Biology Class 9 Notes- Chapter 5

FUNGI AND ALGAE

QNo.1: What are fungi? Write down general characters of fungi.

Ans. Fungi are multicellular, non-chlorophylous, eukaryotic organisms having cell wall. General characters of fungi are given under:

Ø  Fungi are non-chlorophylous.

Ø  Cell wall is made up of fungal cellulose.

Ø  They are coenocytic (multi-nucleated).

Ø  Fungal body is called mycelium, which is made up of thread like cells called hyphae (sing. hypha).

Ø  Reserve food is in the form of glycogen particles and oil globules.

Ø  They reproduce asexually by means of spores, by budding or by fermentation.

Ø  Sexually they reproduce by conjugation (Isogamy).

Ø  Mode of nutrition may be saprophytic, parasitic and symbiotic.

Ø  They either have evolved from an alga or from certain unflagellated protozoa.

Ø  The fungi are distinguished among themselves primarily by their sexual reproductive structures.

Ø  Common examples of fungi are Yeast, Agaricus, Penicillium, Rhizopus etc.

QNo.2: Write a note on some members of fungi.

1.      Agaricus (Mushroom): Some species of Agaricus are commonly cultivated as food, for example the button mushroom, Agaricus campestris. Many of them have high protein content, as well as delicate flavor.

2.      Penicillium: It is one of the economically important fungi. They are the source of the penicillin antibiotic. Other species of the genus give flavors and aromas to cheese.

3.      Ustilago: They are responsible for rust and smut disease of cereals.

QNo.3: What is the importance of fungi?

Ans.

1.      Food: Mushrooms are the source of food. Some mushrooms like toad stool or death-stool are very poisonous. Yeasts are used in brewing, and in cheese and organic acid production industries.

2.      Medicine: Antibiotics like Penicillin, Chloromycetin, Neomycin, Terramycin etc. are prepared from fungi.

3.      Soil Fertility: Some of them maintain soil fertility by decomposing dead organic matter.

4.      Fermentation: Ethanol, organic acids, alcoholic beverages and B-group vitamins are manufactured by fermentation process of fungi.

5.      Human Diseases: Fungi cause a number of human diseases like aspergillosis (ear and lung diseases), moniliasis (skin, mouth and gums) diseases.

6.      Plant Diseases: The fungal diseases of plants are loose-smut of wheat, late-blight of potato, downy and powdery mildews etc.

QN.4: What are algae?

Ans.

Ø  They belong to kingdom Protictista (Protista). The members of this group are unicellular, as well as multicellular, eukaryotic and photosynthetic.

Ø  Previously they were regarded as plants and placed in Thallophyta.

Ø  Algae are classified on the basis of pigment they contain. Therefore, there are green, brown, golden brown and red algae. All algae contain chlorophyll which is masked by pigment they contain.

Ø  Algae are also grouped according to chemistry of cell wall and chemical compound used to store excess food.

Ø  Common examples of algae are Chlamydomonas, Spirogyra, Ulva etc.

QNo.5: Write a note on chlamydomonas.

Ans.

Ø  It is a fresh water alga. It grows in still water of ponds, pools, ditches, tanks and lakes. It grows abundantly in polluted water.

Ø  It is unicellular, eukaryotic, green and motile alga. It is spherical or oval shaped with pointed anterior end. It has cell wall, nucleus and two flagella.

Ø  Cell wall is thin but firm and transparent. It is made up of cellulose and pectin.

Ø  Cytoplasm has outer thin region and inner thick region. Cytoplasmic organells are present in extension of pyrenoid and eye spot. A large cup shaped chloroplast is present at the posterior end of cell.

Ø  Pyrenoid is starch manufacturing factory and eye spot is sensitive to intensity of light.

Ø  Nucleus is circular and present at cup shaped cavity of chloroplast.

QNo.6: Write a note on spirogyra.

Ans.

Ø  Spirogyra is a green fresh water alga that float freely on slow running streams and stagnant water.

Ø  It is unicellular but grows in colonial form as filament, which form a unbranched chain. All cells in the filament are alike.

Ø  Outer wall of each cell is made up of pectin and cellulose. A layer called primordial utricle encloses the large vacuole.

Ø  The chloroplast is ribbon shaped. Number of chloroplast varies from 1 to 14 according to species. Chloroplasts are spirally arranged in protoplasm.

Ø  Nucleus is present in center of cell. It is suspended by cytoplasmic strands.