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Biology NCERT

Plant Growth and Development NCERT Highlights Line by Line

Home Plant Growth and Development NCERT Highlights Line by Line for Class 11 & NEET Understand the hormonal control of plant life. This resource gives you Plant Growth and Development NCERT Highlights Line by Line, covering all five major plant growth regulators and their physiological effects. Key lines on photoperiodism, vernalization, and seed dormancy are underlined to help you focus on high-priority conceptual topics. Summary of Chapter: Plant Growth and Development NCERT Highlights Line by Line Growth is defined as an irreversible permanent increase in size of an organ, part, or individual cell. Plant growth is generally indeterminate, meaning plants retain the capacity for unlimited growth due to the presence of meristems (the open form of growth). Stages and Rates of Growth Plant growth is divided into three phases: Meristematic Phase: Characterized by constant cell division in the root and shoot apices. Cells are rich in protoplasm and have large nuclei. Elongation Phase: Cells posterior to the meristematic region undergo rapid enlargement and formation of new cell wall material. Maturation Phase: Cells attain their maximal size and specific function, leading to differentiation. Growth Rates: The increased growth per unit time. Arithmetic Growth: Only one daughter cell continues to divide, while the other differentiates. Example is found in root elongating at a constant rate. A plot of length against time is a straight line. Geometric Growth: Both progeny cells retain the ability to divide. The growth curve is Sigmoid (S-shaped), showing a Lag phase, a Log (Exponential) phase (where growth is fastest), and a Stationary phase. Development, Differentiation, and Plasticity Development: It is the sum of growth and differentiation. It is a sequence of events from seed germination to senescence. Differentiation: Cells maturing to perform specific functions, often losing the capacity to divide (e.g., forming water-conducting tracheary elements). Dedifferentiation: Living differentiated cells regaining the capacity of division (e.g., formation of interfascicular cambium). Redifferentiation: Dedifferentiated cells losing the capacity to divide again and maturing (e.g., secondary cortex cells). Plasticity: The ability of plants to follow different pathways in response to environment or phases of life to form different kinds of structures. Example: Heterophylly in Buttercup (leaves in air are different from leaves in water) and in Cotton and Larkspur (juvenile leaves differ from mature ones). Plant Growth Regulators (PGRs) PGRs are small, simple molecules of diverse chemical composition. They are also called plant hormones or phytohormones. PGR Key Functions and Discovery Highlights Auxins Discovery: First isolated by F.W. Went from oat coleoptile tips, following the work of Charles and Francis Darwin on phototropism in canary grass.   Functions: Initiate rooting in stem cuttings, promote flowering (pineapples), prevent fruit drop at early stages, and cause apical dominance (inhibition of lateral buds by the apical bud). 2, 4-D (a synthetic auxin) is used as a weedicide to kill dicot weeds. Gibberellins (GAs) Discovery: Identified from the fungal disease ‘Bakanae’ (foolish seedling) of rice caused by the fungus Gibberella fujikuroi. GA3 is the most studied form.   Functions: Cause elongation of the axis (increasing length of grape stalks), delay senescence, and promote bolting (internode elongation) in cabbages and beet. Increase sugarcane yield by up to 20 tonnes per acre. Cytokinins Discovery: Active substance Kinetin was crystallized from autoclaved herring sperm DNA; it does not occur naturally in plants. Zeatin was isolated from corn-kernels and coconut milk.   Functions: Synthesised where rapid cell division occurs (roots, developing shoots). Promote production of new leaves, help overcome apical dominance, and promote nutrient mobilisation (delaying leaf senescence). Ethylene Discovery: Cousins confirmed a volatile substance from ripened oranges hastened the ripening of stored unripened bananas. It is a gaseous PGR.   Functions: Promotes rapid fruit ripening (associated with Respiratory Climactic), breaks seed/bud dormancy, initiates germination (peanut seeds), and promotes root growth and root hair formation. Causes the triple response (horizontal growth, swelling of axis, apical hook formation) in dicot seedlings. Abscisic Acid (ABA) Discovery: Known as inhibitor-B, abscission II, or dormin. It is often called the stress hormone.   Functions: Stimulates the closure of stomata (tolerance to water stress), promotes seed dormancy (helps seeds withstand desiccation), and inhibits seed germination. It acts as an antagonist to GAs in most situations. Photoperiodism and Vernalisation Photoperiodism: The response of plants to the relative lengths of day and night. Short Day Plants (SDP): Require a light period less than a critical duration to flower. Long Day Plants (LDP): Require a light period exceeding a critical duration to flower. Day Neutral Plants (DNP): Flowering is independent of light duration. The site of light perception is the leaves. A hypothetical flowering hormone called Florigen is thought to migrate from leaves to shoot apices to induce flowering. Vernalisation: The requirement for a period of low temperature for some plants to flower. It prevents pre-cocious reproductive development. Examples: Winter varieties of Wheat, Barley, and Rye. Also seen in Biennials (like Sugarbeet, Cabbages, Carrots), which are monocarpic plants that usually flower and die in the second season. Exposing them to cold simulates flowering.

