Class 11 Biology Chapter 2 Biological Classification

Class 11 Biology Chapter 2 Biological Classification, AHSEC Class 11 Biology Question Answer, HS 1st year Biology notes to each chapter are provided in the list so that you can easily browse throughout different chapter Assam Board Class 11 Biology Chapter 2 Biological Classification Question Answer and select needs one.

Class 11 Biology Chapter 2 Biological Classification

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Also, you can read the SCERT book online in these sections Solutions by Expert Teachers as per SCERT (CBSE) Book guidelines. These solutions are part of SCERT All Subject Solutions. Here we have given Assam Board Class 11 Biology Chapter 2 Biological Classification Solutions for All Subject, You can practice these here.

Biological Classification

Chapter – 2


Q.1. Who was the pioneer in the scientific basis of classification?

Ans :- Aristotle was the pioneer in the scientific basis of classification.

Q.2. Who proposed a ‘Two Kingdom’ system of classification?

Ans :- Linnaeus proposed a ‘Two Kingdom’ system of classification.

Q.3. Write the names of kingdoms classified by Whittaker?

Ans :- The name of kingdom are Monera, Protista, Fungi, Plantae and Animalia.

Q.4. What are the main criteria used by Whittaker in his classification?

Ans :- The main criteria for classification used by Whittaker are – Cell structure, thallus Organisation, mode of nutrition, reproduction and phylogenetic relationships.

Q.5. What was the basic difference in wall composition of fungi and green plants?

Ans :- Fungi had chitin in their walls while green plants had a cellulosic cell wall.

Q.6. Which type of organism were included in the kingdom Monera?

Ans :- All prokaryotic organisms are grouped in kingdom Monera.

Q.7. Write the different forms of bacteria on the basis of shape.

Ans :- On the basis of shape, bacteria are classified into 4 categories – Spherical (coccus), rod-shaped (bacillus), comma shaped (vibrio) and spiral (spirillum).

Q.8. Write a special feature on spiral cyanobacteria.

Ans :- Cyanobacteria have chlorophyll a similar to green plants and are photosynthetic autotrophs.

Q.9. What is heterocyst?

Ans :- It is a kind of enlarged thick-walled cell intermixed with vegetative cells of multicellular cyanobacterium.

Q.10. What is microplasma?

Ans :- The microplasma are organisms that completely lack a cell wall. They are the smallest living cells known and can survive without oxygen.

Q.11. Write the names of organisms grouped under chrysophytes.

Ans :- Chrysophytes includes diatoms and golden algae.

Q.12. What is a pellicle and where is it present?

Ans :- In Euglenoids, instead of a cell wall, they have a protein rich layer called pellicle which makes their body flexible.

Q.13. What is the other name of Saprophytic protists?

Ans :- Slime mould.

Q.14. Write the name of groups of protozoa.

Ans :- The name of groups of protozoa are – amoeboid protozoa, flagellated protozoa, ciliated protozoa and sporozoans.

Q.15. Write one example of flagellated protozoa and ciliated protozoa.

Ans :- Flagellated protozoa – e.g. Trypanosoma.

Ciliated protozoa – e.g. Paramoecium.

Q.16. Write a source of antibiotics.

Ans :- The source of antibiotics is Penicillium.

Q.17. Define the term mycelium.

Ans :- The body of yeast consists of long, slender, thread like structure called hyphae. The network of hyphae is known as mycelium.

Q.18. What are saprophytes and parasites?

Ans :- Some fungi are heterotrophic and draw nutrition from dead decaying organic matter.

Parasites draw food from living organisms.

Q.19. What are lichens?

Ans :- Lichen is an association between algae and fungi.

Q.20. What are the different mode of reproduction in fungi?

Ans :- The different mode of reproduction in fungi are – Vegetative method, sexual and asexual method of reproduction.

Q.21. What is the other name of fungi belongings to Ascomycetes? Give one example.

Ans :- Sac fungi, e.g. penicillium.

Q.22. What is an ascocarp?

Ans :- Ascospores are produced endogenously in sac like ascus. The ascus is arranged in fruiting body called ascocarp.

Q.23. What are the commonly known forms of basidiomycetes?

Ans :- The commonly known forms of basidiomycetes are mushrooms, bracket fungi or puffballs.

Q.24. What are the deuteromycetes known as imperfect fungi?

Ans :- Deuteromycetes are known as imperfect fungi because only the asexual or vegetative phase of this fungi is known.

Q.25. Write few examples of Deuteromycetes.

Ans :- Alternaria, Colletotrichum, Trichoderma.

Q.26. Who discovered plant virus and who coined the name?

Ans :- Iwanowski discovered plant virus and the name virus was given by Beijerinek.

Q.27. Write 2 diseases caused by virus in animals.

Ans :- The disease caused by virus in animals are – leaf mumps and small-pox.

Q.28. What is the algal component and fungal component in a lichen called?

Ans :- The algal component is known as phycobiont and the fungal component is known as mycobiont in lichen.


Q.1. Why was the Two-Kingdom system of classification inadequate?

