Biology: The Living World - NCERT

• Biology is the study of life, exploring the structure, function, growth, origin, evolution, and distribution of living organisms
• NCERT textbooks are commonly used in India for secondary and higher secondary education, covering fundamental concepts in biology

The Living World

• Living organisms exhibit characteristics like growth, reproduction, metabolism, consciousness, and cellular organization
• Growth involves an increase in mass and number of cells
• Reproduction results in the production of progeny, either sexually or asexually
• Metabolism comprises all chemical reactions occurring within a living organism
• Consciousness is the awareness of the surroundings and the ability to respond to external stimuli
• Biodiversity refers to the variety of living organisms present on Earth
• Taxonomy is the science of classification, nomenclature, and identification of organisms
• Nomenclature is the system of assigning scientific names to organisms, with two components: generic name and specific epithet
• A hierarchical classification system includes kingdom, phylum/division, class, order, family, genus, and species

Biological Classification

• The five-kingdom classification system, proposed by R.H. Whittaker, includes Monera, Protista, Fungi, Plantae, and Animalia
• Monera includes prokaryotic organisms like bacteria, archaea, and cyanobacteria
• Protista includes unicellular eukaryotic organisms like protozoans, algae, and slime molds
• Fungi are eukaryotic, heterotrophic organisms with cell walls made of chitin
• Plantae includes multicellular, eukaryotic organisms with cell walls made of cellulose, capable of photosynthesis
• Animalia includes multicellular, eukaryotic, heterotrophic organisms without cell walls
• Viruses are non-cellular entities that replicate inside a host cell, consisting of a protein coat (capsid) and nucleic acid (DNA or RNA)

Plant Kingdom

• Algae are chlorophyll-bearing, simple, thalloid, autotrophic organisms
• Algae are classified into Chlorophyceae (green algae), Phaeophyceae (brown algae), and Rhodophyceae (red algae)
• Bryophytes are non-vascular plants that include mosses, liverworts, and hornworts
• Pteridophytes are vascular plants that include ferns, horsetails, and club mosses
• Gymnosperms are plants with naked seeds, such as conifers, cycads, and ginkgo
• Angiosperms are flowering plants with seeds enclosed within fruits, divided into dicots and monocots
• Plant life cycles exhibit alternation of generations between haploid gametophytes and diploid sporophytes

Animal Kingdom

• Animals are multicellular, heterotrophic organisms lacking cell walls
• Animal classification is based on body symmetry, coelom, germ layers, and segmentation
• Porifera (sponges) are characterized by pores, canals, and choanocytes
• Coelenterata (cnidarians) have radial symmetry and cnidocytes
• Platyhelminthes (flatworms) are bilaterally symmetrical, acoelomate organisms
• Aschelminthes (roundworms) are pseudocoelomate organisms with a complete digestive system
• Annelida are segmented worms with a true coelom
• Arthropoda are characterized by jointed appendages and an exoskeleton
• Mollusca have a soft body, usually protected by a shell
• Echinodermata have radial symmetry and a water vascular system
• Chordata possess a notochord and a dorsal nerve cord
• Chordata are divided into Urochordata, Cephalochordata, and Vertebrata

Morphology of Flowering Plants

• Morphology deals with the study of the form and features of different plant organs
• Roots anchor the plant and absorb water and minerals
• Stems support leaves, flowers, and fruits; conduct water and minerals; and store food
• Leaves are the primary photosynthetic organs of plants
• Inflorescence is the arrangement of flowers on the floral axis
• Flowers are the reproductive units of angiosperms
• Fruits develop from the ovary after fertilization and contain seeds
• Seeds contain an embryo and stored food reserves

Anatomy of Flowering Plants

• Anatomy is the study of the internal structure of plants
• Plant tissues are classified into meristematic and permanent tissues
• Meristematic tissues are actively dividing cells responsible for plant growth
• Permanent tissues are derived from meristematic tissues and have specific functions
• Simple permanent tissues include parenchyma, collenchyma, and sclerenchyma
• Complex permanent tissues include xylem and phloem, responsible for conduction
• The tissue system includes epidermal, ground, and vascular tissue systems
• Plant anatomy varies among different plant organs and between monocots and dicots

