For Advertisment 0300 - 9247011 A> “ C9 nF ee cdl: > ww re 3 EN S oar aesCONTENTS Chapters Description Page number 1 Homeostasis 1-16 2 Support & Movement’ | 17-39 3 Coordination & Control | 40-62 4 Reproduction 63-81 5 Growth & Development | 82-91 6 Chromosomes & DNA | 92-104 7 Cell Cycle 105-113 8 Variation & Genetics | 114-124 9 Bio Technology 125-132 10 . Evolution 133-141 11 Ecosystem 142-151 12 | Some Major Eco System | 152-160 13 = | Man & His Environment | 161-169-CLASS: XIL ole BIOLOGY NOTES, Definitio . The self maintaining system of the internal stability of the body is known as homeostasis. FEED BACK SYSTE: Homeostasis requires a check & balance mechanism operating in the body. This check & balance mechanism is known as feedback mechanism. Types of feed back system: There are two types of feed back system. + Negative feed back * Positive feed back Negative feed back: It refers to opposite effect produced in relation to any change in body fluids. Positive feed back: It refers to the series of similar effects produced which leads to the : enhancement of change under consideration. OSMOREGULATION: It involves maintaining balance b/w water & solute contents of cell. Hypotonic soluton: If the concentration of the solution is lower than the concentration of the cell sap, then such a solution is called hypotonic solution. Hypertonic solution: If the concentration of the solution is higher than the concentration of cell sap then such a solution is called hypertonic solution. Plasmolysis: The shrinkage of protoplasm due to exosmosis is called plasmolysis.-CLASS: XII BIOLOGY NOTES Osmotic pressure: The potential energy of water molecules is known as water potential or osmotic pressure. Isotonic solution: The concentration of this solution is equal to the cell sap concentration. e Turgor_presure: Due to endosmosis the protoplasm of a cell expands & a starts to apply a Pressure on the cell wall. This pressure is known as turgor pressure & in this condition the cell is said to be turgid. Wall Pressure: ‘The pressure which is applied by the cell wall on the protoplasm due to the turgor pressure is called wall pressure. OSMOREGULATION IN PLANTS: Plants are distributed in different habitats on the basis of the availability of water. * Hydrophytes © Halophytes © Mesophyies * Xerophytes HYDROPHTES: = Definition: The plants which are found in fresh water either partly or completely sub merged are termed as hydrophytes e.g. Hydrilla, water Lilly, iotus, etc Characteristics of hydrophytes: Their roots are poorly developed because they have no problem in the absorption of waier. + The stems & leaves generally lack cuticle on their surface. Stomata are very large & present only on the upper surfaces of leaf. HALOPHYTES: Definition: The plants growing in saline places are called halophytes. Characteristics of halophyte: + Their roots grow with the surface of soil because they have to absorb water from the upper surface of soil. + The cells of the roots develop high water potential which brings in water by osmosis. + The excess salt can be stored in cells or excreted from salt glands on the leaves. : + E.g. glasswort such as Atriplex species, Chenopodium species.CLASS: XII 3 _ BIOLOGY NOTES MESOPHYTES: Definition: These are most of the plants which grow in moderate water availability. Characteristics of Mesophytes: They can easily compensate the water lost by transpiration through absorbing water from the soil. * To present the excessive transpiration they have thick cuticle on their outer surface e.g. Brassica campestris, Rosa indica, Mangifera indica. XEROPHYTES: Definition: The plants living in dry places such as deserts, steep hills ete. are known as xerophytes, Characteristics of Xerophytes: * The water potential of their roots is very low. * Their leaves are mostly modified into spines + In most of the cases, the stem is green to perform photosynthesis. * They have very thick cuticle e.g. Opuntia species, Euphorbia cadicifolia etc. SEED / SPORES AS ADAPTATIONS IN LIFE CYCLE DURING DROUGHT CONDITIONS Land plants produce seeds or spores during their life cycle. These structures have following important characteristics, * Concentrated protoplasm © Covered by a protective wall. ADAPTATION FOR BALANCE BETWEEN TRANSPIRATION & WATER UPTAKE Deep article roots e.g. Acacia + Superficial horizontal roots e.g. cacti * Desert plants have less number of stomata, sunken stomata, having epidermis, folding of leaves. + Folding of leaves + Storage of water in parenchymatous cells e.g. succulent plants (Suaeda fruiticosa) EXCRETION IN PLANTS: Exeretion in plants is not a serious problem because. ‘+ The rate of catabolic process in much less than the animals of same weight. + Waste products of catabolism are used by green plants in their anabolic process. However, the plants release some substances from their body.GLASS: XI 4 BIOLOGY NOTES * The plants release excess water in the form of vapour through stomate. This process is called transpiration. Some plants of land release water (in liquid form) by the hydathodes during night by the process of guttation. ‘ TRANSPIRATION GUTTATION 7 Water is released in the form of|Water is released in the form of vapour Higuid By stomata By hydathodes During daytime During night time * Green plants in light release oxygen due to photosynthesis. In dark plants release CO2 because respiration is going on whereas photosynthesis is not. ZOOLOGY OSMOREGULATION IN TERRESTRIAL ANIMALS Arthropods & vertebrates maintain osmoregulation by the following methods: Water proof external covering storing & excreting solid wastes Use of metabolic waste. Storing the waste Water proof external coverings: + Reptiles, birds & mammals have water proof keratinized epidermis © The insects have water proof exoskeleton which is made up of chitin. Storing & Excreting Solid Wastes: 7 Reptiles birds & insects excrete uric acid as nitrogenous waste while water is absorbed in Cloaca. Use Of Metabolic Water: Some mammals like camel, kangaroo, rat etc. make use of water produced during the breakdown of body fats. : Storing the wastes: Mammals do retain some urea in their kidney which helps in the reabsorption of water. OSMOREGULATION IN AQUATIC ANIMALS: There are two methods of osmoregulation in aquatic animals. * Osmoregulation by contractile vacuole. * Osmoregulation by producing dilute urine. osmoregulation by contractile vacuole: Fresh water protoctists like amoeba, paramecium, etc have one or more contractile vacuole. The excess water is stored in contractile vacuole & when it is completely filled water is discharged out of the body through a pore into the surrounding water. :CLASS: XII BIOLOGY NOTES Osmoregulatoin by producing dilute urin Fresh, water animals like fishes remove excess water by passing large quantities of very dilute urine, Osmoregulation in aquatic(marine)animals: + Marine bony fishes drink water constantly to conserve water in their bodies. The salts teken in along with water are excreted by special excretory cells in the gills. + In cartilaginous fishes, like shark, slightly hypertonic osmotic pressure of body fluids is present as compared to the surrounding water excess salts are removed by special glands in their rectum. EXCRETION IN ANIMALS: In exeretion nitrogenous metabolic wastes are released from the body. There are different types of nitrogenous metabolic wastes such as: Ammonia, urea, uric acid, Creatinin etc. AMMONTA (NHs): Ammonia is a toxic gas. Excreting ammonia by an animal is advantageous due to the reason that its diffusion is rapid across the plasma membrane or body surface & also due to the fact that it does not require energy. However, its removal requires a lot of water for its dilution. UREA (COCNH2)2: Urea is relatively less soluble in water & about 100,000 times less toxic than ammonia. Urea is produced in the liver by a metabolic cycle that combines NH3 & CO2. In addition to mammals, most amphibians, sharks & some bony fishes also excrete. URIC ACID (C503 N4Ha): Tt is a relatively large molecule with extremely low solubility in water. Uric acid is excreted by terrestrial animals such as birds, many reptiles, insects, etc. EXCRETION IN HYDRA: In hydra nitrogenous waste is in the form of NH3. Almost all the cells of hydra are in direct contact with water, so NHs is removed by simple diffusion from external surface as well as the internal surface into the external & internal water of gastrovascular cavity. EXCRETION IN PLANARIA: In Planaria the excretory organs are called flame cell or protonephridia. The excretory system of planaria is composed of tubules, therefore it is called tubular excretory system, Mechanism Of Excretion: The flame cells have the direct contact with the tissue fluids, Each flame cell is hollow inside & bears a tuft of cilia, which beat like a flame, water along with ammonia diffuse from the tissue fluid into the lumen of flame cell. The-CLASS: XII BIOLOGY NOTES beating of cilia propels this sol excreted out by excretory pores, n into the excretory canal where it is to be EXCRETION IN EARTHWORM: Earthworms have combined excretory & osmoregulatory organs called metanephridia which are arranged segmentaliy. Structure Of Metanephridia: Each metanephridium is a highly coiled tubule immersed in coelomic fluid & surrounded by a network of capillaries. Its internal opening called nephrostome which lies in the colon while the external openings or nephridiopore opens outside in skin, Working Of Metanephridia Due to the beating of cilia of nephrostome, coelomic fluid is pumped into the excretory tubule. Here selective reabsorption of useful substances also occurs which are taken back by the blood into the circulation. Finally the excretory fluid (urine) is transferred into. the bladder which excretes it outside through nephridiopore, EXCRETION IN COCKROACH: In cockroach, the excretory organs are called malpighian tubules which arise from the junction of midgut & hindgut. Working of malpighian tubules: Cells of malpighian tubules absorb the excretory wastes along with some useful substances present in haemolymph. In the latter part of the tubule, the useful substances are reabsorbed and the uric acid is discharged into the rectum, In the rectum the reabsorption of salts & water takes place & uric acid is released in almost dry form from the body. EXCRETION IN MAN In human body homeostasis is maintained by the following organs. Kidneys: They maintain osmoregulation & eliminate nitrogenous wastes, excess salts & water. Liver: Liver excretes nitrogenous wastes, bile pigments etc Skin It exeretes salts & some other substances along with sweat during perspiration, @LIVER - AN IMPORTANT HOMEOSTATIC ORGAN: 1.Metabolism Of Carbohydrates & Lipids:CLASS: XII BIOLOGY NOTES * It maintains concentration of glucose in the blood. + It removes lipids from the blood cither by oxidation ot by modification & subsequently stored as fat. ‘DSyntlegis Of Important Substances: It can also synthesize non essential aminoacids as well as plasma proteins like prothrombin, globulin, ete, 3.Deamination & Urea_ Formation: The body cannot store excess aminoacid so any excess amino acid is broken down. Deamination takes place in which amino group is released from the amino acids. This amino is converted into urea is orinithine cycle. This urea is released into the stream which carries it to the kidney for its elimination outside the body. 4.Production Of Bile: Bile is a yellowish green alkaline fluid containing bile pigments (such as bilirubin & biliverdin) salts, cholesterol, phospholipids & mucus. Bile salts are involved in the emulsification of fats in small intestine while the bile pigments are excretory products. 5.Detoxification: Liver can modify the structure of many drugs & poison to make them harmless. % 6.Formation Of Cholestrol: Cholesterol is chiefly synthesized in the liver & if it is in excess amount. it is released in bile, 7 7.Thermoregulation: Due to its efficient blood supply, large size & high metabolic rate, liver plays an important role in maintaining body temperature, 8.Storage Of Vitamins: Liver stores a number of vitamins such as A, B, D. URINARY SYSTEM OF MAN The urinary system of man consists of the following part A pair of kidneys A pair of ureter Urinary bladder Urethra KIDNEYS: Locati A pair of kidney is located against the dorsal body wail in a retroperitoneal position in the superior lumber region. The kidneys extend from T12 - L3. The tight kidney is positioned slightly lower than the left.CLASS: XIL BIOLOGY NOTES Shape & Colour: Each kidney is dark red in colour & it is bean shaped. In the concave side there is a notch called hilus. An adult kidney is about 10cm long, 6em wide & 3cm thick. Peritonium: Each kidney is enclosed by a thin membranous covering called peritoneum. Adipose Capsule: - In a living person a fatty mass, the adipose capsule surrounds each kidney. Internal Structure: The kidney is composed of three distinct regions, Renal Corte: This is the outer region which is light in colour. Renal Medulla: Deep in the cortex is a darker reddish brown area, the renal medulla. The medulla has many triangular regions with a striped appearance, the medullary pyramids. The Pyramids are separated by extensions of cortical tissue which are called renal columns. Renal pelvis: On the inner side of medulla is a flat cavity called renal pelvis which continues to the ureter. The extensions of the pelvis are called calyces which form cup shaped areas which enclose the tips of the pyramids & drain it into the pelvis URETERS From the pelvis a narrow tube or ureter arises which brings urine into the urinary bladder.CLASS: Xi es BIOLOGY NOTES URINARY BLADDER & URETHRA Both the wrethras open into a sac like organ which is called urinary bladder, It stores urine for a short period. Then it passes through a narrow duct which is known as urethra. By the help of urethra the urine is discharged out of the body. NEPHRONS Nephrons are the structural & functional unit of kidney. Each kidney consists of about 1 million nephrons. STRUCTURE OF NEPHRON: A nephron is a tubular structure which is composed of following parts. Malpighian body Proximal convoluted tubule Loop of Henle Distal convoluted tubule Collecting duct. 1. Malpighian Body: « Itlies in the cortex of kidney. * It is composed of cup ~ like Bowman's capsule, Inside this cup lies a dense network of capillaries known as glomerulus. 2. Proximal Convoluted Duct: The Bowman's capsule gives out a coiled tubule known as proximal convoluted tubule. It lies in the cortex region. 3. Loop of Henle: The proximal convoluted duct narrows & descends down into the medulla, makes a u-turn & comes back into the cortex. This narrow u-shaped part is called loop of Henle. Distal Convoluted Duct: The ascending limb of loop of Henle becomes larger in diameter in the cortex & forms a coil called distal convoluted duct. 5. Collecting duct: The distal convoluted duct finally opens into a common collecting duct which receives urine from a number of nephrons & drains into the pelvis of the kidney. 6. BLOOD VESSELS OF NEPHRON: Blood supply to the glomerulus of a nephron begins as an afferent arteriole arises from renal artery. From the glomerulus blood is carried by the efferent arteriole to the capillary network. One of the network called peritubular capillaries is associated with proximal & distal convoluted ducts while the other are called vasa recta runs straight parallel beside the limbs of loop of Henle.CLASS: XI -10- BIOLOGY NOTES REGULATORY FUNCTIONS OF KIDNEY. ‘Nephrons are the functional units of kidney & they perform regulatory function. This process is completed in the following stages. * Ultra filtration © Reabsorption * Tubular secretion * Counter Current Exchange ULTRAFILTRATION: * In the I"stage non selective ultra filtration of blood occurs while passing through the glomerulus's of malpighia body. * Two factors are responsible for this ultra filtration. Factor # 1 Both the capillary walls of glomerulus & the walls of Bowman's capsule are sieve like in nature which permit all the molecules except plasma proteins & blood cells to pass through them. Factor # 2 Blood pressure in glomerulus is high because the diameter of efferent arteriole is much less than that of afferent arteriole. Thus # hydrostatic pressure is generated which forces the smailer molecules of blood from glomerulus into the Bowman's capsules. REABSORPTION: * Active reabsorption of the glomerulus filtrate occurs in the proximal convoluted duct, So a large amount of filterate is reabsorbed & returned to circulation. Here glucose, amino acid water, salts are reabsorbed. * Reabsorption of water also occurs when the filterate from the proximal convoluted duct passes into the descending limb is almost impermeable to other solutes. * The ascending limb is impermeable to water. Here reasborption of sodium & chloride ions takes place through active transport. * The distal convoluted duct is slightly hypotonic to the blood plasma. In this region concentration of various salts is adjusted under the influence of hormones. In the collecting duct of nephron water is reabsorbed in the presence of antidiuretic hormon TUBULAR SECRETION: At the level of both proximal as well as distal convoluted ducts, some poisonous substances as well as nitrogenous substances such as ammonia, urea, uric acid creatinine are secreted from the blood directly into the filtrate by active transport.