Biology (Class 11) — Free Notes (CBSE & HBSE)
Free Class 11 Biology notes — Living World, Biological Classification, Plant and Animal Kingdom, Morphology and Anatomy, Cell, Biomolecules, Cell Division, Photosynthesis, Respiration, Plant Growth, Breathing, Circulation, Excretion, Locomotion and Neural Control — with diagrams, MCQs and important questions for CBSE, HBSE and NEET. Free Class 11 Biology course on SikshaSarovar.
Free, chapter-wise Biology notes for Class 11 on Siksha Sarovar, aligned to NCERT and both CBSE and Haryana Board (HBSE). Covers 18 chapters with explanations, worked examples and board-pattern practice questions.
Chapters covered (18)
- The Living World — This chapter introduces the fundamental question of what defines a living organism, the vast diversity of life, and the systematic ways biologists organize and name living things.…
- Biological Classification — This chapter traces the history of classification systems and details R. H. Whittaker's Five Kingdom Classification — Monera, Protista, Fungi, Plantae and Animalia. It covers the…
- Plant Kingdom — This chapter surveys Kingdom Plantae in detail — from the simple algae through bryophytes, pteridophytes and gymnosperms to the advanced angiosperms. It explains the…
- Animal Kingdom — This chapter establishes the framework for classifying the diverse animal kingdom using fundamental criteria such as levels of organisation, body symmetry, germ layers, presence…
- Morphology of Flowering Plants — This chapter describes the external form (morphology) of angiosperms — the root, stem and leaf and their modifications, the inflorescence and the flower with its parts,…
- Anatomy of Flowering Plants — This chapter explores the internal structure (anatomy) of angiosperms — the plant tissues (meristematic and permanent), the tissue systems (epidermal, ground and vascular), the…
- Structural Organisation in Animals — This chapter moves from the cell to the level of the multicellular animal body, showing how cells of similar origin and function group into tissues , tissues into organs , and…
- Cell: The Unit of Life — The cell is the basic structural and functional unit of life. This chapter establishes the cell theory , contrasts prokaryotic and eukaryotic cells, and explores cell…
- Biomolecules — Living organisms are made of a limited set of chemical elements organised into biomolecules . This chapter analyses the chemical composition of living tissue, distinguishes…
- Cell Cycle and Cell Division — This chapter covers the cell cycle (interphase and M phase), the process of mitosis (equational division) and meiosis (reductional division), cytokinesis, and the biological…
- Photosynthesis in Higher Plants — This chapter explains how green plants synthesise food using light energy. It covers the site of photosynthesis (chloroplasts), photosynthetic pigments, the light reaction…
- Respiration in Plants — This chapter explains how plants break down food (glucose) to release energy in the form of ATP. It covers cellular respiration, glycolysis, fermentation (anaerobic respiration),…
- Plant Growth and Development — Plant Growth and Development explains how plants increase in size irreversibly and progress through orderly developmental phases from seed to senescence. The chapter covers growth…
- Breathing and Exchange of Gases — Breathing and Exchange of Gases describes how oxygen is supplied to cells and carbon dioxide removed during cellular respiration. The chapter covers respiratory organs across…
- Body Fluids and Circulation — Body Fluids and Circulation explains how blood and lymph circulate to deliver nutrients and gases and remove wastes. The chapter covers blood composition (plasma and formed…
- Excretory Products and their Elimination — This chapter explores how animals, especially humans, remove harmful nitrogenous wastes to maintain homeostasis. It covers the different modes of excretion (ammonotelism,…
- Locomotion and Movement — This chapter examines how animals move and change position. It covers the types of movement (amoeboid, ciliary, muscular), the detailed structure of skeletal muscle and its…
- Neural Control and Coordination — This chapter studies how the nervous system coordinates and integrates the body's activities. It covers the structure and types of neurons, the generation and conduction of a…
The Living World: What is Living and Diversity in the Living World
What is 'Living'?
Defining 'living' is not simple. No single property is exclusive to life, but a combination of defining features distinguishes living organisms from non-living matter.
| Feature | Description |
|---|---|
| Growth | Increase in mass and number of cells; in living things growth is intrinsic (from inside). Non-living objects (e.g., mountains, crystals) grow by extrinsic accumulation on the surface. |
| Reproduction | Production of offspring with features similar to parents — sexual, asexual, budding, fragmentation. Not an all-inclusive trait (e.g., sterile mules, infertile humans). |
| Metabolism | Sum total of all chemical reactions in the body. This is a defining and exclusive feature of all living organisms. |
| Cellular organisation | All living things are made of one or more cells — the basic structural and functional unit. |
| Consciousness | Ability to sense surroundings/stimuli and respond. Considered the defining property of living organisms. |
| Self-replication, self-regulation, self-organisation | Living systems maintain and reproduce themselves. |
NEET Trap: Growth and reproduction are NOT defining/exclusive properties of living things, because some organisms (mules, worker bees) cannot reproduce, and non-living objects can grow. The truly defining properties are metabolism, cellular organisation, and consciousness.
Twin Defining Features
- Metabolism — no non-living object exhibits metabolism. Isolated metabolic reactions in a test tube are neither living nor non-living — hence they are 'living reactions'.
- Consciousness — patients in coma supported by machines still show this property at the cellular level. Humans are the only organisms aware of themselves.
Diversity in the Living World
The number of species known and described ranges between 1.7 and 1.8 million. This is the planet's biodiversity.
- New organisms are continuously being discovered and named.
- To study such enormous diversity, a system of identification, nomenclature, and classification is essential.
- Nomenclature — standardised naming; only possible when the organism is already described correctly (identification).
- Identification — determining that an organism is the same as a known one.
Frequently asked questions
Are these Biology notes free?
Yes — all Biology notes on Siksha Sarovar are free to read, no account required.
Do the notes follow CBSE and HBSE?
Yes. Notes are NCERT-aligned and include both CBSE and Haryana Board (HBSE) exam guidance, important questions and MCQs.
Can I prepare for board exams here?
Yes — each chapter includes key concepts, formulas, important questions and practice MCQs for board exam revision.