NCERT Solutions for Class 11 Biology Chapter 2 - Biological Classification

1. Discuss how classification systems have undergone several changes over some time?

Ans: Biological categorization is the scientific method of grouping organisms into hierarchical groups and subgroups based on their similarities and differences. Scientists have developed various classification systems, which have undergone several revisions over time. Previously, Aristotle developed an artificial classification system that classified animals and plants according to their habitat. Aquatic (fish, whales), terrestrial (reptiles, cattle), and aerial (birds) are examples (e.g., bat, birds). Morphology, anatomy, physiology, reproduction, ontogeny, cytochemistry, and other factors were used to classify organisms back then. Following that, creatures were categorized using a phylogenetic framework based on evolutionary links. It uses cytotaxonomy, chemotaxonomy, numerical taxonomy, and cladistic taxonomy to classify organisms.

2. State two economically important uses of:

(a) Heterotrophic bacteria (b) Archaebacteria

Ans: Some heterotrophic bacteria are decomposers; they are used as natural scavengers, decomposing dead bodies and organic wastes to release raw resources, allowing organic matter to be reused. They also assist with sewage disposal, manure production, and other tasks.

• Symbiotic bacteria aid in nitrogen-fixing in the atmosphere.

• Bacteria are used in the manufacturing of lactic acid, curd, cheese, butter, vinegar, and other industrial products. Pseudomonas, Xanthomonas, and other bacteria are utilized in the production of serum, vaccines, vitamins, enzymes, antibiotics, and other products.

Archaebacteria:

• Archaebacteria are used to produce gobar gas from manure and sewage, and they cause cellulose fermentation in ruminants.

• Archaebacteria can be found in the guts of ruminants like cows and buffaloes, and they aid in digestion.

3. What is the nature of cell walls in diatoms?

Ans: Diatoms' cell walls are known as frustules. The cell wall is primarily made up of cellulose that has been impregnated with glass, similar to silica. It is made up of two overlapping halves (or theca) that fit together like the two halves of a soapbox or a petri dish. Epitheca refers to the upper half (lid), whereas hypotheca refers to the lower half (case). Fine patterns, pits, pores, and ridges can be found on the outer layer. Diatoms' siliceous frustules are resistant to degradation. They generate large mounds of diatomite or diatomaceous earth at the bottom of water reservoirs. It may extend for hundreds of meters in some regions, from which it can be mined.

4. Find out what do the terms ‘algal bloom’ and ‘red tides’ signify?

Ans: An algal bloom is a fast growth in populations of algae and other phytoplankton, particularly cyanobacteria, in organically rich water bodies. The creatures’ density may prevent light from reaching lower depths in the water body. A rise in nitrate levels, a mineral ion required for algal and bacterial growth, causes algal blooms. Agricultural fertilizers, which are leached — into water systems from the soil, or sewage effluent could be the source of increasing nitrate. Because of the high concentration of photosynthetic accessory pigments, red tides are generated by a sudden, often dangerous growth of marine phytoplankton, particularly dinoflagellates, which color the seared, brown, or yellowish. Some dinoflagellates, such as Gonyaulax, create toxins that can harm fish and invertebrates or accumulate in the food chain, providing a risk to humans who consume shellfish and other seafood. These phytoplanktonic blooms are thought to be caused by nutrient-rich inputs from the land, upwelling oceanic waters, and the activation of cyst-like structures on the seabed.

5. How are viroids different from viruses?

Ans: Viroids are the tiniest known infectious disease pathogens, consisting of a single-stranded RNA molecule. They don't have a capsid and don't have any proteins attached to them. Only plants are infected by viruses. Viruses, on the other hand, have genetic material that is protected by a protein or lipoprotein coat. Viruses have four forms of genetic material: double-stranded DNA, double-stranded RNA, single-stranded DNA, and single-stranded RNA. They can infect both plants and mammals.

6. Describe briefly the four major groups of protozoa.

Ans: Protozoans are all heterotrophic, meaning they exist as predators or parasites. Animal relatives are thought to be their ancestors. Based on locomotory organelles, they are divided into four classes.

(i)Amoeboid Protozoans: Amoeboid protozoans are creatures that dwell in freshwater, seawater, or moist soil. As in Amoeba, they move and seize their prey by generating pseudopodia (fake feet). Some of them are parasites, such as Entamoeba.

(ii) Flagellated Protozoans: This group includes both free-living and parasitic protozoans. For locomotion, they have flagella. The parasitic forms, such as Trypanosoma, cause disorders like sleeping sickness.

(ii) Ciliated Protozoans: Ciliated protozoans are aquatic, actively moving organisms with thousands of cilia. They have a cavity (gullet) on the cell surface that opens to the outside. Water packed with food, such as paramecium, is directed into the gullet by the coordinated movement of rows of cilia.