Structural Organisation in Animals

• Animal tissues are classified into epithelial, connective, muscular, and neural tissues
• Epithelial tissues cover and protect body surfaces and line body cavities and organs
• Connective tissues support and connect different tissues and organs
• Muscular tissues are responsible for movement
• Neural tissues transmit electrical signals
• Organs are composed of different tissues organized to perform specific functions
• Organ systems consist of multiple organs working together
• Earthworm, cockroach, and frog are examples used to study animal morphology and anatomy
• Earthworms have a segmented body, and a closed circulatory system
• Cockroaches have an exoskeleton and an open circulatory system
• Frogs have a moist skin, and undergo metamorphosis

Cell: The Unit of Life

• Cells are the basic structural and functional units of life
• Cell theory states that all living organisms are composed of cells and that all cells arise from pre-existing cells
• Prokaryotic cells lack a membrane-bound nucleus and organelles; examples include bacteria and archaea
• Eukaryotic cells have a membrane-bound nucleus and organelles; examples include plant, animal, fungal, and protist cells
• Cell organelles include the nucleus, endoplasmic reticulum, Golgi apparatus, lysosomes, mitochondria, plastids, vacuoles, ribosomes, and cytoskeleton

Biomolecules

• Biomolecules are organic molecules found in living organisms
• Carbohydrates are composed of carbon, hydrogen, and oxygen; examples include sugars and starches
• Proteins are composed of amino acids and perform various functions in the cell
• Lipids are hydrophobic molecules that include fats, oils, and waxes
• Nucleic acids (DNA and RNA) store and transmit genetic information
• Enzymes are biological catalysts that speed up biochemical reactions

Cell Cycle and Cell Division

• The cell cycle is the sequence of events that a cell undergoes from one division to the next
• The cell cycle includes interphase (G1, S, and G2 phases) and M phase (mitosis or meiosis)
• Mitosis is a type of cell division that results in two daughter cells identical to the parent cell
• Meiosis is a type of cell division that results in four daughter cells with half the number of chromosomes as the parent cell
• Mitosis is important for growth, repair, and asexual reproduction
• Meiosis is essential for sexual reproduction, producing genetic variation

Transport in Plants

• Plants transport water, minerals, and organic nutrients through vascular tissues
• Water is absorbed by roots and transported to the rest of the plant through xylem
• Transpiration is the loss of water vapor from the leaves
• Phloem transports sugars produced during photosynthesis from sources to sinks
• Water movement occurs via diffusion, osmosis, and active transport
• Long distance transport of water is explained by the cohesion-tension-transpiration pull model

Mineral Nutrition

• Plants require essential mineral elements for growth and development
• Macronutrients are required in large amounts; examples include nitrogen, phosphorus, and potassium
• Micronutrients are required in small amounts; examples include iron, manganese, and zinc
• Mineral deficiency can cause various symptoms in plants

Photosynthesis in Higher Plants

• Photosynthesis is the process by which plants convert light energy into chemical energy
• Photosynthesis occurs in chloroplasts and involves two main stages: the light-dependent reactions (in the thylakoid membrane) and the Calvin cycle (in the stroma)
• Light-dependent reactions convert light energy into ATP and NADPH
• The Calvin cycle uses ATP and NADPH to fix carbon dioxide and produce sugars
• Factors affecting photosynthesis include light intensity, carbon dioxide concentration, and temperature

Respiration in Plants

• Respiration is the process by which plants break down organic compounds to release energy
• Glycolysis occurs in the cytoplasm and converts glucose into pyruvate
• The Krebs cycle occurs in the mitochondria and oxidizes pyruvate to produce carbon dioxide and ATP
• The electron transport chain occurs in the mitochondrial membrane and generates ATP
• Aerobic respiration requires oxygen, while anaerobic respiration does not

