Fungi and its Economic Importance - Questions & Answers

1. Which is the most common variety of cultivated mushroom ?
Answer: White button mushroom (Agaricus bisporous) is the most common variety of cultivated mushroom.

2. What is meant by "mushroom seed" ?
Answer: "Mushroom seed" refers to the mycelium of the selected type of mushroom that is introduced into the compost for cultivation.

3. What is done in the step called "casing" ?
Answer: In the casing step, a thin layer of soil is spread over the compost to give support to the mushroom, provide humidity, prevent quick drying, and regulate temperature.

1. Choose the correct answer from the options given below :

(i) Production of ethanol (C₂H₅OH) occurs in one of the life processes of :
(a) Bread mould
(b) Yeast
(c) Mushroom
(d) Penicillium
Answer: (b) Yeast

(ii) Which among the following statements is incorrect about fungi ?
(a) They are multicellular organisms except yeasts.
(b) They are heterotrophic and are either parasitic or saprophytic.
(c) They prefer cold and dry conditions to grow.
(d) They are immobile unlike bacteria.
Answer: (c) They prefer cold and dry conditions to grow.

(iii) Yeast is used in the production of :
(a) Ethyl alcohol
(b) Acetic acid
(c) Cheese
(d) Curd
Answer: (a) Ethyl alcohol

(iv) Which of the following is a unicellular organism ?
(a) Rhizopus
(b) Mould
(c) Yeast
(d) Mushroom
Answer: (c) Yeast

(v) The scientific name of white button mushroom is :
(a) Volvariella
(b) Aspergillus
(c) Pleurotus
(d) Agaricus bisporus
Answer: (d) Agaricus bisporus

(vi) The entire mass of hyphae is termed as :
(a) Sporangium
(b) Sporangiophore
(c) Both (a) and (b)
(d) Mycelium
Answer: (d) Mycelium

(vii) The heterotrophic mode of nutrition in fungi is:
(a) Symbiotic
(b) Saprophytic
(c) Parasitic
(d) Holozoic
Answer: (b) Saprophytic

(viii) The stored food material in Yeast is in the form of :
(a) Glycogen and fat
(b) Starch and Cellulose
(c) Glycogen and Protein
(d) None of these
Answer: (a) Glycogen and fat

(ix) Which of the following properties of fungi separates them from plants ?
(a) Absence of chlorophyll
(b) Autotrophic mode of nutrition
(c) Lack of a stem
(d) Poisonous and non-edible
Answer: (a) Absence of chlorophyll

(x) The main products produced by microorganisms during fermentation are :
(a) Ethanol or lactic acid
(b) Ethanol and uric acid
(c) Amino acid and lactic acid
(d) Ethanol or uric acid
Answer: (a) Ethanol or lactic acid

(xi) The cultivation of white bution mushroom involves five major steps, which are :
(1) Caring (2) Spawning
(3) Preservation (4) Crapping and Harvesting
(5) compasting
The correct sequence will be :
(a) (2), (4), (3), (1), (5)
(b) (4), (5), (1), (2), (3)
(c) (5), (2), (1), (4), (3)
(d) (1), (3), (5), (4), (2)
Answer: (c) (5), (2), (1), (4), (3)

1. Fill in the blanks :

(a) The specific genus to which several species of yeast belong is Saccharomyces.

(b) Yeast is a unicellular fungi.

(c) Alcoholics may develop body ailments like liver cirrhosis due to over consumption of alcohol.

(d) The curd from which moisture has been removed is termed as cottage cheese.

(e) Cheese is a good source of vitamin A and B.

1. Define the terms : (a) Fermentation (b) Spawning
Answer:
(a) Fermentation is a process in which microorganisms (like yeast and bacteria) break down carbohydrates into simpler products (ethanol or lactic acid) in the absence of oxygen.
(b) Spawning is the process in mushroom cultivation where "mushroom seed" (mycelium of the selected mushroom) is introduced into the prepared compost and allowed to spread for a couple of days.

2. Where can the mould Rhizopus be most easily found ?
Answer: Rhizopus is most easily found growing on moist bread, as well as on a variety of other organic matter such as fruits, animal dung, and leather goods, especially in warm and humid climates.

3. Write the chemical equation of fermentation.
Answer: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + 2ATP

4. Name three vitamins which are richly found in mushrooms.
Answer: Niacin, pantothenic acid, and biotin.

5. Describe the role of certain fungi in industrial production.
Answer: Fungi like yeast (Saccharomyces cerevisiae) are used in breweries for alcohol production through fermentation, and in bakeries for bread-making by producing carbon dioxide to make the dough rise. Certain species of Penicillium are used to process flavoured cheeses and to produce essential antibiotics like penicillin.

6. Differentiate between :
(a) Saprophyte and Parasite
(b) Aerobic and anaerobic respiration with regard to the products formed.
Answer:
(a) A saprophyte obtains its nourishment by extracellularly digesting dead and decaying organic matter (like Rhizopus on bread). A parasite obtains its nourishment directly from living host organisms, often causing diseases.
(b) In aerobic respiration (in the presence of oxygen), glucose is completely broken down to form carbon dioxide, water, and large amounts of energy. In anaerobic respiration (in the absence of oxygen, as seen in yeast), glucose is incompletely broken down to form ethanol (ethyl alcohol) and carbon dioxide, along with 2ATP of energy.

1. Discuss the role of yeasts in bakeries and breweries.
Answer: In breweries, yeast breaks down carbohydrates (like grape sugar or barley maltose) into ethanol and carbon dioxide in the absence of oxygen through fermentation, producing alcoholic beverages like wine and beer. In bakeries, yeast is added to dough, where it ferments the sugar to produce carbon dioxide. This gas makes the dough rise (leavening) to about three times its original volume, and upon baking, expands to give the bread a soft, spongy texture.

