Class 11 Biology Notes

Class 11 Biology is the foundation of the CBSE syllabus and NEET, and it is where most of the theory-heavy scoring sits. These chapter-wise notes follow the NCERT order exactly, so you can revise in sequence or jump straight to the chapter that needs work. Each page carries the key facts, the few equations that matter, exam pointers and solved examples.

• The Living World — characteristics of living organisms and the need for classification, taxonomy, taxonomical aids and binomial nomenclature.
• Biological Classification — the five-kingdom system, Monera, Protista, Fungi, Plantae and Animalia, plus viruses, viroids, prions and lichens.
• Plant Kingdom — algae, bryophytes, pteridophytes, gymnosperms and angiosperms, with their life cycles.
• Animal Kingdom — the basis of classification and the major phyla from Porifera to Chordata.

• Morphology of Flowering Plants — root, stem and leaf and their modifications, inflorescence, flower, placentation, fruit and seed, plus the families.
• Anatomy of Flowering Plants — meristematic and permanent tissues, tissue systems, and dicot versus monocot anatomy including secondary growth.
• Structural Organisation in Animals — epithelial, connective, muscular and neural tissues, and the frog as a representative animal.

• Cell: The Unit of Life — prokaryotic and eukaryotic cells, the organelles, and the nucleus.
• Biomolecules — carbohydrates, proteins, lipids, nucleic acids, enzymes and the metabolites in living systems.
• Cell Cycle and Cell Division — interphase, mitosis, meiosis and the significance of each.

• Photosynthesis in Higher Plants — the light reactions (Z-scheme), the Calvin cycle, the C4 pathway and photorespiration.
• Respiration in Plants — glycolysis, the Krebs cycle, the electron transport chain and oxidative phosphorylation.
• Plant Growth and Development — growth phases, plant hormones, photoperiodism and vernalisation.

• Breathing and Exchange of Gases — the respiratory system, mechanism of breathing, respiratory volumes, gas exchange and transport.
• Body Fluids and Circulation — blood, blood groups, coagulation, the cardiac cycle and double circulation.
• Excretory Products and their Elimination — the human excretory system, nephron, urine formation and hormonal regulation.

• Locomotion and Movement — the types of movement, the 206 bones of the human skeleton, the vertebral column, skull and ribs, the three classes of joint, the three muscle tissues, the sliding filament mechanism and the movement disorders.
• Neural Control and Coordination — organisation of the nervous system, structure and types of a neuron, the synapse and neurotransmitters, receptors for taste, smell and sight, the divisions of the brain, the spinal cord and the reflex arc.
• Chemical Coordination and Integration — the endocrine glands, the hormones of the pituitary, thyroid, parathyroid, adrenal and pancreas, the two routes of hormone action, negative feedback control and the endocrine disorders.

Two representative questions you are likely to meet, worked through in full.

Example 1: State the rules for writing a scientific name, using Mangifera indica as the example.

Solution: The scientific name is written with the genus first (capitalised) and the species second (lowercase), both italicised or underlined when handwritten, and followed by the abbreviating author — Mangifera indica is the mango. The same format holds whatever the language of the name.

Example 2: How many ATP (net) and NADH molecules does one molecule of glucose produce during glycolysis in a plant cell?

Solution: Glycolysis breaks glucose into two pyruvate molecules, giving a net 2 ATP (4 produced minus 2 consumed in the energy-investment phase) and 2 NADH per glucose. The pyruvate then enters the Krebs cycle, so glycolysis is only the first stage of aerobic respiration.