(iv) Sporozoans are parasitic organisms that go through a life cycle that includes an infectious spore stage. There are no locator organs. N. Plasmodium has a bad effect on the human population because it causes malaria.

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

Ans: Plants that eat insects, such as Drosera, Nepenthes, and Utricularia, are somewhat heterotrophic. The nitrogen content of these plants is low, although they are otherwise autotrophic. They capture a variety of insects to get nitrogen from them. The rest of the food, namely carbohydrates, is produced by the photosynthesis process.

8. What do the terms phycobiont and mycobiont signify?

Ans: A lichen is a structurally organized object made up of a fungus and an alga that is permanently associated. Mycobiont refers to the fungal component of lichen, while phycobiont refers to the algal component. Both mycobiont and phycobiont are part of a symbiotic relationship in which the fungus is the dominant partner and the algae are the submissive. The fungus provides the structural covering that protects alga from adverse conditions like drought, heat, and other environmental factors. It also absorbs moisture from the air and binds the lichen to rock, tree bark, leaves, and other similar structures. By converting carbon dioxide into organic food, the alga prepares organic food. Cyanobacteria (blue-green algae) can fix atmospheric nitrogen in addition to preparing food if the algal component is cyanobacteria (blue-green algae).

9. Give a comparative account of the classes of kingdom Fungi under the following:

(i) mode of nutrition (ii) mode of reproduction

Ans: 

10. What are the characteristic features of Euglenoids?

Ans: The most fascinating species are the euglenoid flagellates, which combine animal and plant features. The following are the distinguishing characteristics:

• They are flagellates with only one cell.

• There is no defined cellulose cell wall in these protists. Instead, a thin membrane known as a pellicle protects the cells. Protein, fat, and carbs make up the pellicle.

• These protists have one or two flagella, which aid them in swimming. If there are two flagella, one is long and the other is short. They have two longitudinal rows of fine hairs and are tinsel-shaped. Each flagellum has its granule at the base. A bulge known as the paraflagellar body connects the two flagella.

• The cell's anterior end has an eccentric mouth, or cytostome, that leads into a flask-shaped chamber, such as the gullet or cytopharynx. The gullet is a big basal reservoir that opens up.

• The cytoplasm of one end of the reservoir has an orange-red stigma (eyespot). The eyespot is a curving plate that contains the red pigment astaxanthin and is covered with orange-red granules. Photoreceptors are found in both the paraflagellar body and the eyespot.

• A contractile vacuole with several feeding channels can be detected just below the reservoir. Osmoregulation is aided by the contractile vacuole. It expands and pumps the contents of its fluid into the reservoir.

• Euglenoids are either holophytic or photoautotrophic in their feeding.

• Ectoplasm and endoplasm are two types of cytoplasm. The nucleus is big and located in the center of the cell. During cell division, the envelope and nucleolus remain.

• Each chloroplast is made up of a granular matrix with 10-45 dense bands running through it and a three-membraned envelope. Chlorophyll –b is a photosynthetic pigment found in them. Carbohydrates are stored in the form of paramylon bodies, which are dispersed throughout the body. Carbohydrates are stored as paramylon bodies, which are dispersed throughout the cytoplasm.

• Longitudinal binary fission is used in asexual reproduction. Before cell division, the flagellum is replicated.

• When conditions are unfavorable, the euglenoids produce cysts to prolong the dry period.

• There is no evidence of sexual reproduction.

11. Give a brief account of viruses with respect to their structure and nature of genetic material. Also, name four common viral diseases.

Ans: Virus (L. toxic fluid) is a category of ultramicroscopic, non-cellular, extremely infectious organisms that reproduce exclusively intracellularly — within the living host cells – without the need for growth or division. They are inert particles outside of the host cells. They are nucleoproteins that have one or more nucleic acid molecules, such as DNA or RNA, enclosed in a protein or lipoprotein sheath. The nucleoid (genome) and capsid are the two sections of a virus. In some circumstances, an envelope and a few enzymes are present.

• Nucleoid: The viral chromosome is represented by the nucleoid, which is a nucleic acid found in the virus. It is made of a single nucleic acid molecule. It might be linear or circular, using DNA or RNA as the nucleic acid. It is the section of the virus that uses the host cell's metabolic machinery to synthesize and assemble viral components.

• Capsid: It's a protein that encases genetic material. Capsomeres are protein components found in capsids. The nucleoid is protected by the capsid from physical and chemical agents.

• Envelope: The envelope is a loose outer covering seen on some viruses, such as animal viruses (e.g., HIV), but not on plant or bacterial viruses. It is made up of viral protein, as well as lipids and carbohydrates from the host. Spikes, or outgrowths, may be present. Peplomers are components of envelope proteins. A virus that does not have an envelope is known as a naked virus.

