Important Questions Class 11 Biology Chapter 2

Biological Classification Class 11 Important Questions and Answers

Chapter 2 of CBSE Class 11 Biology is about ‘Biological Classification’. The process of grouping living organisms based on similarities and dissimilarities they exhibit is known as biological classification. Based on his study, Linnaeus classified living organisms into two broad kingdoms. The Plant Kingdom, which is called Plantae, and the Animal Kingdom which is also called Animalia. These groups are further subdivided into groups, subgroups, again based on the nature they exhibit. This process of forming the different groups is called the Biological Classification of living beings. The chapter in the NCERT book summarises all this essential information.

Biological classification is a very important aspect because organisms are usually grouped together based on their unique characteristics, which often provides useful information about its evolutionary history as well as about the other organisms related to it. Biological Classification also helps in the correct identification of various organisms. It helps to know the origin and evolution of organisms. It helps determine the exact position of the organism in the classification. It helps to develop phylogenetic relations between different groups of organisms.

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Important Questions Class 11 Biology Chapter 2 with Solutions

Solving questions from our question bank of Important Questions Class 11 Biology Chapter 2 helps students to enhance  and reinforce their knowledge related to a particular topic. Our experienced faculty  at Extramarks understands this crucial method of imparting education. Therefore, we focus on developing content that includes all the necessary questions and solutions related to the topics covered  in the chapter. The Class 11 Biology Chapter 2 Important Questions covers the concepts of classification based on similarities, identification, evolution, position in their kingdom and phylogenetic relation between different groups of organisms.

Given below are some of the important questions and solutions from our Important Questions Class 11 Biology Chapter 2 

Q1. Discuss how the classification system has undergone several changes over a period of  time. 

A1. 

Aristotle classified plants as herbs, shrubs, and trees.  Besides  plants, he also classified animals into two groups based on the red blood cells. One contains red blood cells, and one without them. After the failure of this classification, Carolus Linnaeus introduced a two-kingdom classification, which was divided into two parts, Plantae, and Animalia. As suggested by the name Plantae contained the plant species while Animalia contained the animal species. Due to the absence of classification of eukaryotes, prokaryotes, single cells and multicellular organisms, this classification was found insignificant. 

R.H Whittaker further discovered the classification of five kingdoms- Monera, Protista, Fungi, Plantae and Animalia. These were classified based on the mode of reproduction, the mode of nutrition, the structure of cells, and body organisation. 

Q2. What are imperfect fungi? 

A2.

Imperfect fungi classify the fungi group that does not show a sexual phase. In other words, the sexual stages are not observed in them. E.g., Deuteromycetes.

Q3. All eukaryotic unicellular organisms belong to 

1. Monera
2. Protista
3. Fungi
4. Bacteria

A3.

Protista (b) is the right answer.

Explanation:

Protista is a group in which all the eukaryotic organisms are placed.

Q4. Describe the four major groups of Protozoa briefly. 

A4.

Protozoa contain a heterotrophic mode of nutrition and are microscopic, which means they are not visible to the naked eye. They are unicellular and are divided into four main groups – 

• Amoeboid protozoa or sarcodes – They are commonly found in fresh or seawater. Their appearance is jelly, and they are unicellular. They undergo the process of phagocytosis to capture their prey through pseudopodia, also known as false feet.
• Flagellated protozoa or zooflagellates – As per their name, the flagellated protozoa contain an outgrowth called flagella which helps to capture the prey. They are free living in nature and do  not contain cell walls. 
• Ciliated protozoa or ciliates are found in aquatic water and form a large group of protozoa. They contain small outgrowths throughout their entire body surface, called cilia. Cilia help in the movement of the protozoans. 
• Sporozoans are uninucleated and do not contain flagella or cilia. They contain endoparasites and a group of other pathogens like plasmodium. 

Q5. State important uses of (a) heterotrophic bacteria and (b) archaebacteria. 

A5.

Important uses of Heterotrophic bacteria:

Heterotrophic bacteria are decomposers and help form organic manure called humus. Aside from this, they also contain bacteria like Rhizobium and Lactobacillus. Rhizobium helps in the nitrogen fixation process that occurs in plants, and Lactobacillus helps in the formation of curd. 

Important uses of Archaebacteria

Archaebacteria are used in bleaching minerals and as a polymerase enzyme in recombinant DNA technology. One of the major examples of archaebacteria is Methanobacterium which helps in the production of methane, which acts as a fuel. 

