2 Marks Questions
1. Differentiate between cryptogams and phanerogams.
A: Cryptogams are non-flowering, seedless spore bearing plants. They include thallophyta, bryophyta and pteridophyta. Phanerogams are flowering, seed producing plants. They include gymnosperms and
2. How does holdfast cell differ from other vegetative cells of Spirogyra filaments ?
A: Holdfast cell is colorless due to absence of chloroplasts and does not show cell division.
3. Distinguish between Zygophore and zygospore of Rhizopus.
A: Zygophore is the sexual hypha formed during sexual reproduction of Rhizopus. Zygospore is the fertilized product of gametangial copulation which contains many diploid nuclei.
4. Write about ‘peristome’ in Funaria. Give its function.
A: The whorls of peristomal teeth present in the operculum are called peristome. It shows peristomal teeth in two whorls of 16 each.
They are hygroscopic and help in liberation of spores.
5. Distinguish between annulus and stomium of Pteris.
A: A ring like portion of the sporangial jacket with vertically elongated cells is called annulus. A group of long, flat and thin walled cells in the sporangial jacket that help in dehiscence
of sporangium is called stomium.
6. In which plant do you find mixed type of sorus? Define it.
A: Pteris. A mixed sorus is one in which both old and young sporangia
are arranged irregularly.
7. How is coralloid root useful for Cycas plant?
A: The coralloid root of Cycas lodges bluegreen algae like Anabaena cycadacearum and Nostoc punctiforme which help in nitrogen
8. Name the species of Cycas that grow wild in Tirumala hills. What is its common name?
A: Cycas beddomi, Madras Cycas.
9. Name the organism from which streptomycin is obtained. Who isolated it?
A: Streptomyces griseus, Waksman.
10. Define botulism. Name the bacterium responsible for botulism.
A: Botulism is a type of food poisoning caused by toxins from Bacteria.
e.g.: Clostridium botulinum.
11. Define peplos and peplomers. Give an example.
A: The outer envelope of a virus made up of lipids, proteins and carbohydrates is called peplos. The subunits of peplos are peplomers.
e.g.: Influenza virus.
12. Name any fungus and the nematode that transmit viruses in plants.
A: Fungus - Olpidium brassicae. Nematode - Xiphenema and
4 Marks Questions
1. Elucidate the dioecious conjugation in Spirogyra.
A: Scalariform conjugation in Spirogyra is also called Dioecious
1. It occurs between two different filaments, one male and the other female called dioecious filaments.
2. During this process the two filaments come and lie parallel to each other.
3. Bud like outgrowths form from two cells lying opposite to each other called papillae.
4. The two papillae grow towards each other and form a conjugation tube due to break down of cell walls between them by the action of the enzyme cytase.
5. Many such conjugation tubes formed between two filaments appear like a ladder, hence called scalariform conjugation.
6. The protoplasts of both cells on either sides of the conjugation tube form aplano gametes.
7. The gamete from each male filament moves slowly into the female filament and fuses with the female gamete to form a diploid zygote in
the female filament.
8. Thus the male filament shows empty cells after fertilization and the female filament is filled with zygotes.
9. This kind of conjugation where both the gametes are structurally alike but functionally dissimilar is called physiological anisogamy.
2. Explain the conjugation in bacteria.
A: Conjugation is a type of genetic recombination in bacteria.
1. It was first reported by Lederberg and Tatum in Escherichia coli.
2. The circular DNA present in the cytoplasm of bacteria is called plasmid or F factor.
3. The bacterial cells with F factor are called donors or F+ cells.
4. The cells without F factor are called acceptors or F− cells.
5. The F+ cells have sex pili, but F− cells do not have sex pili.
6. During conjugation F+ cells and F− cells come together and bind up with the help of sex pili.
7. Thus a conjugation tube is established between F+ and F− cells.
8. The F plasmid in the F+ cell replicates and one of the copies moves into the F− cell through the conjugation tube.
9. Thus the F− cell that receives F plasmid becomes F+ cell. Then the conjugants separate.