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Class 11th Biology NCERT Notes and Solutions (Non-Rationalised)
1. The Living World
This chapter addresses the fundamental question of "what is living?" by exploring the defining characteristics of life, such as metabolism, cellular organisation, and consciousness, while also discussing non-defining features like growth and reproduction. It delves into the immense biodiversity on Earth, emphasizing the need for a systematic classification system or taxonomy. Key concepts include nomenclature, specifically the universal system of binomial nomenclature proposed by Carolus Linnaeus, which assigns a two-part scientific name (e.g., Mangifera indica) to each organism. The chapter explains the hierarchical classification system, arranging organisms into successive levels: species, genus, family, order, class, phylum/division, and kingdom. It also describes various taxonomic aids like the herbarium, botanical gardens, museums, and zoological parks that help in the identification and study of organisms.
2. Biological Classification
This chapter outlines the scientific journey of classifying organisms, culminating in the widely accepted Five Kingdom classification proposed by R.H. Whittaker. This system groups organisms into five kingdoms—Monera, Protista, Fungi, Plantae, and Animalia—based on key criteria like cell structure (prokaryotic/eukaryotic), body organisation (unicellular/multicellular), mode of nutrition (autotrophic/heterotrophic), and phylogenetic relationships. The chapter details the unique characteristics of each kingdom, such as the prokaryotic nature of Monera (bacteria), the diverse unicellular eukaryotes in Protista, the saprophytic nature of Fungi, the photosynthetic ability of Plantae, and the heterotrophic, motile nature of Animalia. It also briefly introduces acellular entities like viruses, viroids, and lichens, which do not fit into this five-kingdom scheme.
3. Plant Kingdom
This chapter provides a comprehensive overview of the diversity within the Kingdom Plantae. It classifies plants into five major groups: Algae, Bryophytes, Pteridophytes, Gymnosperms, and Angiosperms. For each group, it describes the characteristic features, habitat, structure, mode of reproduction, and economic importance. A central theme is the concept of alternation of generations, the life cycle pattern that alternates between a haploid gametophytic phase and a diploid sporophytic phase. The chapter traces the evolutionary trend from simple, aquatic forms like algae to the highly complex and dominant terrestrial flowering plants (angiosperms), highlighting key adaptations like the development of vascular tissues and seeds.
4. Animal Kingdom
This chapter presents a systematic classification of the vast Animal Kingdom based on fundamental features of body organisation. These features include levels of organisation (cellular, tissue, organ), body symmetry (radial, bilateral), nature of the coelom (body cavity: acoelomate, pseudocoelomate, coelomate), germ layers (diploblastic and triploblastic), and the presence of a notochord. The chapter provides a detailed description of the distinct characteristics and representative examples of major invertebrate phyla, from Porifera (spenges) and Cnidaria to Arthropoda (the largest phylum) and Mollusca. It then covers the phylum Chordata, highlighting its key features and further classifying it into subphyla and classes, including the vertebrates (fishes, amphibians, reptiles, birds, and mammals).
5. Morphology Of Flowering Plants
This chapter focuses on morphology—the study of the external form and features of flowering plants (angiosperms). It systematically describes the structure and functions of different plant parts. This includes the root system (taproot, fibrous root, and their modifications for storage, support, and respiration), the stem (nodes, internodes, and modifications), the leaf (venation, types, phyllotaxy - arrangement of leaves), and the reproductive parts. The chapter details the structure of a flower, different types of inflorescence (arrangement of flowers), and concepts like placentation (arrangement of ovules). It concludes with the structure of fruits and seeds, which are essential for plant identification and understanding their ecological adaptations.
6. Anatomy Of Flowering Plants
This chapter shifts from external to internal structure, exploring the anatomy of flowering plants. It describes the different types of plant tissues, classifying them into meristematic tissues (responsible for growth) and permanent tissues. Permanent tissues are further divided into simple tissues (parenchyma, collenchyma, sclerenchyma) and complex tissues, which include xylem (for water conduction) and phloem (for food transport). The chapter provides a detailed anatomical description of the internal structure of the dicotyledonous and monocotyledonous root, stem, and leaf, highlighting the arrangement of vascular bundles and other tissues. The process of secondary growth, which increases the girth of the stem and root in dicots, is also explained.
