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Today we will discuss about the world of Fungi.

Definition of Fungi
A kingdom of eukaryotic, spore forming and saprophytic organisms that grow in irregular masses, without roots, stems, or leaves, and are devoid of chlorophyll or other pigments capable of photosynthesis. E ach organism (thallus) is unicellular to filamentous, and possesses branched somatic structures (hyphae) surrounded by cell walls containing chitin and containing true nuclei.

PROPERTIES FUNGI

  1. Heterotrophic nutrition (parasitic or saprophytic)      
  2. Terrestrial
  3. Thallus body
  4. Reserve food material is glycogen
  5. Cell wall- chitin
  6. Pseudoparenchyma
  7. Nonflowering
  8. Microscopic or macroscopic
  9. Reproduction- vegetative, asexual and sexual
  10. Eg. Yeast, Mucor, etc


a.  Mushroom


b.  Sporangium of Mucor

Classify fungi up to subdivisions and mention characteristic features of each subdivision. (6)

Ans.
Main classification of fungi:
Fungi are classified into four classes such as:
1. Phycomycetes eg. Mucor, 2. Ascomycetes eg. Yeast (Saccharomyces), 3. Basidiomycetes, eg. Agaricus, and 4. Deuteromycetes eg. Fusarium.
Class 1. Phycomycetes: The hyphae of the fungi of this class are aseptate. They are coenocytic in nature eg. Mucor.
Class 2. Ascomycetes: The hyphae of the fungi of this class are septate i.e. separated by partition walls. They perform asexual reproduction by the formation of ascospores, which are produced endogenously within the ascus eg. Saccharomyces.
Class 3. Basidiomycetes: The hyphae of the fungi of this class are septate i.e. separated by means of partition walls. They perform asexual reproduction by the formation of basidiospores, which are produced exogenously from the basidium eg. Agaricus.
Class 4 Deuteromycetes: The hyphae of the fungi of this class are septate i.e. with partition walls. Their asexual reproduction occurs by different types of conidia but never occurs by means of ascospores or basidiospores, eg. Fusarium, Helminthosporium etc.

  1. Write six important characteristic features of Fungi. (6)
    Ans. Characteristics of Fungi:
    1. Chlorophyll less thallophytic plants are fungi. Simple thallus like plant body without differentiation into root, stem and leaves.
    2. Fungi can live either in presence or absence of light in aquatic and terrestrial conditions.
    3. They cannot manufacture their own food as they are achlorophyllous. Therefore, the fungi live either as parasites or as saprophytes. Sometime they live symbiotically. Saprophytic fungi derive their food matters by diffusion from dead decaying organic matters. Parasitic fungi derive their necessary food matters form living host plant by means of sucking roots called haustoria.
    4. The fungi may be unicellular or multicellular. In multicellular forms, the plant body is made up of a large number of branched threads like structures. Each of these structures is called the hypha and a collection of hyphae is called mycelium. The mycelium may be septate (with partition wall). Aseptate multinucleated unicellular hyphae are also called coenocyte.
    5. Parasitic fungi may be ectoparasite and endoparasite. The parasites again may be of two types obligate parasite and facultative parasites.
    Saprophytic fungi may be again divided into two types obligate saprophyte and facultative saprophyte.
    Ectoparasite: Those parasitic fungi live on the outer surface of the host body, eg. Olpidium.
    Endoparasite: Those parasitic fungi live within the host body, eg. Puccinia recondita.

Obligate parasite: Those fungi which maintain their mode of life totally as a parasite in their life cycle are called obligate parasite, eg. Puccinia.
Facultative parasites:
Those fungi which in their earlier stage live as a parasite but later on, according to circumstances, live as saprophytes, eg. Aspergillus.
Obligate saprophyte:
Those fungi which live totally as a saprophyte in their life cycle, eg. Saprolegnia.
Facultative saprophyte:
Those fungi in their earlier stage lead their mode of life as saprophytes and later on according to circumstances, lead their life as parasites causing disease, eg. Pestalotia.
In some cases fungi live in close association with the roots of gymnosperms and angiosperms and this sort of association is called mycorrhiza. Those fungi which are associated with the higher plants are called mycorrhizal fungi.
6. In most of the cases, the cell wall is composed of a complex nitrogenous substance, called chitin. Besides this cell wall materials of hyphae may be cellulose, pectose and mannan, glucan, etc.

3. Write one scientific name of an edible fungus. (1)
Ans. Morchella esculenta and Agaricus bisporus.

4. Write the name of the fungus from which Penicillin was invented. (1)
Ans. Penicillium notatum.

5. Write four characters of yeast, which justify its inclusion in fungi. (3)
Ans. Due to the following reasons yeast is included in fungi:
a. Yeast is unicellular.
b. Yeast is achlorophyllous.
c. Its cell wall contains chitin.
d. It can reproduce vegetatively, asexually and sexually.

