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Q1. Write any two distinguishing characters of dinoflagellates.

Solution

1)Dinoflagellates have stiff plates of cellulose on the outer surface. 2)Their rapid multiplication gives a red appearance to the sea which is known as red tides.

Q2. Draw a well-labelled diagram of Nostoc.

Solution

Q3. What is Plasmodium?

Solution

Plasmodium is the aggregation of slime moulds which grow and spread on a large area over several feet under suitable conditions.

Q4. What is mycorrhiza?

Solution

Mycorrhiza is the symbioant association of fungi with the roots of higher plants.

Q5. What are chemosynthetic bacteria? State their importance.

Solution

Chemosynthetic bacteria oxidise substances such as ammonia, nitrites and nitrates and use the released energy for the synthesis of ATP. Chemosynthetic bacteria help in recycling nutrients such as phosphorus, nitrogen, sulphur, iron etc.

Q6. What are lichens?

Solution

Lichens are a mutually useful symbiotic association between algae and fungi.

Q7. Name the protein-rich layer in Euglena which replaces the cell wall.

Solution

Pellicle

Q8. Name the organisms which were placed under kingdom Plantae before the five kingdom classification. Why?

Solution

Bacteria, cyanobacteria, fungi, mosses, ferns, gymnosperms and angiosperms were placed in kingdom Plantae because these organisms possess a cell wall.

Q9. Define plasmogamy.

Solution

Plasmogamy is the fusion of protoplasms of motile or non-motile gametes.

Q10. Why are deuteromycetes called imperfect fungi?

Solution

Only asexual and vegetative phases of deuteromycetes are known; hence, they are called imperfect fungi.  

Q11. To which kingdom do bacteria belong?

Solution

Bacteria belong to kingdom Monera.

Q12. What is the name of the fully formed virus particle?

Solution

The name of the fully formed virus particle is called virion.

Q13. Write a short note on Cyanobacteria.

Solution

Cyanobacteria: They are also called blue-green algae. They are unicellular, colonial or filamentous. They are found in fresh or marine water. Some of them are also terrestrial. They show the presence of rigid cell walls. In motile cyanobacteria, flagellum is present. Cyanobacteria are photoautotrophs and show the presence of chlorophyll a. Cyanobacteria can fix atmospheric nitrogen in specialised cells called heterocysts. Anabaena and Nostoc are examples of cyanobacteria.

Q14. Explain the terms mycobiont and phycobiont.

Solution

Mycobiont is the fungal component of a lichen which provides shelter and absorbs minerals and water for the algae.  Phycobiont is the algal component of lichen which prepares food for fungi.  

Q15. How is a viroid different from a virus?

Solution

A viroid lacks the protein coat which is present in a virus.

Q16. Give any two examples of insectivorous plants.

Solution

Bladderwort, Venus fly trap

Q17. Name any one disease caused by viroids.

Solution

Potato spindle tuber disease is caused by viroids.

Q18. Give two examples of cyanobacteria.

Solution

Nostoc Anabaena

Q19. A virus is considered a living organism and an obligate parasite when inside a host cell. However, a virus is not classified along with bacteria or fungi. What are the characters of a virus which are similar to non-living objects?

Solution

The characters showing that viruses are non-living:

They do not show cellular metabolism and lack respiration.

They have no proper cellular structure.

They are active only when they are inside the living host cells.

Q20. A virus is considered as a living organism and an obligate parasite when inside a host cell. However, a virus is not classified along with bacteria or fungi. What are the characters of a virus which are similar to non-living objects?  

Solution

Characterisics of virus similar to non-living objects are as follows:  

Viruses do not have any specific cellular structure.

They do not have their own metabolism.

They show absence of growth.

Irritability is absent.

They can be crystallised.

Q21. What is diatomaceous earth?

Solution

The accumulation of large amounts of cell wall deposits left back by diatoms over billions of years is called diatomaceous earth.

Q22. Name the group of fungi which are also known as sac fungi.

Solution

Ascomycetes  

Q23. What are the criteria used to classify fungi in different classes?

Solution

Criteria used to classify fungi in different classes:  1. Morphology of the mycelium  2. Mode of spore formation and fruiting bodies

Q24. Draw a labelled diagram of tobacco mosaic virus (TMV).

