Economic Importance of Fungi

White button mushroom (Agaricus bisporous).

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 .

(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.

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.

The chemical equation of fermentation is:

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

Three vitamins which are richly found in mushrooms are:

1. Niacin
2. Pantothenic acid
3. Biotin

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

(a) Differences between Saprophyte and Parasite:

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

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.

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.

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.

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.

(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.

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

(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.

(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.

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.

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.

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.

(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.