Plant Growth and Development

• Plant growth is the increase in size and mass, while development includes all changes in the life cycle of a plant
• Plant hormones (phytohormones) regulate plant growth and development
• Auxins promote cell elongation and apical dominance
• Gibberellins promote stem elongation and seed germination
• Cytokinins promote cell division and delay senescence
• Abscisic acid (ABA) promotes dormancy and stress tolerance
• Ethylene promotes fruit ripening and abscission
• Photoperiodism is the response of plants to the relative lengths of day and night
• Vernalization is the requirement of cold treatment to induce flowering

Digestion and Absorption

• Digestion is the process by which complex food substances are broken down into simpler forms
• The human digestive system includes the alimentary canal and digestive glands
• The alimentary canal consists of the mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anus
• Digestive glands include salivary glands, gastric glands, liver, pancreas, and intestinal glands
• Digestion involves mechanical and chemical processes
• Nutrients are absorbed in the small intestine
• Undigested and unabsorbed substances are eliminated through egestion

Breathing and Exchange of Gases

• Respiration involves the exchange of oxygen and carbon dioxide between the organism and the environment
• Human respiratory system includes the nasal passages, pharynx, larynx, trachea, bronchi, and lungs
• Alveoli are the sites of gas exchange in the lungs
• Breathing involves inhalation and exhalation
• Respiratory volumes and capacities are measured by spirometry
• Exchange of gases occurs by diffusion
• Oxygen is transported by hemoglobin in red blood cells
• Carbon dioxide is transported in dissolved form, as bicarbonate ions, and bound to hemoglobin
• Respiratory disorders include asthma, emphysema, and bronchitis

Body Fluids and Circulation

• Body fluids include blood and lymph
• Blood consists of plasma and formed elements (red blood cells, white blood cells, and platelets)
• Red blood cells (erythrocytes) transport oxygen
• White blood cells (leukocytes) are involved in immune responses
• Platelets (thrombocytes) are involved in blood clotting
• Blood groups are determined by antigens on the surface of red blood cells
• The human circulatory system includes the heart and blood vessels
• The heart pumps blood through arteries, veins, and capillaries
• The cardiac cycle includes atrial and ventricular systole and diastole
• Blood pressure is the force exerted by blood against the walls of blood vessels
• Lymph is a fluid that circulates in the lymphatic system
• Circulatory disorders include hypertension, coronary artery disease, and heart failure

Excretory Products and Their Elimination

• Excretion is the process of removing waste products from the body
• Human excretory system includes the kidneys, ureters, urinary bladder, and urethra
• The kidneys filter blood and produce urine
• Nephrons are the functional units of the kidneys
• Urine formation involves filtration, reabsorption, and secretion
• Regulation of kidney function involves hormones like ADH and aldosterone
• Excretory disorders include kidney failure, kidney stones, and uremia

Locomotion and Movement

• Movement is a characteristic feature of living organisms
• Types of movement include amoeboid, ciliary, and muscular movement
• Human skeletal system includes bones and joints
• Muscles are responsible for movement
• Skeletal muscles are attached to bones and produce movement
• Muscle contraction involves the sliding of actin and myosin filaments
• Neuromuscular junction is the site of contact between a motor neuron and a muscle fiber
• Skeletal disorders include arthritis, osteoporosis, and gout

Neural Control and Coordination

• The nervous system controls and coordinates body functions
• Neurons are the structural and functional units of the nervous system
• The human nervous system includes the central nervous system (brain and spinal cord) and the peripheral nervous system (nerves)
• The brain is the control center of the nervous system
• The spinal cord transmits signals between the brain and the rest of the body
• Nerve impulses are transmitted by electrical and chemical signals
• Synapses are the junctions between neurons
• The endocrine system consists of glands that secrete hormones
• Hormones regulate various body functions
• Endocrine disorders include diabetes, thyroid disorders, and growth disorders