Solution

Q25. Write the name of fungi which is used extensively in genetic work.

Solution

Neurospora

Q26. Who proposed the five kingdom classification?

Solution

R. H. Whittaker proposed the five kingdom classification.

Q27. Explain genetic material in viruses.

Solution

Viruses contain either RNA or DNA as genetic material. The genetic material of a virus is infectious. Viruses which infect plants have single-stranded RNA. Viruses which infect animals have either single-stranded or double-stranded RNA or double-stranded DNA. Bacteriophages have double-stranded DNA.

Q28. Explain the steps of the sexual cycle of fungi.

Solution

The sexual cycle of fungi occurs in three steps: 1.Plasmogamy: Protoplasms of two motile or non-motile gametes fuse. 2.Karyogamy: Fusion of nuclei of two gametes. 3.The zygote undergoes meiosis resulting in the formation of haploid spores.

Q29. Explain the alternation of generation in plants.

Solution

Alternation of generation is observed in plants. Plants show two phases in their life cycle—the diploid sporophyte phase and the haploid gametophyte phase—which alternate with each other.

Q30. Write any two features of spores of slime moulds.

Solution

Features of slime moulds: 1)Spores survive for many years under adverse conditions. 2)They possess true cell walls.

Q31. Explain the groups of protozoa.

Solution

There are four groups of protozoa: 1. Amoeboid Protozoans: Amoeboid protozoans live in fresh or sea water or in moist soil. They have pseudopodia to capture their prey. The body surface of marine amoeboid protozoans is covered with silica shells. Examples: Amoeba, Entamoeba 2. Flagellated Protozoans: Flagellated protozoans are either free-living or parasitic. Parasitic forms cause certain diseases such as sleeping sickness. These protozoans have flagella for locomotion. 3. Ciliated Protozoans: These protozoans have numerous cilia on their body. Because of the cilia, they are actively moving organisms. Cilia help in locomotion and allow food laden water to enter the organism’s body. These organisms are aquatic. Examples: Paramecium 4. Sporozoans: These protozoans have an infectious spore stage in their life cycle. They are parasites. Example: Plasmodium (which causes malaria)

Q32. Describe the three groups of archaebacteria.

Solution

The three groups of archaebacteria are 1. Methanogens: Methanogens grow in marshy areas and in the stomach of ruminants. Methanogens are responsible for the production of biogas from animal dung. 2. Halophiles inhabit extreme salty areas. 3. Thermoacidophiles inhabit areas which are acidic and rich in sulphur with high temperature. They are mostly found in hot springs.

Q33. What are coenocytic hyphae?

Solution

Hyphae which are continuous tubes filled with multinucleated cytoplasm are called coenocytic hyphae.

Q34. Write about the contributions of the following scientists:

M. W. Beijerinck

W. M. Stanley

Solution

M. W. Beijerinck: He demonstrated that the extract of an infected tobacco plant causes infection in a healthy plant. He called this fluid as contagium vivum fluidum.

W. M. Stanley: He showed that viruses could be crystallised and the crystals are largely made of proteins.

Q35. Describe the formation of haploid spores in fungi.

Solution

In sexually reproducing fungi, hyphae of two compatible mating types fuse. In some fungi, the fusion of haploid cells immediately forms diploid cells (2n), but in some ascomycetes and basidiomycetes, the fusion results in an n+n stage, i.e. single cell with two nuclei. Such a condition of cell is called the dikaryon condition and the stage is known as dikaryophase. The polar nuclei of the cells then fuse, and the cell becomes diploid. Reduction division occurs inside the fruiting bodies resulting in the formation of fungi.

Q36. Write any two features of viroids.

Solution

Features of viroids:

A viroid is a free RNA of low molecular weight.

It lacks a protein coat which is found in viruses.

Q37. Draw a labelled diagram of a bacteriophage.

Solution

Q38. Name the RNA particle causing symptoms like those of a virus.

Solution

An RNA particle causing symptoms like those of a virus is called a viroid.

Q39. Give one example of flagellate protozoan.

Solution

Trypanosoma

Q40. Write the names of the five kingdoms proposed by Whittaker.

Solution

The five kingdoms proposed by Whittaker are Monera, Protista, Fungi, Plantae and Animalia.

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