Q6. Give a detailed account of the classes of Kingdom Fungi under the following: 

(i) Mode of nutrition

(ii) Mode of reproduction

A6.

(i) Mode of nutrition – It is the way to obtain food and is mainly divided based on autotrophic and heterotrophic. The kingdom of fungi is divided into four main classes. Phycomycetes are obligate parasites that feed on dead and decaying matter. Ascomycetes are sporophytic and are also defined under decomposition. Basidiomycetes grow on logs or tree stumps and cause diseases like rust in plants. Deuteromycetes are a group of fungi that contain sporophytic fungi and parasites. 

(ii) Mode of Reproduction – Reproduction is the process through which organisms multiply and divide. Reproduction in the Phycomycetes fungi takes place through zoospores that are produced in sporangium. Ascomycetes reproduce through ascospores which are present in the sac-like structure inside ascocarps. Basidiomycetes reproduce through the process of fragmentation, while Deuteromycetes reproduce through asexual spores called conidia. 

Q7. Please give a brief account of viruses concerning their structure and nature of genetic material. Also, name four common viral diseases. 

A7.

A virus is an infectious agent activated inside the host body. Their genetic material is not defined; it is either RNA or DNA. But never both. They are surrounded by a protein cover and are crystalline in structure. The virus that infects plants contains single-stranded RNA as the genetic material, and the virus that infects animals contains double-stranded RNA or DNA as their genetic material. One of the common diseases of the virus is AIDS, Herpes, Rabies, and Influenza. 

Q8. Find out what the terms ‘algal bloom’ and ‘red tides’ signify. 

A8.

An algal bloom is the growth of algae and other phytoplankton on the surface of water bodies. They prevent the penetration of sunlight from reaching the depth of the water bodies. The algal growth on the surface competes for dissolved oxygen resulting in the death of water animals. Algal blooms are mainly caused by a rise in the nitrate level of the water bodies. 

Red tides are generated when there is a sudden rise in the photosynthetic accessory pigments; due to the rise of the accessory pigment, there is a sudden growth of phytoplankton which create toxins that can harm flora and fauna of the water bodies. 

Q9. Plants are autotrophic. Can you think of some heterotrophic plants? 

A9.

Based on the difference in the mode of nutrition, plants are based on two main types. Autotrophic and Heterotrophic. Autotrophic plants produce their food and energy, and heterotrophic plants depend on insects and other plants for their food and energy. Plants like Drosera and nepenthes come under heterotrophic plants as they feed on insects to get nitrogen which is then used for photosynthesis. 

Q10. What do the terms Phycobiont and Mycobiont signify? 

A10.

The terms Phycobiont and Mycobiont are a part of the lichen. Lichen refers to a symbiotic association between algae and fungi, where the fungi derive nutrition from the algae through which photosynthesis takes place. And in turn, fungi provide shelter to algae. Phycobiont is a term which refers to the algal component, while Mycobiont refers to the fungal component of the lichen. 

Q11. Mycobiont and Phycobiont are found in  

1. Mycorrhiza
2. Root
3. Lichens
4. BGA

A11.

Option (c ) is the right answer.

Explanation – The terms Phycobiont and Mycobiont are a part of the lichen. Phycobiont is a term which refers to the algal component, while Mycobiont refers to the fungal component of the lichen. 

Q12. How is the five-kingdom classification advantageous over the two-kingdom classification? 

A12.

The two kingdom classifications included only Plantae and Animalia, which were divided based on their mode of nutrient. In contrast, the five-kingdom classification is divided based on the cell wall, body organisation, mode of reproduction, nuclear envelope and mode of nutrition. The five kingdom classification is given by R.H. Whittaker, which includes monera, protista, fungi, plantae and animalia. 

Q13. The difference between virus and viroid is  

1. Absence of protein coat in viroid but present in the virus
2. Presence of low molecular weight RNA in viruses but absence in viroid
3. Both a and b
4. None of the above

A13.

The correct option is ( a )

Explanation – A virus contains genetic material as single or double-stranded RNA or DNA and is enveloped in a protein coat. At the same time, a viroid contains a genetic material formed by circular, single-stranded RNA, which is not protected by a protein coat. 

Q14. Diatoms are also called ‘pearls of the ocean’. Why? What is diatomaceous earth? 

A14.

Diatoms are the major producers in the marine ecosystem. The outer covering of the diatoms is made of silica, so it leaves behind many cell deposits at the ground of the water body. Hence, they are called pearls of the ocean. The accumulation of the silica left behind at the base is called diatomaceous earth. It is used in polishing stuff and infiltration. 