Chemical Coordination and Integration

• The endocrine system coordinates body functions through hormones
• Hormones are chemical messengers secreted by endocrine glands
• The hypothalamus controls the pituitary gland
• The pituitary gland secretes hormones that regulate other endocrine glands
• The thyroid gland secretes thyroid hormones, which regulate metabolism
• The adrenal glands secrete hormones that regulate stress response
• The pancreas secretes insulin and glucagon, which regulate blood sugar levels
• The gonads secrete sex hormones, which regulate reproduction
• Hormone action involves binding to receptors on target cells

Reproduction in Organisms

• Reproduction is the process by which organisms produce offspring
• Asexual reproduction involves a single parent and produces genetically identical offspring
• Sexual reproduction involves two parents and produces offspring with genetic variation
• Modes of asexual reproduction include fission, budding, fragmentation, and vegetative propagation

Sexual Reproduction in Flowering Plants

• Flowering plants reproduce sexually through flowers
• Flowers contain male (stamen) and female (pistil) reproductive structures
• Pollination is the transfer of pollen from the stamen to the pistil
• Fertilization is the fusion of male and female gametes to form a zygote
• Seeds develop from ovules after fertilization
• Fruits develop from the ovary after fertilization
• Methods of pollination include self-pollination and cross-pollination
• Agents of pollination include wind, water, insects, and animals

Human Reproduction

• Human reproduction involves sexual reproduction
• The male reproductive system includes the testes, vas deferens, seminal vesicles, prostate gland, and penis
• The female reproductive system includes the ovaries, fallopian tubes, uterus, vagina, and mammary glands
• Gametogenesis is the process of forming gametes (sperm and egg)
• Menstrual cycle is the cyclical changes in the female reproductive system
• Fertilization is the fusion of sperm and egg to form a zygote
• Implantation is the attachment of the embryo to the uterine wall
• Pregnancy (gestation) is the period of development of the embryo in the uterus
• Parturition is the process of childbirth

Reproductive Health

• Reproductive health refers to the overall well-being of the reproductive system
• Sexually transmitted infections (STIs) are infections spread through sexual contact
• Birth control methods include barrier methods, hormonal methods, and surgical methods
• Infertility is the inability to conceive after a year of unprotected intercourse
• Assisted reproductive technologies (ART) include IVF, GIFT, and ZIFT

Principles of Inheritance and Variation

• Genetics is the branch of biology that deals with heredity and variation
• Heredity is the transmission of traits from parents to offspring
• Variation is the differences among individuals within a population
• Mendel's laws of inheritance describe the patterns of inheritance
• Genes are the units of inheritance
• Alleles are alternative forms of a gene
• Genotype is the genetic makeup of an organism
• Phenotype is the observable characteristics of an organism
• Chromosomal theory of inheritance states that genes are located on chromosomes
• Linkage is the tendency of genes located close together on a chromosome to be inherited together
• Crossing over is the exchange of genetic material between homologous chromosomes
• Mutations are changes in the DNA sequence

Molecular Basis of Inheritance

• DNA is the genetic material in most organisms
• DNA structure is a double helix composed of nucleotides
• DNA replication is the process of copying DNA
• Transcription is the process of synthesizing RNA from DNA
• Translation is the process of synthesizing proteins from RNA
• The genetic code is the set of rules by which information encoded in genetic material (DNA or RNA) is translated into proteins
• Gene expression is the process by which genetic information is used to synthesize functional gene products (proteins)

Evolution

• Evolution is the change in the heritable characteristics of biological populations over successive generations
• Evidence for evolution includes fossils, comparative anatomy, embryology, and molecular biology
• Theories of evolution include Lamarckism, Darwinism, and the modern synthetic theory
• Natural selection is the process by which organisms with advantageous traits are more likely to survive and reproduce
• Genetic drift is the random change in allele frequencies in a population
• Speciation is the process by which new species arise
• Human evolution involves the development of modern humans from ape-like ancestors