“CLASS: Xi Ms BIOLOGY NOTES COUNTER - CURRENT EXCHANGE: There are two counter current systems operating in the medulla which are involved in the exchange of solutes & water. * One of the counter current is termed as counter current multiplier in the loop of Henle. It is involved in developing the concentration of ions actoss r the medulla, During the passage of isotonic filtrate through the descending limb the reabsorption of water turns the filtrate gradually hypertonic to the tissue fiuid. While in the ascending limb the sodium & chioride ions are actively removed from the filtrate thus reducing the hyper toxicity & tuning it into hypotonic. Due to the hypertonic environment in medulla, almost 90% of water of the filtrate is reabsorbed. © The other counter current system is composed of Vasa recta, the blood vessels that run parallel to the loop of Henle. The blood supply to the vase recta provides sufficient movement & oxygen to the cells of medulla & also takes away the water absorbed from the filtrate. collecting Loop of Henle tubule sco mater serpin = concentrated urine Urine: After the above mentioned processes the filtrate is converted into urine which is transferred in to the collecting duct from where it is bought into the renal pelvis, Composition of Urine: Water = 95% Solid wastes = 5% u COMPONENTS COMOSITION (Concentration / 100cm*) i Water 95.00 Proteins 00.00 Glucose 00.00 Urea 020.00 Creatinine 0.3 -0.70 Ammonia 0.3-0.70 Uric acid 0.3 Sodium 03 Chlorides 0.60 ° [Ca, Mg, K, PO, So} 0.47CLASS: Xil 12. BIOLOGY NOTES pH 5.00 EFFECTS OF HORMONES ON THE WORKING OF KIDNEY: Following types of hormones effect the working of kidney * Antidiuretic hormone or vasopressin. * Aldosterone * Parathyroid hormone ANTIDIURETIC HORMONE: Site of Secretion: Posterior lobe of pituitary gland. Function of ADH: It increases the reabsorption of water in the collecting duct. ALDOSTERONE: Site of Secretion: ‘Adrenal cortex. Function of aldosterone: It increases the reabsorption of sodium ions in the nephron PARATHYROID HORMONE: Site of Secretion: Parathyroid Glands Function of parathyroid hormone: It regulates the concentration of calcium ions in blood. It increases the reabsorption of Ca** in nephrons. KIDNEY PROBLEMS: There are following types of kidney problems. « Kidney stones + Lithotripsy ¢ Renal failure + Dialysis + Kidney transplant KIDNEY STONES (CALCULUS): Kidney stones or calculi are mainly composed of calcium oxalate or phosphate. Oxalate rich food: Tomato, Spinach, Leafy vegetables.CLASS: Xi 13 BIOLOGY NOTES Infective Stones: About 20% of calculi are termed as infective stone. These calculi consist of combination of Ca, Mg NH, (PO4)2. LITHOTRIPSY (TREATMENT OF CALCULI) Lithotripsy is a recent method for removing kidney & uretral stones, Procedure of Lithotripsy: In this process shock waves or ultrasonic waves are used to break up calculi for removal. RENAL FAILURE: It is a condition in which there is a reduction in the ability of the kidneys to filter waste products from the blood & excrete them in urine, Complications due to renal failure: Due to renal failure nitrogenous wastes start accumulating in the blood which leads to the symptoms such as nausea, loss of appetite, vomiting, weakness, breathlessness, high blood pressure etc. In severe cases it leads to coma & death, DIALYSIS Introduction: It is a techniques used to remove waste products from the blood & excess fluids from the body as a treatment for renal failure. : Methods of Dialysis: There are two methods of dialysis. * Haemodialysis * Peritoneal dialysis Haemodialysi: In this dialysis kidney machine or an artificial kidney containing a fluid (the dialysate) is used. During this dialysis the blood from the body is pumped repeatedly through a tube of partially permeable membrane (dialysis membrane) bathed in dialysate. While passing through the dialysis the nitrogenous wastes & excess salts are diffused out from the blood into the dialysate through the dialysis membrane. Thereafter the blood is returned to the circulation, It goes on for 6-10 hrs. EX fo = ma ees fe Ee oeCLASS: XII “14 BIOLOGY NOTES Peritoneal Dialysi This dialysis requires an abdominal incision. Through the incision a catheter is inserted into the peritoneal cavity. Dialysate from a bag attached to the catheter passes into the cavity where it is left for several hours. During this period waste materials from the vessels living to transferred into the dialysate. The fluid is then allowed to drain out through the catheter. The process takes about an hour & it is repeated during the day or night. KIDNEY TRANSPLANT: In young patients, having kidney failure transplantation of a healthy kidney is along term solution, It is a surgical procedure & successful in 80% of the cases. THERMOREGULATION: It is the maintenance of body temperature within a range in at enables the body to function efficiently. The normal temperature range for active life is 10°C to 35°C for most of the organisms, ADAPTATIONS OF PLANTS TO LOW / HIGH TEMPERATURE (BOTANY): LOW TEMPERATURE: The low temperature at the level of freezing point causes in crystals formation in cells. This is avoided by the plants by developing freezing tolerance in which the composition of solutes of cell is altered in a way that ice crystals are formed in the cell wall rather than the cytosol. HIGH TEMPERATURE: igh temperature is more harmful than low temperature since enzymes are denatured. The principal way to cool down the plant in this situation is transpiration. At 40°C or above most of the plant cells synthesize that shock-CLASS: XIl 215: BIOLOGY NOTES proteins that protect enzymes & other proteins from denaturing due to high temperature, Shiny cuticle, small leaf surface area, wilting also provides protection from heat. THERMOREGULATION IN ANIMALS: SOURCES OF BODY HEAT GAIN & HEAT LOSS: HEAT GAIN: There are two methods of heat gain in enimal body. * Externally heat is obtained by solar radiations. * Internally heat is obtained as a by product of metabolism & muscular contraction. POTKTLOTHERMS OR COLD BLOODED ANIMALS OR ECTOTHERMS: Poikilotherms are those animals whose body temperature changes according to the environmental temperature. EXAMPLE: Invertebrates, fishes, amphibian & most reptiles. HOMEOTHERMS OR WARM BLOODED ANIMALS OR ENDOTHERMS Homeotherms are those animals which have a constant body temperature is independent of the environment. EXAMPLES: Mammals, Birds whic! MEANS OF THERMOREGULATION IN ANIMALS: There are two types of thermoregulation, © Behavioural regulation * Physiological regulation BEHAVIOURAL REGULATION: Many animals can increase or decrease heat loss by changing their location. This is a type by behavioural regulation. PHYSTOLOGICAL REGULATION: It is extribited by slight change in the blood circulation pattern change in the rate of metabolism, cooling by evaporative heat loss & activation of certain muscles. THERMOREGULATION IN MAMMALS (MAN): MECHANISM OF THERMOREGULATION IN COLD TEMPERATURE: * Physiological Mechanism * Behavioural MechanismCLASS: Xil =16- BIOLOGY NOTES Physiological Mechanism: A. Non - Shivering Thermogenesis: 1. Erection Of Hair: In furry animals the hair in vertical position can trap a thick layer of stationery air next to the skin. Due to this, heat loss from the skin is reduced, 2.Reduction in blood flow towards skin: In cold temperature the owing of the arteriole or vaso constriction occurs so lesser blood is supplied to the body surface to conserve the body heat. 3.Sub-cutaneous fat accumulation: In mammals fat is stored in adipose tissue below the skin. The fat is a bad conductor of heat so it functions as a chemical insulator. B. Shivering Thermogenesis: In cold temperature shivering begins in the body, which generates heat in muscles. Behavioural Mechanism: Behavioural mechanisms include moving to a warmer place, huddling close together with each other, in humans putting additional clothes, MECHANISM OF THERMOREGULATION IN HOT TEMPERATURE: + Physiological mechanism * Behavioural mechanism Physiological Mechanism * Secretion of sweat from the sweat glands in the skin. *s To promote heat loss vaso-dilation of arterioles of skin occurs. * Reduction of sub cutaneous fat © Loss of heat by breathing. Behavioural Mechanism: Behavioural mechanism means moving to cooler location, use of thin clothes, etc. ROLE OF BRAIN IN TEMPERATURE REGULATION OR THERMOREGULATION: : Hypothalamus is the part of brain which has thermoregulatory centre. It is commonly called the thermostat of the body. The hypothalamus is set at a particular temperature called the set point. Any change in the body temperature below or above the sct point is detected by the hypothalamus & instructions are sent to appropriate organs to bring the body temperature back to normal, FEVER (PYREXIA): Definitior Pyrexia is defined as: “The body temperature above the normal set-point i.e. 37°C or 98.6°F". CAUSES OF PYREXIA: Bacterial infections * Viral infections * Non infectionsASS: BIOLOGY NOTES Chapter 2 SUPP: MOVEMEN’ TS SUPPORT IN PLANTS: There are three types of cells in a plant body: i) Parenchyma il) Collenchyma iif) Selerenchyma (@) PARENCHYMA: ‘These cells are found in epidermis, cortex and pith. These are alive cells with intercellular spaces. STRUCTURE OF A PARENCHYMATOUS CELL: They usually have thin primary wall but no secondary wall. Inside the cell there is a large central- vacuole which is surounded by peripheral layer of eytoplasm. SUPPORT BY A PARENCHYMATOUS CELL: ‘They take in water by endosmosis and become extended. These extended parenchyma are turgid, exert an internal pressure called turgor pressure. Due to the turgor pressure the plant organs remain firm and rigid. (ii) COLLENCHYMA: ‘These cells are found in the hypodermis of a dicot stem, ‘These are also alive cells without intercellular spaces. STRUCTURE OF A COLLENCHYMATOUS CELL: Their cell wall has irregular thickness due to the thickness of wall all the inter-cellular spaces are filled, SUPPORT BY A COLLENCHYMATOUS CELL: Collenchyme functions as an important supporting tissue in young plants. (iii), SCLERENCHYMA: Sclerenchyma are mostly dead cells which lack intercellular spaces. Tracheids and vessels of xylem are composed of sclerenchymatous cells. STRUCTURE OF A SCLERENCHYMATOUS CELL: ‘They have uniformly thick, highly lignified secondary walls. In most of the cases they lack protoplasm,-CLASS: XIL -18- BIOLOGY NOTES SUPPORT BY A SCLERENCHYMATOUS CELL: Sclerenchyma are the main supporting cells in a woody plant. TYPES OF SCLERENCHYMATOUS CELL: 1- FIBERS: Fibers are very elongated cells with tapering ends. They are tough and strong but flexible, Example: Cotton fibers. 2 SCLEREIDS: ‘These are variable often irregular in shape. Example: Simple unbranched sclereids are generally called stone cells which are common in nuts and hard parts of seeds. THE THREE BASIC TYPES OF PLANT TISSUE cell walls with lignin intracellular Parenchyma Tissue Sclerenchyma Tissue Collenchyma Tissue a lengthwise b crass section SECONDARY GROWTH GROWTH: ‘The irreversible increase in the length and the weight of an organism is called growth. GROWTH IN A PLANT BODY: There are two types of growth in a plant body: () Primary growth Gi) Secondary growth @ PRIMARY GRowTH: The increase in the length of a plant due the activity of apical meristem is called primary growth. SECONDARY GROWTH: The increase in the width of stem due to the activity of vascular cambium and cork cambium is known as secondary growth. MECHANISM OF SECONDARY GROWTH: w FOMATION OF CAMBIUM RING:CLASS: XII -19- BIOLOGY NOTES In the dicot stefn vascular cambium is present between xylem and phloem, At the time of Secondary growth strips of meristematic cells are appeared in the medullary rays, These sitips spread laterally and combine with the vascular cambium. These strips of meristematic cells are known as inter fasicular camnbium and the vascular cambium is also known as fasicular cambium, When both of these cambiums are combined a ring of meristematic cells are formed which is known as cambium ring. FORMATION OF SECONDARY TISSUES: ‘The cambium ring starts to form secondary tissues by rapid cells divisions. This ring forms secondary xylem towards the inner side while secondary phloem towards the outer side. The activity of this ring is more rapid towards the inner side therefore a large amount of secondary xylem is formed inside the stem. 1- SECONDARY XYLEM AND SECONDARY PHLOEM: » ‘The secondary xylem is also known as wood, which is composed of following components: 1- ‘Tracheids 2 Vessels 3- Wood parenchyma 4 Wood fibers In contrast to the secondary xylem the secondary phloem consists of following components: I- Sieve tubes 2 Companion cells 3. Bast parenchyma 4- Bast fibers EFFECTS OF THE FORMATION OF SECONDARY XYLEM: ‘As we know that most of the components of secondary xylem are composed of-dead sclerenchyma which is very hard tissue because it contains highly lignified secondary walls. Due to the formation of secondary xylem primary cortex is crushed and the epidermis of the stem is ruptured from various places. These ruptured areas of epidermis are known as lenticels, FORMATION OF CORK CAMBIUM: ‘After the formation of secondary xylem and secondary phloem a ring of meristematic cells also appears in the outer region of primary cortex. This ring is known as Cork cambium (phallogen). This ring of meristematic cells also forms secondary tissues towards inside es well as outside. It forms secondary cortex (Phelloderm) towards the inner side and cork towards the outer side, The secondary cortex overcomes the function of primary cortex and the cork replaces the fumction of epidermis, XYLEM AFTER SECONDARY GROWTH: ‘After the secondary growth two types of xylem or wood can be seen in a dicot stem. i) HEART WOOD: ~ This xylem is unable to transport water and dissolved substances, ii). SAP WOOD: ‘This is the functional xylem inside the dicot stem. ANNUAL RINGS:CLASS: XI -20- BIOLOGY NOTES The plants of temperate regions accumulate secondary xylem in the form of concentric layers which are known as annual rings. Each annual ring consists of two zones. An inner zone of spring-wood and an outer zone of summer-wood. The age of a plant can be calculated by the counting of these rings, Primary Phinem Primery Xylem ‘i Vascular Cembiom Epidermis Cont {AlEary secondary Endodor Tissue devalapment Pericycle Secondary Phloem Secondary Xylem Epidormis, Cortex and Endadermis Boing Shed 1B) New secondary Pesidarm tissues crush the antadissiies primary tissues imary Phioe {0} Paridern places ‘outer aximary protective tissue Vascular Cambium Rays 2 MOVEMENT IN PLANTS Definition: Any action taken by living organs to reduce its irritability produced by stimuli is known as ‘movement. TYPES OF MOVEMENT IN PLANTS: 1- Autonomic or spontaneous movement. 2. Paratonic or induced movement. 7 AUTONOMIC MOVEMENT: Such plant movement which appears due to intemal stimulus is known as autonomic movement, ‘There are three types of autonomic movement: aCLASS: XIL 21 : BIOLOGY NOTES @— Locomotary movement (i) Growth and curvature movement ‘Turgor movement () | LOCOMOTARY MOVEMENT: DEFINITON: Movement of whole plant body or an organ or material within a plant cell from one place to another is called locomotary movement, EXAMPLES: 1- The streaming movement of cytoplasm 2+ Chromosomal movement during cell di 3+ Ciliary movement or movement due to flagella, Gi) GROWTH AND CURVATURE MOVEMENT: ‘The beneficial changes due to the differences in the ratio of growth of different parts are called growth and curvature movement. There are two types of this movement. ()— Nutation (®)Nastic movement @ — NUTATIO The growth in the apex of young stem takes place in zigzag manner due to an alternate change in growth rate an opposite side of the apex. EXAMPLE: movement of climber around any rope. (b) NASTIC MOVEMENT: ‘This movement occurs due to the differences in the rate of growth on two opposite sides of a plant organ. EXAMPLE: opening of the petals. (ii) IURGOR MOVEMENT: ‘This movement appears due to change in the turgidity of cells. EXAMPLE: movement of leaves of Touch-me-not. PARATONIC MOVEMENT: Those plant movements which appear due to the external stimuli are known as paratonic movement ‘There are two important types of these movements: (Tropic movement (i) Nastic movementCLASS: Xl 2. BIOLOGY NOTES @ TROPIC MOVEMENT OR TROPISM: Tropic movements are growth responses in which plant organs move in particular directions. ‘There are following types of tropism. (a) PHOTOTROPISM: ‘The tropic movement due to the stimulus of light is called phototropism. EXAMPLES: The upward movement of shoots towards the light is called positive phototropism and downward movement of roots away from light is called negative phototropism, (0) GEOTROPISM: The tropic movement due to the stimulus of gravity is known as geotropism. EXAMPLE: The downward movement of root towards the gravity is called geotropism and the upward movement of shoot away from gravity is called negative geotropism the growth of secondary and tertiary roots is called transversal geotropism. (© CHEMOTROPISM: The tropic movement due to the stimulus of certain chemicals is known as chemotropism, EXAMPLE: The growth of pollen tube towards the ovary. (a) HYDROTROPISM: The tropic movement due to the stimulus of water is called hydrotropism. EXAMPLE: Roots are positively hydratropic, © THIGMOTROPISM: The tropic movement due to the stimulus of touch is called thigmotropism. EXAMPLE: The coiling ofa tendril around a rope. NASTIC MOVEMENT: 5 ‘Those plant movements which appear due to the diffused stimuli in which there is no particular direction of movement are called nastic movement. There are two important types of nastic movement. (a) PHOTONASTIC: ‘The nastic movement caused by light is known as photonastic. EXAMPLE: The flowers of Oxalis and Protulaca open in day and close at night while flowers of Nicotiana close in day and open at night. ()) HAPTONASTIC: Haptonastic movements are caused due to the stimuli of touch. EXAMPLE: These movements are found in insectivorous plants. aa UPPOR’ MOVE) INA Ss SUPPOR. In an animal body the support is provided by the skeleton, which is tough and rigid frame work which provides protection, shape and support to the body organ. It is composed of inorganic or organic substances or both. MAJOR FUNCTIONS OF SKELETAL SYSTEM: (1) SUPPORT AND SHAPE:CLASS: Xi 23 BIOLOGY NOTES Bones support soft tissues and serve as attachment sites for most muscles and provide shape to the body. (2) PROTECTION: Bones protect the inner sensitive organs of the body such as skull protects brain, spinal cord is protected by vertebral column, lungs and heart are protected by rib-cage. (3) MOVEMENT: The elements (bones) of skeleton system act as lever during the movement. (4) MINERAL HOMEOSTASIS: Bones keep calcium, phosphorous, sodium and potassium. Through negative feed back mechanisms, bones can release or take up minerals to maintain homeostasis, (3) BLOOD CELL PRODUCTION: Red blood corpuscles, white blood corpuscles and platelets are produced in bone marrow, which is a connective tissue found with in certain bones. TYPES OF SKELETON Le HYDROSTA: TIC SKELETON: In animals that lack a hard skeleton a fluid filled gastro vascular cavity or coelom ccan act as hydrostatic skeleton. It is found in cnidarians, annelids and other soft-bodied invertebrates. Example: Sea anemone, earthworm etc. ot ‘EXOSKELETON: The skeleton, which is fouhd outside the body of an animal, is called exoskeleton. Ttis inert and non-living. Examples: - PROTOZOANS: - Radiolarian (silica) Foraminifera (Limy shell) MOLLUSCS: - —_Limy shell CRUSTACEANS: - Chitinous YexosKELETON OF ARTROPODS: ‘The arthropods have highly complex exoskeleton, This skeleton has variety of adaptations. ‘The invagination of exoskeleton forms firms ridges and bars for muscle for attachment. ‘This skeleton is thin, soft and flexible at joints, ‘This skeleton has sensory receptors called sensilla, It permits gaseous exchange, | fecovsts or MOULTING: ‘The shedding of the old skeleton at the different stages of growth and a new one is formed. This process is known as ecdysis. ENDOSKELETON:CLASS: XI 24. BIOLOGY NOTES 1) The skeleton, which is found inside the body of an animal, is called endoskeleton, 2) This skeleton is composed of bones, cartilage or both. Both bones and cartilage are rigid connective tissue, which are consisting of living cells embedded in the matrix of protein called collagen. INE: ‘ 1) Its the most rigid form of connective tissue. 2) _ Thecollagen fibres of bones are hardened by the deposition of | Calcium phosphate. 3) __ The long bones consist of an outer shell of compact bone, with spongy bone in the interior. 4) The outer compact shell provides an attachment site for muscle. The spongy bone is light, rich in blood vessels and highly porous. 5) The cavity of spongy bone contains bone marrow where biood cells are formed, 6) There are three types of cells associated with bones. i) Bone forming cell (osteoblast) i) Mature bone cell (osteocytes) Dissolving cells of bones (osteoclast) J CARTILAGE: 1) Itis much softer than bones because the collagen fibres do not contain calcium phosphate, 2) It is found at the articulating surface of bones and also found in flexible portions of nose and extemal ear (Pinna), ~ 3) The living cells of cartilage are called chondrocytes. 4) There is no blood vessels penetrate into the cartilage, 5) There are two types of cartilage. () _-HYALINE CARTILAGE: Itis the most abundant type in human body. It is found at the moveable joints. (iii) FIBRO CARTILAGE: Ithas matrix-containing bundles of collagen fibres. It forms an extemal pinnae of ears and in the epiglottis. : HUMAN SKELETONBIOLOGY NOTES Human Skeleton Mania thandiole Vortebras scapula nt | eae + Pats Sacrum carpal wat Pratarigos: Femur Pat ‘Tarvals: Motatarsate Phalages: Human skeleton is composed of 206 bones and it is divided into two parts. 