Ans :- The Two-Kingdom system of classification was found inadequate because this system did not distinguish between eukaryotes and prokaryotes, unicellular and multi- cellular organisms and photosynthetic and non-photosynthetic organisms.

Q.2. Write the distinguishing characters of Monera?

Ans :- The distinguishing characters of Monera are –

(i) It includes all prokaryotic unicellular organisms.

(ii) Lock of well – defined nucleus and membrane bound cell – organelle e.g. – bacteria.

Q.3. Bacteria as a group shows the most  extensive  metabolic diversity, justify?

Ans :-  Some bacteria are autotrophic i.e. they synthesise their own food. They may be photosynthetic autotrophic or chemosynthetic autotrophic. The majority of bacteria are heterotrophs, i.e. they do not synthesise their own food but are dependent on other organism for food.

So, it can be said bacteria as a group shows the most extensive metabolic diversity.

Q.4. Give important characteristic features of Cyanobacteria.

Ans :- The important characteristic features of Cyanobacteria are

(i) They are unicellular, colonial or filamentous structures.

(ii) They reproduce asexually by means of akinete, endospore, heterocyst etc.

(iii) The colonies are generally surrounded by gelatinous sheath.

(iv) They are the earliest oxygen photosynthesizer.

Q.5. Write a note on heterotrophic bacteria.

Ans :- Heterotrophic bacteria are the mostly decomposer. They are helpful in making curd from milk, production of antibiotics, fixing nitrogen in legume roots etc. Some are pathogens causing damage to human beings, crops, farm animals and pets.

Q.6. Write down the distinguishing features of Protista.

Ans :- The important features of Protista are – 

(i) They are unicellular eukaryotic forms with true nuclei.

(ii) They possess cilia, flagella, pseudopodia for locomotion.

(iii) They have both autotrophic and heterotrophic nutritions.

(iv) The protist cell body contained a well defined nucleus and other membrane – bound organ cells.

Q.7. What is ‘diatomaceous earth’?

Ans :- Due to the presence of silicas , the  walls of the diatoms are nearly indestructible and therefore they leave behind large amount of fossil cell wall deposits at the bottom of the oceans. This accumulation over million years is referred to as ‘diatomaceous earth’.

Q.8. Why are diatoms known as ‘golden brown algae’?

Ans :- Diatoms are the most beautiful microscopic organism because of their wonderful sculpture of their cell wall and golden brown colour. Due to this resemblance of algal external feature, diatoms are referred as golden brown algae.

Q.9. Write a note on any 2 group of protozoans.

Ans :- Amoeboid protozoan :- This organism live in fresh water, sea water or moist soil. They move and capture their prey by putting out pseudopodia as in Amoeba Marine forms have silica shells on their surface. 

Flagellated protozoan :- The members of this groups are either free-living or parasite. They have flagella. The parasitic forms cause disease such as sleeping sickness e.g. Trypanosoma.

Q.10. What are the major classification of fungi?

Ans :- The major classification of fungi are –

(i) Phycomycetes 

(ii) Ascomycetes

(iii) Basidiomycetes

(iv) Deuteromycetes.

Q.11. Write a note on kingdom Plantae.

Ans :- Plantae includes all chlorophyll containing organism which are known as plants. A few members are partially heterotrophic such as insectivorous plants or parasites. The plant cells have a eukaryotic structure with prominent  chloroplast and cell wall made of cellulose. Plantae include algae, bryophyte, pteridophyte, gymnosperm and angiosperms.

Q.12. Describe briefly about Tobacco Mosaic virus.

Ans :- Tobacco Mosaic virus is rod shaped in appearance. TMV is composed of nucleic acid (only RNA) and protein. The inner RNA core tube is covered by a protein coat called capsid. The protein coat is composed of subunits  called capsomere. These capsomere are arranged in helical or polyhedral forms. The capsid protects the nucleic acid during unfavourable conditions. It also facilities nucleic acid entry into host cell.

Q.13. Why is virus regarded as an entity between living and non-living?

Ans :- Virus is regarded as an entity between living and non-living because it shows both living and nonliving characteristics.

(a) Virus as non-living entity :-

(i) It does not respire.

(ii) It has no cellular structure.

(b) Virus as living entity :-

(i) Virus can reproduce.

(ii) Virus consists of protein and nucleic acid.


Q.1. Describe the classification proposed by Whittaker.

Ans :- Whittaker proposed a Five Kingdom classification. It is superior to the old system as it represents the better relationship in regards to both levels of organisation and nutritive modes.

According to five kingdom classification organism have been classified into five groups called Kingdoms namely-

(a) Monera :- This group includes the prokaryotic animals. Bacteria are the sole members of kingdom Monera. The moneras do not possess true nuclei. They possess rigid cell wall. They function as decomposers and mineralizes in the biosphere.

(b) Protista :- These are unicellular eukaryotic forms with true nuclei. They possess membrane bound cell organelle like mitochondria, ER, golgi bodies etc. They often possess cilia, flagella, pseudopodia etc. for locomotion. They have both autotrophic and heterotrophic mode of nutrition. e.g. Amoeba, Euglena etc.