7. Structural Organisation In Animals
This chapter examines how animal cells are organised into tissues, organs, and organ systems. It provides a detailed description of the four primary types of animal tissues: epithelial tissue (for covering and protection), connective tissue (for support and binding, e.g., bone, cartilage, blood), muscular tissue (for movement), and nervous tissue (for control and communication). To illustrate how these tissues are integrated into functional units, the chapter presents a detailed study of the morphology and anatomy of three representative animals: the earthworm (Phylum Annelida), the cockroach (Phylum Arthropoda), and the frog (Class Amphibia), describing their digestive, circulatory, respiratory, nervous, and reproductive systems.
8. Cell - The Unit Of Life
This foundational chapter explores the cell as the basic structural and functional unit of all living organisms. It reinforces the Cell Theory and provides a detailed comparison between simple prokaryotic cells (lacking a membrane-bound nucleus) and more complex eukaryotic cells (with a true nucleus). The chapter offers a comprehensive tour of the eukaryotic cell, describing the intricate structure and specific functions of various membrane-bound organelles. These include the nucleus (control centre), mitochondria ("powerhouse of the cell"), endoplasmic reticulum, Golgi complex, lysosomes, and plastids (like chloroplasts for photosynthesis). The roles of the cell membrane, cell wall, and cytoskeleton are also elucidated.
9. Biomolecules
This chapter delves into the chemistry of life, exploring the diverse organic molecules that constitute living cells, known as biomolecules. It discusses the structure, classification, and functions of the four major classes of biomacromolecules: Carbohydrates (for energy), Proteins (built from amino acids, performing various functions), Lipids (for energy storage and membranes), and Nucleic Acids (DNA and RNA, which store and transmit genetic information). A significant focus is placed on enzymes, which are proteinaceous biological catalysts that speed up metabolic reactions. The chapter explains the mechanism of enzyme action and the factors that affect their activity, providing a molecular basis for understanding life processes.
10. Cell Cycle And Cell Division
This chapter explains the life of a cell through the cell cycle, the sequence of events by which a cell duplicates its genome, synthesizes other constituents, and eventually divides. The cycle consists of two main phases: Interphase (the preparatory phase, comprising G1, S, and G2 stages) and the M phase (the division phase). It provides a detailed account of the two types of cell division. Mitosis is an equational division that produces two genetically identical daughter cells, crucial for growth and repair. Meiosis is a reductional division that occurs in germ cells to produce four haploid gametes, essential for sexual reproduction and introducing genetic variation.
11. Transport In Plants
This chapter explores the vital mechanisms that plants use to transport water, minerals, and food. It covers short-distance transport mechanisms like diffusion, facilitated diffusion, and active transport, as well as plant-water relations involving osmosis and water potential. For long-distance transport, it details the upward movement of water through the xylem, largely driven by the transpiration pull theory. It also explains how food, primarily sucrose, is translocated from the leaves to other parts of the plant through the phloem, according to the pressure-flow or mass-flow hypothesis.
12. Mineral Nutrition
This chapter focuses on how plants obtain and utilize inorganic nutrients from the soil. It explains the criteria for the essentiality of a mineral element and the technique of hydroponics used to study mineral requirements. The chapter classifies essential elements into macronutrients and micronutrients based on their quantitative requirements and details the specific roles and deficiency symptoms of each. A major focus is on the mechanism of nitrogen metabolism, including the crucial process of biological nitrogen fixation by microbes like Rhizobium, which converts atmospheric nitrogen into a form usable by plants.
13. Photosynthesis In Higher Plants
Photosynthesis is the vital anabolic process where green plants synthesize food using light energy. This chapter details the mechanism of photosynthesis, identifying the chloroplast as its site. It describes the roles of photosynthetic pigments like chlorophyll. The process is divided into two stages: the light-dependent reactions, where light energy is captured to produce ATP and NADPH, and the light-independent reactions (or Calvin cycle), where this chemical energy is used to fix CO₂ into carbohydrates. The chapter explains the different pathways of carbon fixation, primarily the C3 pathway and the adaptive C4 pathway, and discusses the various factors that influence the rate of photosynthesis.
14. Respiration In Plants
Respiration is the catabolic process of breaking down complex organic molecules to release energy in the form of ATP (Adenosine Triphosphate), the energy currency of the cell. This chapter explains the mechanism of cellular respiration in plants. It details the steps of aerobic respiration, which involves the complete oxidation of glucose. The process includes three major stages: Glycolysis (the breakdown of glucose into pyruvate, occurring in the cytoplasm), the Krebs cycle (or citric acid cycle, in the mitochondrial matrix), and Oxidative Phosphorylation via the electron transport system on the inner mitochondrial membrane, where the majority of ATP is generated.