1) Axial skeleton 2) Appendicular skeleton J AXIAL SKELETON: Ttis composed of: ‘Skull 7 Nertebral column 3 Ribs and sternum (SKULL: Itis made up of Cranium and Facial bone. Cranium Bones: These bons form the brain box. There ae following eight cranium bones * Frontal, © Parietal (paired bone). * Temporal (paired bone). © Occipital. * Sphenoid, + Ethmoid, Facial Bones:- There are ten facial bones which form the front part of face. Maxilla,, Palatine, Zygomatic. Lactimal, ‘Nasal, Vomer (unpaired bone). Inferior Conchae. Mandible (unpaired bone). ADAMJEE COACHING CENTRECLASS: XIL -26- BIOLOGY NOTES rt tie tod ie etree (raat ene (ii) VERTEBRAL COLUMN: * It is extended éom skull to the pelvis to form backbone, which protects the spinal cord. © Itis composed of 33 bones (vertebrae), but after fusion there are 26 bones. (iii) RIB CAGE: It is composed of 12 pairs of ribs that articulate thoracic vertebrae, Ten of them connect anteriorly with sternum. The lower two pairs of ribs are called “floating ribs”, because they do not attach with the stemum. (2) APPENDUCULAR SKELETON: “Tis composed of pectorial girdle, pelvic girdle and limb bones. UG) Pectoral girdle: A pair of pectoral girdles, at shoulder, holds the arms to the axial skeleton. Each pectoral girdle Consists of a Scapula and a Clavicle. Pelvie girdle: The pelvic girdles serve fo attach the leg with the vertebral column at hip region. ingle called Innominate bone, which is composed of Ilium, Ischium and Pubis. Fore limb: ~ © It consists of 1 humerus, 2 radius and ulna, 8 capals, 5 metucarpals and 14 phalanges. (iv), find limbs: ‘Thehind limb consist of femur, 1 Patella, 2 tibia and fibula, 7 tarsals, 5 metatarsals and 14 phalanges en TS The regions of skeleton where two or more bones meet together are called joints.CLASS: Xl -27- BIOLOGY NOTES. ciassirrca TION OF JOINTS (1)~{ON THE BASIS OF MOVEMENT: IMMOVEABLE JOINT! They do not allow any movement e, i) PARTIALLY MOVEABLE JOINT! They allow a little movement e.g. joints b/w ribs & vertebrae, ily“ FREELY MOVEABLE JOINTS: - They allow movement, joints in skull. a) Hinge joint: - It allows movement in one plane e.g. elbows and knee joint. b) Ball and socket joint: - It allows movement in many planes e.g shoulder and hip joint. ¢) Pivot joint; - It allows a twisting movement e.g. itis present in elbow. 4) Sliding joint: - in this type of joint bones slide over another e.g. joints in ankle and wrist ©) Gliding jojat: - By this joint bones move easily over one another e.g. joint b/w the vertebrae. ON THE BASIS OF STRUCTURE: i) Fibrous joints: - These joints are held together by short fibres embedded in connective tissue such joints are present in the skull which fix teeth into jaws. ii) Cartilaginous Joints: The bones held together by fibrous cartilage. e.g, joints in vertebrae. iil) Synovial joints: These joints contain a cavity filled with fluid and ere adapted to reduce friction between the moving bones. This joint is surrounded by a layer of connective tissue called fibrous capsule. Inside the eapsule a membrane is present which is called synovial membrane. This membrane secretes a fluid called synovial fluid which acts as a lubricant and a buffer solution some parts of capsule may be modified to form distinct alignment, which held the bone together.CLASS: XI -28- BIOLOGY NOTES DEFORMITIES OF SKELETON ) GENETIC DISORDERS: i) Cleft palate (Hare lip) it) Microcephaly (Small head) iii) Arthritis or Osteoarthritis ® HORMONAL DISORDERS: Osteoporosis: ‘This disorder is found in elderly women because level of their estrogen secretion falls, Complication: Due to the deficiency of estrogen the bones become porous, thin and week, consequently easily breakable,-CLASS: XI -29 _BIOLOGY NOTES Bones ovieoporess Closeup vow (ONAL DEFIC The curving of bones in children due to the deficiency of vitamin D or calcium, 7 DISC SLIP: Introduction: 1) The vertebrae of our body are provided with intervertebral disc which act as shock absorber. 2) Ifdue to a physical trauma the cartilaginous ring of a disc ruptures and displaces, it 7 is called a dise slip. Complication: This protrusion presses upon the spinal nerve between the vertebrae causing severe pain and inability to move. Treatment: Prolong rest on a hard bed and use of painkillers help repair the damage, ® SPONDYLOSIS: Introduction: 5 Spondylosis is a deformity of the joints of two vertebrae particularly of the ‘This result in pressing upon the nerves emerging from the spinal cord and result in severe pain in neck, shoulders and upper limb ete, Treatment: ‘The pain is relieved by wearing a hard coller around the neck. | ADAMJEE COACHING CENTRE |-CLASS: XII -30- BIOLOGY NOTES Examples of Disc Problems Normat Dise ARTHRITIS: Introduction: Itis a condition in which a joint becomes swollen, painful and immovable. ‘Causes: It may be hereditary may be due to a viral infection or due to an injury or some time only due to aging. Complication: The joint become very stiff and hard to move, and the person becomes crippled. Treatment: The only remedy is replacement of the affected joints by artificial joints made up of rubber and plastic. Introduction:ee | CLASS: Xil a3 BIOLOGY NOTES a It is the severe pain of the hind limb, which occurs when a nerve of the sciatica plexus is being pressed. EH i Causes: It may be due to disc slip in the lower abdomen, a trauma or due to a damage to branch of sciatic nerve by the needle of a syringe. Complication: It makes the leg highly painful and virtually immovable. Recovery is very slow and often not complete. Sciatica pe RL iepeaerenae Ny Cis pore ot — REPAIR OF A BROKEN BONE f Fractured bone: f Bones are living tissue and whenever broken, start healing like any other damaged f tissue of the body does. A broken bone is said to be a fractured bone. Treatment of a fractured bone: ‘After a fracture the bone is made immovable for a few weeks by wrapping the affected area into a plaster (i.e, a cast of plaster of Paris), re ADAMJEE COACHING CENTRE5: XI 32 BIOLOGY NOTES MUSCULAR SYSTEM: Smooth Cardiae Skeletal Muscles | yng Mai 1) Onsmooth | 1) Cardiac muscles a oe muscles bands have light & are absent. dark band. 2) They are “They are 2) They are i cutieaneedt ances ee 3) Their nucleusis | 3) Their mucleus is | 3) Their nucleus is present in present in the |” present in the peripheral region centre. centre. iY Muscle fibres are | 4) They are spindle | 4) They are PS vlindral & shape and | cylindrical and unbranched. unbranched. | _ branched. 3) They are 3) They are see cee involuntary in |” involuntary in action. action. ; © These muscles ese muscles are | are present in 6) These muscles : present on the the alimentary | are present in skeleton. canal and blood | the Heart. \ MUSCLES: 1) The muscles that are attached bones are called skeletal muscles, 2) These muscles are voluntary in action. 3) They have light and dark bands so called striated muscles, 4) They muscles are attached to bone by a bundle of collagen, Non-elastic fibres known as tendons. 5) Onthe basis of tendons there are two types of Skeletal muscles. the skeleton & associated with the movement of i) Bieep: . ‘Those muscles, which are connected with the bone by the help of two tendons, Example: - Flexor . fi) Tricep:CLASS: Xi 3h BIOLOGY NOTES: ‘Those muscles, which are connected with the bone by the help of three tendons. Example: - Extensor 6) Fach muscle is an elongated mass of million of fibres called muscle fibres. 7) All the muscle fibres are surrounded by tough smooth connected tissue, 8) The end of the muscle that remains relatively fixed when muscle contracts is called origin, the end that moves is called insertion. Thick part between the two ends is called the belly. SKELETAL MUSCLE FIBRE 1) Each muscle consists ofa large number of muscle fibres or cells. 2) Each muscle fibre is long cylindrical cell with multiple oval nuclei, which are arranged in periphery. 3) Skeletal muscle fibre is large cells their diameter is 10- 100 jum. 4) Sarcolemm: The cell membrane of a muscle fibre is called sarcolemma, 5) Sarcoplasm: The cytoplasm of a muscle fibre is called sarcoplasm. Which contains large amount of stored glycogen and have unique oxygen-binding protein called myoglobin (a red pigment that stores oxygen). 6) Myofibrits: Tn the sarcoplasm there are large numbers of protein filaments, which are arranged parallel to each other, these filaments are called myofibrils. The diameter of each myofibril is about 1-2 um. 7) Light and dark band: ‘On a myofibril light and dark areas are present alternately. The light bend are called I bband, white the dark band are called A band. 8) H=line: Each A-band has a lighter stripe called H-line, %) ine: ‘The T-band has a dark line in the middle region called Z-line. 10) Sarcomere: The region of a myofibril between two Z-lines is called sarcomere and itis the smallest contractile unit of muscles fibres, MYOFILAMENTS: ‘The myofibril contains two types of protein filaments called myofilaments. ULTRA STRUCTURE OF MYOFILAMENT i) 2 3) 4) Myofilament is made up of thick and thin filament, ‘I'he central thick filament extend the entire length of the A-band the thin filaments extend across the I-band and partly into A-band. ‘The thick filament which is about 1énm in diameter is composed of myosin protein, ‘The thin filaments are 7-8 nm thick and composed of chiefly actin molecules. Cross Bridges: The region where myosin and actin filaments fixed together during muscle contractile are called cross bridges.CLASS: XI 34. BIOLOGY NOTES SLIDING FILAMENT MODEL: 1) When muscle fibre contracts the thin and thick filaments undergo shifting. ‘The I-band reduces in length and Z-line get closer. 2) H. Huxley and A.F. Huxley suggested a hypothesis in 1954 to explain all events in muscle contraction this is called “Sliding filament model” of muscle contraction. 3) According to this concept the thin filaments slide over the thick filaments, in this way actin and myosin filaments overlap to greater degree, 4) Thus the Z-line is brought closer together, I- band shortens and H-line disappears. 5) In this process actin and myosin proteins are attached to form actinomyosin, Relaxed sarcomere c= = (Zine) (eases clin 7 actin myosin Gross-bridge forms between filaments Power stroke: fe filaments slide p 7 eachother © Cross-bridge is broken rd Another cross-bridge forms Another power stroke (toward * center of sarcomere) ENERGY REQUIRED FOR MUSCLE CONTROL 1) Energy requires for muscle contraction comes from the ATP supply of mitochondria. 2) ATP is maintained by the aerobic break down of glucose in muscle cells, which comes from stored glycogen in the cell. 3) When more energy is required due to high metabolism, it is provided by another energy storing substance called creatin phosphate. 4) Sometimes oxygen deficiency or very high metabolism, ATP are produced by anaerobic breakdown of glucose into lactic acid and lactic acid accumulation cause muscle fatigue. Muscle Fatigue: Muscle fatigue is a state of physiological inability to contract, Muscle fatigue results due to the accumulation of lactic acid in the muscle, which is formed by the enaerobie breakdown| CLASS: XIL -35- BIOLOGY NOTES. of glucose. Accumulation of lactic acid causes muscle pH to drop, so the muscle is unable to contract fora while. ABNORMAL MUSCLE CONTRACTION: @) Tetany: Tetany is a sudden involuntary contraction of striated muscle, which is caused by ow level of calcium in the blood. : | Hence the muscle fibres are held under a constant contraction, 3 Tetany of the respiratory organs if not treated immediately may prove fatal, Q) Cramps: Tis also a type of tetanic contraction, which is commonly called a muscle pull. It is usually occurs in a limbs muscles. It occurs due to dehydration, electrolyte imbalance or ‘low blood sugar level 4 ANTAGONISTIC MUSCLES: Definition: (i) Skeleton muscles work in pairs, with one muscle working against the other. Such a set of D 2) 3) } muscles is called antagonistic muscles, Example: Moves the limb forward. Moves the limb backward. ‘Abductor: Moves the limb away from the body. Adductor: Moves the limb towards the body Rotator Muscles: Help the limb to rotate in all the directions even in a circle, Flexor: Two parts of limb become closer. Extensor: Two parts of limb move away. LOCOMOTION IN PROTOZOA: (@) Locomotion IN EuGLENA: Locomotory Organs: Euglena moves with the help of flagellum, Mechanism of Locomotion: Flagellum is at its anterior end of the body and pulls the organism forward, As the flagellum is whipped backward the organism moves forward. Euglena is able to change its direction by the active contractile myonemes which run along the length of its body. When they contract the shape of the body is changed as well as its direction, Euglenoid Movement: First, body becomes short and wider at the anterior end then in the middle and later at the posterior end, ‘This movement is called Euglenoid movement. LOcoMOTION In PARAMECIUM: Locomotory Organs: Paramecium moves with the help of cilia, this movement is also called ciliary ‘movernent,CLASS: XIL -36- BIOLOGY NOTES Gil) Cilia: 1) Cilia are short, fine thread-like extension of the cell membrane. The length of cilia ranges from many microns to many hundred microns and the diameter varies in from 0.1 -05p. 2) A cilium consists of nine peripheral double fibrils giving the appearance of 8 shaped figure and two central small fibrils. All these fibrils run longitudinally through the cilium these are covered with the extension of membrane. Mechanism of Locomotio: Al the cilia do not move simultaneously, a branch of cilia move in a progressive wave ~ like manner at a time, The wave starts at the anterior end and progresses in the backward. Locomotion is brought about by alternate power strokes or effective strokes and recovery strokes. A powerful backward stroke of hundreds of cilia pushes the body forward. LOCOMOTION IN AMOEBA: Locomotory Organ: ‘The amoeba is a unicellular organism and has no special organs of locomotion, $0 Jocomotion is carried by Pseudopodia. Mechanism of Locomotio) During locomotion a blunt pscudopodium is formed in the direction of movement. Simultaneously the pseudopodia on the opposite side are withdrawn. This type of locomotion is called pseudopodia locomotion. SOL - GEL THEORY: Introduction: This theory was formed by Hymen (1917) and later supported by Mast (1927). This theory explains the mechanism of the formation of a pseudopodium. Explanation: According to Mast the body of Amoeba is differentiated into three parts. () A thin and elastic plasma lemma, Gi)_An outer non ~ granular ectoplastn,CLASS: Xii 37 BIOLOGY NOTES (iii), Inner granular endoplasm: The endoplasm is furtier differentiated into an outer jelly like PLASMAGEL and inner more fluidly PLASMASOL. (1) According to this theory the formation of pseudopodium is based upon spontaneous reversible sol - gel phenomenon. 2) In this process first the plasma gel is changed into sol, so the inner protoplasm : flows into this sol, which applies a pressure on plasmolemma to form a pseudopodium. After the formation of pscudopodium the sol is again converted into plasma gel. Plasmagel Plasmasol Plasma membrane LOCOMOTION IN ANIMALS * LOCOMOTION IN EARTHWORM: ‘ SKELETON: The earthworm has hydrostatic skeleton, in which the coelomic fluid exerts 2 pressure on the body wall. : MUSCLES: Two sels of muscles are found in earthworm which are known as circular muscles and longitudinal muscles. LOCOMOTORY ORGANS: There are numerous bristles on the ventral surface on the body ‘which acts as the locomotory organs. These organs are known as Setae. MECHANISM OF LOCOMOTION: ‘© The anterior half of the animal becomes thin and elongated due to the contraction of circular muscles. Then its mouth is attached on the soil which acts as a sucker and firmly grasps the soil. * Then the setae of this region protrude out by the contraction of protractor muscles, these setae firmly grip the soil. L + Now the posterior half of the body contracts due to the longitudinal muscles. Then the setae of this region are protruded out to take firm grip of the soil. ‘+ When the posterior half is completed anchored, the mouth and the setae of the anterior half are withdrawn and the animal begins to elongate moving forward.CLASS: XiL 238. BIOLOGY NOTES Movement Longitudionat muxcle —| contructed * LOCOMOTION IN JELLY FIs) ‘STRUCTURE: The jelly fish bas an umbrella-shaped body which has a mouth at the anterior ‘end which opens into 2 cavity, known as gastrovascular cavity. MECHANISN: It swims by the contraction of its muscle cells forcing the water powerfully out of its mouth and umbrella to create a jet propulsion effect. “* LOCOMOTION IN SNAIL: SKELETON: The snail hes an hydrostatic skeleton, LOCOMOTORY ORGAN: Like other molluscs the snail also has a muscular foot for locomotion. : ‘MECHANISM OF LOCOMTOION: Snail moves by the contractions of muscles inside the foot. These contractions are brought about under the influence of hydrostatic pressure of the body fluid. The waves of muscle contraction from the anterior towards the posterior end of the body push the animal forward. ‘+ LOCOMOTION IN STAR FISH: SKELETON: The star fish has an exoskeleton in the form of spines on the skin. LOCOMOTORY ORGANS: The locomotory organs of star fish are called muscular Tube Feet, The upper part of tube foot is a bulb shaped Ampulla, whereas its bottom part is a Sucker. All the tube feet are connected with the water vascular system, MECHANISM OF LOCOMOTION: ‘+ When ampulae contract water forces the tube feet to lengthen and suckers become attached to an object. When sucker muscles contract the water is pushed back into the ampulae, making the tube fect flaccid, losing the grip and the star fish is pulled forward, madreporite ampullae ** LOCOMOTION IN COCKROAC!CLASS: XI BIOLOGY NOTES SKELETON: The cockroach has an exoskeleton which is made up of chitin. MUSCLES: Inside the exoskeleton striated imuscles are present and the locomotion is brought about by the interaction of muscular and exoskeletal system, MECHANISM OF LOCOMOTION: ‘+ The cockroach has antagonistic muscles which work in opposition to one another. Contraction of these flexor and extensor muscles move the appendages and the animal, -ADAMJEE COACHING CENTRECLASS: XI ~40- BIOLOGY NOTES Raa COORDINATI || CONTROL CONTROL IN PLANTS CONTROL THROUGH PLANT HORMONES: The plants respond to a variety of stimuli like animals some of their parts having special tissues which produce special chemicals for control mechanism and also function as coordination chemicals. These chemical messages are called hormones. The plant hormones are also called phytohomones or growth regulators. The first phytohomone was discovered by fret went in 1926 while studying the phenomenon of phototropism in oat coleoptile. He used the name of “Auxin (to increase)” for this hormone. MECHANISM OF CONTROL AND COORDINATION IN PLANTS: The plant hormones control and coordinate the plant responses in two ways. + By shaving movement and regulating various metabolic functions. * By controlling and initiating growth at various regions of plants. BIOLOGICAL CLOCK & CIRCADIAN RHYTHMS: + Living organisms when repeat their biological or behavioral activities at regular intervals, this behavior is called biological rhythms or biorhythms * The rhythmic movement of plant is not only controlled by light intensity and temperature changes but due to an independent time measuring system called biological clock. * When biorhythms occur with @ frequency of about 24° hrs then they are called circadian rhythms e.g. a bean plant will continue its sleep movement even if kept in constant light or darkness. PHOTOPERIODISM: The response of plants to relative length of the day and night is called photoperiodism. RESPONSES TO ENVIRONMENTAL STRESSES: Changes in environmental conditions are the big threats for living organisms especially for plants. These factors which change the normal condition of light, COz, nutrients, temperature, etc. cause severe stresses on plants. The common environmental stresses for plants are. 1. WATER SHORTAGE: In dry condition, the guard cells of leaf become flaccid to close the stomata. In this way the transpiration is stopped. The dry condition also stimulates increased synthesis and release of abscisic acid. This hormone helps in keeping stomata close. These plants produce deeper root system.CLASS: Xi} Ale BIOLOGY NOTES 2, OXYGEN DEFFICIENC Those plants which grow in wet habitat or marshes, they develop aerial roots to absorb oxygen. 