Economic Importance of Fungi

Which is the most common variety of cultivated mushroom ?

Answer

White button mushroom (Agaricus bisporous).

What is meant by "mushroom seed" ?

Answer

Mushroom seed consists of mycelium of the selected type of mushroom that is introduced into the compost and allowed to grow.

What is done in the step called "casing" ?

Answer

A thin layer of soil is spread over the compost on which mushroom seed had been spread earlier. This is called Casing. It is done in order to provide support to growing mushrooms and prevent quick drying of compost.

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

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

Answer

Yeast

Reason — Yeast respires anaerobically to form ethanol and carbon dioxide.
Ethanol is produced during anaerobic respiration. Bread mould mainly decomposes organic matter. It does not produce ethanol. Mushroom is a fungus that absorbs nutrients from organic matter. It does not produce ethanol.

Which among the following statements is incorrect about fungi ?

1. They are multicellular organisms except yeasts.
2. They are heterotrophic and are either parasitic or saprophytic.
3. They prefer cold and dry conditions to grow.
4. They are immobile unlike bacteria.

Answer

They prefer cold and dry conditions to grow.

Reason — Fungi prefer warm and humid climate.
Most fungi are multicellular except yeast. Yeast is unicellular. Fungi cannot make their own food. They obtain nutrition from dead and decaying matter or from living hosts. Fungi do not move from place to place.

Yeast is used in the production of

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

Answer

Ethyl alcohol

Reason — Yeast respires anaerobically to form ethyl alcohol and carbon dioxide.
Acetic acid is produced by Acetobacter bacteria. Cheese is made using lactic acid bacteria and enzymes like rennet. Curd is formed by Lactobacillus bacteria.

Which of the following is a unicellular organism ?

1. Rhizopus
2. Mould
3. Yeast
4. Mushroom

Answer

Yeast

Reason — Yeasts are one-celled fungi.
Rhizopus is multicellular, made of thread-like structures called hyphae. Mould is mostly multicellular organisms. Mushroom is multicellular.

The scientific name of white button mushroom is :

1. Volvariella
2. Aspergillus
3. Pleurotus
4. Agaricus bisporus

Answer

Agaricus bisporus

Reason — Agaricus bisporus is the most common edible mushroom also known as white button mushroom.
Volvariella is an edible mushroom but not the white button mushroom. Aspergillus is a type of fungus used in industrial processes and can also cause diseases. Pleurotus is an edible mushroom but not the white button mushroom.

The entire mass of hyphae is termed as :

1. Sporangium
2. Sporangiophore
3. Both (a) and (b)
4. Mycelium

Answer

Mycelium

Reason — The thread like hyphae together form mycelium.
Sporangium is a structure in fungi where spores are produced and stored. Sporangiophore is a specialized stalk that bears the sporangium.

The heterotrophic mode of nutrition in fungi is:

1. Symbiotic
2. Saprophytic
3. Parasitic
4. Heterozoic

Answer

Saprophytic

Reason — Most of the fungi show saprophytic mode of nutrition. Some may also show parasitic mode of nutrition.
In symbiotic mode, two organisms live together and both benefit. In parasitic mode, fungi live on living hosts and harm them. Heterozoic is used for animals that ingest food, fungi do not ingest food.

The stored food material in Yeast is in the form of :

1. Glycogen and fat
2. Starch and Cellulose
3. Glycogen and Protein
4. None of these

Answer

Glycogen and fat

Reason — Yeast stores food material in the form of Glycogen and fat in fat vacuoles.
Starch is mainly in plants. Cellulose is a structural component of plant cell walls, not stored food. Protein is not a storage food material in yeast.

Which of the following properties of fungi separates them from plants ?

1. Absence of chlorophyll
2. Autotrophic mode of nutrition
3. Lack of a stem
4. Poisonous and non-edible

Answer

Absence of chlorophyll

Reason — Fungi are differentiated from the plants as they don't have chlorophyll and their body is not differentiated into roots, stems and leaves.
Plants are autotrophic, fungi are heterotrophic. Some plants also do not have a true stem. Some fungi are edible while some plants are also poisonous.

The main products produced by microorganisms during fermentation are:

1. Ethanol or lactic acid
2. Ethanol and uric acid
3. Amino acid and lactic acid
4. Ethanol or uric acid

Answer

Ethanol or lactic acid

Reason — The main products produced by microorganisms during fermentation are ethanol or lactic acid and also acetic acid in some cases.
Uric acid is a waste product in animals, not fermentation. Amino acids are not fermentation products.

The cultivation of white button mushroom involves five major steps, which are :

1. Caring
2. Spawning
3. Preservation
4. Crappping 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

5, 2, 1, 4, 3

Reason — Preparation of nutrient-rich compost bed for mushroom growth is composting.
Mixing mushroom spores into compost is spawning.
Maintaining proper temperature, humidity, and conditions for growth is caring.
Mushrooms grow and are collected is cropping and harvesting.
Post-harvest storage and processing is preservation.

Fill in the blanks:

1. The specific genus to which several species of yeast belong is ............... .
2. ............... is a unicellular fungi.
3. Alcoholics may develop body ailments like ............... due to over consumption of alcohol.
4. The curd from which moisture has been removed is termed as ............... .
5. Cheese is a good source of vitamin ............... and ............... .

Answer

1. The specific genus to which several species of yeast belong is Saccharomyces .
2. Yeast is a unicellular fungi.
3. Alcoholics may develop body ailments like Liver cirrhosis due to over consumption of alcohol.
4. The curd from which moisture has been removed is termed as cottage cheese .
5. Cheese is a good source of vitamin A and B .

