NCERT Class 11 Biology Chapter 2 Notes Biological Classification- Download PDF Notes

CBSE Quick Revision Notes Class 11 Biology Chapter 2: Biological classification is a scientific process of grouping organisms based on their similarities and differences. These notes detail how living organisms are categorised into different kingdoms based on their characteristics. The chapter explains various classification systems, including two-kingdom and three-domain classification. The biological classification NCERT Notes for Class 11 Biology help you revise crucial concepts given in the NCERT Book in no time during the CBSE Board exam preparation. NCERT Solutions and having revision notes for Class 11 Biology Chapter 2 handy are beneficial to save you time.

This Story also Contains

1. NCERT Class 11 Chapter 2 Class Notes
2. Introduction
3. Five Kingdom Classification
4. Kingdom Monera
5. Kingdom Protista
6. Kingdom Fungi
7. Kingdom Plantae
8. Kingdom Animalia
9. Viruses, Viroids, Prions and Lichens
10. Benefits of NCERT Class 11 Biology Chapter 2 Notes:
11. Tips to learn NCERT Class 11 Biology Chapter 2 Notes:
12. Most Important Questions Class 11 Biology Chapter 2
13. Approach to Solve Questions of Class 11 Biology Chapter 2

Understanding this chapter is essential for comprehending the diversity of life forms, relationships, and revolutionary history. These notes, available in easy-to-understand format, help students understand key concepts quickly and effectively. Download the CBSE Notes for Class 11 Biology, Chapter 2, PDF to use it offline anywhere. Students must go through each topic in the biological classification of Class 11 biology in the easiest and most effective way possible with the help of NCERT Notes for Class 11.

Also, students can refer to:

• NCERT Solutions for Class 11 Biology Chapter 2 Biological Classification
• NCERT Exemplar Class 11 Biology Chapter 2 Solutions Biological Classification

NCERT Class 11 Chapter 2 Class Notes

The summarized notes are given below-

Introduction

Biological classification is the method of arranging organisms into groups based on morphological, physiological, genetic and evolutionary relationships. It helps in the systematic identification, study, and understanding of biodiversity.

Early Classification System

In the early stages, organisms were broadly classified into two kingdoms, plantain, and Amalia. However, the system had many limitations as it did not distinguish between prokaryotic and eukaryotic organisms or unicellular and multi-cellular forms.

Five Kingdom Classification

R.H. Whittaker, in 1969, proposed the five-kingdom classification, which is widely accepted.

The table compares and contrasts the five kingdoms' various qualities.

Kingdom Monera

Kingdom Monera includes prokaryotic unicellular organisms that lack a true nucleus and membrane-bound organisms. The genetic material is present as a nucleoid in the cytoplasm. The cell wall and bacteria are made of peptidoglycan. Archaebacteria have different cell wall compositions, making them resistant to extreme conditions. Monerans reproduce asexually through binary fission, budding, etc. Some bacteria are autotrophic(photosynthetic or chemosynthetic), while others are heterotrophic (parasitic, saprophytic, or symbiotic). They play an important role in decomposition, nitrogen fixation, and biotechnology; Examples include E.coli, Lactobacillus, Nostoc, and Anabena.

Different shapes of bacteria

Kingdom Protista

The protist kingdom consists of unicellular eukaryotic organisms that exhibit animal-like, plant-like or fungus-like characteristics, Protista are highly diverse and serve as a link between prokaryotes and multicellular eukaryotes. They reproduce asexually(binary fission, budding) and sexually(syngamy, conjugation). Some protists, like diatoms and dinoflagellates, are photosynthetic autotrophs, while others, like Amoeba and Paramecium, are heterotrophic and ingest food. Many protists, such as Plasmodium, Trypanosoma and Euglena, have complex lives. Protists are commonly found in aquatic environments and play a key role in nutrient cycling and the food chain.

Chrysophytes:

Chrysophytes, including diatoms and golden algae, are microscopic photosynthetic protists found in freshwater. and marine environments. They have a silica base cell wall known as the frustule, which forms diatomaceous earth over time. They reproduce both asexually and sexually and exhibit features of both plants and animals. Their ability to survive under extreme conditions makes them ecologically significant.

Dinoflagellates:

Dinoflagellates are unicellular, mostly marine plankton that have two flagella, making them highly motile. Their cell walls contain cellulose and can be photosynthetic or heterotrophic. Some species also exhibit bioluminescence, producing a glow in the ocean at night. Examples include Gonyaulax, which causes red tides. They reproduce mainly by binary efficiency and are important in the marine food chain.