Biology NCERT

Respiration in Plants NCERT Highlights Line by Line

Home Respiration in Plants NCERT Highlights Line by Line for Class 11 & NEET Master cellular respiration with our focused revision tool. We provide Respiration in Plants NCERT Highlights Line by Line, detailing the metabolic pathways from glycolysis to the electron transport system. Every essential line from the textbook is summarized in simple text, giving you a powerful resource to ace your NEET biology preparation. Summary of Chapter: Respiration in Plants NCERT Highlights Line by Line Respiration is the breaking of the C-C bonds of complex compounds through oxidation within the cells, leading to the release of a considerable amount of energy. The compounds that are oxidised during this process are known as respiratory substrates. Usually, carbohydrates are oxidised to release energy, but proteins, fats and even organic acids can be used. The energy released is not used directly but is used to synthesise ATP, which is broken down whenever energy is needed. Hence, ATP acts as the energy currency of the cell. Do Plants Breathe? Plants require O2 for respiration and release CO2. Unlike animals, plants have no specialized organs for gaseous exchange but have stomata and lenticels. Reasons for absence of respiratory organs: Each plant part takes care of its own gas-exchange needs. There is very little transport of gases from one plant part to another. Plants do not present great demands for gas exchange. Roots, stems and leaves respire at rates far lower than animals do. The distance that gases must diffuse even in large, bulky plants is not great. In thick woody stems, living cells are organised in thin layers inside and beneath the bark; the interior contains dead cells (pith) that provide mechanical support. Glycolysis (EMP Pathway) The term glycolysis has originated from the Greek words, glycos for sugar, and lysis for splitting. The scheme of glycolysis was given by Gustav Embden, Otto Meyerhof, and J. Parnas, and is often referred to as the EMP pathway. In anaerobic organisms, it is the only process in respiration. It occurs in the cytoplasm of the cell and is present in all living organisms. In this process, glucose undergoes partial oxidation to form two molecules of Pyruvic acid (3-carbon). Steps: Sucrose is converted into glucose and fructose by the enzyme invertase. Glucose is phosphorylated to Glucose-6-phosphate by Hexokinase (uses 1 ATP). Key Step: Fructose-6-phosphate is converted to Fructose-1,6-bisphosphate (uses 2nd ATP). Splitting occurs: Fructose-1,6-bisphosphate splits into PGAL (3-phosphoglyceraldehyde) and DHAP (Dihydroxy Acetone Phosphate). Energy Yield: There are two steps where ATP is generated directly (Substrate Level Phosphorylation): conversion of 1,3-bisphosphoglyceric acid (BPGA) to 3-phosphoglyceric acid (PGA) and Phosphoenolpyruvate (PEP) to Pyruvic acid. NAD+ is reduced to NADH + H+ during the conversion of PGAL to BPGA. Net Products: 2 Pyruvic Acid + 2 ATP + 2 NADH. Fermentation (Anaerobic Respiration) Occurs in many prokaryotes and unicellular eukaryotes. Alcoholic Fermentation: Yeast performs this. Pyruvic acid is converted to CO2 and Ethanol. Enzymes involved: Pyruvic acid decarboxylase and Alcohol dehydrogenase. Lactic Acid Fermentation: In some bacteria and animal muscles (during exercise when oxygen is inadequate), pyruvic acid is reduced to Lactic acid by Lactate dehydrogenase. Drawbacks: Hazardous products (acid/alcohol) are formed. Energy production is low (less than 7% of energy in glucose is released). Yeasts poison themselves to death when the concentration of alcohol reaches about 13%.   Aerobic Respiration For aerobic respiration to take place, pyruvate enters the mitochondria. The crucial events are:    Link Reaction: Pyruvate is transported into the mitochondria and undergoes oxidative decarboxylation by the enzyme complex Pyruvate dehydrogenase.   Pyruvic acid + CoA + NAD+ -> Acetyl CoA + CO2 + NADH + H+ Acetyl CoA then enters the Krebs Cycle. Tricarboxylic Acid Cycle (TCA / Krebs Cycle): Starts with the condensation of Acetyl CoA with Oxaloacetic acid (OAA) and water to yield Citric acid. Enzyme: Citrate synthase. Citrate is isomerised to Isocitrate. Two successive steps of decarboxylation lead to the formation of alpha-ketoglutaric acid (5C) and then Succinyl-CoA (4C). GTP synthesis: Conversion of Succinyl-CoA to Succinic acid produces GTP (Substrate level phosphorylation). FADH2 production: Conversion of Succinate to Fumarate reduces FAD+ to FADH2. Summary: For every 2 molecules of Acetyl CoA (from 1 Glucose): 4 CO2, 6 NADH, 2 FADH2, and 2 ATP/GTP are produced. Electron Transport System (ETS) and Oxidative Phosphorylation: Located in the inner mitochondrial membrane. Electrons from NADH (Complex I) and FADH2 (Complex II) are passed through carriers to generate a proton gradient. Complex I: NADH dehydrogenase. Complex II: FADH2 transfers electrons to Ubiquinone. Complex III: Cytochrome bc1 complex. Complex IV: Cytochrome c oxidase (contains Cytochromes a and a3, and two copper centres). Cytochrome c: A small protein attached to the outer surface of the inner membrane, acts as a mobile carrier between Complex III and IV. Final Acceptor: Oxygen acts as the final hydrogen acceptor interacting with protons to form metabolic water. Complex V (ATP Synthase): Protons return from inter-membrane space to the matrix through F0, driving F1 to synthesize ATP. Ratio: Oxidation of 1 NADH produces 3 ATP; 1 FADH2 produces 2 ATP. The Respiratory Balance Sheet Calculations are based on assumptions (sequential pathway, NADH transferred to mitochondria, no intermediates withdrawn). Net Gain: 38 ATP molecules for one glucose molecule (in aerobes). Fermentation yields only 2 ATP. Amphibolic Pathway Respiration is traditionally a catabolic process (breakdown). However, intermediates of the pathway are withdrawn to synthesize other substrates (e.g., Acetyl CoA used to synthesize fatty acids). Since it involves both breakdown (catabolism) and synthesis (anabolism), the respiratory pathway is better termed an Amphibolic Pathway. Fatty acids enter as Acetyl CoA. Proteins enter as Pyruvate or Acetyl CoA (after deamination). Respiratory Quotient (RQ) The ratio of the volume of CO2 evolved to the volume of O2 consumed. RQ = CO2 evolved / O2 consumed. Carbohydrates: RQ = 1.0. Fats: RQ is less than 1. For Tripalmitin, RQ = 0.7. Proteins: RQ = 0.9. Organic Acids: RQ > 1.

Biology NCERT

Photosynthesis in Higher Plants NCERT Highlights Line by Line

Home Photosynthesis in Higher Plants NCERT Highlights Line by Line for Class 11 & NEET Master plant physiology with our focused revision tool. We provide Photosynthesis in Higher Plants NCERT Highlights Line by Line, detailing the historical experiments, light and dark reactions, and the factors affecting photosynthesis. Every essential line from the textbook is summarized, giving you a powerful resource to ace your NEET biology preparation. Summary of Chapter: Photosynthesis in Higher Plants NCERT Highlights Line by Line Photosynthesis is a physico-chemical process by which green plants use light energy to drive the synthesis of organic compounds. It is the basis of life on earth because it is the primary source of all food and is responsible for the release of oxygen. Early Experiments Joseph Priestley (1770): Performed the bell jar experiments with a candle and a mouse. He concluded that a burning candle or an animal that breathes the air, both somehow damage the air. But when he placed a mint plant in the same bell jar, he found that the mouse stayed alive and the candle continued to burn. He hypothesized that plants restore to the air whatever breathing animals and burning candles remove. Jan Ingenhousz: Used a similar setup but placed it in sunlight and darkness. He showed that sunlight is essential to the plant process. He observed that in an aquatic plant (Hydrilla), small bubbles were formed around the green parts while in the light, but not in the dark. He identified these bubbles to be of oxygen. Julius von Sachs (1854): Provided evidence for the production of glucose when plants grow. Glucose is usually stored as starch. He showed that the green substance (chlorophyll) is located in special bodies (chloroplasts) within plant cells. T.W. Engelmann: Using a prism, he split light into its spectral components and then illuminated a green alga, Cladophora, placed in a suspension of aerobic bacteria. The bacteria were used to detect the sites of O2 evolution. He observed that the bacteria accumulated mainly in the region of blue and red light of the split spectrum. This described the first action spectrum of photosynthesis. Cornelius van Niel: A microbiologist who made a significant contribution working on purple and green sulphur bacteria. He demonstrated that photosynthesis is essentially a light-dependent reaction in which hydrogen from a suitable oxidisable compound reduces carbon dioxide to carbohydrates. In green plants, H2O is the hydrogen donor and is oxidised to O2. In purple and green sulphur bacteria, the hydrogen donor is H2S, and the oxidation product is sulphur or sulphate, not O2. Hence, he inferred that the O2 evolved by the green plant comes from H2O, not from CO2. Where does Photosynthesis take place? It takes place in the green leaves and other green parts of the plants. Within the leaves, the mesophyll cells possess a large number of chloroplasts. The Chloroplast contains a membranous system consisting of grana, the stroma lamellae, and the fluid stroma. Membrane System (Grana): Responsible for trapping the light energy and also for the synthesis of ATP and NADPH (Light Reactions). Stroma: Enzymatic reactions synthesize sugar, which in turn forms starch (Dark Reactions or Biosynthetic Phase). Pigments involved in Photosynthesis A chromatographic separation of the leaf pigments shows that the colour is not due to a single pigment but due to four pigments: Chlorophyll a (bright or blue-green), Chlorophyll b (yellow-green), Xanthophylls (yellow), and Carotenoids (yellow to yellow-orange). Chlorophyll a is the major pigment responsible for trapping light. The absorption spectrum of chlorophyll a and the action spectrum of photosynthesis (rate of photosynthesis) overlap, showing that photosynthesis is maximum in the blue and red regions of the spectrum. Accessory pigments (Chl b, xanthophylls, carotenoids) absorb light and transfer the energy to chlorophyll a. They also protect chlorophyll a from photo-oxidation. Light Reaction (Photochemical Phase) Includes light absorption, water splitting, oxygen release, and the formation of high-energy chemical intermediates, ATP and NADPH. Photosystems: Pigments are organised into two discrete photochemical Light Harvesting Complexes (LHC) within the Photosystem I (PS I) and Photosystem II (PS II). Each photosystem has all the pigments (except one molecule of chlorophyll a) forming a light harvesting system also called antennae. The single chlorophyll a molecule forms the reaction centre. In PS I, the reaction centre chlorophyll a has an absorption peak at 700 nm (P700). In PS II, the reaction centre has an absorption peak at 680 nm (P680). The Electron Transport Z-Scheme: In PS II, the reaction centre chlorophyll a absorbs 680 nm light causing electrons to become excited and jump into an orbit farther from the atomic nucleus. These electrons are picked up by an electron acceptor and passed to an electrons transport system consisting of cytochromes. This movement is downhill (in terms of redox potential scale). The electrons are then passed to the pigments of PS I. Simultaneously, electrons in the reaction centre of PS I are also excited when they receive red light of wavelength 700 nm and are transferred to another acceptor molecule. These electrons are moved downhill again to a molecule of NADP+ reducing it to NADPH + H+. This whole scheme of transfer of electrons, starting from the PS II, uphill to the acceptor, down the electron transport chain to PS I, excitation of electrons, transfer to another acceptor, and finally down to NADP+ is called the Z-Scheme. Splitting of Water: The electrons that were moved from PS II must be replaced. This is achieved by electrons available due to splitting of water. The splitting of water is associated with PS II (2H2O -> 4H+ + O2 + 4e-). This creates oxygen, one of the net products of photosynthesis. The water splitting complex is located on the inner side of the thylakoid membrane. Cyclic and Non-cyclic Photo-phosphorylation Non-Cyclic: Both ATP and NADPH + H+ are synthesised. Involves both PS I and PS II. Occurs in grana lamellae. Cyclic: Only PS I is functional. The electron is circulated within the photosystem and the phosphorylation occurs due to cyclic flow of electrons.