3. SALT STRESS: The plants especially halophytes have salt glands in their leaves where desalination occurs. Those plants which grow in saline soil are called halophyte. |. HEAT STRES: In plants there are two methods to tolerate the heat stress: + Transpiration has 2 cooling effect on the plant body. By this method the effects of heat are reduced. * About 40°C plant cell start synthesizing relatively lerge quantities of special proteins called heat shock proteins. §. COLD STRESS: * Plants respond to cold stress by altering the lipid composition of membrane. + In freezing condition, changes in solute composition of cell also occurs by producing different polymers of fructose (fructans) which allow the cytosol to super cool without ice formation, RESPONES TO HERBIVORY: Plants overcome excessive herbivory by developing forms and production of distasteful or toxic compounds. PLANT HORMONES (PHYTOHORMONE) Phytohomones are synthesized by plants in minute concentration and exert their effect by alteringing gene expression or inhibiting enzymes or changing properties of membrane. TYPES OF PHYTOHORMONES. There are five types of phytohomones Auxins Gibberellins Cytokinins Abscisic acid Ethene AUXINS: Discovery: The first auxin was discovered by fret went in 1926 in Oat coleoptile, Chemical nature: * Indol acetic acid (IAA) © Indol butyric acid (IBA) © Naphthalene acetic acid (NAA) Site of Synthesis:CLASS: XIL 42 BIOLOGY NOTES It is synthesized at the apices of stem and root, young leaves and young embryo. Role of Auxi Cell division and cell elongation. It stimulates cell division and cell enlargement and bring about increase in length of plant. Initiation of Roots: Auxin also initiates development of adventitious roots when applied at the cut base of stem. Abscission: In nature leaves and fruits when auxin production diminishes, a layer of thin walled cells is formed at the base of petiole and stalk of fruit, This layer is called abscission layer and causes fall of leaves and fruit with slight jerk. Growth of Fruit: ‘Auxin produced in young embryo promotes he growth of fruit. Parthenocarpv: Use of auxin helps in producing parthenocarpic or seedless fruits. Apical Dominance: Besides growth promoting function, auxin also has inhibitory effect on growth. Growth of apical bud inhibits growth of lateral buds beneath the stem This phenomenon is termed as apical dominance, removal of apical buds initiates growth of lateral buds with more leaves and axillary bud. Weedicide Auxins are selective weed killer. 2-4 dichlorophenoxyacetic acid (2-4-D) is used to kill weeds in lawns & cereal crops. 2. GIBBERELLIN, covery: Gibberellins was discovered by T. Yabuta & T. Hayashi in a fungus called Gibberella fujikuroi. This fungus causes foolish seeding (Bakannae) disease in rice. In this disease the infected rice seedlings elongated and ultimately fall over without producing gains. Chemical Nature: The chemical nature of Gibberellins is Gibberellic acid. 70 types of gibberellins have been discovered.CLASS: XII AR BIOLOGY NOTES Role of Gibberellin: Cell division and cell elongation: Like auxin Gibberellin also promotes cell division and cell elongation. Control of dwarfism: Gibberellins can control genetic and physiological dwarfism in plants. Seed Germination: They promote the synthesis of a-amylase enzyme is dormant seeds due to the production of this enzyme, the seed starts to germinate. Parthenocarpy: These hormones help in the formation of seedless fruits which are called pathenocarpic fruits. Increase of crop vield: ‘The crop yield of sugar cane can be increased by the application of gibberellin about 50 tons / acre Formation of flower and growth of pollen tube They stimulate flowering and the growth of pollen tubes during fertilization. 3. CYTOKININS: Discovery: ~ Cytokinins was discovered by Miller in coconut milk. Chemical nature: Chemically there are two types of cytokinins + Kinetin: "It is a synthetic cytokinin. « Zeatin: It is found in maize grain, Role of Cytokinins: Cell Division: They initiate rapid cell division only in the presence of auxin. Delay in Senescence: They also cause delayed senescence Breaking of Seed Dormancy: They break seed dormancy and promote fruit development in some species. 4. ABSCISIC ACID (apa): In contrast to growth promoting hormones abscisic acid is growth inhibitor produced by plants during adverse environmental conditions such as drought condition, Role of abscisic acid: ‘* It increases dormancy in buds & seeds. * It causes stomata to close. + It turns leaf primordia into scales, 5. ETHENE:-CLASS: XII Eto BIOLOGY NOTES It is a gas which also acts as a growth inhibitor. R of ethene: «It triggers ripening of fruits. + It contributes in leaf abscission & also breaks the dormancy of seeds & buds 7 * It also initiates flowering in plants e.g. pineapple. ZOOLOGY ORD) TI Ci OL IN S NERVOUS COORDINATION: Nervous coordination is brought about by means of nervous system, In this method communication takes place by electrochemical messages called nerve impulses. RECEPTORS: ‘Neurones receive information about any change in external or internal environment of the body through sensory cells on organs called receptors for e.g. skin. EFFECTOR: . The organs, tissues or cells of the body which translate the message of central nervous system into an action are called effectors e.g. muscles. Nervous system Iceni neraT| CNS PNS Central nervous system Peripheral nervous system eg. Brain + spinal cord e.g. Nerves. Information > Receptors > Sensory neuron > CNS > Motor neuron > effectors > action URO. A neuron is a special kind of animal cell, which can generates and conduct electric current. STRUCTURE OF NEURON: ‘A neuron is composed of following parts: . Soma or cell body * Dendrites * Axon Soma or Cell Body:-CLASS: XiL AS BIOLOGY NOTES * The soma or cell body contains cytoplasm & nucleus. * In addition to typical cell organelles it contains Niss! substances which consist of ribosomes Dendrites: * From the soma, arise a number of thread-like processes, the dendrites which receive stimuli and convey them to the soma, Axon: ‘Axon is a long cytoplasmic process which usually arises opposite to dendrites. It ends in knob like structures which are called axon terminals. The axons of some neurons are covered by a myelin sheath, NEURQ Denarites _-< ‘Axon Tarminals.(Fecelvers}f (tramertttars) ‘Schwann's Colts (they make the myelin) Node ot ‘Axon (tha conducting Myelin Sheath ber) (insulating fatty layer that speecs tranemiscion) TYPES OF NEURONS: There are three types of neurons. + Sensory neurons * Motor neurons + Inter neurons Sensory Neurons: It carries sensory information from recepior to the other neurons or directly to CNS. Motor Neuron Tt takes commands of the control centre (CNS) to the effectors. Inter Neurons: It is found in central neurons system,-CLASS: XII AG. BIOLOGY NOTES FUNCTION OF NEURON: A neuron is the functional unit of nervous system. It is induced in communication by receiving stimuli, integrating various stimuli and sending appropriate instructions to some of the effector organs. NEUROGLIA (GLIAL CELLS): ‘Neurons in CNS are associated with other types of cells called neuroglia, Functions Of Neuroglia: © Seperation of neurons from one another. * They also perform the phagocytic function. * They synthesize myelin, ‘Neuroglial Cells of the CNS Astrocyte NERVE IMPULSE The electrochemical signal developed by # neuron for communication is called nerve impulse. DEVELOPMENT OF NERVE IMPULSE: Most of the neurons develop an impulse in the following way. Resting membrane potential (RMP) Propagation of impulse Synapse. Action potentialCLASS: Xi Te BIOLOGY NOTES Resting membrane potential (RMP) Tt was first studied in squids that unstimuleted inactive neurolemma (plasma membrane of neuron) maintains a charge of -65mv (variable b/w - 40mv - 90 my). This electrical potential is called resting membrane potential Action potential: Tt is @ temporary & focal reversal of the polarity of the neurolemma which arises when neruolemma is stimulated. During the action potential the polarity of neurolemma first changes to +40 my (i.e. depolarization and then restores to -65 my again (i.e. repolarization) Propagation of impulse: The action potential developed locally spreads along the entire neurolemma is called propagation of nerve impulse. Synapse: The region where the impulse moves from one neuron to another is called synapse. It consists of three components + Presynaptic membrane * Synaptic cleft * Post synaptic membrane Pre-synaptic membrane: It is found at the axon terminal. Synaptic Cleft: It is a narrow space b/w the pre & post synaptic membrane Postsynaptic membrane: It is found in the dendrites of the other neuron. Neurotransmitter: Those chemicals which transfer the nerve impulse from one neuron to the other Axon neuron are called neurotransmitters. e.g. acetylcholine, nonepinephrine, glycine, gaba, serotonin, dopamine, etc. REFLEX ACTION Reflex actions are automatic, involuntary responses which occur cither due to internal or external stimuli e.g. hand withdrawal in a painful stimulus, knee jerk, blinking of eyes, ete MECHANISM OF REFLEX ACTION: ‘A reflex involves usually two neurons, a sensory and a motor neuron, The pathway of such transmission is called reflex arc. In this case, since only one synapse is involved so such reflex is called monosynaptic EVOLUTION OF NERVOUS SYSTEM: * Diffused nervous system + Centralized nervous system DIFFUSED NERVOUS SYSTEM: This is found in Cnidarians and echinoderms. In hydra & other Cnidarians because of the radial symmetry, there are no anterior and posterior ends. The-CLASS: XII ~48- BIOLOGY NOTES nervous system consists of a network which is woven through the tissues of the body, The flow of information through the network (nerve het) is in diffused form. CENTRALIZED NERVOUS SYSTEM: It is the characteristic of bilaterally symmetrical animals which have definite anterior and posterior ends. For example planaria is a simple animal which has the simplest form of centralized nervous system. It consists of an anterior part from which is connected with the sensory organs from the brain of planaria to cord like nerves running longitudinally through the body. HUMAN NERVOUS SYSTEM The human nervous system is of centralized type, It can be divided into following components. * Central Nervous System (CNS) «Peripheral Nervous System (PNS) CENTRAL NERVOUS SYSTEM: The CNS consists of a brain and a spinal cord. Both brain and spinal cord are protected by bony structures, the skull and the vertebral column respectively. Both brain and spinal cord are also enclosed inside a tough connective tissue cover called meninges. A plasma like fluid the cerebro spinal fluid (CSF) bathing i je the meninges. eo oitectory mentor : ‘expat ne 2 ioe . ‘gland 79 There are three parts of brain: © Fore brain © Mid brain © Hind breinCLASS: Xil -49- BIOLOGY NOTES 1. FORE BRAIN: The fore brain can be divided into two regions. * Telencephalon * Diencephalon I. TELENCEPHALON: ‘The telencephelon is the largest part of fore brai two cerebral hemisphere or cerebrum. It is differentiated into CEREBRAL HEMISPHERE: Each hemisphere consists of two regions. Gray matter or cerebral cortex: It is the outer part of hemisphere it is the seat of all conscious activities and it is the placé which is involved in Intelligence, reasoning, memory etc. It is also divided functionally into an anterior frontal lobe, a lower central temporal lobe a parietal lobe and a dorsal occipital lobe. White Matter: It is the inner part of hemisphere. COORDINATION B/W TWO CEREBRAL HEMISPHERE: The activity of the two cerebral hemispheres is coordinated by corpus callosum. ul. DIENCEPHALO! It consists of thalamus and limbic system. (a) THALAMU! The thalamus is a clearing house for sensory impulses. It is also involved in the perception of pleasure and pain, (b) LIMBIC SYSTEM: There are following parts of limbic system. Hypothalamus: + It regulates homeostasis and pituitary gland. * It also regulates body temperature, blood pressure, hunger, thirst, aggression, pleasure & pain. Amygdala: It produces sensation of pleasure, punishment and sexual responses. Hippocampus: It is involved in long term memory. 2. MID BRAL The mid brain is relatively very small. It receives and.integrates sensory information like vision, odour as well 2s sensory information from the spinal cord & relays them to fore brain. 3. HIND BRAL-CLASS: XII -50- BIOLOGY NOTES There are following parts of hind brain. I. Medulla oblongata I. Cerebellum Ul. Pons IV. Reticular formation (i) MEDULLA OBLONGATA: it controls breathing, heart beat, blood pressure, coughing, swallowing, sneezing, vomiting, digestion, hiccupping, etc. (ii) CEREBELLUM: It is responsible for muscular coordination, balance etc, (iii) PON: It regulates activities like muscular coordination, facial expressions, breathing & sleeping. (iv) RETICULAR FORMATION: It lies in medulla, pons & mid brain. It monitors the messages to which the nervous system should react and to which it should ignore. BRAIN STEM: The brain stem consists of mid brain, medulla obligation & pond. SPINAL CORD It is a thick, whitish nerve cord that lies below the skull, extends down through the neural canal of vertebrae up to the hips. Structure of Spinal Cor In cross section, the spinal cord is differentiated into two areas, an outer called white matter an inner grey called grey matter. The outer region consists of neurons while the inner consists of nerve fibres of grey matter.CLASS: Xit 251 BIOLOGY NOTES Functions of Spinal Cord: Spinal cord serves as an express way for signals between autonomic nervous systems and brain. It is also the control centre for many reflexes. PERIPHERAL NERVOUS SYSTEM The peripheral nervous system (PNS) consists of following nerves. * Cranial nerves connected with brain 12 pairs, * Spinal nerves connected with spinal cord 31 pairs The PNS transmits signals between CNS & the rest of the body. TYPES OF NERVOUS SYSTEM ON THE BASIS OF NERVES I. Somatic nervous system Il, Autonomic nervous system 1. SOMATIC NERVOUS SYSTEM: The nerves which are related to the skeletal muscles constitute the somatic nervous system. 2. AUTONOMIC NERVOUS SYSTEM The nerves that deal smooth muscles, heart & glands constitute the autonomic nervous system. It is further divided into parasympathetic & sympathetic nervous system. (i) Parasympathetic Nervous System: It promotes all the internal responses e.g. contraction of pupil of cye, digestion of food, slow heart beat. (ii) Sympathetic Nervous System: It prepares the body for highly energetic activities such as light response. It increases the heart beat breathing rate, slows digestion, dilates pupil etc. Somaue Motor NeuronCLASS: Xi -52- BIOLOGY NOTES RECEPTORS DEFINITION: Receptors are cither modified neurons or epithelial cells which occur either singly or in groups with other cell types e.g. In eyes, They receive stimuli either from external or internal environments and transfer them to CNS in the form of impulse. : TYPES OF RECEPTORS: Receptors are classified into following types. Thermo receptors: They detect changes in temperature. Mechanoreceptors: They detect sound, motion, position in relation to gravity, touch, pressure, Chemoreceptor: They detect chemicals dissolved in fluid medium surrounding them, Photoreceptors: They detect visible & ultra violet light. Pain receptors: They detect tissues damage. WORKING OF SENSORY RECEPTOR IN SKIN In mammals including man, the skin contains receptor for at least five different sensations of touch, pressure, cold, warmth & pain. These receptors are classified into two groups. Free nerve endings: They are the simplest type which lie in epidermis or dermis. They are of different type and involved in touch, pressure, pain, heat & cold. Encapsulated receptors: The nerve endings of these receptors are enclosed in capsule of connective tissue. The skin contains following types of encapsulated receptors. Meissner’s Corpuscle: These receptors are mostly found in hairless areas such as finger tips, palms, soles, etc. These are sensitive to touch. Pacinian’s Corpuscles: ‘These receptors are located in dermis as well as in some internal organs & freely movable joints. They respond to rapid change in pressure associated with touch & vibration. EFFECTS OF DRUGS ON COORDINATION: A drug is a chemical substance which produces a specific physiological response in the body. Some drugs are useful medically & others act on brain producing artificial pleasure feeling. NICOTINE:CLASS: Xil 53 BIOLOGY NOTES It is a drug found in tobacco. It acts as a stimulant & is responsible for dependence on tobacco. It mimics the acetylcholine & directly stimulates variety of sensory receptors. Effects of nicotine Tn habitual smokers, the drug increases the heart beat & narrows the blood vessel (increases the blood pressure) and stimulates the nervous system, In this way it reduced fatigue, increasing alertness and improving the concentration. NERVOUS DISORDERS 1. PARKINSON’S DISEASE disorder caused either by degeneration or damage to nerve tissue within the basal ganglia of brain, Effects: The disease effects both the sides of the body and causes stiffness, weakness & trembling of the muscles. Treatment: Leodopa, which the body converts into dopamine is usually the most effective drug. 2,__ALZHEIMER’S DISEAS! Introduction: It is a progressive degeneration of neurons of brain. Effects: It causes dementia (loss of memory) + The disease progresses in three broad stages. * The patient notices his forgetfulness * There is a severe loss of memory particularly of recent event psychosis such as hallucinations & paranoid delusions. EPILEPSY: Introduction: Epilepsy is a tendency to recurrent seizures or temporary alterations in one or more functions. Effects: * The seizures may be spontaneous or due to some stimuli such as flashing light, * The seizures may be generalized or partial, The generalized seizure is characterized hy complete unconsciousness, stiff body with jerks. In partial seizure there is a momentary loss of consciousness. Treatmen: ‘Anticonvulsant drugs are used. CHEMICAL COORDINATIO GLANDCLASS: XII 5d BIOLOGY NOTES A cell, a tissue or an organ which secretes a substance is called a gland. There are two types of glands in our body. * Exocrine glands * Endocrine glands EXOCRINE GLAND: These glands contain ducts by which they transfer their secretions to the target site e.g. liver, pancreas, ete. ENDOCRINE GLAND: ‘The ductless glands of the body are called endocrine glands. These glands transfer their secretion though blood to the target cells e.g pituitary gland, adrenal gland, pancreas. HORMONES: * The secretions of endocrine glands are called hormones. + A minute quantity of hormone may have a profound effect on an organisms activities like behaviour, development growth, reproduction, etc. CHEMICAL NATURE OF HORMONE: Hormones are organic molecules which can be divided chemically into following types. 