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.

Benefits of NCERT Solutions for Class 11 Biology Chapter 2 Biological Classification

The NCERT Solutions for Class 11 Biology will render abundant benefits to the students who are preparing for their Class 11 Biology exams.

Some of the benefits of NCERT Solutions for Class 11 Biology Chapter 2 are as follows:

1. NCERT-based questions are very frequently asked in the CBSE exams, so studying these NCERT questions and answers can elevate the learning experience with better practice.

2. From the NCERT study material, all the important topics from Chapter 2 are highlighted and thus the students can study topics like  Viroids, Prions, and Lichens accordingly. 

3. Chapter 2 Biology Class 11 Biological Classification NCERT solutions will provide you with the knowledge of diversity in living organisms and animal kingdoms.

4. This Chapter deals with Kingdom Monera, Kingdom Protista, Kingdom Fungi, Kingdom Plantae, and Virus, included for class 11 biology.

5. Each Concept like the animal kingdom is explained in a very easy way. 

6. NCERT is like the ‘bible’ of CBSE exams, and thus it must be mandatorily referred to by the Class 11 Biology student, as context out of the NCERT syllabus is impossible to appear in the exam.

7. NCERT answers will give a fair idea to the students on how to answer the questions appropriately in the exam.

8. The question pattern and the marks distribution scheme can be well understood by studying the NCERT study material.

NCERT Solutions for Class 11 Biology Chapter 2: Quick Overview of Topics Covered

Important Study Materials for Chapter 2 - Biological Classification

Conclusion 

You are advised to refer to the 11th biology chapter 2 exercise solutions or download the FREE PDF of biological classification NCERT solutions. A better understanding of key concepts such as Kingdom Monera, Protista, Animalia, Plantae, viruses, viroids, and lichens is explained easily. Apart from that, you may practice biological classification class 11 questions and answers that are important and given in this article and know the preparation tips on how to study Class 11 Biology Chapter 2 effectively. 

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