This chapter is a major pillar of the Biology syllabus. These solutions ensure students grasp the fundamental differences between prokaryotes and eukaryotes, which is essential for all future units in Biology.
NEET frequently features questions on the characteristics of Protists and the classification of Fungi. These solutions provide the specific NCERT-based examples and keywords that examiners look for in both school and competitive papers.
Yes, they are fully updated. They are useful because they focus on the core evolutionary relationships (Phylogeny) and the specific unique traits of each kingdom, ensuring students are prepared for the latest medical entrance exam patterns.
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NCERT Solutions Class 11 Biology Chapter 2 - Biological Classification
NCERT Solutions for Class 11 Biology Chapter 2 (Biological Classification) delve into the scientific procedure of grouping organisms into different categories based on their similarities and differences. This chapter moves from the general concept of living things to the specific Five Kingdom System proposed by R.H. Whittaker, which remains the standard for modern biological study.
NCERT Solutions for Class 11 Biology Chapter 2 by ALLEN are prepared by expert faculty to help students navigate the vast diversity of life forms, from microscopic bacteria to complex fungi. The solutions focus on the structural and reproductive features that distinguish each kingdom, making complex topics like viral replication and fungal life cycles easier to grasp. Mastering this chapter is essential for NEET aspirants, as it carries high weightage and forms the basis for the subsequent chapters on Plant and Animal Kingdoms. These solutions provide the conceptual depth needed to understand the unique characteristics of Archaebacteria, the diverse nature of Protists, and the symbiotic relationships of Lichens.
This chapter examines the criteria used to classify life into distinct kingdoms based on cell structure, body organization, and mode of nutrition. The key lessons include:
Kingdom Monera: Studying bacteria as the sole members, including Archaebacteria (extremophiles) and Eubacteria (true bacteria like Cyanobacteria).
Kingdom Protista: Understanding single-celled eukaryotes, including Chrysophytes, Dinoflagellates, Euglenoids, Slime moulds, and Protozoans.
Kingdom Fungi: Analyzing the morphology and reproduction of fungi, and their classification into Phycomycetes, Ascomycetes, Basidiomycetes, and Deuteromycetes.
Kingdom Plantae & Animalia: A brief introduction to eukaryotic chlorophyll-containing organisms and heterotrophic multicellular organisms (detailed in Chapters 3 and 4).
Viruses, Viroids, Prions, and Lichens: Studying acellular entities that do not find a place in Whittaker's five-kingdom classification.
Discuss how classification systems have undergone several changes over a period of time?
Ans. Classification systems have undergone several changes with time. Initially, Linnaeus proposed the Two Kingdom Classification, which included Plantae and Animalia. Later, R.H. Whittaker proposed the Five Kingdom Classification consisting of Monera, Protista, Fungi, Plantae and Animalia. The criteria used for classification included cell structure, body organisation, mode of nutrition, reproduction and phylogenetic relationships. With advances in molecular biology and our knowledge of evolutionary relationships, classification systems have been further modified.
State two economically important uses of:
(a) heterotrophic bacteria
(b) archaebacteria
Ans.
(a) Heterotrophic bacteria : Many of them have a significant impact on human affairs. They are helpful in making curd from milk, production of antibiotics, fixing nitrogen in legume roots.
(b) Archaebacteria : Methanogens are used for the production of biogas (gobar gas).
Methanogens present in the rumen of cattle help in cellulose digestion and methane production.
What is the nature of cell-wall in diatoms?
Ans. In diatoms the cell walls forms two thin overlapping shells, which fit together as in a soap box. The walls are embedded with silica and thus the walls are indestructible.
Find out what do the terms 'algal bloom' and 'red tides' signify.
Ans.Algal bloom :
The rapid increase or excessive growth of algae in water bodies due to nutrient enrichment, especially nitrates and phosphates, is called an algal bloom.
Red tides :
The rapid multiplication of red dinoflagellates, particularly Gonyaulax, in the sea is called a red tide. It may make the sea appear red and the organisms may release toxins that are harmful to marine life.
How are viroids different from viruses?
Viroids
Viruses
Viroids are smaller infectious agents.
Viruses are comparatively larger infectious entities.
They consist of a small, circular, single-stranded RNA molecule.
They contain DNA or RNA as genetic material.
They do not have a protein coat.
Their genetic material is surrounded by a protein coat called capsid.
Viroids were discovered by T.O. diener.
Viruses were first described by D.J. Invanowsky in tobacco mosaic disease.
Describe briefly the four major groups of protozoa.
Ans. All protozoans are heterotrophs and live as predators or parasites. They are be-lieved to be primitive relatives of animals. They are classified into four groups on the basis of locomotory organelles.