Biology NCERT

Biodiversity and Conservation NCERT Highlights Line by Line

Home Biodiversity and Conservation NCERT Highlights Line by Line for Class 12 & NEET Master the intricacies of biological diversity and conservation strategies with our focused revision tool. We provide Biodiversity and Conservation NCERT Highlights Line by Line, detailing the levels of diversity, patterns of distribution, and critical conservation methods. Every essential line from the textbook is summarized and cited, giving you a powerful resource to ace your NEET biology preparation. Summary of Chapter: Biodiversity and Conservation NCERT Highlights Line by Line Biodiversity is the term popularised by the sociobiologist Edward Wilson to describe the combined diversity at all levels of biological organisation. The three most important levels are: Genetic Diversity: A single species might show high diversity at the genetic level over its distributional range. For example, the medicinal plant Rauwolfia vomitoria growing in different Himalayan ranges shows variation in the potency and concentration of the active chemical reserpine. India has more than 50,000 genetically different strains of rice and 1,000 varieties of mango.   Species Diversity: The diversity at the species level. For example, the Western Ghats have a greater amphibian species diversity than the Eastern Ghats.   Ecological Diversity: At the ecosystem level, India (with deserts, rain forests, mangroves, coral reefs, etc.) has a greater ecosystem diversity than a Scandinavian country like Norway.   Global and Indian Biodiversity Estimates: According to the IUCN (2004), the total number of plant and animal species described is slightly more than 1.5 million. A more conservative and scientifically sound estimate by Robert May places the global species diversity at about 7 million. Animals make up more than 70% of all species, while plants comprise no more than 22%. Among animals, insects are the most species-rich group (making up >70%).   The number of fungi species is more than the combined total of fishes, amphibians, reptiles, and mammals.   India has only 2.4% of the world’s land area, but its share of global species diversity is an impressive 8.1%. This makes India one of the 12 mega diversity countries of the world. Patterns of Biodiversity: Latitudinal Gradients: Species diversity generally decreases as we move away from the equator towards the poles. Tropics harbour more species than temperate or polar areas. The Amazonian rain forest in South America has the greatest biodiversity on earth. Reasons for high tropical diversity: Speciation is a function of time: Tropics have remained relatively undisturbed for millions of years, allowing for a long evolutionary time.   Stable Environment: Tropical environments are less seasonal, relatively more constant, and predictable, promoting niche specialisation.   Solar Energy: More solar energy is available in the tropics, contributing to higher productivity.   Species-Area Relationships: German naturalist Alexander von Humboldt observed that within a region, species richness increased with increasing explored area, but only up to a limit. The relationship is a rectangular hyperbola described by the equation log S = log C + Z log A, where S is Species richness, A is Area, Z is slope of the line (regression coefficient), and C is Y-intercept . The value of Z lies in the range of 0.1 to 0.2 for most groups. However, for very large areas like entire continents, the slope is steeper (Z = 0.6 to 1.2). For frugivorous birds and mammals in tropical forests, the slope is 1.15.   Importance of Species Diversity:  David Tilman’s experiments showed that plots with more species showed less year-to-year variation in biomass and that increased diversity contributed to higher productivity.   Rivet Popper Hypothesis: Proposed by Stanford ecologist Paul Ehrlich. He compared the ecosystem to an airplane and species to rivets. Removing rivets (extinction) may not initially affect flight safety, but losing key rivets on the wings (key species that drive major ecosystem functions) is a serious threat . Loss of Biodiversity:  The IUCN Red List (2004) documents the extinction of 784 species in the last 500 years. Recent extinctions include the Dodo (Mauritius), Quagga (Africa), Thylacine (Australia), Steller’s Sea Cow (Russia), and three subspecies of tiger (Bali, Javan, Caspian). Amphibians appear to be more vulnerable to extinction. The Evil Quartet (Causes of Biodiversity Loss): Habitat Loss and Fragmentation: The most important cause. The Amazon rain forest (lungs of the planet) is being cut for cultivating soya beans or raising beef cattle.  Over-exploitation: “Need” turning to “greed” led to the extinction of Steller’s sea cow and passenger pigeon. Alien Species Invasions: The Nile perch introduced into Lake Victoria led to the extinction of >200 species of cichlid fish. Invasive weeds like carrot grass (Parthenium), Lantana, and water hyacinth (Eicchornia) pose threats. The illegal introduction of African catfish (Clarias gariepinus) threatens indigenous catfishes. Co-extinctions: When a species becomes extinct, the plant and animal species associated with it in an obligatory way also become extinct (e.g., host fish and its parasites, coevolved plant-pollinator mutualism).  Biodiversity Conservation: Why Conserve? Narrowly Utilitarian: Humans derive direct economic benefits (food, firewood, fibre, industrial products, medicines). More than 25% of drugs are derived from plants. Broadly Utilitarian: Ecosystem services. Amazon forest produces 20% of the earth’s oxygen. Pollination is another crucial service. Ethical: Every species has an intrinsic value, and we have a moral duty to care for them.   How to Conserve? In situ (On site) Conservation: Protecting the whole ecosystem. Biodiversity Hotspots: Regions with very high levels of species richness and high degree of endemism (species confined to that region). There are 34 hotspots in the world. Three cover India: Western Ghats and Sri Lanka, Indo-Burma, and Himalaya. Protected Areas: India has 14 biosphere reserves, 90 national parks, and 448 wildlife sanctuaries. Sacred Groves: Tracts of forest set aside where all trees and wildlife are venerated. Found in Khasi and Jaintia Hills (Meghalaya), Aravalli Hills (Rajasthan), Western Ghats (Karnataka/Maharashtra), and Sarguja, Chanda, Bastar areas (Madhya Pradesh). Ex situ (Off site) Conservation: Threatened animals and plants are taken out from their natural habitat and placed in special settings (Zoological parks, botanical gardens, wildlife safari parks). Advanced methods include Cryopreservation of gametes, in vitro fertilization, tissue culture, and Seed banks.  International Conventions: The Earth Summit (1992): Held