(c) Fungi :- Fungi are non-chlorophyllous thallus like organisms with true nuclei and a wall made of cellulose or chitin or both. These are heterotrophic organisms living as saprophyte or parasite. The body is a branched filament known as mycelium, e.g. yeast.

(d) Plantae :- It includes all multicellular photosynthetic organism. They all have a cell wall. Life cycle consists of a haploid gametophyte and a diploid sporophytic generation. e.g. All chlorophyll bearing multicellular organism starting from Algae to Angiosperm.

(e) Animalia :- It includes multicellular phagotrophic consumers. Nutrition is holozoic. They may be mobile or sedentary. e.g. all animals except protozoans.

Q.2. Describe briefly the four major groups of protozoa?

Ans :- The four major groups of protozoa are – 

(i) Amoeboid protozoa

(ii) Flagellated protozoa

(iii) Ciliated protozoa

(iv) Sporozoan 

(i) Amoeboid protozoa :- These organisms live in fresh water, sea or moist soil. They move or catch their prey by putting out pseudopodia (false feet) e.g. amoeba, some forms have silica shells on their surface.

(ii) Flagellated protozoa :- The member of this group are either free-living or parasitic. They have flagella. The parasitic forms causes diseases such as – sleeping sickness e.g. Trypanosoma.

(iii) Ciliated protozoa :- These are aquatic, actively moving organisms because of the presence of cilia. They have a gullet that opens to the outside of the cell surface. The coordinated movement of rows of cilia causes the water laden with food to be steered in the gullet. e.g. para moecium.

(iv) Sporozoan :- This includes organism that have an infectious spore-like stage in their life-cycle. e.g. plasmodium (malarial parasite) Which causes malaria.

Q.3. Write short notes on :

(i) Dinoflagellate

(ii) Euglenoid

(iii) Chrysophyte

Ans :- (i) Dinoflagellate :- These are mostly marine and photosynthetic. Depending on the main pigment present on their cell, they may appear yellow, green, blue or red. The cell wall has stiff cellulose on the outer surface. Two flagella are present; one lies longitudinally and the other transversely in a furrow between the cell wall plate. Red dinoflagellate undergo rapid multiplication, which make the sea appear red in colour (red-tides). Toxin if released by large number of dinoflagellate may even kill the fishes present.

(ii) Euglenoid :- Most of these organism are fresh water organism found in stagnant water. They have a protein rich layer called pellicle instead of a cell wall which makes their body flexible. They have two flagella, one short and the other long one when sunlight is present, they behave like autotroph but when deprived of sunlight, they behave like heterotrophs. e.g. euglena.

(iii) Chrysophytes :- This group includes diatoms and golden algae. They are found in fresh water as well as in marine environment. They float passively in water current (plankton). Most of them are photosynthetic. The cell wall forms two thin overlapping shells which fit together. The walls are embedded with silica, thus the wall of diatoms are indestructible and therefore they leave behind large amount of fossil cell wall deposits at the bottom of the oceans. This accumulation over billion of years is referred to as ‘diatomaceous earth’.

Q.4. Describe briefly the different classes of fungi?

Ans :- The kingdom fungi is divided into four classes :

(i) Phycomycetes

(ii) Ascomycetes

(iii) Basidiomycetes

(iv) Deuteromycetes

Phycomycetes :-

(i) The members of phycomycetes are found in aquatic habitat and on decaying wood on damp places.

(ii) Mycelium is septate and coenocytic.

(iii) Asexual reproduction by zoospores or alpanospores.

(iv) Spores are produced endogenously in sporangium.

(v) Zygospores are formed by fusion of two gametes. e.g. Rhizopus, Mucor.

Ascomycetes :-

(i) These are commonly called sac-fungi.

(ii) They are mostly multicellular (penicillium) or unicellular (yeast) saprophytic, decomposers, parasitic or coprophilous (grow on dung).

(iii) Mycelium is branched and septate.

(iv) Asexual spores are conidia produced exogenously on special mycelium called conidiophores.

(v) Sexual spores are called ascospores which are produced endogenously in sac-like asci.

(vi) Asci are arranged in different type of fruiting bodies called ascocarps. e.g. Neurospora, Claviceps.

Basidiomycetes :-

(i) These are commonly called mushrooms, bracket fungi or puff balls.

(ii) They grow in soil, on logs and in living plant bodies as parasites. e.g. rust and smut.

(iii) Mycelium is branched and septate.

(iv) Vegetative reproduction is by fragmentation.

(v) Plasmogamy occurs by the fusion of somatic cells.

(vi) Basidiospores are exogenously produced on the basidium.

(vii) Basidium are arranged in fruiting bodies called basidiocarps. e.g. Agaricus, Puccinia.


(i) Commonly known as imperfect fungi.

(ii) They reproduce only by asexual spores known as conidia.

(iii) Mycelium is septate and branched.

(iv) Some members are saprophytes or parasites. e.g. Alternaria, Colletotrichum.

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