Influenza, polio, measles, chickenpox, hepatitis, AIDS, bird flu, SARS (Severe Acute Respiratory Syndrome), and other viral infections are common.

12. Organise a discussion in your class on the topic – ‘Are viruses living or nonliving?

Ans: Viruses are thought to be a bridge between non-living and living things. It's tough to tell whether they're alive or dead. Viruses have some characteristics that indicate their non-living nature, while others indicate their alive nature.

They have the appearance of non-living items.

• Protoplast deficiency.

• Crystallization ability.

• Inability to live without the assistance of a living cell.

• A high specific gravity that can only be found in non-living things.

• The inability to breathe.

• The lack of an energy storage system.

• Lack of division and development. Different sections are synthesized independently instead.

Viruses are similar to living organisms in that they are made up of organic macromolecules that are only found in living organisms.

• Genetic material is present.

• The ability to multiply or reproduce, but only inside the confines of a live cell.

• Mutation occurrence.

• Enzyme transcriptase is found in the majority of viruses.

• Vitamins such as riboflavin and biotin are found in some viruses, such as the Pox virus.

• Autoclaving and ultraviolet light both ‘kill' viruses.

• They reproduce by Penicillium type. Even variances can be passed on.

• They take over the host cell's biosynthetic machinery and manufacture substances necessary for their replication.

NCERT Solutions for Class 11 Biology Chapter 2 - Biological Classification

Chapter 2 Biology Class 11 NCERT Solutions will provide you with the knowledge of diversity on living organisms and animal kingdom.

What is Biological Classification?

Biological classification is a process by which the scientists have categorized all organisms in a hierarchical structure of groups and subgroups based on their features and environment.

Aristotle was the first scientist to classify the organisms on a scientific basis. He classified the plants on the basis of morphological features and classified them into trees, shrubs and herbs.

Linnaeus classified the plant and animal kingdoms as per the characteristics.

RH Whittaker classified the living organisms into five kingdoms: Monera, Protista, Fungi, Plantae and Animalia. He classified the organisms based on their following characters:

1. Cell type

2. Cell Wall

3. Nuclear membrane

4. Body organization

5. Mode of nutrition

Classification of Five Kingdoms

Monera Kingdom: 

This kingdom includes prokaryotic microorganisms like bacteria. Bacteria are prokaryotes.

Features

• They do not have well-defined nuclei. 

• Membrane-bound cell organelles are absent.

• They live in extreme habitats like springs, snow, and deep oceans as free-living or parasites.

Shape

On the Basis of their Shape, they are Classified into:

• Coccus (cocci) - Spherical

• Bacillus (bacilli) - Rod-shaped

• Vibrium (vibrio) - Comma-shaped

• Spirillum (spirilla) - Spiral-shaped

Nutrition

Bacteria Show a Wide Range of Modes of Nutrition. They may be

• Autotrophic

• Chemotrophic

• Saprophytic

• Heterotrophic

    Bacteria

      |

________________________________

          |         |

              Archaebacteria                         Eubacteria

                  |                                   |

             Halophiles       Photosynthetic autotrophs

  Thermoacidophiles     Chemosynthetic autotrophs

  Methanogens   Heterotrophic bacteria

    Basophiles

Archaebacteria is responsible for the production of methane (biogas) from the dung of the animals. They also help in the degradation of waste materials. 

Eubacteria is used in the process of making cheese, curd, vinegar and wine. They also play a major role in the digestion of food in humans.

Protista Kingdom: 

This kingdom includes unicellular eukaryotes.

Features

• They have a well-defined nucleus and membrane-bound organelles. 

• They reproduce sexually and asexually.

• They reside in marine water and are photosynthetic.

• Due to the presence of different pigments, they have the appearance of yellow, green, brown and red.

Habitat

Based on habitat, Protista is divided into five groups.

• Chrysophytes

• Dinoflagellates

• Euglenoid

• Slime mould

• Protozoans

Functions

Chrysophytes include diatoms and golden algae known as desmids. The cell wall of the diatom is embedded with silica and forms two thin overlapping sheaths as in a soapbox. Diatoms are used in polishing, filtration of oils and syrups.

Dinoflagellates

They are marine and photosynthesis microorganisms. They help in photosynthesis in marine plants. One kind of dinoflagellate is Gonyaulax that is red and they undergo rapid multiplication and form red tides.

Euglenoid

They are freshwater organisms found in the standing water. In presence of sunlight, they behave as autotrophs (utilizes its chloroplasts to produce its sugar through photosynthesis) and in the absence of sunlight, they behave as heterotrophs.

Slime Moulds

They are saprophyte, which is dependent on dead and decaying organic matter. They form an aggregation called plasmodium. During unfavourable conditions, they form highly resistant spores.

Protozoan

Protozoans are heterotrophs. They are predators or live as parasites.