Biology NCERT

Ecosystem NCERT Highlights Line by Line

Home Ecosystem NCERT Highlights Line by Line for Class 12 & NEET Master the functional unit of nature with our focused revision tool. We provide Ecosystem NCERT Highlights Line by Line, detailing the flow of energy, cycling of nutrients, and the dynamic changes within ecological communities. Every essential line from the textbook is underlined and summarized, giving you a powerful resource to ace your NEET biology preparation. Summary of Chapter : Ecosystem NCERT Highlights Line by Line An Ecosystem is a functional unit of nature where living organisms interact among themselves and also with the surrounding physical environment. Structure of Ecosystem: Interaction of biotic and abiotic components results in a physical structure. Stratification is the vertical distribution of different species occupying different levels (e.g., trees occupy top vertical strata, shrubs the second, and herbs/grasses the bottom layers). The four important functional aspects of an ecosystem are: Productivity Decomposition Energy Flow Nutrient Cycling Productivity: A constant input of solar energy is the basic requirement for any ecosystem to function and sustain. Primary Production: Amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis. Expressed in terms of weight (g⁻²) or energy (kcal • m⁻²). Gross Primary Productivity (GPP): Rate of production of organic matter during photosynthesis. A considerable amount of GPP is utilized by plants in respiration (R). Net Primary Productivity (NPP): Gross primary productivity minus respiration losses (R). GPP – R = NPP. NPP is the available biomass for the consumption to heterotrophs (herbivores and decomposers). Secondary Productivity: Rate of formation of new organic matter by consumers. Decomposition: Decomposers (e.g., earthworms, bacteria, fungi) break down complex organic matter into inorganic substances like carbon dioxide, water, and nutrients. The raw material for decomposition is Detritus (dead plant remains like leaves, bark, flowers, and dead animal remains). Steps of Decomposition: Fragmentation: Detritivores (e.g., earthworms) break down detritus into smaller particles. Leaching: Water-soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts. Catabolism: Bacterial and fungal enzymes degrade detritus into simpler inorganic substances. Humification: Accumulation of a dark-coloured amorphous substance called Humus (highly resistant to microbial action, undergoes decomposition at an extremely slow rate, acts as a reservoir of nutrients). Mineralisation: Humus is further degraded by some microbes and release of inorganic nutrients occurs. Factors affecting decomposition: It is largely an oxygen-requiring process. Warm and moist environment favors decomposition; low temperature and anaerobiosis inhibit it. Energy Flow: Sun is the only source of energy for all ecosystems on Earth (except deep sea hydro-thermal ecosystem). Of the incident solar radiation, less than 50% is Photosynthetically Active Radiation (PAR). Plants capture only 2-10% of the PAR. Energy flow is unidirectional (Sun →  Producers →  Consumers). Trophic Levels: Organisms occupy a specific place in the food chain known as their trophic level. Producers (First), Herbivores (Second), Carnivores (Third). 10% Law: Proposed by Lindeman. Only 10% of the energy is transferred to each successive trophic level from the lower trophic level. The remaining 90% is lost as heat. Food Chains: Grazing Food Chain (GFC): Begins with producers. (Grass →   Goat →   Man). Detritus Food Chain (DFC): Begins with dead organic matter. Made up of decomposers (saprotrophs). Ecological Pyramids: Graphical representation of the trophic structure. Pyramid of Number: Usually upright (e.g., Grassland). Can be inverted (e.g., Single tree ecosystem with many parasites). Pyramid of Biomass: Usually upright. Inverted in aquatic ecosystems (Small standing crop of phytoplankton supports a large standing crop of zooplankton). Pyramid of Energy: Always Upright. Energy is always lost as heat at each step; it can never increase. Ecological Succession: The gradual and fairly predictable change in the species composition of a given area. The entire sequence of communities that successively change in a given area are called Sere. Primary Succession: Occurs on newly cooled lava, bare rock, newly created pond (slow process). Secondary Succession: Occurs in areas where natural biotic communities have been destroyed (e.g., burned forests, flooded lands). Faster than primary succession. Types: Hydrarch Succession: Takes place in wet areas (Pond →   →   →   Forest). Xerarch Succession: Takes place in dry areas (Rock →   →   →   Forest). Both successions lead to a medium water condition called Mesic condition. Pioneer Species: The species that invade a bare area. Lichens on rocks (secrete acids to dissolve rock); Phytoplankton in water. Climax Community: A community that is in near equilibrium with the environment. Nutrient Cycling (Biogeochemical Cycles): The movement of nutrient elements through the various components of an ecosystem. Standing State: The amount of nutrients (C, N, P, Ca, etc.) present in the soil at any given time. Gaseous Cycles: Reservoir is the atmosphere or hydrosphere (e.g., Nitrogen, Carbon). Carbon Cycle: 71% of global carbon is dissolved in oceans. Atmosphere contains only about 1%. Photosynthesis fixes 4 × 10¹³ kg of carbon annually. Decomposers also release CO₂. Sedimentary Cycles: Reservoir is Earth’s crust (e.g., Phosphorus, Sulphur). Phosphorus Cycle: Phosphorus is a constituent of biological membranes, nucleic acids, and cellular energy transfer systems. The natural reservoir is rock (contains phosphorus as phosphates). weathering releases minute amounts into soil solution. There is no respiratory release of phosphorus into the atmosphere (unlike carbon). Ecosystem Services: The products of ecosystem processes (e.g., purifying air/water, mitigating floods, generating fertile soil). Robert Costanza and colleagues have put an average price tag of US 33 trillion a year on these fundamental ecosystem services (nearly twice the global GNP). Soil formation accounts for about 50% of this cost.

