CHAPTER 2 BIOLOGICAL CLASSIFICATION
Q1. Discuss how classification systems have undergone several changes over a period of
time?
Ans- The two kingdom classification didn’t include all categories of organisms and grouping
was not based on all aspects of organisms. So it was changed and finally five system of
classification was devised by Whittaker in 1969. It takes the account of cell organization,
nature of cell wall, mode of nutrition, habitat, reproduction, ecological roles and
evolutionary relationship etc. The five kingdoms are Protista, Fungi, Plantae and Animalia.
Q2. State two economically important uses of
a- Heterotrophic bacteria b- Archaebacteria
Ans- a. Uses of Heterotrophic bacteria-
They help in setting of curd from milk
They help in nitrogen fixation in rood nodules of leguminous bacteria
b. Uses of Archaebacteria-
They help in the production bio-gas such as methane.
They help in digestion of cellulose in the gut of ruminant animals like cows, buffaloes.
Q3. What is the nature of cell wall in diatoms?
Ans- i. In Diatoms the cell walls form two thin overlapping shells which fit together as in a
soap box.
ii. These walls are embedded with silica forming siliceous deposits which are indestructible.
iii. They pile up at the bottom of the water reservoirs and form big heaps as diatomaceous
earth.
iv. Diatomite is used in filtration of sugars, alcohol and antibiotics.
Q4. Find out what do the terms algal bloom and red tides signify?
Ans-
Algal bloom – When the algae in water body have excessive growth due to theenrichment of
excessive nutrients in it, this refers to algal bloom.
Red tides- When the sea appears red due to the rapid multiplication of red dinoflagellates
eg- Gonyaulax, it is called as red tides.
Q5. How are viroids different from viruses?
Viruses Viroids
1. They have a protein coat 1. They do not have a protein coat.
2. The genetic material may be either 2.The genetic material is RNA.
DNA or RNA
3. They can infect plants, animals and 3.They can infect only plants.
bacteria.
Q6. Describe briefly the four major groups of protozoa.
Ans- Protozoa are microscopic unicellular protists with heterotrophic mode of nutrition.
They may be holozoic or parasitic. These are divided into four major groups.
i. Amoeboid protozoans-
* They are unicellular
*Found in fresh water or marine and in soil
*they have pseudopodia for movement and food capture
*Marine forms have silica shells on their surface
Eg- Amoeba, Entamoeba (a parasite)
ii. Flagellated protozoans-
* Unicellular, free living or parasitic
*They have flagella for movement and food capture
Eg- Trypanosoma (parasite causing Sleeping sickness in humans.)
Leishmania (causes kala-azar)
iii. Ciliated protozoans-
*Aquatic actively moving unicellular organisms.
*They have cilia for movement and food capture.
*Movement of cilia in a co -ordinated manner steers the food to the cavity
calledgullet on the surface of the body.
Eg- Parmoecium.
iv. Sporozoans-
* They have spore like stage in their life cycle.
Eg- Plasmodium which causes malaria.
Q7. Plants are autotrophic. Can you think of some plants which are partially heterotrophic?
Ans- Yes, Majority of the plants are autotrophic, they produce their own food with the help
of chlorophyll. Some are partially hetero trophic such as-
a. Insectivorous plants-eg- Pitcher plant, Venus fly trap, Bladder wort.
b. Parasitic plants eg- cuscuta, Loranthus, Mistletoe.
Q8. What do the terms Phycobiont and mycobiont signify?
Ans- The algal component of lichen is called phycobiont and fungal component is known as
mycobiont. Phycobiont prepare food for fungi and mycobiont provides shelter and absorbs
minerals and water for its partner. This kind of relationship is known as symbiotic
relationship, the organisms in association are called symbionts.
Q9. Give a comparative account of the classes of Kingdom fungi under the following-
i. mode of nutrition ii.mode of reproduction
Ans-
Class of fungi Mode of nutrition
Phycomycetes These are obligate parasites on plants
Ascomycetes They are saprophytic, parasitic or coprophilous
Basidiomycetes Some mushrooms are saprophytes and some are
parasitic
Deuteromycetes They are saprophytes or parasites.
Class of fungi Mode of reproduction
Phycomycetes True spores are produced in sporangia. Sexual reproduction takes
Asexual reproduction takes place by place by the fusion of
zoospores or by aplanospores gametes and formation of
zygospores
Ascomycetes Asexual reproduction takes place by Sexual reproduction takes
conidiophores which are produced in place by ascospores which
the conidia are produced in sac like asci
or ascus. These asci are
arranged in fruiting bodies
called ascocarps.
Basidiomycetes Vegetative propagation occurs by Sex organs absent,
fragmentation. asexual spores are plasmogamy between the
absent. different strains results in
dikaryotic face and forms
basidium which produces
basidiospores. Basidia are
arranged on fruiting bodies
called basidiocarps.
Deuteromycetes They reproduce only by asexual spors Sexual cycle or perfect stage
known as conidia is unknown.
Q10. What are the characteristic features of euglenoids?
1. These are unicellular flagellate protists. They are devoid of cellulosic cell wall.
2. The body is covered by a thin flexible pellicle.
3. They bear two flagella, usually one long and one short.
4. They swim actively in a liquid medium using the flagella.
5. Nutrition is holophytic. They also have chloroplasts. example -Euglena.
Q11. Give a brief account of viruses with respect to their structure and nature of genetic
materials. Also name four common viral diseases.
Answer-
i. Viruses are non-cellular organisms.
ii. They remain inert outside the living cell. They have genetic material as DNA or
RNAs. No virus has both RNA and DNA.
iii. Plant infecting viruses have single stranded RNA but animal infecting viruses
possess either single or double stranded RNA or double stranded DNA.
Viruses cause diseases like smallpox, influenza, AIDS, mumps etc.
Q12. Organize a discussion in your class on the topic are viruses living or non-living?
Answer with the- why does this are the intermediates between living and non-living.
Theyresemble non-living objects in the following features,
1. lacking protoplasm.
2. Ability to get crystallized, example TMZ, poliomyelitis virus.
3. Inability to live independent of a living cell.
4. high specific gravity which is found only in non-living objects.
5. absence of respiration, absence of energy storing systems.
Viruses they resemble living beings in the following ways-
1 it is formed of organic macromolecules which occur only in living beings.
2.Presence of genetic material.
3. Ability to multiply or reproduce.
4. occurrence of mutations.
5.Occurrence of enzymes.
6. They take over biosynthetic machinery of the host cell and produce chemicals
required for its multiplication.
Q13. What are bacteriophages?
Answer- Bacteriophages or bacterial viruses are the viruses which infect bacteria. They
have double stranded DNA as their genetic material. A protein coat called capsid made
of small subunits called capsomeres protects the nucleic acid. These capsomeres are
arranged in helical or polyhedral geometric forms.