Define the terms

(a) Fermentation

(b) Spawning

Answer

(a) Fermentation is a process in which the microorganisms (yeast and bacteria) break down carbohydrates into simpler products (ethanol or lactic acid) in the absence of oxygen.

(b) Spawning is defined as introduction of mushroom seed or mycelium of selected mushroom into compost.

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.

Write the chemical equation of fermentation.

Answer

The chemical equation of fermentation is:

$\underset{\text{Glucose}}{\text{C}_6\text{H}_{12}\text{O}_6} \longrightarrow \underset{\text{Ethanol}}{2\text{C}_2\text{H}_5\text{OH}} + 2\text{CO}_2$

Name three vitamins which are richly found in mushrooms.

Answer

Three vitamins which are richly found in mushrooms are:

1. Niacin
2. Pantothenic acid
3. Biotin

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

Differentiate between:

(a) Saprophyte and Parasite

(b) Aerobic and anaerobic respiration with regard to the products formed.

Answer

(a) Differences between Saprophyte and Parasite:

(b) Differences between aerobic and anaerobic respiration with regard to the products formed:

Discuss the role of yeasts 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.

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. Spawning — '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.

Would you consider bacteria and yeast as plants? Give reason.

Answer

We cannot consider bacteria and yeast as plants. The reasons for it are as given below:

1. They lack chlorophyll (except a few bacteria). Their mode of nutrition is heterotrophic instead of autotrophic.
2. Bacteria are prokaryotic and lack membrane bound organelles.
3. Fungi is multicellular but it is not differentiated into root, stem and leaves.

Both bacteria and yeast reproduce by asexual method, but how does this method differ in them ?

Answer

Bacteria reproduces by cell division or binary fission. The circular DNA duplicates. The cell expands and the two DNA are pulled apart. The cell constricts at the middle separating the two cells.
Fungi like yeast reproduce by budding. In budding, a small bud or daughter cell is formed on the parent cell. The bud continues to grow until it separates from the parent cell, forming a new cell.

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?

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

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

Answer

(a) 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.

(b) If the moist bread was placed in a refrigerator, moulds would not appear. Fungi like bread mould (Rhizopus) grow very quickly in warm and humid conditions. The low temperature inside the refrigerator would prevent its growth.

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

Draw a neat diagram of the unicellular fungus 'Yeast' and label its six important parts.

Answer

Below is the diagram of Yeast with its six important parts labelled:

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.

(b) Label the parts shown as 1, 2 and 3.

(c) Name two suitable habitats of the organism shown.

(d) Mention its main mode of reproduction.

(e) What specific kinds of digestion occur in it ?

Answer

(a) The organism show in figure is bread mould.
Common Name — Moulds
Scientific Name — Rhizopus

(b) The parts are:

• 1 → Sporangium
• 2 → Spores
• 3 → Hyphae

(c) They prefer warm and humid climate and organic material like fruits, bread, leather etc. to grow.

(d) It shows asexual reproduction as well as sexual reproduction. Asexually it reproduces by spore formation. A few hyphae become erect (sporangiophores) and swell at the tip to form sporangium. The sporangium containing spores burst to spread the spores. The spore germinates to form hyphae when it finds favorable conditions.

(e) Extracellular digestion.

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.

(b) Name two vitamins which are abundantly found in this mushroom.

(c) What do you understand by 'spawning' (second step in mushroom cultivation) ?

Answer

(a) Agaricus bisporous

(b) Biotin (Vitamin B₇) and Niacin (Vitamin B₃)

(c) The process of introducing mushroom mycelium (the vegetative part of the fungus) into a suitable growing medium is known as spawning. After spawning, the mycelium spreads throughout the substrate. It is similar to sowing seeds in agriculture.

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.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

A is True and R is False.

Reason — A is True as fungi do not contain chlorophyll. They are saprotrophic. They can be unicellular (like yeast) or multicellular.
R is False as fungi do not contain chlorophyll and cannot perform photosynthesis. They are heterotrophic by nature.

Therefore, A is True and R is False is the correct option.

Assertion (A): Antibiotics like penicillin are obtained from fungi.

Reason (R): Some fungi produce chemicals that can inhibit the growth of bacteria.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

Both A and R are true and is the correct explanation of A.

Reason — A is true as antibiotics like penicillin are obtained from fungi such as Penicillium.
R is true as some fungi produce chemicals that inhibit the growth of bacteria.

Therefore, Both A and R are true and R is the correct explanation of A is the correct option.

Assertion (A): Fungi are more closely related to animals than to plants.

Reason (R): Fungi cell walls are made chitin, not cellulose.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

Both A and R are true and R is the correct explanation of A.

Reason — A is true as fungi share a closer evolutionary relationship with animals than with plants.
R is true as fungi cell walls are made chitin, not cellulose.

Therefore, Both A and R are true and R is the correct explanation of A is the correct option.

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 moist conditions for proper growth ?

(b) Name the biological process by which converts sugar into alcohol and write reaction involved.

(c) How does the mode of nutrition in mushroom differ from that of green plants ?

Answer

(a) Mushrooms are fungi and lack chlorophyll, so they do not need light for photosynthesis. They need in warm conditions, for optimal enzyme activity. They require moist conditions to absorb nutrients easily. They grow best in dark environment to prevents drying and mimics their natural habitat.

(b) Fermentation converts sugar into alcohol.

C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂

(c) Mushroom feeds on dead and decaying organic matter whereas green plants prepare their own food by photosynthesis using sunlight, carbon dioxide, and water.