Biology NCERT

Organisms and Populations NCERT Highlights Line by Line

Home Organisms and Populations NCERT Highlights Line by Line for Class 12 & NEET Master the principles of ecology with our focused revision tool. We provide Organisms and Populations NCERT Highlights Line by Line, detailing the levels of ecological organization, environmental factors, population dynamics, and species interactions. Every essential line from the textbook is underlined and summarized, giving you a powerful resource to ace your NEET biology preparation. Summary of Chapter : Organisms and Populations NCERT Highlights Line by Line Ecology is the study of the interactions among organisms and between the organism and its physical (abiotic) environment. The basic levels of ecological hierarchy are: Organisms → Populations →  Communities →  Biomes. Organism and its Environment: Ecology at the organismic level is essentially Physiological Ecology, which tries to understand how different organisms are adapted to their environments. The rotation of the Earth around the Sun and the tilt of its axis cause annual variations in temperature and duration of day and night, resulting in the formation of major Biomes (e.g., deserts, forests, grasslands). The most ecologically relevant environmental factors are: Temperature: The most important environmental factor. Organisms that can tolerate a wide range of temperatures are eurythermal (e.g., humans, cats, dogs), and those restricted to a narrow range are stenothermal (e.g., polar bears, most reptiles). Water: Life originated in water. Organisms that can tolerate a wide range of salinity are euryhaline (e.g., salmon, eels), and those restricted to a narrow range are stenohaline (e.g., freshwater fishes, most marine invertebrates). Light: Source of energy for autotrophs. Many plants are dependent on sunlight to meet their photoperiodic requirement for flowering. Soil: Affected by climate, weathering process, and development of the topsoil. Soil characteristics (like pH, mineral composition, and topography) determine the vegetation in an area. Responses to Abiotic Factors: Regulate: Organisms that maintain a constant internal body temperature and osmotic concentration (Homeostasis) despite changes in the external environment. All birds and mammals, and a very few lower vertebrate and invertebrate species, are regulators. The success of mammals is largely due to their ability to maintain a constant body temperature. Conform: Organisms whose body temperature or osmotic concentration changes with the ambient temperature or concentration. Most animals and nearly all plants are conformers. Partial Regulators: Can regulate up to a limited external range, beyond which they conform. Suspend: Organisms can cope with stressful conditions by temporarily suspending metabolic activities. Migration: Temporary movement from the stressful area to a more hospitable area (e.g., Keoladeo National Park, Bharatpur, hosts Siberian Cranes). Hibernation: Winter sleep to escape cold (e.g., Bears). Aestivation: Summer sleep to escape heat and desiccation (e.g., Snails and fish). Diapause: A stage of suspended development in zooplanktons in lakes and ponds under unfavourable conditions. Adaptations: Kangaroo rat in North American deserts can meet all its water requirements through internal fat oxidation (a metabolic process) without drinking water. Desert plants (e.g., Opuntia) have thick cuticles, sunken stomata, and their leaves are reduced to spines (to minimize transpiration). They use the CAM pathway to keep stomata closed during the day. Allen’s Rule: Mammals from colder climates generally have shorter ears and limbs to minimise heat loss. Polar seals have a thick layer of fat (blubber) below their skin to act as an insulator and reduce heat loss. Altitude Sickness (in humans at high altitudes >3,500m) is caused by the body not getting enough oxygen due to low atmospheric pressure. The body compensates by increasing red blood cell production, decreasing binding affinity of hemoglobin, and increasing breathing rate. Population Ecology Population Attributes: Birth Rates (Natality) and Death Rates (Mortality): Expressed as change in number (increase or decrease) with respect to members of the population. Sex Ratio: Expressed as the ratio of male to female individuals (e.g., 60% of the population are females). Age Pyramids: Plotting the percentage of individuals of a given age group (pre-reproductive, reproductive, post-reproductive) against age. The shape of the pyramid indicates the growth status of the population (Expanding, Stable, Declining). Population Growth: The size of a population changes depending on four processes: Natality, Mortality, Immigration, and Emigration. If $N_t$ is population size at time $t$, then $N_{t+1} = N_t + [(B+I) – (D+E)]$. Growth Models: Exponential Growth: When resources are unlimited, the growth is exponential. Represented by the equation: $frac{dN}{dt} = rN$. Where $r$ is the intrinsic rate of natural increase. The resulting curve is J-shaped. Logistic Growth: When resources are limited (realistic). The population exhibits the Verhulst-Pearl Logistic Growth model. $frac{dN}{dt} = rN left(frac{K – N}{K}right)$. Where $K$ is the carrying capacity (maximum population size the environment can sustain). The resulting curve is S-shaped. The initial phase is lag phase, followed by acceleration and deceleration, and finally the asymptote (where $N=K$). Species Interactions: Organisms interact with each other in various ways: Interaction Type :  Species A →  Species B  Mutualism (+ , + )               →   Lichens (algae + fungi), Mycorrhizae (fungi + plant roots)  Commensalism  (+ , 0 )     →   Orchid on a mango branch, Cattle egret and grazing cattle  Predation  (+ , – )                 → Tiger and deer, Carnivorous insects and prey  Parasitism  (+ , -)                → Human liver fluke (endoparasite), Lice on human hair (ectoparasite)  Competition ( – , – )              →  Finches competing for seeds  Amensalism ( – , 0 )            → Penicillium secretes antibiotic that kills bacteria  Predation: Predators play three important roles: transfer energy, keep prey populations under control (biological control), and maintain species diversity by reducing the population of a single superior competitor (e.g., Starfish Pisaster removal caused extinction of 10 invertebrate species in an area). Competition: Gause’s Competitive Exclusion Principle states that two closely related species competing for the same limited resources cannot coexist indefinitely; the competitively inferior one will be eliminated. Resource partitioning (choosing different times for foraging) allows co-existence (e.g., MacArthur’s Warblers). Parasitism: Ectoparasites (e.g., lice, Cuscuta plant on hedge plants) and Endoparasites (e.g., Plasmodium, liver fluke). Parasites have evolved specialized adaptations like loss of sense organs,