(i) Amoeboid protozoans : These organisms live in fresh water, sea water or moist soil. They move and capture their prey by developing pseudopodia (false feet) as in Amoeba. Some of them such as Entamoeba are parasites.
(ii) Flagellated protozoans : The members of this group are either free-living or parasitic. They have flagella for locomotion. The parasitic forms cause diseases such as sleeping sickness e.g., Trypanosoma.
(iii) Ciliated protozoans : These are aquatic, actively moving organisms because of the presence of thousands of cilia. They have a cavity (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 into the gullet e.g., Paramecium.
(iv) Sporozoans : This includes diverse organisms that have an infectious spore like stage in their life cycle. The most notorious is Plasmodium (malarial parasite) which causes malaria which has a staggering effect on human population.
Plants are autotrophic. Can you think of some plants that are partially heterotrophic?
Ans. Some insectivorous plants like Drosera, Nepenthes, are partially heterotrophic plant. These plants are deficient in nitrogen content but are otherwise autotrophic. They, trap various insects to obtain nitrogen from them. Rest, the food i.e., carbohydrate is manufactured by themselves.
What do the terms phycobiont and mycobiont signify?
Ans. In lichen, the algal component is called the phycobiont and the fungal component is called the mycobiont. The phycobiont prepares food by photosynthesis, while the mycobiont provides shelter, water and minerals.
Give a comparative account of the classes of Kingdom Fungi under the following:
(i) mode of nutrition
(ii) mode of reproduction
Ans.
Class
Mode of nutrition
Mode of reproduction
Phycomycetes
Saprophytic, parasitic or symbiotic
Asexual reproduction by zoospores or aplaospores, sexual reproduction may be isogamous, anisogamous or oogamous.
Ascomycetes
Mostly saprophytic; some parasitic
Asexual reproduction by conidia ; sexual reproduction by ascospores produced in asci
Basidiomy cetes
Mostly decomposers; some parasitic
Asexual spores generally absent ; sexual reproduction by basidiospores produced on basidia
Deuteromy cetes
Mostly saprophytic some parasitic
Only asexual reproduction is known; conidia are produced
What are the characteristic features of Euglenoids?
Ans. Euglenoids :
Majority of them are fresh water organisms found in stagnant water. Instead of a cell wall, they have a protein rich layer called pellicle which makes their body flexible.
They have two flagella, a short and a long one. Though they are photosynthetic in the presence of sunlight, when deprived of sunlight they behave like heterotrophs by predating on other smaller organisms. Interestingly, the pigments of euglenoids are identical to those present in higher plants. Example: Euglena
Give a brief account of viruses with respect to their structure and nature of genetic material. Also name four common viral diseases.
Ans. Viruses are acellular infectious entities. They consist of genetic material surrounded by a protein coat called capsid. The capsid is made up of subunits called capsomeres.
The genetic material of viruses may be DNA or RNA. A virus generally contains only one type of nucleic acid. Some viruses also have an additional envelope around the capsid.
Four common viral diseases are:
Common cold
Influenza
Polio
AIDS
Organise a discussion in your class on the topic - Are viruses living or non-living?
Ans. Viruses show both living and non-living characteristics.
Living characteristics:
They contain genetic material in the form of DNA or RNA.
They reproduce inside a living host cell.
They can undergo mutation and evolution.
Non-living characteristics:
They are acellular.
They do not possess their own metabolic machinery.
Outside a living host cell, they remain inactive.
They can be crystallised.
Conclusion:
Viruses are considered to occupy a borderline position between living and non-living. They become active and multiply only inside a living host cell.
3.0Key Features of NCERT Solutions for Class 11 Biology Chapter 2
Criteria-Based Clarity: The solutions clearly explain the five criteria used by Whittaker (cell structure, thallus organization, mode of nutrition, reproduction, and phylogenetic relationships) to help students understand the logic of the system.
Comparative Fungal Analysis: Detailed tables comparing the four classes of fungi based on their habitat, mycelium type, and mode of asexual/sexual reproduction, which is a frequent NEET topic.
Virus vs. Viroid Distinction: Step-by-step breakdown of the differences between viruses (protein coat + nucleic acid) and viroids (free RNA without protein coat), preventing common exam confusion.
Cyanobacteria and Nitrogen Fixation: Expert explanations on the role of specialized cells like heterocysts in Cyanobacteria for fixing atmospheric nitrogen.
Prepared by Expert Faculty: Prepared by ALLEN subject experts, ensuring that every definition and biological process is technically accurate and aligned with the latest NCERT syllabus.
Visual and Descriptive Explanations: The solutions use descriptive language to help students visualize the "step-like" evolution of complexity from Monera to Animalia.