Chapter 2 Biology Class 11 Biological Classification NCERT Solutions

Chapter 2 Biology Class 11 Biological Classification NCERT Solutions

Hello students  today we are going to discuss about Class 11 biology chapter 2 biological classification Solutions. Just keep this statement in your mind! The more you practice, better will be your final CBSE Board performance. Reading our biological classification NCERT Solutions and understanding all the topics clearly is the only thing you must to do. You should also practice. Spend some quality time in solving our previous years Biological classification question papers and mock tests. It boosts your exam paper writing practice. Here, you might make mistakes while practicing. Learn from your mistakes and take care of not repeating them. In this article will learn about the chapter 2 biology class 11 biological classification NCERT solutions. Go through them and  Prepare yourself for CBSE board exam.

Chapter 2 biology class 11 Textbook Solutions

Important points to Remember about Biological classification 

  1. Biological classification of plants and animals was first proposed by Aristotle on the basis of simple morphological characters. 
  2. Linnaeus later classified all living organisms into two kingdoms Plantae and Animalia. 
  3. Whittaker proposed an elaborate five kingdom classification Monera. Protista, Fungi, Plantae and Animalia. 
  4. The main criteria of the five kingdom classification were cell structure, body organisation. mode of nutrition and reproduction, and phylogenetic relationships.
  5. In the five kingdom classification, bacteria are included in Kingdom Monera Bacteria are cosmopolitan in distribution. These organisms show the most extensive metabolic diversity. Bacteria may be autotrophic or heterotrophic in their mode of nutrition. 
  6. Kingdom Protista includes all single-celled eukaryotes such as Chrysophytes. Dinoflagellates, Euglenoids. Slime-moulds and Protozoans. 
  7. Protists have defined nucleus and other membrane bound organelles. They reproduce both asexually and sexually. 
  8. Members of Kingdom Fungi show a great diversity in structures and habitat. Most fungi are saprophytic in their mode of nutrition. They show asexual and sexual reproduction. Phycomycetes, Ascomycetes. Basidiomycctes and Deuteromycetes are the four classes under this kingdom.
  9. The plantae includes all eukaryotic chlorophyll-containing organisms. Algae bryophytes. pteridophytes, gymnosperms and angiosperms are included in this group. 
  10. The life cycle of plants exhibit alternation of generations - gametophytic and sporophytic generations. 
  11. The heterotrophic eukaryotic, multicellular organisms lacking a cell wall are included in the Kingdom Animalia.
  12.  The mode of nutrition of these organisms is holozoic. They reproduce mostly by the sexual mode. 
  13. Some acellular organisms like viruses and viroids as well as the lichens are not included in the five kingdom system of classification.

NCERT solutions for class 11 Biology chapter 2 Biological Classification 

1. Discuss how classification systems have undergone several changes over a period of time.

Answer : Thousands of years ago, humans realized that there are large number of organisms and that is difficult to know all of them. Some people start sought procedures to facilitate their study. For that purpose, Aristotle (384-322 BC) tried to group them together and create a special way to name them; For this, he considered its degree of simplicity or complexity and its behavior; He also thought that inferior beings and other superior ones, among them the human being.

In the 18th century, Carlos Linnaeus (1707-1778) took into account the similarities in form and structure of an organism had with other forms of life. He believed that animals are most similar in shape belonged to the same group, and less similar could be part of different groups. He called each large group of organisms as kingdom; this division included other smaller ones, until almost all the organisms occupied a place in its system of organization. He also thought about the importance of giving a specific name to each organism. They called this grouping system classification. 

For a long time, the best known Biological classification was the one that grouped all living things into animals and plants . But when devices such as the microscope invented and some organisms were discovered that showed their own characteristics, different from those two groups. After 200 years of Linnaeus' research, scientists have developed a classification that groups living beings into five kingdoms given by R.H Whittaker. 

Classifying helps us to organize, to order. In our daily life we ​​classify, group different objects, plants or animals, even without giving that name to our way of proceeding. The order that we obtain by grouping what we want to know or the things we have, makes our task easier. In all the previous centuries, by ordering and studying the world of living beings, the human being has made very valuable advances. By classifying living things, people have come to recognize that plants and animals are no less important than we are. This has allowed us to locate the place that people have among them, not above them.