1. Peptide hormones: ‘They occur as short chain of amino acids (e.g. glucagons, ADH, oxytocin, etc.) as well as long chains of amino acids (e.g. insulin prolactin, etc). The former are called peptide hormones while latter are called protein hormones. 2 Modified aminoacids hormones: Few hormones consist of modified aminoacids e.g. thyroxine, epinephrine, nonepinephrine. 3. Steroid hormones: ‘These are lipid in nature examples are estrogen, progesterone, testosterone, aldostesone etc. HORMONE ACTION: Two main models have been proposed to explain the hormone action. However both models agree on the first step that the target cells have specific receptors in their plasma membrane,penta CLASS: Xil -55- BIOLOGY NOTES Model #1 ‘According to this model, the receptor molecule is linked with an enzyme adenylate cyclase on the inner side of the plasma membrane. The hormone receptor finding turns slow adenylate cyclase into active form which converts ATP into cyclic AMP (adenosine mono phosphate) in the cytoplasm. The cyclic AMP serves as second messenger. It then activates specife enzymes which bring about the appropriate response with in the cell. This model is related to peptide hormones. Adenylate cyclase>receptor in plasma membrane > ATP-> AMP Model #2 ‘This model is related to steroid hormones, These hormones are fat soluble. Therefore they can directly diffuse through the plasma membrane into the cell. In the cytoplasm, they find specific receptor which carry them into the nucleus where the hormone receptor complex directly activates the appropriate genes. FEED BACK MECHANISM: The hormone action is regulated by feed-back mechanism. The feed back is said to be negetive feedback if further secretion of hormone is inhibited. In the feedback, an increase in the concentration of secreted hormone facilitates the process of its further secretion. ENDOCRINE SYSTEM HYPOTHALAMUS It is an important part of the fore brain. + Its neuro secretary cells produce hormones called releasing & inhibiting hormones. * Some of its cell secrete anti diuretic hormones (ADH) & oxytocin which are actually stored in their nerve endings located in posterior pituitary gland. PITUITARY GLAND: (HYPOPHYSIS) + Itis a small pea sized structure which is attached with the hypothalamus of brain. * It is also called the master gland of the body because it controls the functions of other endocrine glands. SECRETIONS | TARGET | ACTION OF PITUITARY | (HORMONES) | SITE HORMONE G LAND LOBES Posterior Lobe | Antidiuretie Kidney | Tnerense hormone absorption of water. Contraction of uterus at the time of delivery. Oxytocin tientCLASS: XII -56- BIOLOGY NOTES Mammary | mereases milk “ production & Glands | secretion. ‘Anterior ‘Adreno-Cortico | Adrenol | Controls the Lobe tropic hormone | Cortex | secretion of (ACTH) steroid Thyroid Thyroid | hormones stimulatin hormone (TSH) [Gland | Controls the release of thyroid hormone, Follicle Ovaries [Formation of stimulating Graffian.follicle hormone Testis | Formetion of sperms Lutenising Ovaries | Controls the hormone (LH) secretion of progesterone Testis | Controls the secretion of testosterone. Prolactin Mammary | Development of Gland” | mammary glond & milk. production Somatotropie Most Controls protein hormone (STH) or | cells of | synthesis, cell growth hormone | the bedy _| division, (GH) protein metabolism & growth. CONDITIONS RELATED TO ABNORMAL PITUITARY OUTPUT Gigantism: It occurs due to hyper secretion of STH during childhood. Acromegaly: This abnormal condition appears due to the hyper secretion of STH after adulthood. In this condition the bones, cartilage and other soft tissues in hands, feet & jaws thicken abnormally. Dwarfism: This con childhood. ition is produce due to the hypo secretion of STH during THYROID GLAND Introduction: ‘The human thyroid gland is located at the base of neck in front of trachea. Hormones: Thyroid glands secrete hormones. - Ts (Teraiodothyroxine) - Ts (Triodithyroxine)CLASS: XII 257 BIOLOGY NOTES Functions of hormones: * Both T3 & T4 play an important role in controlling the metabolism of the body. * Calcitonin maintains the calcium level in blood & bones Disorders of thyroid gland: Cretinism: The hypothyroidism in early age is called cretinism which is characterized by stimulated growth mental retardation, etc. Myxedema: The hypothyroidism in old age is called myxedema which is characterized by over weight, sluggish dry skin, hair loss, intolerant of cold, confused & depressed individual. Goiter: The enlargement of thyroid gland due to the deficiency of iodine is called goiter. Hyperthyroidism: In case of higher levels of thyroid hormones, hyperthyroidism is produced which is characterized by protrusion of eye balls (exopthalmia), increased heart beat, heat intolerance, high blood pressure, profuse sweating & weight loss. PARATHYROID GLANDS There are four parathyroid glands inside the thyroid gland. Hormon These glands secrete panathyroid hormone (PTH) Function of PTH: PTH increase reabsorption of calcium in the kidneys as well as it induces demineralization of osteoclast cells of bones to release calcium in the blood. PANCREAS There are patches of pancreatic cells known as Is lets of langerhans which are endocrine glands. The islets consist of two distinct types of cells that are a- cells & B-cells, Alpha — Cells: ‘These cells secrete glucagons hormone. Beta — Cells: These ceils secrete insulin. Functions of Glucagon: Glucagon is scercted in response to the decrease in blood glucose level whose set point is about 90 mg/100 ml of blood. Functions of insw Insulin is secreted in response to higher level of glucose in blood. It stimulates liver, muscle & adipose cells for uptake of glucose. It also promotes the synthesis of proteins & fats.CLASS: Xi 58 BIOLOGY NOTES Deficiency of Insulin: The deficiency of insulin causes diabetes mellitus. ADRENAL GLAND Adrenal gland is located on each kidney & it consists of two parts, an outer cortex & an inner medulla. Adrenal Cortex: It secretes following cortico - steroid hormones. Cortisol Cortisol promotes the hydrolysis of muscle proteins to amino acids It also reduces the inflammatory responses & pain. Disorders due to abnormal cortisol level: (1) The hyper secretion of cortisol results in cushing syndromes which is characterized by obesity, muscle wasting, hyper tension, diabetes. (2) The hypo secretion of this hormone courses addisons disease which is characterized by weakness weight loss, low blood sugar & reduced blood pressure, Aldosterone: It increases the reabsorption of Na+ and Cl- ions by the kidney, maintaining fluid volume & blood pressure. Androgens: + These hormones are similar to testosterone. + They cause development of secondary male characteristic. + Adrenal Medulla: Adrenal Medulla secretes adrenaline (epinephrine) & non-advenalline (non ~ epinephrine) under conditions of stress to bring about fight‘or flight, response in emergency conditions. Epinephrine increases heart beat, blood glucose, breathing rate & metabolic rate. The primary function of non-epinephrine is to sustain blood pressure, THYMUS GLAND This gland is situated in the upper part of the chest & consist of two lobes that join in front of trachea, * It secretes several hormones including thymosin that stimulates the development & differentiation of lymphocyte. PINEAL GLAND: + Itisa tiny cone shaped body within the brain * I secretes melatonin at night. It produces biorhythms GONAD! Teste * The male gonads or testes secrete androgens, the most important of which is testosterone. + It stimulates bones & muscles growth & development of male secondary sexual characteristics. OvariesCLASS: Xil 59 BIOLOGY NOTES The ovaries secrete two hormones. © Estrogen * Progesterone Estrogen: It maintains female reproductive system & development of the secondary sexual characteristics in female. Progesterone: It maintains the uterus which supports the growth & development of an embryo, ANIMAL BEHAVIOURS The response of an animal in relation to its internal or external environment is called animal behaviour. The scientific study of the nature of behaviours is known as ethology. TYPES OF BEHAVIOUR: There are two basic types of behaviours ‘Innate (instinctive) behaviour © Learned behaviours I. INNATE BEHAVIOUR Tnnate behaviours are automatic, pre-programmed, genetically determined, stereo type activities which do not include any learning. Types of Innate Behaviour: (i) Kinases: In this kind, the rate of movement is related to the intensity of the stimulus rather than its direction. Example:- Wood lice move about quickly in dry conditions but slow down & stop in humid areas. (ii) Taxes: This bebaviours is related to the direction of stimulus. Example: A moth flies towards the light in the phototaxis. (iii) Reflexes: ‘These are stereo-typed, short-lived, rapid responses mediated by nervous system. Exampl + Knee jerk, blinking of eye. (iv) Fixed Action Pattern: (FAP) This Kind of innate behaviour is triggered or released by an external sensory stimulus known as sign stimulus or releaser. Example: Male three spined stick-back fish which attacks other males that enter his territory. It was found that the releaser of the attack is the red belly. II. LEARNED BEHAVIOUR: It refers to a more or less permanent change in the behaviour which occurs as @ result of experience.-CLASS: XII 60- BIOLOGY NOTES Types of Learned Behaviours There are following types of learned behaviours. Habituation Imprinting Classic conditioning Operant conditioning Latent learning Insight learning 1. Habituatio: It is the simplest type of learned behaviours in which animal stops responding to a repeated stimulus which is neither beneficial nor harmful, Example: Birds feeding along a road side. 2, Imprinting: The term imprinting was coined by Konard Lorenz in 1930. It occurs during very early stage in the life of birds & mammals & the animal is primed to learn a specific information which is then incorporated into an innate behvaiour. Example:- Ducklings follow the first large noisy moving object they see after hatching. 3. Classic Conditioning: It is associated with reward or punishment, Ivan Pavlov, a Russian physiologist in 1902 performed classic experiment on digestion in dogs. Experiment: Pavlov first placed dried meat powder into a dogs mouth causing release of saliva. Thereafter, he rang a bell just before presenting meat powder. The process was repeated several times. Later, the dog started salivating at singing of the bell rather than seeing the meat, Bofore conditioning FooD SALIVATION (wes) (wer) BELL NO RESPONSE a During conditioning BELL+ — SALIVATION FooD wes) wer) ioning, BELL SALIVATION (cs) (er)CLASS: Xil 61 BIOLOGY NoTES 4. Operant conditioning: © In this kind of learning en animal learns to associate one of its behaviour to receive an award or punishment, + An American psychologist, B.F. Skinner developed a box called Skinner box for his experiments with hungry pigeons or mie on conditioning. * Inside the box there was lever which operated a food supply.CLASS: XII 62 BIOLOGY NOTES 5. Latent Learning: : This type of learning is not associated with a particular stimulus & is not normally rewarded or punished e.g. If a rat is placed in a maze it was observed that using its natural ability. The rat very soon finds its way out of the maze. 6. Insight Learning: Solving a problem without trial & error learning is called insight learning, It is the most developed form of learning behaviour. c.g. Insight learning was performed in (Chimpanzees) presented with a bunch of bananas too high to reach & few boxes. Some chimpanzees piled up boxes to make stand for themselves. BIOLOGICAL RHYTHMS: DEFINITION: Some organisms do some activities at regular intervals irrespective to the season or day length. This kind of behaviour so called time biology or biological rhythms. It indicates the existence of a biological clock within the organism, Types of Biological Rhythms: There are two types of biological rhythms: « Exogenous rhythms * Endogenous rhythms (i) Exogenous Rhythms: These rhythms are controlled by external changes such us 24-hr cycle of light & dark. (ii) Endogenous Rhythms: These rhythms are controlled by biochemical & physiological changes. EXAMPLES OF RHYTHMICAL BEHAVIOUR Breeding Season: Many animals do not breed all the year round & there is a specific time of their breeding. Biannual Migration: Salmons & eels migrate between sea water & fresh water more than once in their life cycle. A number of birds also have migratory life cycles. Daily Rhythm: ‘Animals are active for only a part of 24-hr cycle. Examples: + Some function at dawn (crepuscular) * Some function in night (nocturnal) « Some function in the day (diurnal)CLASS: XIL alseere Bere “ _ REPRODUCTION BIOLOGY NOTES The ability of living organisms to produce new organisms of their own kind is called reprodiiction. REPRODUCTION IN PLANTS There are two types of reproduction in plants: 1- Asexual reproduction 2 Sexual reproduction ASEXUAL REPRODUCTION “The reproduction in which sexes are not involved is called asexual reproduction. ‘There are following methods of asexual reproduction in plants. ¥ BY SPORES OR SPORULATON: The spores are formed by a sporophyte plant by meiosis, Therefore these spores are haploid (p) in nature. The spores develop into new haploid organisms. The formation of spores is called sporulation, Sporulation occurs in bacteria, fungi, mosses, ferns, etc. Prep. By:- Raza Mehdi ¥ VEGETATIVE PROPOGATION: Vegetative propagation involves the separation of a part of the parent plant, which then develops into a new plant. ¥ APOMIXIS: The formation of seed without fertilization is called apomixis. In this process a diploid cell in ovule is directly converted into an embryo (i.e. no reduction division & gametic fusion). v VEGETATIVE PROPAGATION IN AGRICULTURE: ¥ CUTTING: Cutting is 2 very common method of vegetative propagation. Mostly house plants, woody omamentals & trees are grown by this method. In most of the cases, the cuttings of plants are used for vegetative propagation. But the leaves of some plants are also used for this purpose. Exemple: Bryoplyllum In some cases cuttings are taken from specialized storage stems. For example: a potato can be cut up into several pieces each with a vegetative bud or eye that regenerates into a whole plant. ¥ TISSUE CULTURE (TEST-TUBE CLONING & RELATED TECHNIQUES) or CLONING: A group of genetically identical offsprings produced by asexual method is called clone & the technique to make a clone is called cloning. EXPLANATION: _Itis possible to grow whole plants by culturing smallest plants (pieces of tissue cut from the parent plant) or even single parenchyma cells on an artificial ‘medium containing nutrients & hormones. The cultured cells divide & form an undifferentiated callus form shoots & roots with fully differentiated cells. All of these experiments end performed ina test tube, therefore, these small plants developed by the callus are called test-tube plants which are transferred to soil where they continue their growth.-CLASS: XIl 64 BIOLOGY NOTES ADVANTAGES & DISADVANTAGES OF TISSUE CULTURE & CLONING v ADVANTAGES: Many plants can be grown in sterile areas ensuring a much greater survival rate than seed grown plants. In these techniques, the plants are grown in sterile conditions. Therefore, they are not attacked by the pathogens in the initial stage of life. ‘The manufacturing of used chemicals by plant cultures e.g. production of shikonin, a dye used in silk industry & in the treatment of burns has been produced commercially. ¥ DISADVANTAGES: Plants propagated in this way may be unstable or non fertile, These plants have unusual chromosome number e.g. when oil palms produced by tissue culture ‘were produced by Malaysia (1970s) they turned out to be sterile. SEXUAL REPRODUCTION: ‘The reproduction in which a new individual is developed by the fusion of dissimilar gametes (i.e. male & female gametes) is called sexual reproduction. TYPES OF SEXUAL REPRODUCTION IN PLANTS: v ISOGAMY: ‘The reproduction in which male & female gametes are similar in morphology & physiology is called isogamy. This is the simplest type of sexual reproduction. Y ANISOGAMY: This is the sexual reproduction in which male & female gametes differ either in morphology or in physiology. ¥ OOGAMY: * The sexual reproduction in which male & female gametes differ both in morphology & physiology is called oogamy. ¥ HETEROGAMY: In bryophytes a most successful kind of sexual reproduction is present which is called heterogamy. In this reproduction male gametes are small in size & they can locomote whereas the female gametes are non motile, large in size & they have stored food materials, SEXUAL REPROCUTION IN FLOWERING PLANTS: FLOWER: Flower in the reproductive part of plant, which is actually the modified form of shoot. Explanation: Flower develops from compressed shoots with four whorls of modified leaves separated by very short internodes. These floral leaves are called sepals, petals, stamens & carpels, v¥ MICROSPOROPHYLLS: ‘The stamens are also called microsporophylls. Each microsporophy/ll contains following, three parts: 1. Filament: Its the basal stalk. 2. Connective: It is the middle part, which connects the filament with another. 3. Anther: It is the upper part in which mostly fore pollen sacs or microsporangia are found. Each microsporangium has numerous male gametophytes or pollen grains.CLASS: Xl -65- BIOLOGY NOTES: ¥ MEGASPOROPHYLLS: ‘Megasporophyils are also called carpels. The carpel is flask shiaped body having stigma (head), style (neck) & ovary (basal swollen part) Inside the ovary, ovules (mega sporangia) are found & each ovule has an embryo sac (megaspore) in which a female gamete is present, POLLINAITON: The transfer of pollen grains from anther to the stigma of carpel is called pollination, There are two types of pollination: 1, Self pollination. 2. Cross pollination ¥ SELF POLLINATION: ‘The transfer of pollen grains from the anther of a flower to the stigma of the same flower is called self pollination, v CROSS POLLINATION: The transfer of pollen grains from the anther of a flower to the stigma of another flower is called cross pollination. DEVELOPMENT OF MALE GAMETOPHTE: Inside the microsporangium (polien sac) a large number of diploid cells called microspore mother cells are present. 