Human Health and Disease

• Health is a state of complete physical, mental, and social well-being
• Disease is a condition that impairs normal functioning
• Types of diseases include infectious diseases and non-infectious diseases
• Infectious diseases are caused by pathogens (bacteria, viruses, fungi, and parasites)
• Non-infectious diseases are caused by genetic factors, lifestyle factors, and environmental factors
• Immunity is the ability of the body to resist disease
• The immune system includes the innate immune system and the adaptive immune system
• Vaccines are used to induce immunity to infectious diseases
• Cancer is a disease caused by uncontrolled cell growth
• Drugs and alcohol can have harmful effects on health

Microbes in Human Welfare

• Microbes are used in various ways for human welfare
• Microbes are used in food production (e.g., yogurt, cheese, bread)
• Microbes are used in the production of antibiotics, enzymes, and other products
• Microbes are used in sewage treatment and waste management
• Microbes are used as biocontrol agents and biofertilizers
• Biofertilizers enhance soil fertility
• Biocontrol agents control pests and diseases

Biotechnology: Principles and Processes

• Biotechnology is the use of living organisms or their products to develop or modify products or processes
• Genetic engineering is the manipulation of genes to alter the characteristics of an organism
• Recombinant DNA technology involves the insertion of foreign DNA into a host organism
• Tools of recombinant DNA technology include enzymes, vectors, and host organisms
• Processes of recombinant DNA technology include DNA isolation, DNA fragmentation, gene cloning, and gene transfer

Biotechnology and Its Applications

• Biotechnology has applications in various fields
• Biotechnology is used in agriculture to produce genetically modified (GM) crops
• Biotechnology is used in medicine to produce drugs, vaccines, and diagnostic tools
• Biotechnology is used in industry to produce enzymes, biofuels, and bioplastics
• Biotechnology is used in environmental science to clean up pollution

Organisms and Populations

• Ecology is the study of the interactions between organisms and their environment
• Organisms interact with their environment at different levels: organism, population, community, ecosystem, and biosphere
• Populations are groups of individuals of the same species living in the same area
• Population growth is influenced by birth rate, death rate, immigration, and emigration
• Population interactions include competition, predation, parasitism, mutualism, and commensalism

Ecosystem

• An ecosystem is a community of living organisms and their physical environment interacting as a functional unit
• Ecosystem components include abiotic factors (e.g., temperature, water, light) and biotic factors (e.g., producers, consumers, decomposers)
• Energy flow in an ecosystem is unidirectional
• Food chains and food webs depict the flow of energy and nutrients in an ecosystem
• Ecological pyramids represent the trophic levels in an ecosystem
• Nutrient cycles involve the movement of nutrients through the ecosystem
• Ecosystem services are the benefits that humans derive from ecosystems

Biodiversity and Conservation

• Biodiversity is the variety of life on Earth
• Biodiversity is important for ecosystem functioning and human well-being
• Biodiversity is threatened by habitat loss, overexploitation, invasive species, pollution, and climate change
• Conservation is the protection and management of biodiversity
• Strategies for biodiversity conservation include in situ conservation (protected areas) and ex situ conservation (zoos, botanical gardens)
• Biodiversity hotspots are regions with high levels of biodiversity and high levels of threat
• International agreements and conventions aim to protect biodiversity

Environmental Issues

• Environmental pollution is the contamination of the environment with harmful substances
• Types of pollution include air pollution, water pollution, soil pollution, and noise pollution
• Causes of pollution include industrial activities, agricultural practices, and urbanization
• Effects of pollution include health problems, ecosystem damage, and climate change
• Strategies for pollution control include reducing emissions, treating waste, and promoting sustainable practices
• Climate change is the change in global climate patterns due to increased greenhouse gas concentrations
• Causes of climate change include burning fossil fuels, deforestation, and industrial activities
• Effects of climate change include rising temperatures, sea-level rise, and extreme weather events
• Strategies for mitigating climate change include reducing greenhouse gas emissions and increasing carbon sinks