2. State two economically important uses of: (a) heterotrophic bacteria (b) archaebacteria

Answer : Economic Importance of Heterotrophic Bacteria 

  1. Heterotrophic bacteria are mostly responsible for the decomposition of organic matter such as cellulose, keratin, lignin, chitin, etc.
  2. Heterotrophic Bacteria are mainly used for Production of antibiotics, nitrogen-fixation and Making curd etc. 
  3. Heterotrophic Bacteria which are present in the gut of humans and ruminant organisms help in digestion of food. 
  4. Heterotrophic bacteria are also help in production of vitamins. 
  5. Heterotrophic organisms break down complex organic matter to simple compounds and assimilate them.
Economic Importance of archaebacteria 
  1. Archaebacteria are mainly used for methane production. 
  2. Archaebacteria act on the organic matter and decompose them to release methane gas which is used for cooking and lighting. 
  3. Archaebacteria is also used for enzymes production. 
  4. Enzymes that are usually added to detergents in order to help it maintain its activity even at higher temperature and pH. 
  5. Archaebacteria has potential for bioremediation or help in cleaning.

3. Nature of cell wall in diatoms ?

Answer : Nature of cell wall in diatoms

  1. The structure of cell wall diatoms has distinct properties. These are unicellular or colony forms. 
  2. Each cell is covered with durable silica gel, which is an alternative to the typical cellulose membrane of algae.
  3. The hard shell of diatoms consists of a usually symmetric transparent silica shield.
  4. The structure of the shell, its shape and the ratio of axes and planes of symmetry are the basis of systematics. 
  5. The shape of the cell wall in diatoms is varied: in the form of a ball, disc, cylinder, etc
  6. The cell wall of diatoms is made of amorphous silica with a mixture of minerals (aluminum, iron, magnesium) and an organic component and possibly a protein. 
  7. The thickness of the shell wall depends on the concentration of silicon in the medium and varies greatly: in thin-walled forms - on hundreds of micrometers, on 13 microns of thick walls. 
  8. The Formation of cell wall in diatoms is known as frustule.  
  9. When the diatoms goes for Apoptosis the silica in their cell walls gets deposited in the form of diatomaceous earth. 
  10. And this diatomaceous earth is very soft and quite inert in nature.
  11. Generally It is used in filtration of sugars, oils and for verious industrial purposes.

4. Find out what do the terms 'algal bloom' and 'red - tides' signify?


  1. The red tide is a natural phenomenon which is characterized by producing a change in color of water bodies auch as seas, lakes, rivers or other bodies of water. 
  2. This is cause due to the presence of certain species of marine microalgae dinoflagellates (Gonyaulax). 
  3. The scientific name for this phenomenon is Harmful Algal Bloom.
  4. Algal bloom refers to an increase in the population of algae or blue-green algae. 
  5. The red tide is toxic to humans as well as to various marine species. This is due to the fact that these microalgae are capable of producing certain toxins (amnesic, paralyzing, gastric, etc.) which, by accumulating in the body of mollusks and crustaceans, make their consumption dangerous.

5. How are viroids different from viruses?
  1. The viroids are infectious agents like viruses, with an extracellular cycle characterized by inactivity metabolic and an intracellular cycle that cause infection to the host susceptible, but unlike viruses, viroids have no proteins, no lipids and they are constituted by a short cyclic chain of RNA , (that does not code for proteins). 
  2. It is important to say that both their intracellular and extracellular forms are the same (naked RNA), the mechanisms by which these manage to cause infection are related to the autocatalysis of their genetic material. They themselves constitute a primitive stage of viruses.

6. Describe briefly the four major groups of Protozoa.
Answer : Protozoa are a group of microorganisms that are found in humid or aquatic environments and that could be considered as microscopic animals. However, in some biological classification systems they form a kingdom of their own called Protozoa.

The protozoa distinguishes between the following four major types:

1. Rhizopods :  These members of  protozoa  are characterized by their displacement by pseudopods and formation of protrusions of their cytoplasm and the plasma membrane , projecting them towards where they want to advance. These projections also serve to capture food and introduce it to the cytoplasm (phagocytosis), either by predating other organisms or by assimilating waste organic matter.

2. Flagellated : Cells endowed with one or more flagella, which is the name of the "tails" with which they propel themselves forward in the environment .

3. Ciliates : Its plasma membrane is surrounded by cilia, that is, filaments smaller and more numerous than flagella, which also serve to mobilize.

4. Sporozoans : Parasitic protozoa without much mobility, which have a phase of multiple division known as sporulation: a type of asexual reproduction that consists of producing spores or endospores, resistant structures that generate a new identical individual.

7. Plants are autotrophic. Can you think of some plants that are partially heterotrophic?
Answer: yes, Few are truly heterotrophic plants, they are incapable of making their own food with the help of sunlight and some inorganic substances such as CO2 and H2O. In other words they do not photosynthesize, they do not have leaves it means they do not contain chlorophyll. Their body structure is simple, they only develop an inflorescence, which in some cases can be large. In fact, the largest inflorescences in the world are parasitic plants. Hidden under the ground, these plants have an adapted root system, through haustoria, to penetrate the roots of other plants, normally specific to each parasitic species, and absorb their elaborated sap. The examples include pitcher plant (Nepenthes), Venus fly trap, Bladderwort and sundew plant (Drosera).