Q15. Polluted water bodies contain plants like Nostoc and Oscillitoria. Give reasons. 

A15.

Polluted water bodies have many nutrients and minerals in them. These nutrients include nitrogen and phosphorus, responsible for Nostoc’s growth and Oscillitoria, which are examples of algal bloom. 

Q16. Viruses are known as non-cellular organisms that replicate themselves once they enter and infect the host cell. Which of the following kingdoms given below do viruses belong? 

1. Monera
2. Protista
3. Fungi
4. None of the above

A16.

Option (d ) is the answer. 

Explanation – Viruses do not belong to any of the above groups because they only become activated once they enter the host cell, so technically they are considered dead. 

Q 17. Are chemosynthetic bacteria autotrophic or heterotrophic? 

A17. 

Chemosynthetic bacteria can synthesise their food, which is called autotrophic. Chemosynthetic bacteria convert inorganic compounds into organic compounds through the process of oxidation. 

Q18. Cyanobacteria and heterotrophic bacteria are classified under Eubacteria, which comes under the kingdom Monera as per the “Five Kingdom Classification” given by R.H. Whittaker. Even though the above two bacteria are very different, is this grouping of the two types of taxa in the same kingdom justified? If so, why?

A18.

One of the major differences between cyanobacteria and heterotrophic bacteria is their mode of nutrition. Still, as prokaryotic, they are clubbed together in the Kingdom of Monera. Aside from this, they still have a lot in common, like both contain 70S  ribosomes. Neither has a well-defined nucleus, and the genetic material is present in the cytoplasm.

Q19. At a reproducing stage of their cycle, Ascomycetes fungi produce fruiting bodies like apothecium, perithecium or cleistothecium. How are these three different types of fruiting bodies different from each other? Also, give an example for each of them. 

A19.

When the Ascomycetes fungi undergo a sexual phase, they generate ascocarps. The ascocarps are of three main types. These types are- 

Apothecium – They are also called cup fungi and contain bowl-shaped ascoma. E.g., Peziza

Perithecium – They contain flask-shaped ascoma that has a hole at the top. E.g., Neurospora 

Cleistothecium- The ascoma or the ascocarp present in it is spherical and closed. E.g., Penicillium

Q20. Apart from chlorophyll, algae have several other pigments in their chloroplast. What pigments are found in blue-green, red, and brown algae responsible for their characteristic colours?

A20.

Aside from chlorophyll, algae contain xanthophyll, fucoxanthin and r-phycoerythrin, which impart distinctive colours. Algae under Chlorophyceae impart green colour, commonly known as green algae. Phaeophyceae contain fucoxanthin as a major pigment which imparts brown colour. Similarly, Rhodophyceae imparts red colour with the help of r-phycoerythrin pigment. 

Q21. Give one example of a fungus as a source of antibiotics. 

A21.

Antibiotics are used to inhibit the growth of bacteria and harmful microorganisms. Penicillin is an antibiotic that is derived from the fungus penicillium. It is one of the widely used antibiotics that inhibit cell wall formation. 

Q22. Compare salient features of Monera and Protista.

A22. 

Monera – They contain unicellular bacteria, which are prokaryotic. E.g. cyanobacteria and archaebacteria. They lack a proper well-defined nucleus and nucleolus. Also, their genetic material is present in the cytoplasm. They contain a 70S ribosome.  

Protista – Protista includes photosynthetic algae, moulds and protozoans that are eukaryotic. They are diverse and can be found in aquatic and parasitic forms. 

Q23.Some symbiotic organisms are very good pollution indicators composed of chlorophyllous and non-chlorophyllous members. Describe them. 

A23.

The symbiotic organism that is a very good pollution indicator is called Lichens. They have a symbiotic relationship with fungi and algae. The fungal component is called Mycobiont, where the fungi derive nutrition from the algae through which photosynthesis takes place. And in turn, fungi provide shelter to algae. Phycobiont is a term which refers to the algal component.

Q24. Discuss the salient features of the virus with the help of a diagram.

A24.

 A virus contains genetic material in the form of single or double-stranded RNA or DNA and is enveloped in a protein coat. The salient features of the virus are – 

1. They are enclosed with a capsid protein capsule. 
2. They can reproduce in the host cell after becoming active.
3. They are obligate parasites that are non-cellular.
4. They are responsible for viral diseases like mosaic, vein clearing etc.

Q25. Write a short note on methanogens. 