4 Each microspore mother cell forms four haploid microspores by meiosis 4 Each microspore divides into two cells by mitosis. One cel is called generative cell & the other is known as tube cell. ‘The microspore is surrounded by a thick resistant -wall. In this condition the microspore is considered as immature male gametophyte. DEVELOPMENT OF FEMALE GAMETOPHYTE: + The female gametophyte or embryo sac develops inside the mega sporangium or nucellus ofovule. f + One cell is mega sporangium becomes distinet, which is called megaspore mother cell, E + The megaspore mother cell (2n) forms four haploid cells by meiosis, which are called i linear tetrad. E + The linear tetrad contains four haploid megespores. Out of them three are disintegrated & the remaining one megaspore develops into female gametophyte. ‘+ The haploid nucleus of megespore forms cight nuclei by three mitotic divisions. *F Outof these eight nuclei, two are fused to form a diploid secondary nucleus. & In this stage, the embryo sac contains seven nuclei three nuclei towards chalaza are called antipoduls & duce nuclei towards the micrupylar end are culled egy upparatus, + The egg apparatus contains two synergids & one egg nucleus or female gamete. Prep. by:-Raza Mehdi DOUBLE FERTILIZATION: * Afier the pollination, the pollen grain is transferred onto the stigma where it germinates, During the germination inner layer intine ruptures the exine at any germ pore & comes out in the form of a tube, which is called pollen tube.CLASS: Xi 66. BIOLOGY NOTES This pollen tube grows downward towards the ovulé & finally it enters into ovule through microphyle. % The nuclei of tube ceil & generative cells are shified into the pollen tube. + When the generative nucleus enters into the pollen tube, it divides to form two male gametes, ++ When the pollen tube penetrates into the embryo sac its tip bursis & both male gametes are discharged into the embryo sac. First male gamete is fused with egg nucleus to form diploid oospore. This fusion is called syngamy. The second male gamete is combined with secondary nucleus to form triploid Gn) endosperm nucleus ‘© In this way fertilization takes place twice in an embryo sac, therefore this process is called double fertilization, which was discovered by Nawaschin in 1898, CHANGES IN OVULE AFTER DOUBLE FERTILIZATION: Afier double fertilization, the ovule is converted into a seed. In this process following changes take place: , 4) The oospore is changed into an embryo cotyledons, plumule & radicle, ii) The endosperm nucleus forms a nutritive tissue, which provides nourishment to the developing -mbryo, this tissue is called endosperm. i) The integuments form seed coats. iv) Micropyle also persists in seeds. ‘The seed is dehydrated until its water contents become 5 to 15% of its weight. INFLORESCENCE ‘The arrangement of flowers on floral axis is called inflorescence. TYPES OF INFLORESCENCE: 1. Racemose 2. Cymose RACEMOSE: * The inflorescence in which the apical growth of branch remains continues is called racemose, * The arrangement of flower is acropetal (young flowers inside) * The opening of flowers is centripetal. * The floral axis in racemose inflorescence is known as peduncle, Types of Racemose Peduncle elongated Peduncle shortened Peduncle flattened Spikelet inflorescence. vy PEDUNCLE ELONGATED: There are following types of this inflorescence: 1. RACEME: In this inflorescence the flowers are pedicellate & bisexual e.g. Serbania sesban, 2, SPIKE:CLASS: XI -61- BIOLOGY NOTES: In this type the flowers are sessile & bisexual e.g. Amaranthus. 3. CATKIN: In this type the flowers are sessile & unisexuel e.g. mulberry. 4. SPADIX: Tn this inflorescence the flowérs are surrounded by a large bract called spathe e.g, banana, v PEDUNCLE SHORTENED: There are two types of this inflorescence. 1. CORYMB: In this inflorescence the flowers have the pedicels of unequal length & all these pedicels originate from different points, The lower flowers have large pedicels while the upper flowers have short pedicels e.g, Iberis 2. UMBEL: In this type all the pedicels of flowers have equal length & they originate from the same point e.g. Corrfander. yY PEDUNCLE FLATTENED/HEAD OR CAPITULUM The flattened peduncle has a mass of small sessile flower (florets) with one or more ‘whorls of bracts at the base forming an involucre, Mostly there are two types of florets on head: Ray florets: ‘These are marginal florets, Disc florets: There are central florets e.g. Helianthus annus (sunflower) & Tagetes erectus (marry gold) v SPIKELET INFLORESCENCE: It is a kind of racemose inflorescence . There are three types of bracts at its base called glumes , ‘The lower two glumes are without flowers are called empty glumes. The third slume has flower in its axile & called lemma, Just opposite to lemma, there is small bractiole called palea This type of inflorescence is found in family Poaceae. * * oe E cymos' [ ‘The inflorescence in which the apical growth of branch is stopped is called cymose i In this inflorescence, the arrangement of flowers is basipetal (ie. old flowers inside & young flowers outside) The opening of flowers is centrifugal. Types of cymose inflorescence: There are two kinds of eymose inflorescence Y UNIPAROUS (MONOCHASIAL)CYME: In this inflorescence main axis soon ends into a flower & produces only one lateral branch at a time ending in a flower. There are two types of uniparous cyme i.e, scorpoid cyme and helicoids cyme, someone: se 1, SCORPOID CYME: In this type the succeeding branches (flowering branches) are produced on alternate sides eg, cotton 2, HELICOID CYME:CLASS: Xil 68 BIOLOGY NOTES In this type of cyme the succeeding branches are produced on the s ame side eg sundew. ¥ BIPAROUS (DICHASIAL) CYME: In this type of cyme, the main axis terminates into a flower & produces two flowers on either sides. This mode is followed by each succeeding flowers. .g. pink- night jasmine, ¥ COMPOUND CYMOSE (VERTICELLASTER): In this type of inflorescence, initially biparous cyme appears which is followed by uniparous. This inflorescence is the characteristic feature of family Labiateae (mint family) TYPES OF PLANT ON THE BASIS OF SEX MONOECIOUS: The plants having both type of flowers ie. staminate & carpellate on the same plant body are called monoecious e.g. Achyranthus aspera & Zea mays DIECIOUS: These plants bear staminate & carpellate flowers on separate plant bodies. e.g papaya, SEED DORMANC DEEINITION: Dormant means sleeping or resting, mostly this term is used for ungerminating seeds. SIGNIFICANCE OF SEED DORMANCY: Seed dormancy increases the chances for the germination of seed at a particular time & place most advantageous to the seedling, BREAKING OF SEED DORMANCY: Breaking dormancy generally requires certain environmental conditions, % Sceds of desert plants germinate only after a substantial rain fal. “ Many seeds require intense heat to break dormancy. ‘> Some seeds require exposure of cold. + Some types of seeds require light for germination. + Some seeds have hard seed coats which need a chemical treatment to dissolves. Therefore, when they pass through the digestive tract of grazing animals, the seed coat is dissolved & the seed is ready to germinate. PARTHENOCARPY: (Formation Of Seedless Fruits) ‘The formation of fruit by an ovary without fertilization is called parthenocarpy e.g, banana & seed less grapes are parthenocarpic fruits, GERMINATION OF SEED: DI TON: The process in which a dormant embryo is converted into a seedling is called germination of seed. TYPES OF SEED GERMINATION: There are three types of seed germinatior Epigeal germination, Hypogeal germination Vivipary germinationLAS: BIOLOGY NOTES + EPIGEAL GERMINATION: ‘The germination in which the cotyledons come out of the soil due to the enlargement of hypocotyl is called epigeal germination. Example: germination of castor oil seed. + HYPOGEAL GERMINATION: “The germination in which the cotyledons remain inside the soil is called hypogeal germination. Example: pea, maize ete : VIVIPARY GERMINATION: Vivipary is a special type of sced germination in which the seed starts to germinate inside the fruit which is still attached with the parent plant & due to the increase in the weight of seedling the fruit falls on the ground & the seedling is converted into a new plant. Example:- coconut, palms, etc, TRAN: ON TO FLOWERING STAGE (SEED TO SEEDLING) Germination of a seed produces a seedling. After germination primary growth occurs in the plant in this growth apical meristem takes part. In this way a young seedling becomes a young, plant with soft stem & leaves. Some plants umdergo secondary growth. In this growth they increase their breadth. These growths are regulated by some hormones. e.g axons. Then other hormones become activated to produce reproductive parts ie. flowers. These hormones are called flowering hormones e.g. florigen. VERNALIZATION DEFINITION: ‘Promotion of flowering by a cold treatment given to the imbibed sceds or young plants is known as vernalization. EXPLANATION: Many plants require cold treatment for germination e.g. pine seeds will not germinate if, ‘not exposed to cold temperatures similarly, turnip & sugar beet will not produce flowers if not ‘exposed to cold winter temperatures. According to scientist such as Gamer & Lysenko if the seeds of winter wheat varieties are subjected to low temperature of 0.5°C for a few weeks & then sown in spring will bear the fruit in the same year. In other words they will behave as spring variety ‘This phenomenon which shortens the vegetative period & hastens flowering is called vernalization, PHOTOPERIODISM DEF! ‘The relative length of day & night to which plant is exposed is called photoperiod & the response of 2 plant due to this photoperiod is called photoperiodism. There are three types of plants on the basis of photoperiodism. 1. LONG-DAY PLANTS: ‘Those plants which require long days & short night for flowering are called long day plants. ‘There plants flower only when the light period exceeds a certain critical length in each 24-hr cycle. Examples: Reddish, spinach, petunias, lettuce.-CLASS: XIL -70- BIOLOGY NOTES 2. SHORT-DAY PLANTS: ‘Those plants which require short days & long nights for flowering are called short-day plants. Short day plants flower only when the light period is shorter than a critical length in each 24-hr cycle. For cocklebar this is 14 ¥, hrs. Examples: Chrysanthemum, cocklebar 3. DAY-NEUTRAL PLANTS: ‘Those plants which are not affected by the change in the duration of day light are called day-neutral plants. They produce flowers throughout the year. Examples: Tomato, cotton. ELOWERING HORMONE FLORIGEN & PHYTOCHROME PHYTOCHROME: Phytochrome comprises of protein & a pigment. It is distributed through out the plant in ‘minute quantities. It was isolated in 1960 & it exists in two interconvertible forms: Phytochrome 660 (P : Phytochrome 730 (P ™) + PHYTOCHROME 660 (P™) It absorbs red light “* PHYTOCHROME 730 (P™) tabsorbs light in the far red region of spectrum. + FLORIGEN: Florigen is the flowering hormone. This hormone is synthesized in leaves & then it is transferred into the apical regions. Therefore, most of the flowers are formed in the apices, FERTILIZATION IN VITROCVF) VIVO: inside the body VITRO: outside the body This field involves dissecting out whole ovules & placing them in a suitable nuttient solution. Ifit is done carefully the egg (zygote) will develop into a mature embryo. Embryo culture techniques are important in the development of new crop (Importance). Prep, By :- Raza Mehdi REPRODUCTION IN ANIMALS ‘The process in which one or two parent organisms form a new individual is called Reproduction. TYPES OF REPRODUCTION: ‘There are two main modes of reproduction in animals (Asexual Reproduction, Gi) Sexual Reproduction. (1) ASEXUAL REPRODUCTION: This is a primitive type of reproduction in which a new individual is formed by just a single parent i.e., no involvement of gametes and fertilization, ‘There are following types of asexual reproduction.CLASS: Xi 7 BIOLOGY NOTES Qo (i) (it) (iy) @) (b) (2) FISSION: This is the simplest method of asexual reproducticii in which the parent body divides into two or more parts each of which develops into e new individual, There are two types of fission, BINARY FISSION: In binary fission the parent body forms two offsprings. MULTI FISSION: In multiple fission the parent body divides into more than two daughter organisms, EXAMPLES: Amoeba, Paramecium, Plasmodium, BUDDINC In this reproduction, a small outgrowth develops on some part of the parent body and is called a bud. This bud increases its size and finally itis separated from the parent body and stars its independent life. EXAMPLES: Hydra , Corals. REGENERATION: This is the process of re-growing the missing parts. It is common in worms and echinoderms. The sponges also pass through a same process called fragmentation in which their body divides into many small pieces or fragments. Then each fragment develops into a new organism. PARTHENOGENESI: ‘The formation of a new animal by an unfertilized egg is called Parthenogenesis. . EXAMPLE: Parthenogenesis is commonly found in some insects like honey bees, ants ete TWINS ‘Twins are the two children which develop and are born together. ‘There are two types of twins, IDENTICAL OR MONOZYGOTIC TWINS: Identical twins are exactly alike and of the same sex because both of them develop from just one zygote. FRATERNAL OR DIZYGOTIC TWINS: Internal twins are the children which develop from two independent eggs and cach egg is fertilized by a separate sperm. There twins are not identical. SEXUAL REPRODUCTION: Itis the type of reproduction which involves sex cells. The male gametes or sperm fuses with a female ovum to form @ zygote which develops into a new individual. si "ANCE OF SEXUAL REPRODUCTION: Sexual reproduction is important to avoid genetic monotony which is the result of asexual reproduction. Sexual reproduction produces an endless variety of organisms. ‘This diversity of characteristics in a species increases the chances of survival. ‘The genetic variation plays an important role in the identification of individuals,CLASS: XIL 2 BIOLOGY NOTES: NECESSITIES OF SEXUAL REPRODUCTIO! ‘Sexual reproduction requi () —_ Gametogenesis. (i) Mating and fertilization, GAMETOGENES| Formation of gametes is called gametogenesis. In animals, the gametes are produced in specific organs which are called gonads. There are two types of gonads. (i) Testes or male gonads. Gi) Ovaries or female gonads, TESTES: Ovaries form female gametes or eggs, ‘+ SPERMATOGENESIS: It is a process of cell division by which sperms are formed from germ cells present in testes. This process is competed in following steps: STEP #1: Germ cells in testes first transform mitotically into spermatogonia and then into primary spermatocytes. STEP #2: Each primary spermatocyte divides meiotically into two secondary spermatocytes. STEP #3: Secondary spermatocytes also divide to form genetically different haploid spermatids, STEP #4: Each spermatid develops into a sperm. DURATION OF OOGENESIS: This process is completed in about ten weeks, “ OOGENESI It is a process of cell division by which ova are formed from germ cells present in the ovaries. This process is completed in the following steps: STEP #1: Germ cells in ovary divide mitotically to form oogonia which develop into primary oocytes, STEP #2: ‘The primary oocytes undergo first meiotic division to form two unequal cells, a large secondary oocyte and a smaller polar body. STEP #3: Both secondary oocyte and polar body further divide to form a large haploid ovum or egg and three haploid polar bodies (non-functional cells) DURATION OF OOGENESIS: This process completes is about a month. MATING AND FERTILIZATION: Mating is the process in which male ond female contribute their gametes for the process of fertilization. There are two types of fertilization, EXTERNAL FERTILIZATION:Raa 5 CLASS; XII Te BIOLOGY NOTES ‘The process of fusion ofa sperm and ovum outside the body of female in an aquatic medium is called external fertilization. ‘Example: Fertilization in amphibians and sessile animals. INTERNAL FERTILIZATIO! ‘The fertilization in which the eggs are fertilized inside the body of the female is called internal fertilization. Example: Fertilization in terrestrial animals. SEX TYPES IN ANIMALS: ‘There are two sex types in animals. () HERMAPHRODITE: ‘Those animals in which both sexes are present in one body are called hermaphrodite. Example: Tapeworm, Earthworm etc. (ii) UNISEXUAL: ‘Those animals in which only one sex is present inside a body are called unisexual. EXAMPLE: Mammals, birds etc. OVIPARITY: : ‘The egg laying animals are called oviparity animals, EXAMPLE: Fishes, Reptiles, Birds. IVIPARITY: The animals which give birth to their young ones ere called viviparous, EXAMPLE: Most mammals. MALE REPRODUCTIVE SYSTEM Male reproductive system in human is composed of following organs. TESTES: ‘Testes are the primary sex organs in male. They are oval organs located outside the body in a thin walled pouch called scrotum. Each tests is about 4 to Scm long and 2.5m wide. INTERNAL STRUCTURE: Each testis is surrounded by a thick, fibrous capsule which is composed of white connective tissue. Extension of the capsule project into the interior of the testis and divide each testis into about 250cone shaped. The lobules contain seminiferous tubules in which sperms develop. FUNCTION! PERMAT! 2 ‘The formation of sperms is called spermatogenesis. 2: HORMONE PRODUCTION: “Testes prepare and secrete a hormone testosterone. This is the male sex hormone, DUCT! “The male reproductive system is composed of following types of ducts. 1: EPIDIDYMIS: Epididymis is a tightly coiled series of thread like tubules that form a comma shaped structure on the posterior side of testis. It is 6meters long,CLASS: XII -74- BIOLOGY NOTES FUNCTION: In epididymis, sperms complete their maturation and are stored for about 20days, 2: VAS DEFERENS: It is @ thick walled, muscular cord like organ. FUNCTION: Their thick walls of smooth muscles create peristaltic movement, which rapidly squeeze the sperms from epididymis to the urethra. 3: URETHRA: ‘Urethra extends from the base of the urinary bladder to the tip of the penis. FUNCTIONS: It conducts either urine or semen which passes through the penis to the outside of the body. EXTERNAL GENI of the male include the scrotum and the penis (male coupulatory ACCESSORY GLANDS AND SEMENS: 1:SEMINAL VESICLE: ‘The seminal vesicles are two copulated sacs about Scm long located at the base of urinary bladder. : FUNCTION: It produces about 60% of the fluid volume of semen, Its thick, yellowish secretion is rich ‘in fructose, vitamin C, prostaglandins and other substances which nourish and activate the sperm. 2: PROSTATE GLAND: It isa single gland, encircles the upper part of the urethra just below the urinary bladder. EUNCTION: Prostate gland secretes a milky fluid that plays a role in activating sperms. BULBOURETHRAL GLANDS (COWPER’S GLAND): ‘These are tiny, pea shaped glands inferior to the prostate glands, EUNCTION: ‘They produce a thick, clear which drains into the urethra before semen. Prep. By :- Raza Mehdi SEMEN: ‘Semen is a milky white, some what sticky mixture of sperm and accessory glands secretion. VOLUME: 2-Sml NUMBER OF SPERMS: 50 - 100 millions/ml pH: 72-16SL GLASS: XII -15- BIOLOGY NOTES FEMALE REPRODUCTIVE SYSTEM ‘The female reproductive system consists of two types of organ. (Primary sex organ. (ii), Accessory organ. PRIMARY SEX ORGAN: In female reproductive system ovaries are the primary sex orjans. There are two ovaries in a female body. They lie on either of uterus. EXTERNAL STRUCTURE OF OVARY: ‘Shape: Ovaries are almond shaped. ength is 4em, width is 2.Scm, thickness is 1.5em approximately, Attachment: Ovaries are attached to the uterus by the ovarian ligaments. INTERNAL STRUCTURE OF OVARY: Ovary is composed of two basic parts. Cortex:Cortex is the outer part of the ovary. Medula: It is the inner past of the ovary. loosely packed fibrous tissues, FUNCTIONS OF OVARY: L.OOGENESIS: ‘The formation of eggs or ova is called oogenesis (Eggs or ova are the female gametes). In the two ovaries about 200,000 eggs are found, how ever, only 450 eggs become ‘mature in the fertile period of life. 2.HORMONES: — Ovaries produces two hormones. “ Oestrogen: It is secreted from follicles. % Progesterone: Iti secreted from corpus luteum, ‘These hormones produce female secondary characters. ACCESSORY ORGANS: They include following orgens: Fallopian tubes, Uterus. Vagina. External genitilia, composed by blood vessels, nerves and FALLOPIAN TUBES: ‘Two fallopian tubes are present attached to either side of the uterus. ize: Length of each tube is about 10cm, Basic Structure: They are internally lined with cilia which move the egg towards uterus. The distal end of each tube is expanded and has finger like projections called fimbriae which partially surround the ovary. Functions: ‘% Itreceives egg from ovary. % Itprovides a suitable place for the fertilization. 