Biology NCERT

Biotechnology and its Applications NCERT Highlights Line by Line

Home Biotechnology and its Applications NCERT Highlights Line by Line for Class 12 & NEET Master the real-world impact of genetic engineering with our focused revision tool. We provide Biotechnology and its Applications NCERT Highlights Line by Line, detailing the use of biotech in agriculture, medicine, and ethics. Every essential line from the textbook is underlined and summarized, giving you a powerful resource to ace your NEET biology preparation. Summary of Chapter: Biotechnology and its Applications NCERT Highlights Line by Line Biotechnological Applications in Agriculture: The Green Revolution succeeded in tripling the food supply but was not enough to feed the growing human population. To overcome this, Genetically Modified Organisms (GMO) (plants, bacteria, fungi, and animals whose genes have been altered by manipulation) are used. GM plants have been useful to make crops more tolerant to abiotic stresses (cold, drought, salt, heat), reduce reliance on chemical pesticides (pest-resistant crops), help to reduce post-harvest losses, and increase efficiency of mineral usage by plants. Bt Cotton: The bacterium Bacillus thuringiensis produces proteins that kill certain insects such as lepidopterans (tobacco budworm, armyworm), coleopterans (beetles), and dipterans (flies, mosquitoes). B. thuringiensis forms protein crystals containing a toxic insecticidal protein. The protein exists as an inactive protoxin but, once ingested by the insect, it is converted into an active form due to the alkaline pH of the gut, which solubilizes the crystals. The activated toxin binds to the surface of midgut epithelial cells and creates pores that cause cell swelling and lysis, eventually causing death. The toxin is coded by a gene named cry. There are a number of them, for example, the proteins encoded by the genes cryIAc and cryIIAb control the cotton bollworms, while that of cryIAb controls corn borer. Pest Resistant Plants: A nematode Meloidegyne incognita infects the roots of tobacco plants and causes a great reduction in yield. A novel strategy was adopted based on the process of RNA interference (RNAi). RNAi takes place in all eukaryotic organisms as a method of cellular defense. This method involves silencing a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA (silencing). The source of this complementary RNA could be from an infection by viruses having RNA genomes or mobile genetic elements (transposons) that replicate via an RNA intermediate. Using Agrobacterium vectors, nematode-specific genes were introduced into the host plant. The introduction produced both sense and anti-sense RNA in the host cells, which formed a double-stranded (dsRNA) that initiated RNAi and silenced the specific mRNA of the nematode.  Biotechnological Applications in Medicine: Genetically Engineered Insulin: Management of adult-onset diabetes is possible by taking insulin at regular intervals. Insulin consists of two short polypeptide chains: chain A and chain B, linked together by disulphide bridges. In mammals, including humans, insulin is synthesized as a pro-hormone which contains an extra stretch called the C peptide. This C peptide is not present in the mature insulin and is removed during maturation. The main challenge for production of insulin using rDNA techniques was getting insulin assembled into a mature form. In 1983, Eli Lilly (an American company) prepared two DNA sequences corresponding to A and B, chains of human insulin and introduced them in plasmids of E. coli to produce insulin chains. Chains A and B were produced separately, extracted and combined by creating disulfide bonds to form human insulin. Gene Therapy: A collection of methods that allows correction of a gene defect that has been diagnosed in a child/embryo. The first clinical gene therapy was given in 1990 to a 4-year-old girl with Adenosine Deaminase (ADA) deficiency. This enzyme is crucial for the immune system to function (SCID). In some children, ADA deficiency can be cured by bone marrow transplantation or enzyme replacement therapy, but neither is completely curative. In gene therapy, lymphocytes from the blood of the patient are grown in culture outside the body. A functional ADA cDNA (using a retroviral vector) is then introduced into these lymphocytes, which are subsequently returned to the patient. However, as these cells are not immortal, the patient requires periodic infusion of such genetically engineered lymphocytes. If the gene isolated from marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure. Molecular Diagnosis: Early detection is not possible with conventional methods (serum and urine analysis). PCR (Polymerase Chain Reaction): Can detect very low amounts of DNA. It is now routinely used to detect HIV in suspected AIDS patients and to detect mutations in genes in suspected cancer patients.   ELISA (Enzyme Linked Immuno-Sorbent Assay): Based on the principle of antigen-antibody interaction. Infection by a pathogen can be detected by the presence of antigens (proteins, glycoproteins, etc.) or by detecting the antibodies synthesized against the pathogen. Probe: A single-stranded DNA or RNA, tagged with a radioactive molecule is allowed to hybridize to its complementary DNA in a clone of cells followed by detection using autoradiography. The clone having the mutated gene will not appear on the photographic film because the probe will not have complementarity with the mutated gene.  Transgenic Animals: Animals that have had their DNA manipulated to possess and express an extra (foreign) gene. 95%27 of all existing transgenic animals are mice. Normal physiology and development: Study of how genes are regulated (e.g., study of complex factors like Insulin-like growth factor).   Study of disease: Models for human diseases like cancer, cystic fibrosis, rheumatoid arthritis, and Alzheimer’s.   Biological products: Transgenic animals can produce biological products. Example: Rosie, the first transgenic cow (1997), produced human protein-enriched milk (2.4 grams per litre). The milk contained the human alpha-lactalbumin and was nutritionally a more balanced product for human babies than natural cow-milk. Transgenic animals are also used to produce alpha-1-antitrypsin used to treat emphysema. Vaccine safety: Transgenic mice are being developed for use in testing the safety of vaccines (e.g., polio vaccine) before they are used on humans. Chemical safety testing: Toxicity testing (more sensitive to toxic substances).   Ethical Issues: The Indian Government has set up organizations such as GEAC (Genetic Engineering Appraisal Committee), which will make decisions regarding the validity

Biology NCERT

Biotechnology Principles and Processes NCERT Highlights Line by Line

Home Biotechnology: Principles and Processes NCERT Highlights Line by Line for Class 12 & NEET Master the tools and techniques of genetic engineering with our focused revision tool. We provide Biotechnology: Principles and Processes NCERT Highlights Line by Line, detailing the creation of recombinant DNA, vectors, and bioreactors. Every essential line from the textbook is underlined and summarized, giving you a powerful resource to ace your NEET biology preparation. Summary of Chapter: Biotechnology: Principles and Processes NCERT Highlights Line by Line Biotechnology deals with techniques of using live organisms or enzymes from organisms to produce products and processes useful to humans. The European Federation of Biotechnology (EFB) has given a definition encompassing both traditional views and modern molecular biotechnology: “The integration of natural science and organisms, cells, parts thereof, and molecular analogues for products and services.” Principles of Biotechnology: Genetic Engineering: Techniques to alter the chemistry of genetic material (DNA and RNA), to introduce these into host organisms and thus change the phenotype of the host organism. Bioprocess Engineering: Maintenance of sterile (microbial contamination-free) ambience in chemical engineering processes to enable growth of only the desired microbe/eukaryotic cell in large quantities. The construction of the first recombinant DNA (rDNA) emerged from the possibility of linking a gene encoding antibiotic resistance with a native plasmid of Salmonella typhimurium. This was accomplished by Stanley Cohen and Herbert Boyer in 1972. Tools of Recombinant DNA Technology: Restriction Enzymes (Molecular Scissors): Hind II was the first restriction endonuclease to be isolated. It always cut DNA at a specific point by recognizing a specific sequence of six base pairs (recognition sequence). Today, we know more than 900 restriction enzymes. Naming: First letter from Genus, second two from species (e.g., EcoRI comes from Escherichia coli RY 13). ‘R’ is the strain, ‘I’ is the order of isolation. Mechanism: Restriction endonucleases inspect the DNA length and bind to specific recognition sequences. They cut the sugar-phosphate backbones. EcoRI recognizes the Palindrome sequence 5′-GAATTC-3′. A palindrome reads the same on the two strands when orientation is kept the same. Sticky Ends: Enzymes cut slightly away from the center of the palindrome, leaving single-stranded portions at the ends called “sticky ends”. These facilitate the action of the enzyme DNA ligase. Cloning Vectors: Plasmids and bacteriophages are used. Features required to facilitate cloning: Origin of Replication (ori): Sequence where replication starts. Also controls the copy number of the linked DNA. Selectable Marker: Helps in identifying and eliminating non-transformants and selectively permitting the growth of transformants. Usually, genes encoding resistance to antibiotics like ampicillin, chloramphenicol, tetracycline, or kanamycin are useful markers for E. coli. Cloning Sites: Recognition sites for restriction enzymes. To avoid complications, the vector should have very few (preferably single) recognition sites. pBR322 is a widely used E. coli cloning vector. It has restriction sites (e.g., BamH I, Sal I in tetracycline resistance gene). Insertional Inactivation: If a foreign DNA is ligated at the BamH I site of the tetracycline resistance gene, the recombinant plasmid loses tetracycline resistance. In Blue-White screening, recombinant DNA is inserted within the coding sequence of an enzyme, $beta$-galactosidase. This results in inactivation of the enzyme. Colonies with non-recombinant plasmids produce a blue colour (due to chromogenic substrate), while recombinants produce white colonies. Vectors for Plants and Animals: Agrobacterium tumefaciens delivers a piece of DNA known as ‘T-DNA’ to transform normal plant cells into a tumor. The Ti plasmid is now modified into a cloning vector which is no longer pathogenic. Retroviruses in animals transform normal cells into cancerous cells; they are now used as vectors to deliver desirable genes. Competent Host: Since DNA is a hydrophilic molecule, it cannot pass through cell membranes. Bacterial cells are treated with a specific concentration of a divalent cation like Calcium, which increases the efficiency of DNA entry. Recombinant DNA can then be forced into cells by incubating on ice, followed by a brief Heat Shock (42°C), and back on ice. Micro-injection: Recombinant DNA is directly injected into the nucleus of an animal cell. Biolistics or Gene Gun: Cells are bombarded with high-velocity micro-particles of gold or tungsten coated with DNA (suitable for plants). Processes of Recombinant DNA Technology: Isolation of Genetic Material: Cells are treated with enzymes like Lysozyme (bacteria), Cellulase (plant cells), or Chitinase (fungus) to break the cell wall. RNA is removed by Ribonuclease, proteins by Protease. Purified DNA precipitates out after adding chilled ethanol and can be removed by spooling. Cutting of DNA: Performed by restriction enzymes. Separation of DNA Fragments: Gel Electrophoresis. DNA fragments are negatively charged and move towards the anode through a matrix (usually agarose, a natural polymer extracted from sea weeds). Smaller fragments move farther. The separated DNA fragments can be visualized only after staining with Ethidium bromide followed by exposure to UV radiation (appear as bright orange bands). The extraction of DNA from the gel piece is called Elution. Amplification of Gene of Interest (PCR): Polymerase Chain Reaction. Multiple copies of the DNA are synthesized in vitro using two sets of primers and the enzyme DNA polymerase. Steps: Denaturation (heating), Annealing (primers bind), and Extension (polymerase adds nucleotides). Thermostable DNA polymerase (isolated from bacterium Thermus aquaticus) is used, which remains active at high temperatures (induced denaturation). Ligation: Joining the gene of interest to the vector. Transformation: Introduction of recombinant DNA into the host. Obtaining the Foreign Gene Product: The ultimate aim is to produce a desirable protein. Cultures can be grown in large volumes (100-1000 litres) in Bioreactors. Stirred-tank bioreactor: Usually cylindrical or with a curved base to facilitate mixing. Sparged stirred-tank bioreactor: Sterile air is sparged (bubbled) through the reactor. Bioreactors have an agitator system, oxygen delivery system, foam control system, temperature control system, pH control system, and sampling ports. Downstream Processing: Includes separation and purification of the biosynthetic product. The product is formulated with suitable preservatives and undergoes strict quality control testing before marketing.