  1. What is ‘Yeast stage’ of Mucor? (2)
    Ans. When Mucor is grown in sugar enriched nutrient medium, the tip of the hyphae break transversely into spherical structures called oidia, which is similar to budding of yeast and hence it is called torula stage or yeast stage of Mucor.
  2. What is haustorium? (1)
    Ans. It is a specialized hypha with a bulbous tip, found in parasitic fungi, which draws nourishment from the host’s body.
  3. Write three main differences between algae and fungi. (3)
Ans.
Algae Fungi
1. Chlorophyll containing plants, hence autophyte.
2. Cell wall composed of cellulose.
3. Reserve food matter is starch.
1. Chlorophyll less plants, hence heterophyte-may be parasite or saprophyte.
2. Cell wall composed of chitin.
3. Reserve food matter is glycogen.
  1. What is pedogamy? (1)
    Ans. The copulation between the mother cell and the bud is known as pedogamy. It is found in Zygosaccharomyces chevalieri.10. What is Blastomycosis? (1)
    Ans. It is a fungal disease of the human skin caused by a yeast like organism, Blastomycosis dermatitidis. The symptoms include raised pustules on the skin and at a later stage lesions may develop on the lung.
  2. Give the names of the causative agents of the following diseases. (4)
    a) Stem rot of jute.
    b) Black stem rust of wheat.
    c) Brown spot disease of rice.
    d) Late blight of potato.
    Ans.
    Macrophomina phaseolina
    Puccinia
    graminis
    Helminthosporium
    oryzae
    Phytopthora
    infestans
  3. Name the edible mushroom, which is cultivated in cold climate. (1)
    Ans. Agaricus campestris and Pleurotus sajarcaju
  4. What is Pseudomycelium? (2)
    Ans. Due to budding process yeast cells sometimes adhere with one another forming chains called pseudomycelium.
  5. Name two poisonous fungi. (2)
    Ans. Boletus satanus and Amanita phalloids
  6. What are coprophilous fungi? (2)
    Ans. The fungi growing as a saprophyte on animal dung is known as coprophilous fungi, eg. Ascobolus.
  7. What are ergotism and aspergillosis? (2+2)
    Ans.
    Ergotism: The disease induced by the consumption of infected rye plant, infected with ergot fungus Claviceps purpurea in higher animals including man. The symptoms include convulsion, spasm and abortion in pregnant female.
    Aspergillosis: The disease of lung in man caused by the fungus Aspergillus, which causes blocking of the respiratory tract.
  8. What is aflatoxin? (2)
    Ans. A carcinogenic toxin produced by fungi like Aspergillus flavus is known as aflatoxin.18. What are shot-gun fungus and ballistospore? (1+1)
    Ans. The mature sporangium of Pilobolus crystallinus is forcibly shot into the air up to a height of 26 feet and hence called shot-gun fungus.
    The spore, which is ejected forcibly from the sporocarp at a great speed is known as ballistospore, eg. Calocera.
  9. Name the fungus which contains carotene. (1)
    Ans. Allomyces and Pilobolus.
  10. Name two Indian species of Saccharomyces and Mucor. (2+2=4)
    Ans.
    a. Saccharomyces cerevisiae and Saccharomyces fructuum
    b. Mucor mucedo and Mucor indicus
  11. Describe the vegetative structure of Yeast (with diagram). (6)
    Ans.
    a. Vegetative body of Yeast is unicellular and varies in shape greatly, i.e. the cell may be oval, rectangular, elongated elliptical in shape. The cell may adhere in chains forming pseudomycelium, which sometimes may be branched.
    b. The diameter of yeast cell ranges from 5-10 micron.
    c. Each yeast cell has a definite cell wall, a nucleus surrounded by cytoplasm, a large central vacuole and cell inclusions embedded in the cytoplasm.
    d. The cell wall contains pectin, lipid polysaccharides, glucan and mannan. Beneath the cell wall, lies the cytoplasmic membrane forming a typical unit membrane.
    e. The cytoplasm is granular with endoplasmic reticulum, mitochondria and ribosomes. The cytoplasm is differentiated into an outer clear ectoplasm and inner granular endoplasm.
    f. The reserve food materials are glycogen, oil globules and protein particles.
    g. The nucleus is distinct, bipartite and surrounded by a double unit membrane with nucleopores.
    h. A large vacuole is present at the centre of cytoplasm. This vacuole contains strands and volutin granules (polymetaphosphate) of dense material linked into a net work.
  12. Describe the vegetative structure of Mucor (with diagram). (6)
    Ans.
    a. The vegetative body is composed of well-developed mycelium, which consists of much branched filamentous coenocytic hyphae {Sin: hypha}(they are devoid of partition walls).
    b. Hyphae get differentiated into a prostrate fixative and absorptive hyphae and the aerial hyphae producing reproductive organ.
    c. The cell wall of hyphae consists of cellulose, pectin and chitin.
    d. Protoplasm is surrounded by a cytoplasmic membrane.
    e. The protoplasts within the cell wall is granular mass with numerous vacuoles, eukaryotic nuclei, cell organelles and storage products (glycogen, oil droplets etc).
  13. What will happen if yeast is placed in 5% sugar solution? (2)
    Ans.
    Since yeast is a physiologically facultative anaerobe, so the following changes would occur to the sugar solution:
    a. Changes in sugar solution under anaerobic condition: Sugar solution will be fermented to ethyl alcohol and evolution of carbondioxide will take place.
    b. Changes in sugar solution under aerobic condition: Sugar solution will be converted to water and carbondioxide.
  14. What do you mean by monokaryon and dikaryon? What is dikaryotization? (2+2)
    Ans. A fungal hypha with cells possessing one nucleus in each is called a monokaryotic hypha or a monokaryon. But a fungal hypha with cells having two nuclei in each, is called as a dikaryotic hypha or a dikaryon.
    The process by means of which the dikaryotic condition is established in a fungus is called dikaryotization.
  15. Why Mucor is a ‘pin-mould’? (2)
    Ans. The tip of the hyphae of Mucor contains a globose sporangium, which appears as a minute pin head under the hand lens and so Mucor is often termed as pin-mould.
  16. Name two diseases caused by fungi in human beings. (2)
    Ans.
    a. Athletes foot disease caused by the fungus Trichophyton interdigitale.
    b. Ringworm disease caused by the fungus Microsporon audouinii

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PpG

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Hi viewers My name is Partha Pratim Goswami, (PpG) I am a teacher by profession. I have been teaching biology, chemistry and physics, sometimes mathematics also for last sixteen years. I would like to share my entire experience with all the viewers across the world through YouTube, which I think is an amazing platform to share all my experiences.

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