2:-UTERUS: Tis pear shaped muscular organ living with vascular tissues. Iis walls are composed of 3 layers. Epimetrium: Outer most serous layer.CLASS: Xi =76- BIOLOGY NOTES ‘Myometrium:It is the middle layer composed of smooth muscles. It plays a vital role during the delivery of the baby. Endometrium:[t is the inner most spongy layer containing vascular tissues. It receives fertilized gg (implantation). Ifthe egg is not fertilized, it shed and menses are produced. Lower part of uterus is called cervix. Its measurement is about 2.Sem.GLASS: XIL -11- BIOLOGY NOTES. VAC ‘Vagina is an elastic, fibro-muscular tube like organ. It is 6~ 10cm in length. Functions: “+ Itréccives the sperms through the penis during mating. 4 Itis also called birth canal because the baby delivers through it. EXTERNAL GENITILI In female the external genitilia is called vulva, It has two openings ie., urethral and vaginal. MENSTRUAL CYCLE It includes all the eyclie changes in the endometrium of the uterus, These changes take place once in a month, At the end of their cycle the endometrium sheds and blood with mucus and epithelial tissues are released through vagina. This is called menstruation. The menstrual cycle is sub-divided into following phases: (Menstruation. (ii) Proliferative phase (Follicle phase). (ii) Ovulation. iv) Secretary phase (Corpus luteum phase). ++ MENSTRUCTION DAY 1-5): During this interval, the thick endometrial-lining of the uterus is sloughing off or becoming detached. This is accomplished by bleeding for 3 to5 days. The detached tissues and blood pass through vagina as the menstrual flow. The average blood loss during this period is 50- 150ml. * PROLIFERATIVE PHASE (DAY 6 - 13): In the phase one of the developing follicles matures more rapidly. This follicle is called graffian follicle. The graffian follicle secretes oestrogen. Due to the rising oestrogen level, the endometrial blood supply is increased. So it again becomes thick and spongy. OVULATION (DAY 14): At the end of the Proliferative phase the graffian follicle ruptured and the oocyte comes out of it enters into the fallopian tube. This release of oocyte from graffian follicle is called ovulation. ‘ SECRETORY PHASE (DAY 15 ~ 28): After ovulation the graffian follicle becomes filled with a fatty yellow mass called the corpus luteum, It secretes a hormone called progesterone. Progesterone is responsible for the further development of the endometrium. It causes endometrial glands to increase in size and to begin secreting nutrients into the uterine cavity. These nutrients will sustain a developing embryo unt itis implanted. If fertilization does not occur, the corpus luteum begins to degenerate towards the end of this period. In this condition itis called corpus albicans. Due to the degeneration of the corpus luteum the progesterone level suddenly decreases, at this stage the endometrium sheds and menses start agein.CLASS: XII -78- BIOLOGY NOTES OQESTROUS CYCLE When eggs mature during breeding season, the hormonal secretion in females initiates certain behavioral changes, indicating their readiness for mating and the animal is said to be in heat. This occurs in a cyclic manner called the oestrous cycle, HORMONAL CONTROL IN FEMALE REPRODUCTIVE SYSTEM In female, the reproductive hormones are secreted from different sites. The details of these sites are as follows: (Hypothalamus. ) Pituitary gland. Ovary. HYPOTHALAMUS: Itis the lower part of the brain. It secretes one hormone, GONADOTROPIC RELEASING HORMONE (GaR#): Itcontrols the secretion of the reproductive hormones from pituitary glands, PITUITARY GLAND: It secretes following hormones. i: FOLLICLE STIMULATING HORMONE (FSH): : SITE OF SECRETION: It is secreted from the anterior lobe of pituitary gland, (ARGET SITE: Immature follicles. FUNCTIONS: * Maturation of follicles into Graffian follicles, * Stimulates the secretion of oestrogen. * Its decreased level induces ovulation. 2:- LUTEINIZING HORMONE (LH): ‘SITE OF SECRETION: Anterior lobe of pituitary gland. ‘TARGET SITE: Graffian follicle, FUNCTIONS: * Its increased level induces ovulation, * Stimulates the development of corpus luteum, * Controls the secretion of progesterone. 3: PROLACTIN: ‘SITE OF SECRETION: Anterior lobe of pituitary gland, ‘TARGET SITE: Mammary glands. FUNCTIONS: * Maintenance of corpus luteum. * Stimulates milk production. 4:- OXYTOCIN: SITE OF SECRETION: Posterior lob of pituitary gland. TARGET SITE: Uterus and mammary glands, FUNCTIONS: * Contraction of uterus during delivery. * Development of mammary glands, milk production and secretion.‘ -79- 7 BIOLOGY NOTES. OVARY: The ovaries secrete two important hormones. OESTROGEN: SITE OF SECRETION: It is secreted from the developing follicle during the proliferatine phase. ‘TARGET SITE:- Endometrium of uterus; FUNCTION: * Repairs and develops endometrium. * Stops the secretion of FSH and enhances the secretion of LH from pituitary gland at the 14" day of the cycle. "ROGESTERONE: SITE OF SECRETION: Corpus luterm, ‘TARGET SITE: Endometrium of uterus and mammary glands, EUNCTIONS: * Completes preparation and maintains the endometzium for pregnancy. * Stimulates the development of mammary glands. HORMONAL CONTROL BY PLACENTA: PLACENT: The tissue attaching the embryo to the wall of uterus is called placenta. It secretes a hormone called “human chorionic gonadotropin (HCG). FUNCTIONS: HCG acts fike LH and stimulates and maintains corpus luteum within the ovary to keep on secreting progesterone. Placenta elso secretes oestrogen. CONCEPTION AND PREGNANCY Fertilization in human beings is more commonly called conception i.c., to conceive a baby. After fertilization, the zygote divides and forms a ball of cells called blastocyst which travels. down the oviduct and reaches the uterus to be embedded in its wall. This process is called. implantation and it marks the start of pregnancy. PLACENTA: “The tissue attaching the embryo to the wall of uterus is called placenta, FUNCTIONS: ‘CO; and waste from the embryo diffuse out through the placenta to the mother. Placenta also secretes progesterone hormone for maintaining pregnany. AMNIO. In reptiles, birds and mammals, when the embryo becomes implanted in the uterine wall, a clear, extra, embryonic membrane, the amnion develops and surrounds the embryo. The cavity le the amnion is filled with a fluid which is called amniotic fluid. This cavity is known as amnion sac, CHORION AND ALLANTOI: CChorion and allantois are two other membranous sacs associated with most of the amniotic embryos.CLASS: Xi -80- BIOLOGY NOTES FUNCTIONS: ‘These membranes protect the embryo and assist it in nutrition and excretion. [ONS OF AMNION: ‘The amniotic fluid keeps the embryo moist and it also protects the embryo by external jerks. UMBILICAL CORD: ‘A rope like structure formed from the extra embryonic membrane, the allantois is called umbilical cord. FUNCTION! Itconnects the embryo to the placenta, BIRT : Tn human beings the development of fetus is completed in about months (40wecks). After the completion of development, the baby is ready to born. The muscles of the uterus begin to contract and relax due to oxytocin. These strong contractions of the muscles of the uterus are calied labour, LACTATION: ‘After the birth of the baby as the umbilical cord is eut, food supply to the new born is disconnected. It is now fed on a nutritious fluid, the mille which is produced in the mammary glands of the mother. The milk production in mammary gland is controlled by prolactin. TEST TUBE BABIES: ‘Approximately 10% of the couples fail to have children. This condition is called infertility. ‘There are several causes of infertility. In some females, infertility is caused due to the blockage of oviduets so that the sperms cannot reach the egg. This sort of infertility is overcome by a technique called invitro fertilization, INVITRO FERTILIZATION: STEP #1 The oocytes are sucked up from the ovary of the woman before ovulation. STEP #2: ‘These eggs are fertilized outside her body in a laboratory dish with the sperm, STEP #3: Eggs thus fertilized invitro are allowed to develop for a few days in @ laboratory and then itis transferred into the uterus for implantation where it undergoes normal development and is born in @ natural way. SEXUALLY TRANSMITTED DISEASES: GONNORHEA: PATHOGEN: Itis a disease caused by a bacterium Neisseria gonorrhoeae which is introduced in the body through a sexual contact usually through genitals and oral contact. COMPLICATIONS: ‘The bacterium causes wounds in genital tubes and the infected males experience buming sensation during urination with discharge of thick white pus from urethra. In female infectees oviducis become damaged and blocked. If untreated, it can cause infertility in ‘both males and females. An infected mother can transmit these bacteria to her new born baby while he or she is being delivered. These babies more often suffer eye infections and can become blind if not treated immediately.CLASS: XIL -81- _ BIOLOGY NOTES Prep. By :- Raza Mehdi SYPHILIS: PATHOGEN: Iti eased by a Spirochaete bactrim Treponema pallidum, PATHOGENICITY: 7 These bacteria not only damage the reproductive organs but also affect nervaus system and skeletal system in addition to cause a large number of lesions. Co! INS: These conditions often become fatal not only to the infected men and women but also to new bom babies. REMEDY: Prolonged antibiotic treatment is the probable remedy. GENITAL HERPE: PATHOGEN: It is caused by a virus called Herpes simplex. COMPLICATIONS: Itis characterized by painful blisters and ulcers on and around exterhal genital organs, ‘Sexual partners or new born baby receives this infection from body fluids or genital fluids, REMED) Use of ant not cured. 4:- AIDS INTRODUCTION: ‘Acquired immune deficiency syndrome is a fatal disease caused by HIV (Human Immuno- Deficiency virus). PATHOGENICITY: HIV infection destroys the patient's immune system and exposes infected person to all types of infections. ‘MODE OF TRANSMISSION: Genital and other body fluids are a major source of infection, Unscreened blood transfusions. Reuse of syringe needles, New born can also become infected through placenta of HIV I PREVENTIVE MEASURE: * The vaccine for its cure is not yet available, + To reduce the chance of infection ofthese sexually transmitted disease is that both the husband and wife should restrict to each other. jotics protects from the complications of this infection but the disease itself isCLASS: XII 82. BIOLOGY NOTES Chapter GROWTI A permanent irreversible increase in size, weight, shape & structure usually accompanied by a permanent change of form is called growth, DEVELOPMENT: Zygote is actually a foundation cell of a new organism, thus a single called zygote undergoes a series of progressive changes after which it becomes a multicellular adult, There progressive changes are collectively known as development, EMBRYOLOGY: The study of the changes from a zygote to a complete individual is called embryology. GROWTH & DEVELOPMENT IN PLANT: ‘The growth regions in a plant body are called meristems. TYPES OF MERISTEM, ‘There are three types of meristems. 1. Apical Meristems: ‘These meristems are found in the apical regions of a plant. Example: - Root & Shoot apices 2. Lateral Meristem: This meristem is present b/w the vascular bundles of the stem of gymnosperms & most dicots. It is commonly known as cambium. 3. Intercalary Meristem: ‘The meristem which is found at the base of internodes is ealled intercalary Meristem, FUNCTIONS OF MERTSTEM: 1, APICAL MERISTEMS: This meristem is responsible for primary growth, In this growth the length of a plant is increase.CLASS: XII BIOLOGY NOTES 2. LATERAL MERISTEMS: ‘The lateral meristem or cambium performs the function of secondary growth. In this growth the breadth ofthe plant increases. 3... INTERCALARY MERISTEMS: ‘The intercalary meristem forms the lateral organs such as braches, flowers etc, PHASES OF GROWTH: ‘There are three phases of growth. 1. The formative phase. 2. Elongation phase. 3. Maturation or Differentiation phase. 1. THE FORMATIVE PHASE: © This is restricted to the tips of roots & shoots. * In this region the cells constantly divide & thus increase in number. * The cells in these regions are closely packed together & they have thin cellular wall, dense cytoplasm, small vacuoles & large nuclei. 2. ELONGATION PHASE: © This phase occurs immediately behind the formative region. . ‘The cells of this region are unable to divide but they are large in size because they are in turgid condition. © Inthe root, the region of elongation extends over a few millimeters & in the stem over a few centimeters. 3. MATURATION OR DIFFERENTIATION PHASE: * This phase is found behind the region of elongation. * Here the thickening of the cell walls takes place the elongated cells are modified into permanent ones. ‘*_ Inthis phase the cells are adopted to perform particular functions. -ADAMJEE COACHING CENTRECLASS: XII 84 BIOLOGY NOTES CONDITIONS FOR GROWTH: (a) (b) © 1, EXTERNAL CONDITION: Following are the main external conditions, which alter the rete of growth either positively or negatively. @ ‘Temperature: * Temperature plays an important role in growth because most enzymes show their maximum activity at an optimum temperature (b/w 25°C to 37 °C) + Therefore metabolic function of cell, formation of new protoplast & cell division take place rapidly at the optimum temperature. Gi Light: * Lights required for the synthesis & action of chlorophyll without which photosynthesis cannot take place. * Usually light affect the rate of growth in 3 ways. (@) Intensity of light, () Duration of ight (©) Quality of light, Intensity of Light: High intensity of light destroys to chlorophyll, which ultimately affects the rate of photosynthesis. Duration of light affects the growth of vegetative & reproductive structures, Quality of Light: * __ The quality of light also has influence on growth rate such as red light favours elongation of cells & blue light enhances the cell division but retards cell enlargement. . ‘ULV. light destroys the protoplasm & retard the growth. (iif) Oxygen: The supply of oxygen is required for energy production by respiration without oxygen metabolism & growth are stopped. Duration of Light: eet [ |CLASS: Xi 85+ _ BIOLOGY NOTES (iv) Carbondioxide ‘CO; is necessary for photosynthesis & food production, If this process will continue, more food & other compounds for the synthesis of new protoplasm will bee produced. (v) Nutrients: Efficiency & deficiency of different nutrients play an important role in the growth. For example: Plants growing in Nitrogen deficient soil cannot prepare proteins & show stunted growth & development. Prep. By:- Raza Mehdi 2- INTERNAL FACTORS: Internal factors affecting growth include the relative quantities of different hormones present in the body & the genetic constitution of the organism. Growth Correlation “The growth of a plant organ is related with the growth of other organs which takes place in different directions, this relationship between the growth of organism is known as. growth correlation” GROWTH. DEVELOPMENT Ac ANIMALS DEVELOPMENT OF CHIC} 1. EGG: + The egg of a hen is polylecithal type (i.e. it contains large amount of yolk), ‘+ Its released from the ovary as primary oocyte with a diameter of above 3 cm. ©. The protoplasm is restricted to a very small area called Blastodisc or germinal disc. + Itis the process of fusion of sperm with the ovum to form a single diploid cell, which is called zygote,CLASS: XIL -86- BIOLOGY NOTES © Inhen the fertilization is internal & after the fertilization secondary oocyte becomes a mature ovum. * __Itreleases two polar bodies, which degenerate Iater on, © The fertilized ovum during its way through the oviduct is covered by Albumin outside its vitelline membrane. © Outside the Albumin there are two shell membranes & hard porous proteinaceous calcareous shell. © This fertilized egg is laid 24 hours after the fertilization, 3- INCUBATION: * The development of chick inside the ovum requires 36 - 38 °C temperature. * This temperature is naturally provided by the mother hen or artificially in incubator, * At this temperature the chick completes its development & finally its hatching takes place in 21 days. STAGES OF DEVELOMENT: 1, CLEAVAGE: «© Itisa series of repeated mitotic divisions that takes place in the fertilized ovum. © The cleavage in birds is restricted to the blastodisc lying on the top of the yolk towards the animal pole of the zygote. © This type of cleavage is termed as discoid cleavage. * In fish, reptiles & birds flue cleavage is meroblastic type or incomplete type. © The first two cleavages occur at right angle to each other in vertical plane. © The third cleavage occurs in horizontal plane & us a result & blastomeres are formed, © The rest of the cleavages are irregular & form a large number of cells all over the germinal disc, which is termed as blastoderm. 2. MORULA: * Due to the cleavages the embryo becomes a rounded mass of closely packed blastomeres, which resembles a mulberry & therefore is called Morula, 2. BLASTULA:GLASS: Xil__ -87- BIOLOGY NOTES ‘© It is the embryonic stage, which contains a fluid filled cavity, which is called Blastocoels. * Inchick it appears when the Blast dermal cells spl epiblast & the lower leyer hypoblist, 0 two layers, the upper of «© _ Inbiw these layers the blastocoel appears. © The marginal cells of blastoderim are associated with yolk & form the zone of function or area opaca while the central region is termed as area pellucida, 4- GASTRULA: ‘*— Gastrula is the next stage after Blastula & the process of its formation is called Gastrulation. This is the process in which besides cell division, cell migration & their rearrangement at definite locations in the embryo occur. \ * Due to the arrangement of cell 3 germinal layers are formed i.e. ectoderm, ‘ Mesoderm & Endoderm. 1- ENDODERM FORMATION: * Itis represented by the rearrangement of the cells of the area pellucida of Blastoderm. © Some cells of the hypoblast of the area pellucida migrate downward & spread over the yolk to form a floor of the sub germinal cavity. This floor is known es endoderm. * This type of gastrulation is without invagination & archenteron formation. 