Classification of Protozoa

1. Amoeboid Protozoans: They live in fresh and marine water. They have irregular bodies and keep changing their shape.

2. Flagellated Protozoans: They are free-living parasitic microorganisms. Ex: Trypanosoma.

3. Ciliated Protozoans: They are aquatic, actively moving organisms. Ex. Paramecium.

4. Sporozoans: These include spore-forming infectious agents like Plasmodium, which causes malaria.

Fungi Kingdom: This kingdom includes heterotrophic organisms. They rely on extracellular digestion.

Features

• They reside in air, water, soil or animals.

• Fungi are filamentous and form long slender, thread-like structures called hyphate.

• The cell wall is made up of chitin.

• They are saprophytic or parasitic.

• They exist in a symbiotic relationship with algae known as lichens and with roots of higher plants called mycorrhiza.

• Fungi reproduce asexually by vegetative means like fragmentation, fission, buddy or by forming spores called conidia/ sporangia spores/ zoospores.

• Sexual reproduction occurs with the help of oospores, ascopores and basidiospores.

Note: Algae component in a lichen is known as phycobiont and fungal component as mycobiont. Algae prepare food for fungi and fungi provide shelter to algae.

Classification of Fungi

Fungi are classified into various classes on the basis of mycelium mode of spore formation and fruiting bodies.

1. Phycomycetes are parasites on plants. The mycelium is septate and coenocytic.

2. Basidiomycetes include mushrooms/ bracket fungi/ puffballs. Their mycelium is branched and septate.

3. Ascomycetes are known as sac fungi usually multicellular like Penicillium. Their mycelium is branched and septate.

4. Deuteromycetes are known as imperfect fungi since sexual reproduction is not prepared in them. Mycelium is septate and branched.

Plantae Kingdom: This kingdom includes eukaryotic autotrophic, chlorophyll-containing organisms.

Features

• They may be partially autotrophic and partially heterotrophic such as in the case of insectivorous plants like Cuscuta.

• They have a distinct nucleus, chloroplast and cellulosic cell walls.

• Includes algae, bryophytes, pteridophyte, gymnosperms and angiosperms.

Note: Plants are autotrophs that mean they prepare their own food through the process of photosynthesis.

They are heterotrophic partially because partially they depend on other organisms for food requirements.

Animalia Kingdom: 

This kingdom includes heterotrophic eukaryotic, multicellular organisms.

Features

• Their cells do not have cell walls.

• Mode of nutrition is holozoic i.e. ingestion of food.

• They store food material as glycogen or fat.

• Capable of locomotion and have specialized sensory and neuromotor systems.

• They show definite growth patterns.

• They have a sexual mode of reproduction.

Virus

Viruses and viroids are non-cellular organisms. They have both living and non-living characteristics. They form a thin loose covering outside the living cell but inside the host cell, they can multiply. They take over the body of the host and replicate themselves.

They possess genetic material of viruses called DNA or RNA that can grow and multiply inside in the host cell. In humans, it causes various diseases like AIDS, mumps, smallpox, herpes and influenza. In plants, it causes leaf rolling and curling, yellowing and clearing dwarfing and stunted growth.

NCERT Solutions for Class 11 Biology Chapter 2 - Topics Covered 

The topics which are covered for Class 11 Biology Chapter 2 are presented in the table below:

NCERT Solutions for Class 11 Biology Chapter 2 - Important Questions and Answers (Solved) 

1. What are some advantages of the five-kingdom classification over the two-kingdom classification?

Ans. Some of the advantages of the five-kingdom classification over the two-kingdom classification are as follows:

• The five-kingdom classification is based on a cell structure.

• The five-kingdom classification is based on a body structure.

• The nutrition system can be classified clearly. 

• The way of living of the animals is more clear in this system.

• The phylogenetic relationship is understood clearly.

2. What can be an example of an insectivorous plant?

Ans. The Venus flytrap is an example of an insectivorous plant.

3. Illustrate two roles that fungi have in our life?

Ans. Two roles of fungi are as follows:

• Fungi like Agaricus are a source of high nutrients which are used in foods. 

• Fungi provide resistance against pets. 

If you want to practice more Important questions, you can do so by studying the important questions from this link Important Questions for CBSE Class 11 Biology, Chapter-wise Solutions - Free PDF Download

Preparation Tips for the Students - How to Study CBSE Class 11 Biology?

Some preparation tips for the students are as follows:

1. The students are required to understand the concept completely. 

2. They must practice enough questions and solve the exercise questions and answers. 

3. NCERT questions must be studied properly.

4. Previous year question papers must be referred to so that the students know the type and the pattern.

Conclusion 

Hope the students have gained the requisite knowledge and resources from this study material. You are advised to download the free pdf of NCERT questions and answers, in case you still did not download the same. 

Apart from that, you may practice the important questions and answers given in this article and know the preparation tips on how to study Class 11 Biology effectively.