Dinoflagellates

Euglenoids:

Euglenoids, such as Euglena, are unicellular, flagellated protists found in freshwater. They are unique because they show both autotrophic and heterotrophic nutrition, depending on light availability. Instead of a cell wall, they have a protein-rich pellicle, giving them flexibility. They have an eye spot that helps them detect light for photosynthesis. They reproduce by binary fission and are important in aquatic ecosystems.

Euglenoid

Slime Moulds:

Slime moulds are fungus-like protists that exist as amoeboid single cells in favourable conditions but aggregate into a plasmodium under stress. They feed on organic matter, and bacteria play a role in decomposition. Slime modes form fruiting bodies with spores during reproduction that are highly resistant to harsh conditions. They exhibit characteristics of both fungi and protist, making them an extraordinary link between the two groups.

Slime Mould

Protozoans:

Protozoans are unicellular heterotrophic protists found in water soil, and as parasites in animals, They are classified into amoeboid, flagellated, ciliated and sporozoans based on locomotion. Ameoboids-like Amoeba, move using pseudopodia, while flagellates like Trypanosoma use flagella. Ciliates such as Paramecium, which has cilia for movement and feeding, and sporozoans, like Plasmodium, cause diseases like Malaria.

Paramecium

Kingdom Fungi

Kingdom Fungi has eukaryotic, multicellular, heterotrophic organisms with chitinous cell walls. Unlike plants, fungi do not perform photosynthesis. Instead, they obtain nutrients through saprophytic, paracytic or symbiotic relationships. They reproduce asexually via spores, budding and fragmentation and sexually through plasmogamy, karyogamy and meiosis. They are important in decomposition, nutrient cycling and medicine. Some fungi cause diseases in plants and animals. Common examples include mushrooms, Yeast, Rhizopus and Aspergillus.

On the basis of the mycelium mode of spore generation and fruiting bodies, fungi are categorized into distinct classes.

Phycomycetes:

Phycomycetes are also called lower fungi, which include species like Rhizopus and Mucor. They are mostly aquatic or grow on decaying matter and reproduce through asexual(sporangiospores) and sexual(zygospores) methods that help in rapid growth. They play a role in decomposition and industrial processes like alcohol fermentation.

Ascomycetes:

Ascomycetes, also known as sac fungi, include Penicillium, Saccharomyces and Aspergillus. They reproduce asexually by conidia and sexually by forming ascospores in sac-like asci. They are decomposers and pathogens and are used in fermentation. They are important in baking and alcohol production, while Penicillium produces the antibiotic penicillin.

Basidiomycetes:

Basidiomycetes, or club fungi, include mushrooms, puffballs, and rust fungi. Their characteristic feature is the basidium, where sexual spores, called Basidiospores, are produced. They are mostly saprophytic or parasitic, decomposing organic matter or infecting plants. Many basidiomycetes like Agaricus(mushrooms) are edible, while others cause plant diseases like rust or smuts.

Deuteromycetes:

Deuteromycetes, or imperfect fungi, include species like Alternaria and Trichoderma. They reproduce only asexually by conidia, and the sexual stages are unknown. Many are pathogenic or decomposers, while some are beneficial in biocontrol and enzyme production. Trichoderma is used in agriculture for pest control and Alternaria causes plant diseases like leaf spots.

Kingdom Plantae

Kingdom Plantae includes multicellular eukaryotic autotrophic organisms that perform photosynthesis using chlorophyll pigments. They have a cell wall made of cellulose and store food as starch. They play a fundamental role in oxygen production, carbon dioxide, absorption and food chains. They reproduce through seeds, sports and vegetative propagation. They are the primary producers in the ecosystem and provide food, oxygen, medicine and raw materials for human use. The kingdom is divided into major groups:

• Algae, which include simple aquatic photosynthetic organisms. Example- Chlamydomonas, Spirogyra
• Bryophytes, which includes the first land plants which lack vascular tissue. Example- Moss, Liverworts
• Pteridophytes, which are the first vascular plants and reproduce through spores. Example- Ferns, Horsetails
• Gymnosperms that are naked seed plants with cones. Example- Pines, Cycads
• Angiosperms, which include flowering plants with fruits and seeds. Example- Mango, Rose, Wheat

Note: You will study kingdom plantae in detail in the next chapters.