8. What do the terms phycobiont and mycobiont signify? 
Answer: Both the terms Phycobiont and mycobiont are common in biology. Phycobiont is the constituent of lichen algae (symbiotic relationship between algae and fungi) and mycobiont is the fungal component. Both are in a symbiotic relationship in which the algae prepare food for fungi due to the presence of chlorophyll while the fungus provides shelter to the algae and absorbs water and nutrients from the soil.

9. Give Comparative account of the classes of kingdom Fungi under the following :
i) Mode of nutrition 
ii) mode of reproduction 
Answer: The fungi kingdom is one of the groups in which biology classifies known life forms. It is made up of more than 144,000 different species of fungi,  including yeasts , molds, and mushrooms, sharing fundamental characteristics such as immobility, heterotrophic feeding, and certain cellular structures.

Mode of Reproduction
Fungi  reproduce in a sexual and asexual way , always through the production of spores. These are equivalent to the seeds of trees: forms resistant to the environment that, when the optimal conditions finally occur, germinate and create a new specimen of the fungus. The growth of the hyphae once the spores have germinated can be very fast.

Mode of Nutrition :
The nutrition of fungi is always heterotrophic, that is, they cannot generate their own food like plants , but must decompose organic matter from other forms of plant or animal life.
  1. Saprophytic fungi : They feed on the decomposition of waste organic matter
  2. Mycorrhizal : They are nourished through a symbiotic relationship with plants, colonizing their roots and exchanging with them different mineral nutrients and water, generated by the fungus.
  3. Lichenized : They are nourished through symbiotic relationships product of the union of the fungus and an alga or cyanobacteria
  4. Parasites  : They feed directly from the body of other living beings , either established on its surface or colonizing inside their body, causing various damages that can be slight or even lethal.

10. What are the characteristics feature of Euglenoids?
  1. Euglenoids are eukaryotic, single-celled organisms that are not considered plants or animals.
  2. Euglenoids are small organisms, usually measuring between 15 and 40 microns, but there are some species that can get larger (500 microns).
  3.  Majority of Euglenoids are fresh water organisms and found in strangest water.
  4. Instead of cell wall they  have protein rich layer pellicle which makes Euglenoids body flexible.
  5. They carry two flagella in most groups. They move by using their flagella or by euglenoid movements.
  6. Euglenoids are colorless, except for chloroplasts, which are capable of photosynthesis. Some have free life forms and others are parasites.

11. Give a brief account of viruses with respect to their structure and nature of genetic material. Also name four common viral diseases.
Answer: Viruses are made up of DNA or RNA and surrounded by a protein called capsid. Viruses are intracellular parasites that reproduce in host cells and use host enzymes to reproduce. Bacteriophages are viruses that infect only bacteria and reproduce through the lytic or lysogenic cycle. Animal viruses are divided into DNA and RNA viruses, depending on the type of genetic material, surrounded by a protein capsule and externally by a membrane envelope. Viruses that infect animals and humans include the polio virus, the flu virus, the hepatitis virus, the AIDS virus, and the viruses that cause cancer. Most plant viruses are RNA viruses and infect plants mainly through insects. Viruses are small bare RNA molecules with high infectivity.

Common viral disease like Chickenpox.
Flu (influenza), Herpes. Human immunodeficiency virus (HIV/AIDS), Human papillomavirus (HPV), Infectious mononucleosis, Mumps, measles and rubella, Covid 19 etc.

12. Organise a discussion in your class on the topic – Are viruses living or nonliving?
Answer: Viruses do not meet any of the criteria for any of the definitions of life that have been given throughout history from Aristotle to the present. They lack any form of energy and carbon metabolism, and cannot replicate or evolve on their own. They reproduce and evolve only within cells. Without host cells, viruses are "complex inanimate organic matter." Viruses are not alive. The fact that they are composed of molecules found in cells (nucleic acids, proteins, lipids and complex sugars)

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biological classification ?
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What are the most important concepts in ch 2 bio class 11 ncert solutions?
Answer: The most important concepts from the exam point of view in the NCERT Solutions for ch 2 bio class 11 ncert solutions are –
2.1 – Kingdom Monera
2.2 – Kingdom Protista
2.3 – Kingdom Fungi
2.4 – Kingdom Plantae
2.5 – Viruses, Viroids, Prions And Lichens

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