Biology NCERT

Microbes in Human Welfare NCERT Highlights Line by Line

Home Microbes in Human Welfare NCERT Highlights Line by Line for Class 12 & NEET Master the beneficial roles of microorganisms with our focused revision tool. We provide Microbes in Human Welfare NCERT Highlights Line by Line, detailing their applications in household products, industry, sewage treatment, and agriculture. Every essential line from the textbook is underlined and summarized, giving you a powerful resource to ace your NEET biology preparation. Summary of Chapter: Microbes in Human Welfare NCERT Highlights Line by Line Microbes are omnipresent (soil, water, air, inside bodies, thermal vents at 100°C, deep soil, under snow). They include protozoa, bacteria, fungi, microscopic plant viruses, viroids, and prions (proteinaceous infectious agents). Microbes in Household Products: Curd: Lactobacillus and other Lactic Acid Bacteria (LAB) grow in milk and convert it to curd. During growth, the LAB produce acids that coagulate and partially digest the milk proteins. A small amount of curd added to fresh milk as inoculum (starter) contains millions of LAB, which at suitable temperatures multiply, converting milk to curd, which also improves its nutritional quality by increasing Vitamin B12. LAB also checks disease-causing microbes in the stomach. Dough: The dough used for making dosa and idli is fermented by bacteria (puffed-up appearance due to CO2 production). The dough for making bread is fermented using Baker’s yeast (Saccharomyces cerevisiae). Toddy: A traditional drink of some parts of southern India made by fermenting sap from palms. Cheese: Different varieties are known by their texture, flavour, and taste. The large holes in ‘Swiss cheese’ are due to production of a large amount of CO2 by a bacterium named Propionibacterium shermanii. The ‘Roquefort cheese’ is ripened by growing a specific fungus on them. Microbes in Industrial Products: Production on an industrial scale requires growing microbes in very large vessels called Fermenters. Fermented Beverages: Saccharomyces cerevisiae (Brewer’s yeast) is used for fermenting malted cereals and fruit juices to produce ethanol. Wine and beer are produced without distillation (low alcohol); whisky, brandy, and rum are produced by distillation of the fermented broth (high alcohol). Antibiotics: Chemical substances produced by some microbes and can kill or retard the growth of other (disease-causing) microbes. Penicillin was the first antibiotic to be discovered by Alexander Fleming (working on Staphylococci bacteria, he observed a mould Penicillium notatum prevented bacterial growth). Its full potential as an effective antibiotic was established much later by Ernest Chain and Howard Florey. They were awarded the Nobel Prize in 1945. Antibiotics have greatly improved our capacity to treat deadly diseases like plague, whooping cough (kali khasi), diphtheria (gal ghotu), and leprosy (kusht rog). Chemicals, Enzymes, and other Bioactive Molecules: Acids: Aspergillus niger (fungus) → Citric acid; Acetobacter aceti (bacterium) → Acetic acid; Clostridium butylicum (bacterium) → Butyric acid; Lactobacillus (bacterium) → Lactic acid. Enzymes: Lipases are used in detergent formulations (remove oily stains). Pectinases and Proteases are used to clarify bottled juices. Streptokinase produced by Streptococcus and modified by genetic engineering is used as a ‘clot buster’ for removing clots from blood vessels of patients who have undergone myocardial infarction. Bioactive Molecules: Cyclosporin A, used as an immunosuppressive agent in organ-transplant patients, is produced by the fungus Trichoderma polysporum. Statins, produced by the yeast Monascus purpureus, act as blood-cholesterol lowering agents (competitively inhibiting the enzyme responsible for synthesis of cholesterol). Microbes in Sewage Treatment: Municipal waste-water (sewage) contains large amounts of organic matter and microbes. Treatment is done in Sewage Treatment Plants (STPs). Primary Treatment: Physical removal of particles (large and small) through filtration and sedimentation. Floating debris is removed by sequential filtration. Grit (soil and small pebbles) are removed by sedimentation. The solid that settles forms the primary sludge, and the supernatant forms the effluent. Secondary Treatment (Biological Treatment): The primary effluent is passed into large aeration tanks where it is constantly agitated mechanically and air is pumped into it. This allows vigorous growth of useful aerobic microbes into flocs (masses of bacteria associated with fungal filaments to form mesh-like structures). These microbes consume the major part of the organic matter in the effluent, significantly reducing the BOD (Biochemical Oxygen Demand). BOD refers to the amount of oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria. Greater BOD implies higher polluting potential. Once BOD is reduced, the effluent is passed into a settling tank where the bacterial flocs are allowed to sediment. This sediment is called Activated Sludge. A small part of the activated sludge is pumped back into the aeration tank to serve as the inoculum. The remaining major part is pumped into large tanks called anaerobic sludge digesters. Here, other kinds of bacteria (anaerobic) grow and digest the bacteria and fungi in the sludge. During this digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide, and carbon dioxide (Biogas). The effluent from the secondary treatment plant is generally released into natural water bodies like rivers and streams. Microbes in Production of Biogas: Biogas is a mixture of gases (predominantly methane) produced by microbial activity. Bacteria that grow anaerobically on cellulosic material produce a large amount of methane along with CO2 and H2. These bacteria are collectively called methanogens (e.g., Methanobacterium). These are found in the anaerobic sludge during sewage treatment and in the rumen (part of stomach) of cattle (help in cellulose breakdown). The excreta (dung) of cattle, commonly called gobar, is rich in these bacteria. Biogas Plant: Consists of a concrete tank (10-15 feet deep) in which bio-wastes are collected and a slurry of dung is fed. A floating cover is placed over the slurry, which keeps on rising as gas is produced. The biogas plant has an outlet connected to a pipe to supply biogas. The spent slurry is removed through another outlet and may be used as fertilizer. The technology was developed in India mainly due to the efforts of IARI (Indian Agricultural Research Institute) and KVIC (Khadi and Village Industries Commission). Microbes as Biocontrol Agents: Use of biological methods for controlling plant diseases