Kingdom Animalia

Kingdom Animalia consists of multicellular eukaryotic heterotrophic organisms that lack cell walls. Animals are classified based on body symmetry, germ layers, body cavities, and embryonic development. They reproduce asexually, with some species showing asexual reproduction (e.g., budding in Hydra). Animals are crucial for pollination, ecosystem, stability, and human economy through domestication, food production, and companionship. Kingdom is divided into invertebrates(without a backbone) and vertebrates(with a backbone). Examples of animal groups:

• Invertebrates, which includes Porifera and Arthropoda
• Vertebrates that include Pisces and mammals

Note: You will study kingdom Animalia in detail in chapter 4.

Viruses, Viroids, Prions and Lichens

Viruses

Viruses are non-cellular infectious agents that exist at the boundary of living and nonliving. They consist of a protein coat called the capsid and genetic material, either DNA or RNA, but lack cellular structures like cytoplasm and organs. They cannot reproduce independently and require a host to multiply, making them obligate parasites. Some common viral diseases include AIDS, influenza, hepatitis, and COVID-19 in humans. They reproduce through the lytic and lysogenic cycles using the host cellular machinery to generate new virus particles. Due to the ability to mutate rapidly, viruses are challenging to control and can cause Pandemics.

Different shapes and sizes of viruses

Viroids

Viroids are simple infectious agents consisting of a single-stranded circular RNA in the molecule without a protein coat, They are much smaller than viruses and were first discovered by T.O. Diener in 1971. Unlike viruses, viroids do not encode proteins and rely entirely on the host enzymes for replication. They mainly infect plants, causing severe agricultural diseases such as potato spindle tuber disease. Their exact mechanism of pathogenicity is still under research, but they interfere with normal RNA processing in the host. Since viroids lack a protective capsid, they are more susceptible to environmental conditions than viruses.

Lichens

Lichens are a symbiotic association between fungus and algae, where the fungus provides structure and water, while the alga performs photosynthesis. They are found in extreme habitats such as rocks, tree trunks, and Arctic regions, playing an important role in soil formation and ecological balance. They are classified into crustose, foliose and fruticose lichens. They are bio-indicators of air pollution as they are highly sensitive to sulphur dioxide. Additionally, they are used in the production of perfumes and antibiotics due to their unique chemical properties.

Chapter-Wise NCERT Class 11 Notes Biology

The chapter-wise Notes for class 11 biology are given below:

Benefits of NCERT Class 11 Biology Chapter 2 Notes:

• Understanding biodiversity helps in categorising and studying the vast diversity of living organisms.
• Evolutionary insights provide knowledge about how organisms have evolved over time.
• The medical and agricultural applications help gain knowledge of bacteria, fungi, and viruses in medicine and farming.
• The help in easy identification of organisms enabled by systemic classification for scientific study.
• They are essential for being a foundation for higher studies like NEET, medical sciences, biotechnology and research.

Subject Wise NCERT Exemplar Solutions

• NCERT Exemplar Class 11 Solutions
• NCERT Exemplar Class 11 Maths
• NCERT Exemplar Class 11 Physics
• NCERT Exemplar Class 11 Chemistry
• NCERT Exemplar Class 11 Biology

Tips to learn NCERT Class 11 Biology Chapter 2 Notes:

• Use of mnemonics to remember the taxonomic hierarchy.
• Using diagrams to visualise classification to make learning easier
• Making flashcards for key terms like protists and fungi
• Practising MCQ and solving the NCERT questions and sample papers for retention of memory
• Revise the summary notes and important questions frequently.

Most Important Questions Class 11 Biology Chapter 2

Biological Classification is an important chapter in the board and NEET exams that deals with the grouping of living organisms into categories based on common features and evolutionary connections. This chapter brings out key points like the five-kingdom classification, the characteristics of each kingdom, the importance of taxonomy, and the differences between prokaryotic and eukaryotic organisms. A good grasp of this chapter will assist in responding to questions on the classification of organisms, their diversity, and how they play a role in the environment. Mastering this subject is crucial for an in-depth comprehension of biodiversity and ecological interactions, which will enable students to attain good grades in topics like the classification systems, morphological and physiological characteristics, and evolutionary relationships between organisms.

Question: Which one of the following is NOT a feature of the Kingdom Monera?

1. a) Unicellular
2. b) Eukaryotic cells
3. c) No nucleus
4. d) Autotrophic or heterotrophic

Answer: Eukaryotic cells

Question: Which kingdom includes multicellular, autotrophic organisms?