2. Write in proper sequence the five major steps in the cultivation of the common edible mushroom.
Answer: The proper sequence is:
(i) Composting: Preparing a mixture of wheat/paddy straw, chicken manure, and fertilizers, kept at 50°C for a week.
(ii) Spawning: Introducing the "mushroom seed" (mycelium) into the compost.
(iii) Casing: Spreading a thin layer of soil over the compost to provide humidity and support.
(iv) Cropping and Harvesting: Growth stages from mycelium to tiny pin heads, and finally the button stage for harvesting.
(v) Preservation: Increasing shelf life using vacuum cooling, freeze-drying, or gamma radiation.

3. Would you consider bacteria and yeast as plants? Give reason.
Answer: No, they are not considered plants. According to the Five Kingdom classification, yeast (a fungus) lacks chlorophyll and has a heterotrophic mode of nutrition, which distinguishes it from autotrophic plants. Bacteria are prokaryotic organisms, whereas plants are eukaryotic.

4. Both bacteria and yeast reproduce by asexual method, but how does this method differ in them ?
Answer: Bacteria typically reproduce asexually through binary fission, where the parent cell divides equally into two daughter cells. Yeast reproduces asexually primarily through budding, where a small bulb-like outgrowth (bud) emerges on the parent cell, which may eventually detach or form chains of cells.

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) What would happen if the bread was not covered by the bell-jar ?
Answer: The moisture from the bread would evaporate into the surrounding air, causing it to dry out quickly. Since fungi require moisture to thrive, mould growth would be inhibited or slowed down significantly.

(b) What would happen if moist bread was placed in a refrigerator ?
Answer: The cold temperature inside the refrigerator would inhibit the germination and growth of fungal spores, preventing the mould from growing.

(c) What appears first on the bread—the mycelia or the spores ?
Answer: The mycelia (network of hyphae) appear first on the bread as a cottony growth, which later develop sporangiophores bearing spores.

2. Draw a neat diagram of the unicellular fungus 'Yeast' and label its six important parts.
Answer: (A neat oval-shaped diagram of a yeast cell should be drawn and labeled with the following six parts: Cell Wall, Cell Membrane, Cytoplasm, Nucleus, Vacuole, Fat Vacuole, and Glycogen Granule).

3. The figure shown alongside represents an organism. Study the figure and answer the following questions.
(a) Identify the organism and write its common as well as scientific name.
Answer: The common name of the organism is Bread mould. Its scientific name is Rhizopus.

(b) Label the parts shown as 1, 2 and 3.
Answer: 1 — Sporangium; 2 — Spores; 3 — Mycelium (Hyphae).

(c) Name two suitable habitats of the organism shown.
Answer: Moist bread and decaying organic matter (like rotting fruits, animal dung, or moist leather goods).

(d) Mention its main mode of reproduction.
Answer: Asexual reproduction through the formation of spores.

(e) What specific kinds of digestion occur in it ?
Answer: Extra-cellular digestion (saprophytic nutrition) occurs, where penetrating hyphae secrete enzymes into the substratum to digest food outside the cell before absorbing it.

4. These days mushroom cultivation has become a common indoor business. Shalini has grown white button mushrooms which are shown below in the diagram.
(a) Write the scientific name of the mushrooms shown above.
Answer: Agaricus bisporous.

(b) Name two vitamins which are abundantly found in this mushroom.
Answer: Niacin and pantothenic acid (or biotin).

(c) What do you understand by 'spawning' (second step in mushroom cultivation) ?
Answer: Spawning is the process of introducing the "mushroom seed," which consists of the mycelium of the selected mushroom variety, into the prepared compost and allowing it to spread.

(Choose the answer based on the codes given below.)
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

(i) Assertion (A) : Fungi are non-chlorophyllous, saprotrophic plants which can be unicellular or multicellular.
Reason (R) : None of the fungi are autotrophic. They are eukaryotic.
Answer: (d) A is false but R is true. (Fungi are not classified as plants).

(ii) Assertion (A) : Antibiotics like penicillin are obtained from fungi.
Reason (R) : Some fungi produce chemicals that can inhibit the growth of bacteria.
Answer: (a) Both A and R are true and R is the correct explanation of A.

(iii) Assertion (A) : Fungi are more closely related to animals than to plants.
Reason (R) : Fungi cell walls are made of chitin, not cellulose.
Answer: (a) Both A and R are true and R is the correct explanation of A.

1. Fariya visited a small food processing unit in Goa where she observed mushrooms being grown on moist straw in dark, humid rooms. She also learned that in many local fermentation units in Goa, such as breweries and small fruit wine units, yeast is used to convert sugar into alcohol and carbon dioxide. She realised that fungi play an important role in food production, but can also spoil food if conditions are not properly controlled.
(a) Why do mushrooms require dark, warm and moist conditions for proper growth ?
Answer: Mushrooms are fungi that lack chlorophyll, so they do not require sunlight for photosynthesis and can easily grow in the dark. They need warm and moist conditions for their mycelium to spread optimally and to ensure proper germination of spores on organic matter.

(b) Name the biological process by which yeast converts sugar into alcohol and write the reaction involved.
Answer: The biological process is called fermentation (anaerobic respiration).
The reaction is: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + 2ATP

(c) How does the mode of nutrition in mushroom differ from that of green plants ?
Answer: Mushrooms exhibit a heterotrophic (saprophytic) mode of nutrition, meaning they obtain nourishment by secreting enzymes to break down and absorb dead or decaying organic matter. In contrast, green plants have an autotrophic mode of nutrition, using sunlight and chlorophyll to synthesize their own food through photosynthesis.