning. Clostridium botulinum releases toxins under low-oxygen conditions. These toxins are very lethal and can block nerve functions leading to muscular and respiratory paralysis.

Moreover, the chemicals used in the inner coating of the container can be harmful for humans.

Question 3

Would there be any bacteria in an aquarium?

Answer

Yes, bacteria can exist in aquarium. Bacteria can exist practically everywhere, as they can withstand any climatic condition.

Structured / Application / Skill Type

Question 1

If you leave a piece of moist bread covered under a small bell jar at a warm place, mould grows on it in a few days. Answer the following with reference to this observation:

(a) How did the mould get inside the bell-jar?

(b) What would happen if the bread was not covered by the bell-jar?

(c) What would happen if moist bread was placed in a refrigerator?

(d) What appears first on the bread – the mycelia or the spores?

(e) How does bread mould obtain nourishment? What type of nourishment is it – epiphytic, autotrophic, parasitic symbiotic, or saprophytic?

Answer

(a) Moulds are commonly present in air, water, etc. Hence, they were already present when moist bread was kept covered with the bell-jar.

(b) If bread was not covered by the bell-jar, mould would have appeared but after a while. The humid and warm conditions within the bell-jar facilitate rapid production of mould.

(c) Moulds do not grow below freezing point inside a refrigerator.

(d) Mycelia appears first on the bread, not the spores.

(e) Bread Mould obtains its nourishment through extracellular digestion from the substratum where it grows. This mode of nourishment is referred to as saprophytic nutrition.

Question 2

Write in proper sequence the five major steps in the cultivation of the common edible mushroom.

Answer

Five major steps in the cultivation of common edible mushrooms are:

  1. Composting — Composting involves mixing of various components such as
    1. Paddy straw or Wheat
    2. Organic and Inorganic fertilizer
    3. Chicken manure
      The temperature of the compost is kept for about one week under 50°C.
  2. Spawing — 'Mushroom seed' in the form of mycelium of mushroom to be grown is introduced into the heap of compost and left for spreading for around two days.
  3. Casing — It is an important step wherein a thin layer of soil is spread over the compost. It:
    1. Gives support to the mushroom
    2. Prevents quick drying of the compost
    3. Provides humidity
    4. Assists to check temperature
  4. Cropping & Harvesting — The growth occurs in three principal stages:
    1. Mycelium grows within 2-6 weeks
    2. Tiny pin heads
    3. Button stage grows bigger attaining marketable size
    4. Fully grown mushrooms are taken out.
  5. Preservation — Shelf life of mushroom can be increased by the following processes:
    1. Vacuum cooling
    2. Storing at 15 degree Celsius and giving gamma radiation
    3. Freeze drying in a solution of ascorbic acid, citric acid, and brine etc.

Question 3a

Comment on the following:

Denitrifying bacteria are a blessing as well as a curse to farmers.

Answer

Denitrifying bacteria is a blessing to farmers as they control the excess supply of nitrates to plants. Excess nitrates can cause harm to the ecosystem. On the other hand, denitrifying bacteria are a curse to the farmers as they disintegrate soil nitrates to liberate free nitrogen gas into the atmosphere, hence reduces levels of nitrogenous compounds in the soil.

Question 3b

Comment on the following:

Yeast is used in bakeries and breweries

Answer

During the baking process, yeast added to the dough ferments sugar and produces carbon dioxide. This causes the dough to rise and when it is baked, the gas bubbles expand causing the bread to be spongy and light. Hence yeast is used in bakeries.

The greatest importance of yeast to us is through their property of alcoholic fermentation. Fermentation is the process in which the micro-organisms like yeast break down the carbohydrates into simpler products like ethanol and lactic acid. This alcohol is of great commercial importance. Hence, yeast is used in breweries to produce beer and wine from barley maltose and grapes, respectively.

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