1. a) Monera
2. b) Fungi
3. c) Plantae
4. d) Animalia

Answer: Plantae

Question: Which of the following organisms belongs to the Kingdom Fungi?

1. a) Yeast
2. b) Mushroom
3. c) Lichen
4. d) All of the above

Answer: All of the above

Question: Define the term 'Kingdom'.

Answer: A kingdom is the most general taxonomic category to which organisms are assigned. It comprises phyla or divisions that are related to each other. There are five kingdoms known: Monera, Protista, Fungi, Plantae, and Animalia.

Question: What is the role of classification in biology?

Answer: Classification arranges the variety of life into groups so that it is simpler to examine the relationships, features, and evolutionary history of organisms.

Question: Briefly write down the features of the Kingdom Monera.

Answer: Organisms of the Kingdom Monera are unicellular, prokaryotic, have no definite nucleus, and are possibly autotrophic (such as cyanobacteria) or heterotrophic (such as bacteria).

Question: Match the following:

A. Kingdom Monera – i. Unicellular, prokaryotic organisms

B. Kingdom Plantae – ii. Multicellular, autotrophic organisms

C. Kingdom Animalia – iii. Multicellular, heterotrophic organisms

Options:

1. A-i, B-ii, C-iii
2. A-iii, B-ii, C-i
3. A-ii, B-i, C-iii
4. A-iii, B-i, C-ii

Answer: Option 1: A-i, B-ii, C-iii

Question: What is the basis of the five-kingdom classification system?

Answer: The five-kingdom classification system is based on differences in cell structure, mode of nutrition, and other physiological and morphological features of organisms. The five kingdoms are Monera, Protista, Fungi, Plantae, and Animalia.

Question: Distinguish between prokaryotes and eukaryotes.

Answer: Prokaryotes are single-celled organisms that lack a membrane-bound nucleus (e.g., bacteria), whereas eukaryotes possess a distinct nucleus and membrane-bound organelles (e.g., plants, animals, fungi).

Question: Why are cyanobacteria significant in the environment?

Answer: Cyanobacteria are significant as they perform photosynthesis, adding to oxygen production and nitrogen fixation, which helps plants and other organisms in ecosystems.

Question: What are the key differences between fungi and plants?

Answer: Fungi are heterotrophic (they take food from other sources), whereas plants are autotrophic (their food via photosynthesis). Fungi also possess a chitin composition in their cell walls, whereas plants possess cell walls composed of cellulose.

Question: Define the characteristics of the Kingdom Protista.

Answer: Kingdom Protista encompasses unicellular animals that can either be autotrophic or heterotrophic in nature. They possess a developed nucleus, and some examples consist of protozoa (e.g., Amoeba) and algae.

Approach to Solve Questions of Class 11 Biology Chapter 2

This chapter contains a mix of direct, conceptual, and application-type questions. To prepare well:

• Read the NCERT and Exemplar well to know the five kingdoms of life, their features, and the reasons for classification.
• Practice drawing and labelling diagrams of structural features of different organisms belonging to different kingdoms, e.g., prokaryotes vs. eukaryotes cell structure, and features that distinguish plants, animals, fungi, and protists.
• Memorise the distinguishing characteristics of each kingdom—Monera, Protista, Fungi, Plantae, and Animalia—and be able to describe how organisms belonging to each kingdom are categorised.
• Answer all exemplar questions with emphasis on prokaryotes and eukaryotes, different modes of nutrition (heterotrophic, autotrophic, saprophytic), and major plant and animal classification characteristics.
• Discuss the contributions of scientists like Carl Linnaeus (founder of taxonomy) and their impact on the evolution of modern classification systems.
• Learn about classification systems like the Linnaean system and the application of binomial nomenclature in scientifically naming organisms.

Subject-Wise NCERT Solutions

• NCERT Solutions for Class 11 Mathematics
• NCERT Solutions for Class 11 Chemistry
• NCERT Solutions for Class 11 Physics

• NCERT Solutions for Class 11 Biology

Biological classification is an important branch of biology and organises and simplifies the study of life. It provides a clear structure for the identification and understanding of various organisms, their evolutionary relationships and ecological significance. The notes serve as an excellent source for students preparing for competitive exams like NEET, AIIMS and board exams. By mastering this chapter, students can gain deeper knowledge of the biodiversity of life and the interconnectedness of various species.

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