A25.- 

They are microorganisms that produce methane gas. They belong under the Archaebacteria group and cannot be seen with the naked eye. They include various other bacteria, viruses, fungi and algae. 

Q26.

1. What are heterocysts?
2. Write a note on dikaryophase.
3. Differentiate the Protista and Fungi in terms of their nutrition. 

A26.

1. Heterocycles are colourless cells that come under the cyanobacteria group. They are specialised cells that are responsible for nitrogen fixation, and they contain the enzyme nitrogenase. E.g. Nostoc, Anabaena. 
2. Dikaryophase is called a dikaryotic phase. The cells formed in this phase are not diploid but contain two nuclei. This is seen in the fungi group of Basidiomycetes and Ascomycetes. They are an intermediate phase in the life cycle of fungi. 
3. Protista is a unicellular eukaryotic organism. They reproduce through sexual reproduction in the form of gametes. The main three kingdoms of Protista are algae, moulds and protozoans. Most of the Protists are autotrophic, meaning they prepare their food. In contrast, some of them are heterotrophic. On the other hand, Fungi possess a chitin cell wall and are heterotrophic in nature, which means they depend on other organisms for their  survival. 

Q27. Write a short note on Mycoplasma. 

A27.

Mycoplasma was discovered by J.Nowak in 1929 and is termed under the bacteria class. Like any other bacteria, they lack cell walls around their cell membranes. They are also termed the simplest unicellular prokaryotes. And often, they are called PPLO (pleuropneumonia-like organisms). They are defined as one of the smallest prokaryotes that can replicate independently. 

Q28. What are insectivorous plants? Give an example. 

A28.

Plants like pitcher plants are classified under insectivorous plants as their leaves are modified into a pitcher-like shape. They are green plants, and their leaf is modified as a way to trap insects. They are dependent on insects and small animals for nitrogen supply. Hence they are also called carnivorous plants. 

Q29. Explain sexual reproduction in bacteria. 

A29.

There are three main steps for bacterial reproduction. The steps are as follows – 

Conjugation – Lederberg and Tatum first discovered this. The male cell in this phase is also called the donor cell, as its DNA is transferred to the recipient cell.

Transformation– Griffith discovered this phase. This phase is characterised by the death of the donor cell, which releases its DNA content into the external medium. This DNA content then gets incorporated into the active cells. The new cell that incorporates the DNA of the donor cell is called a recipient cell which contains all the characteristics of the donor cell. The recipient cell is also called a recombinant cell.

Transduction – Zinder and Lederberg discover this phase. It is characterised by the transfer of donor genes into the recipient cell with the help of a virus. 

Q30. What are the different groups of fungi?

A30.

Fungi are classified into four main types. The four types are Artificial classification, Natural classification, Phylogenetic classification, and phenotypic classification. They are broadly defined as –

• Artificial classification- Imperfect fungi is the perfect example of Artificial classification. After dividing, they bear no connection to their sexual stage, evolution, or origin. Linneaus proposed this.
• Natural classification – George Bentham and Joseph Dalton Hooker proposed this classification. This is based on natural affinities like the external and internal features of the organisms. 
• Phylogenetic classification – This is the higher fungi classification containing 195 taxes. It is diverse and includes phylogenetic analysis.
• Phenotypic classification – The fungi-based classification is used for study and research purposes. The strains of the cultivated fungi are separated and studied

Q31 What are the characteristic features of euglenoids? 

A31.

Euglenoids are classified under the Protista group; their characteristic feature are- 

They are commonly found in freshwater.

They possess two flagella on the anterior side of their body.

Their cell membrane is also called a pellicle and is rich in protein. 

They are autotrophic during the daytime but act as heterotrophic when light is absent. 

They contain the major photosynthetic pigment chlorophyll that helps in the photosynthesis process.

Euglenoids are the connecting link between plants and animals as they contain characteristics of both groups.

Q32. How many types of bacteria are there? 

A32.

 Bacteria are single-cell organisms that are present in the atmosphere. They are found on surfaces and are not visible to the naked eye. They are classified as rod-shaped, spiral-shaped, comma-shaped and spherical-shaped based on their physical characteristics. 

The rod-shaped bacteria are also known as bacilli.

The spiral-shaped bacteria are known as spirilla.

The comma-shaped ones are known as vibrios, and the Spherical shaped bacteria are known as cocci. 

Further, based on their respiration, they are classified as Aerobic and anaerobic. Aerobic bacteria need oxygen for their growth and development, while Anaerobic bacteria can survive without the presence of oxygen. 

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