15. Plant - Growth And Development
This chapter explores the entire life story of a plant, from seed germination to senescence, covering the processes of growth, differentiation, and development. It discusses how plant growth is measured and the conditions required for it. A key focus is on Plant Growth Regulators (PGRs) or plant hormones. The chapter details the physiological functions of the five major types of PGRs: growth promoters like Auxins, Gibberellins, and Cytokinins, and growth inhibitors like Abscisic Acid and Ethylene. It also explains developmental processes that are responsive to environmental cues, such as photoperiodism (response to day length) and vernalisation (response to low temperature).
16. Digestion And Absorption
This chapter details the process by which the complex food we eat is converted into simple, absorbable forms. It provides a comprehensive tour of the human digestive system, tracing the path of food through the alimentary canal (mouth, oesophagus, stomach, small intestine, large intestine) and explaining the role of associated glands like the salivary glands, liver, and pancreas. The chapter explains the enzymatic digestion of major macromolecules—carbohydrates, proteins, and fats. It concludes by describing the process of absorption of these digested nutrients, primarily in the small intestine, and discusses various disorders of the digestive system.
17. Breathing And Exchange Of Gases
This chapter focuses on the physiological process of respiration in humans, distinguishing between breathing (the mechanical process) and respiration (the biochemical process). It describes the structure and functions of the human respiratory system, from the nasal passages to the alveoli in the lungs. It explains the mechanism of breathing, detailing how the contraction and relaxation of the diaphragm and intercostal muscles lead to inhalation and exhalation. The chapter explains the crucial process of gaseous exchange, which occurs by simple diffusion across the alveolar and tissue membranes, driven by pressure gradients of oxygen and carbon dioxide. The transport of these gases by blood is also discussed.
18. Body Fluids And Circulation
This chapter explores the internal transport system that delivers nutrients and oxygen to cells and removes wastes. It details the composition and functions of body fluids, primarily blood (composed of plasma, RBCs, WBCs, and platelets) and lymph. It explains the different blood groups (ABO and Rh systems) and the mechanism of blood coagulation. The centerpiece of the chapter is the human circulatory system, providing a detailed description of the structure of the human heart and blood vessels. It explains the cardiac cycle and the highly efficient mechanism of double circulation (pulmonary and systemic circuits), which prevents the mixing of oxygenated and deoxygenated blood.
19. Excretory Products And Their Elimination
This chapter deals with excretion, the process of eliminating metabolic nitrogenous wastes to maintain homeostasis. It discusses different excretory products like ammonia, urea, and uric acid. The focus is on the human excretory system, detailing the structure of the kidneys, ureters, urinary bladder, and urethra. The chapter provides a comprehensive explanation of the structure of the nephron, the functional unit of the kidney. It explains the three main steps of urine formation: ultrafiltration in the glomerulus, selective reabsorption of useful substances, and tubular secretion of waste products in the renal tubules.
20. Locomotion And Movement
This chapter explores the mechanisms of movement and locomotion in humans. It introduces the human musculoskeletal system as the framework for movement, comprising the skeleton and muscles. It provides an overview of the skeletal system, detailing the major bones and types of joints. The chapter then focuses on the structure of skeletal muscles and explains the mechanism of muscle contraction through the sliding filament theory. This theory describes how the interaction between actin and myosin filaments, powered by ATP, causes muscle fibres to shorten and generate force, leading to movement.
21. Neural Control And Coordination
This chapter explains the rapid communication network of the body: the nervous system. It describes the structure of the neuron (nerve cell) as the system's basic unit. A key focus is on the generation and conduction of the nerve impulse (action potential) along the axon and its transmission across a synapse to another neuron. The chapter outlines the organisation of the human nervous system into the Central Nervous System (brain and spinal cord) and the Peripheral Nervous System. It also provides a structural and functional overview of major sensory organs, particularly the eye and the ear.
22. Chemical Coordination And Integration
This chapter describes the endocrine system, which provides slower, long-lasting control and coordination through chemical messengers called hormones. It differentiates endocrine glands from exocrine glands and explains the general mechanism of hormone action. The chapter provides a systematic survey of the major endocrine glands in the human body, including the pituitary gland (the master gland), thyroid, adrenal glands, pancreas, and gonads (testes and ovaries). It details the specific hormones secreted by each gland and their crucial roles in regulating metabolism, growth, development, and maintaining homeostasis.