Biology NCERT

Human Health and Disease NCERT Highlights Line by Line

Home Human Health and Disease NCERT Highlights Line by Line for Class 12 & NEET Master the body’s defense mechanisms and pathology with our focused revision tool. We provide Human Health and Disease NCERT Highlights Line by Line, covering common diseases, immunology, AIDS, cancer, and drug abuse. Every essential line from the textbook is underlined and summarized, giving you a powerful resource to ace your NEET biology preparation. Summary of Chapter : Human Health and Disease NCERT Highlights Line by Line Health is defined as a state of complete physical, mental, and social well-being (not merely the absence of disease). Common Diseases in Humans: Pathogens are disease-causing organisms. Bacterial Diseases: Typhoid: Caused by Salmonella typhi. Enters small intestine through contaminated food/water. Symptoms: sustained high fever (39°–40°C), weakness, stomach pain, constipation, headache, loss of appetite. Confirmed by Widal test. Pneumonia: Caused by Streptococcus pneumoniae and Haemophilus influenzae. Infects alveoli (fluid-filled). Symptoms: fever, chills, cough, headache; in severe cases, lips and fingernails turn gray to bluish. Viral Diseases: Common Cold: Caused by Rhinoviruses. Infects nose and respiratory passage but not the lungs. Lasts 3-7 days. Protozoan Diseases: Malaria: Caused by Plasmodium (P. vivax, P. malariae, P. falciparum). P. falciparum causes the most serious (malignant) malaria. Life Cycle: The malarial parasite enters the human body as sporozoites (infectious form) through the bite of an infected female Anopheles mosquito. Parasites multiply within liver cells, then attack Red Blood Cells (RBCs) resulting in their rupture. The rupture releases a toxic substance, haemozoin, responsible for the chill and high fever recurring every 3-4 days. Sexual stages (gametocytes) develop in RBCs. The mosquito takes these up; fertilization and development take place in the mosquito’s gut. Mature sporozoites migrate to the mosquito’s salivary glands.   Amoebiasis (Amoebic Dysentery): Caused by “Entamoeba histolytica” in the large intestine. Houseflies act as mechanical carriers. Symptoms: constipation, abdominal pain, stools with excess mucous and blood clots. Helminthic Diseases: Ascariasis: Caused by Ascaris (common roundworm). Internal bleeding, muscular pain, fever, anemia, blockage of intestinal passage. Elephantiasis (Filariasis): Caused by Wuchereria (W. bancrofti and W. malayi). Chronic inflammation of lymphatic vessels, usually of lower limbs. Fungal Diseases: Ringworm: Caused by Microsporum, Trichophyton, and Epidermophyton. Dry, scaly lesions on skin, nails, scalp accompanied by intense itching. Heat and moisture help fungi grow. Immunity: Innate Immunity: Non-specific defense present at birth. Four barriers: Physical: Skin, Mucus coating (respiratory, gastrointestinal, urogenital tracts). Physiological: Acid in stomach, saliva in mouth, tears from eyes. Cellular: Polymorphonuclear leukocytes (PMNL-neutrophils), Monocytes, Natural Killer (NK) cells, Macrophages (phagocytosis). Cytokine: Virus-infected cells secrete proteins called Interferons which protect non-infected cells from further viral infection. Acquired Immunity: Pathogen-specific, characterized by memory. Primary response is low intensity; Secondary (anamnestic) response is highly intensified. Carried out by: B-lymphocytes: Produce an army of proteins called antibodies into the blood (Humoral Immune Response). T-lymphocytes: Help B-cells produce antibodies and mediate Cell-mediated Immunity (CMI). CMI is responsible for Graft Rejection. Antibody Structure: Represented as H2L2 (two light chains, two heavy chains). Examples: IgA, IgM, IgE, IgG. IgA is present in colostrum (yellowish fluid produced during initial days of lactation). Active vs Passive Immunity: Active is slow (body produces own antibodies). Passive is ready-made antibodies given (e.g., Colostrum, Anti-tetanus serum). Allergy: Exaggerated response of the immune system to antigens (allergens). Involves IgE antibodies. Release of histamine and serotonin from mast cells causes symptoms. Treated with antihistamine, adrenaline, and steroids. Autoimmunity: Body attacks self-cells (e.g., Rheumatoid arthritis). Lymphoid Organs: Primary: Bone marrow (all blood cells including lymphocytes produced) and Thymus (T-lymphocytes mature; degenerates with age). Secondary: Spleen (filter of blood, reservoir of erythrocytes), Lymph nodes, Tonsils, Peyer’s patches (small intestine). MALT (Mucosa-associated lymphoid tissue) constitutes 50% of lymphoid tissue. AIDS (Acquired Immuno Deficiency Syndrome): Caused by HIV (Human Immunodeficiency Virus), a retrovirus (RNA genome). Transmission via sexual contact, contaminated blood, shared needles, or placenta. Mechanism: Virus enters macrophages (acts as HIV factory). RNA genome replicates to form viral DNA via reverse transcriptase. Virus enters Helper T-lymphocytes (TH), replicates, and destroys them. Decrease in TH count leads to opportunistic infections (Mycobacterium, viruses, fungi). Diagnosis: ELISA (Enzyme Linked Immuno-Sorbent Assay). Treatment with anti-retroviral drugs is only partially effective. Cancer: Normal cells show contact inhibition; cancer cells lose this property. Tumors: Benign (confined to original location) and Malignant (mass of proliferating neoplastic cells). Malignant cells starve normal cells and show Metastasis (spread to distant sites via blood). Causes: Carcinogens (physical: X-rays, UV rays; chemical: tobacco smoke; biological: oncogenic viruses). Cellular oncogenes (c-onc) in normal cells can be activated to oncogenes. Detection: Biopsy, Histopathological studies, Radiography (X-rays), CT (Computed Tomography – 3D image), MRI (Magnetic Resonance Imaging – uses strong magnetic fields). Treatment: Surgery, Radiation therapy, Chemotherapy (side effects: hair loss, anemia). α-interferons (biological response modifiers) activate the immune system to destroy the tumor. Drugs and Alcohol Abuse: Opioids: Bind to specific opioid receptors in CNS and gastrointestinal tract. Heroin (Smack) is chemically diacetylmorphine (white, odourless, bitter crystalline compound), obtained by acetylation of morphine from latex of Poppy plant (Papaver somniferum). It is a depressant and slows down body functions. Cannabinoids: Interact with cannabinoid receptors in the brain. Obtained from inflorescences of Cannabis sativa. Includes Marijuana, hashish, charas, ganja. Taken by inhalation/oral ingestion. Affects cardiovascular system. Coca alkaloid: Cocaine (Coke/Crack) from Erythroxylum coca (South America). Interferes with transport of neuro-transmitter dopamine. Potent stimulating action on CNS, producing euphoria and increased energy. Hallucinogens: Atropa belladonna, Datura. Tobacco: Contains Nicotine (stimulates adrenal gland to release adrenaline/noradrenaline, raising BP and heart rate). Smoking is associated with lung cancer, bronchitis, emphysema, coronary heart disease. Adolescence and Drug Abuse: Addiction is a psychological attachment to certain effects (euphoria). Repeated use increases tolerance level of receptors. Dependence is the tendency of the body to manifest a characteristic and unpleasant withdrawal syndrome if the dose is abruptly discontinued. Chronic use leads to Cirrhosis of the liver.