2- MESODERM FORMATION: In chick the formation of Mesoderm & Notochord does not involve invagination of the epiblast. + The epiblast moves downward in the middle of blastodise, then separates & move inward towards the yolk. *# Due to this activity of epiblast a groove is produced which is called primitive Streak. © The primitive streak has a swelling at its anterior end called primitive knot. As more cells are added the primitive streak elongates. It is functionally equivalent to the dorsal lip of the blastopore of frog, © When a number of cells of epibiast pass through into the blastocoel to form a new layer of. cells called Mesoderm, 3- ECTODERM FORMATION: The remaining cells of epiblast after the migration of mesoderm form the surface layer or ectoderm,CLASS: XIl 88- BIOLOGY NoTES NOTOCHORD FORMATION & DEFFERENTIATION OF MESODERM: ‘+ The cells of the primitive streak migrate inward into the sub germinal cavity to form a rod of cells called Notochord. : * The Mesoderm on each side of the Notochord gives rise metamerically arranged somites or epimeres which later gives rise muscles axial skeleton & connective tissues, © Below the epimere the segment of Mesoderm is Mesomere or Nephrostome. * The rest of the Mesaderm is the hypomere or lateral plate. After 24 hrs of incubation the lateral plate forms an outer layer (somatic layer) & an inner layer (splanchnic layer) ‘© The space formed in b/w these two layers is called coelom. ‘+ The somatic layer fuses with the ectoderm & the splanchnic layer with endoderm to form somatoplure & splanchnoplure respectively. NEURULATION: * During the formation of Notochord some of the ectodermal cells of area pellucida lying above the Notochord divide rapidly to form a neural plate on the dorsal surface of the Gastrula. The Neural plate sinks inside the embryo to form e neural groove the mid dorsal line. ee * Both the edges of the neural groove move towards each other & fused together to form a neural tube. ‘* The embryo is now termed as Neurula & the process of its formation is called Neurulation, CELL DIFFERENTIATION & ITS MECHANISM: * All the cells of embryo arise from the same fertilized ovum so all of them have same number & kind of genes. ‘+ From the process of Gastrulation & onward some of the genes are activated & others are switched off, some even forever. MECHANISM OF DIFFERENTIATION: * During the differentiation the genetic expression is ultimately influenced by the cytoplasmic chemical composition, + Therefore we can say that the cytoplasm of unfertilized egg is responsible for later a differentiation of embryonic cells into tissues. Prep. By :- Raza Mehdi é EMBRYONIC INDUCTION & ITS MECHANISM Hans Spemann a classical embryologist who received Nobel Prize in 1935 & his colleague Hilde Mangold in 1924 performed an experiment on embryonic induction.CLASS: Xi -89- BIOLOGY NOTES Experiment #1 ‘They cut the presumptive nervous tissues just above the notochord & transplanted into the belly region of the embryo. Result: = They found that neural tissue failed to develop at the ectopic site, Experiment #2 In another experiment they cut away the presmplive notochord tissue & grafted it under the presumptive belly ectoderm. Result: The belly ectoderm developed into the neural tissue, Conclusion: They concluded that an embryonic tissue influences upon the other embryonic tissue through transmitting some chemical stimulus. This phenomenon is called embryonic Induction, ROLE OF NUCLEUS IN DEVELOPMENT Introduction: The role of Nucleus in development was studied in a uniceliular alga ‘Acetabularta which consists of Rhizoid for attachment & a cytoplasmic stalk with a disc like cap at its terminal end. On the basic of cap there are two species of Acetabularia, 1-Acetabularia mediterranea (disc -shaped cap) 2- — Acetabularia cranulata (lobed cap) EXPERIMENT: Haemmerling cut off a stalk containing cytoplasm of A.cranulata & grafted it on nucleus containing Rhizome of A. mediterranea & vice versa. Result: The caps of the previous type (according to nucleus) were regenerated on both of the grafied stalked species of Acetabularia, Conclusion:It indicates that the process of development of cap was regulated by the nucleus rather than the cytoplasm. ROLE OF CYTOPLASM IN DEVELOPMENT Introduction: The role of cytoplasm in the development was studied in the embryo of frog. The ‘unfertilized ovum of frog has an upper pigmented cytoplasmic half & a lower yolky half. After fertilization just opposite to the point of entrance of sperm-nucleus in the ovum. Some of the pigments of cytoplasm shift upward leaving behind a gray arca in the form of a crescent called Gray Crescent, As a result of first cleavage the zygote divides vertically into two cells through the centre of gray crescent. If the two daughter cells (after the first cleavage) are carefully separated from each other so «each of them develops into a normal tadpole larva, EXPERIME!CLASS: XII -90- BIOLOGY NOTES Hans Speman (1930) misguided the normal plane of first cleavage so one of the two daughter cells received entire crescent while the other non-crescent both of the daughter cells Were separated & allowed fo develop. The cell with gray crescent developed into a tadpole while the other fumed into a mass of cells & died,CLASS: Xi -91- BIOLOGY NOTES CONCLUSION: ‘This experiment indicates that cytoplasm containing gray orescent is required for the normal development of frog. AGING Definition: “The body of multicellular animals undergoes a provess of progressive deioriation, This process is known as aging”. The science of Aging is known as Gerontology. CAUSES OF AGING: 1- GENETIC ORIGIN: © According to Lenard Hayflick & Paul Moor Head, the aging is genetically programmed, © They cultured normal embryonic human cells. It was found that all the cell lines proceeded to divide 50 times than stopped & then entire population died off. © Itproved that normal cells have limited potential of division, 2. GENE MUTATIO! * With the passage of time due to the accumulation of Gene mutations the capacity of self-repair of DNA during its replication is lost. © This results in progressively inadequately function cells that cause the aging. REDUCTION OF AGING: © Itis observed that low fat diet, aerobic, low impact exercises may likely to reduce some effects of aging. REGENERATION De “Itis the ability of living organism to construct its lost parts of the body.” Example: Salamanders & lizards can regenerate their tails. ABNORMAL DEVELOPMENT Definition: — “Deviations in the normal structure & functions of an orgenism during the embryological development is called abnormal development.” ‘The study of such abnormalities is called Teratology. Examples: * — Microcephaly small head * Cleft lip & palate (Hare lip) + Polydactyly ‘Many digits. * Dextracardia Heart toward right side-CLASS: Xi -92- BIOLOGY NOTES CHROMOSOMES: ‘The term chromosome (Gr: Chroma = coloured, Soma = body) is used for the thread like coloured bodies which are found inside the nucleus. This term was introduced by a German embryologist Walther Fleming in 1882 while examining rapidly dividing cells of salamander larvae after treating with Perkin’s Aniline dye, The chromosomes contain hereditary characters in the form of genes, present in pairs in an individual and their ‘umber remains constant generation after generation in a given species. ‘The number of chromosomes varies from species to species. Examples: 1, Penicillium =2 chromosomes 2, Mosquito = 6 chromosomes 3. Drosophila ~ 8 chromosomes 4. Garden Pea= 14 chromosomes =~" 5. Frog = 24chromosomes 6 Human = 46 chromosomes 7. Sugar Can = 80chromosomes 8. Fern = 1000 chromosomes STRUCTURE OF CHROMOSOMES: * Chromosomes can only be seen when the cells are dividing, + Each chromosome consist of two very thin threed called chromatids. + They share a common point of attachment called centromere, * Centromere is small spherical zone on the chromosome, within centromere a disc shape protein structure called kinetochore is present to which the spindle fibers attached during cell division + Each chromatid of a chromosome consist of one or more thin threads called chromonema which contain deeper staining regions slong their lengths, given the threads like appearance of strings of beads, These regions are called chromomeres. + The two chromatids of same chromosome are called sister chromatics and the chromatics of different chromosomes are called non-sister chromatids, TYPES OF CHROMOSOMES: ‘There are four types of chromosomes. 1, Telocentric (Terminal centromere) 2. Acrocentric (Sub-Terminat centromere) 3, Sub-Metacentric (J-shaped chromosomes) 4, Meta centric (V-shaped chromosomes) HOMOLOGOUS CHROMOSOMES: ‘Those chromosomes which are morphologically similar with same set of genes are called “Homologous chromosomes” 7 AUTOSOME: All the chromosomes in a cell except the sex chromosomes are called “Autosomes”,CLASS: Xi -93- BIOLOGY NOTES SEX-CHROMOSOMES: ‘Those chromosomes in a cell by which the sex of organism can be determined are called “Sex chromosomes”. KARYOTYPE: ‘The particular array of chromosomes that an individual possesses is called its <9 Hos wa Walaa BEXKOSREER ab OA aA a SARA iy SEAR aa A cae Ts ea ‘The karyotype of individual is often examined to detect genetic abnormalities, such as those arising from extra or lost chromosomes. CHEMICAL COMPOSITION OF CHROMOSOMES: ‘© Cheriically the chromosome is composed of deoxyribonucleo protein, ‘+ Deoxyribonucleo protein is composed of DNA and Protein, ‘The most abundant chromosomal proteins are called Histones. DNA js made up of billions of units called nucleotides and there are three components of nucleotides i 1. Phosphate group. 2, Deoxyribose sugar. 3. Nitrogenous base. ULTRA STRUCTURE OF CHROMOSOME: Eukaryotic chromosomes are composed of chromatin, a complex of DNA and protein, ‘Most eukaryotic chromosomes are about 60% protein and 40% DNA. A significant amount of RNA is also associated with chromosomes, ‘The of chromosomes exist as one very long double stranded fiber, a duplex. If a strand of DNA from a single chromosome were laid out in a straight line, it would more than 7 feet long. * The DNNA is coiled, thus filing into a much smaller space. The coiling of DNA takes place in a following manner. i) Every 200 nucleotides, the DNA duplex is coiled about a complex of Histones these Histones are rich in Arginine and Lysine amino acids, ii) Each of these Histones ftom the core of an assembly called a nucleosome, fil) The Histones are positively charged therefore DNA is strongly attached to the Histones. iv) Further coiling of the DNA occurs when the string of nucleosome wraps up into higher order coils called super coils.CLASS: XI -94- BIOLOGY NOTES ¥) Highly condensed proteins of the chromatin are called Heterochromatin, while the lower condensed proteins of chromatin are called Euchromatin, CHROMOSOMES AS CARRIER OF GENES: 1. The chromosomes can be separately identified visually, but the genes are very small units and so far have not been seen even with best microscope. 2. The chromosomes and gene behave as hereditary units but the genes can not be considered outside the chromosomes. 3. At the time of meiosis the separation of homologous chromosomes take place which result in the segregation of gene pairs. 4, In the genotype of every individual one member of each pair of genes is contributed by one parent and the other by the other parent. CHROMOSOMAL THEORY OF HEREDITY: ‘The chromosomal theory of inheritance was first formulated by the American biologist Walter Sutton in 1902.CLASS: XI -95- BIOLOGY NOTES ‘The main postulates of this theory are as under, ‘* Reproduction involves the initial union of only two cells, egg and sperm. If Mendel’s model is correct then these two gametes must make equal hereditary contributions, Sperm, however contains little cytoplasm, therefore the hereditary material must reside within the nuclei of the gametes, © Chromosomes segregate during meiosis in a manner similar to that exhibited by the elements of Mendel’s model, ‘* Gametes have one copy of each pair of homologous chromosomes, diploid individuals have two copies. * During meiosis each pair of homologous chromosomes orients on the metaphase plate independent of any other pair, DNA AS A HEREDITARY MATERIAL: ‘The material which transmits the parental characters into the coming generation is called “Hereditary material” +» THE HEREDITARY MATERIAL OF BACTERIA? Fred Griffith in 1928 provided the evidence of hereditary material in bacteria, In this regard he discovered the mechanism of transformation in bacteria (Streptococcos pneumoniae). Transformation: The process in which a bacterium takes the naked DNA of dead bacterium is called Transformation. Fred Griffith did his experiments on two strains of Strept. Pneumoniae ic., S- . [and R-II strains, S-II STRAIN: Smooth colonies on culture medium , capsulated, virulent, R-II STRAIN: Rough colonies on culture medium, non- capsulated, non-virulent. EXPERIMENTS 7 RESULTS S-IIl injected in Mice : Died Rell injected in Mice : ‘Alive ‘S-IT (Boiled injected in Mice) |_: Alive S-I Boiled) + Rl injected |: Died in Mice In transformation was confirmed by Avery, Macleod, and McCarty in 1944, ‘They performed the following experiment. ‘S-III (Boiled) + Endonuclease + R-II injected in Mice and they remained alive. Conclusion: Endonuclease enzyme is called the DNA cutter enzyme, and by the use of this enzyme it was confirmed that the hereditary material of bacterium is DNA. THE HEREDITARY MATERIAL OF VIRUS: Tn virus the hereditary material was detected by Hershey and Chase in 1952.Hershey and Chase began a series began a series of experiments involving a particular type of virus which specifically attacks bacterial cells and is called a bacteriophage. Bacteriophage Tz attacks the bacterium Escherichia coli (E. coli) which lives in the human gut. The phage causes E, coli to produce large numbers of T> phage particles in a very short time. ‘The essence of Hershey and Chase’s experiment involved growing Ts-phage particles in £. coli which had been grown on a medium conizining radioactive isotopes of either sulphur (°5S) or phosphorus (P). The phage protein contains sulphur but not sulphur, phosphorus, and the DNA contains phosphorus but notCLASS: XI 6 BIOLOGY NOTES sulphur. Therefore the phage particles formed in E. coli labeled with radioactive sulphur had incorporated this into their protein coats, whereas those formed in phosphorus-labeled £. coli contained radioactively labeled °"P DNA. The labeled Ty-phage particles were allowed to infect non-radioactively labeled E. coli and after a few minutes the cells were agitated in a blender or liquidizer which stripped off the phage particles from the bacterial walls. The bacteria were then incubated and examined for radioactivity. Conclusion: On the basis of these results Hershey and Chase concluded that it wes the phage DNA and not the protein which entered the bacterial cell and gave rise to large numbers of phage progeny. The experiments demonstrated that DNA is the hereditary material. BRIEF REFERENCE OF DNA STRUCTURI DNA isa very complex molecule which which are called nucleotides. composed of numerous units Nucleotides Phosphoric acid Nucleoside Deoxyribose Sugar _Nitrogenous Bases Purine Bases Pyrimlding Bases Adenine Cytosine Guanine “TFhymine 1, PHOSPHORIC ACID 7 ul HO —P —oH 2, DEOXYRIBOSE SUGAR. OHCLASS: Xil 972 BIOLOGY NOTES O ee i Fe NEA, oy on ow 3. PURINE BASES. Ny. 7 1 aN Bo S, Te GuansnE 4, PYRIMIDINE BASES. ° fae 5 fc 4a™. c cH 7 fi nen ac H On Ce | Sorosuse Nw! “THYME hi 7 ib ~e WATSON AND CRICK MODEL OF DNA: INTRODUCTION: James D. Watson and Francis H. Crick in 1953 suggested a model of DNA, which was based on X-Ray diffraction data provided by Maurice HLF. Willikins. For their pioneer work all the three scientists received Noble Prize in 1962, STRUCTURE OF DNA: Watson and Crick suggested a ladder like organization of DNA. * Bach molecule of DNA is made up of two polynucleotide chains which twisted around cach other and form a double helix. ‘© The uprights of the ladder are made up of sugar and phosphate parts of nucleotide and the rungs are made up of paired nitrogenous bases. © The pairs are always as follows: i) Adenine always pairs with thymine and Cytosine with Guanine, ii) The two polynucleotide chains are complimentary to each other and held together by hydrogen bonds. iii) There are two hydrogen bonds between Adenine and Thymine (A=T) and three between Cytosine and Guanine (C=G).CLASS: XII -98- BIOLOGY NOTES iv) Both polynucleotide strands remain separated by 20 A° distance, ¥) The coiling of double helix is right handed and complete tum occurs after 34 A” In each tum 10 nucleotide pairs are present; therefore the distance between two pairs is about 3,4 A°, REPLICATION OF DNA: ‘The mechenism in which DNA prepares its copies _is called “DNA replication”, MECHANISM: * The Watson ~ Crick Model suggested that the bases for copying the genetic {information are complimentary. * One chain of the DNA molecule may have any conceivable base sequence bout the sequence completely determine that's ofits partner in the duplex. Each chain in the duplex is a complimentary mirror image of the other. To copy the DNA molecule, one need only unzip it and construct a new complimentary chain along each naked strand. REPLICATION IS SEMI CONSERVATIVE: ‘+ The DNA replication suggested by the Watson-Crick Model is called semi conservation because after one round of replication, the original duplex is not conserved; instead, each strand of the duplex becomes part of another duplex. + This prediction of the Watson-Crick Model was tested in 1958 by Mathew Meselson and Frank Stahl. These two scientists grew bacteria for several ‘generations in a medium containing the heavy isotope of Nitrogen (Nj). So the DNA of the bacteria was eventually denser than normal. They then transferred the growing cells to a new medium containing the lighter isotope (Ni) and harvested the DNA at various intervals. * At first the DNA that the bacteria manufactured was all heavy. But as the new DNA that was being formed incorporated the lighter nitrogen. Isotope, DNA density felt. GENES (THE UNIT OF HEREDITARY INFORMATION): * Jn 1902 a British physician, Archibald Garrod worked with William Bateson. He noted that certain diseases with his patients were more prevalent in their families. * Garrod concluded that these disorders were Mendelian traits and that they ‘had resulted from changes in hereditary information that had occurred in the past of an ancestor of the affected families. * He examined many disorders in traits e.g. Alkaptonuria, | + ALKAPTONURIA: In this disease the urine of patient becomes black on exposure to air. Such urine contained homogentisic acid (Alkapton), which is oxidized when exposed to air. Garrod concluded that the patients of this disease lack those enzymes which are responsible for the breakdown of the above amino ac GENOME: “The total genomic constitution of an individual is known as genome”. Diploid (2N) —> 2 genome. Haploid (IN) + 1 genome-GLASS: XIL THE ONE GENE-ONE ENZYME HYPOTHESIS: -99- BIOLOGY NOTES George Beadle and Edward Tatum provided definite evidence of this hypothesis. Creative genetic differences: Beadle and Tatum used a saprophytic fungus Neurospora (Red bread mold) for their experiment. The spores of this fungus can grow in the simple medium prepared by Beadle and Tatum for the preparation of this medium they used sugar, some salts and a vitamin (Biotin). Then they ellowed induced mutations by exposing Neurospora spores to X- Rays. ‘Then they allowed the progeny to grow in the previous medium but they observed that there is no germination in spores. This indicate that there is the effect of such substances which are essential for the germination of spores, and these essential substances are separated by the help of DNA but when X-Rays were applied on DNA they produced certain changes, these changes are known as mutation. The individual in which mutation take place in known as Mutant. Identifying mutant strains of neurospora: 1 2. 3 Conclusion: Beadle and Tatum discovered three different strains of Neurospora by the following method. MUTANT I: These spores start germination when Orinithine, Citrulline and Arginine amino acids were added in the growth medium MUTANT 2: These spores germinate when Citrulline and-Arginine amino acids were added in the medium. MUTANT 3: They need only the addition of Arginine amino acid in the medium, ‘The geneticists concluded that genes produced their effects by specifying the structure of enzymes, and that each gene in codes the structure of the single enzyme, ‘They called this relationship the one gene one enzyme hypothesis. RIBONUCLEIC ACID (RNA) RNA isa type of nucleic acid which is found every where in the cell. # Ttmostly has a single helix structure, © It contains ribose sugar (CsHio0:). © Itcontains Uracil instead of Thymine, i Hoch ou ae IN f 4 we weN CoH u ) a " , tl 7 o=q ft o# on Nw RIBOSE 1 UpacieCLASS: Xil =100- BIOLOGY NOTES TYPES OF RNA: ‘There are three types of RNA. 1. RIBOSOMAL RNA (rRNA): The class of RNA found in ribosomes is called ribosomal RNA, | FUNCTION: During polypeptide synthesis it provides the site on the ribosome where the polypeptide is assembled... 2. TRANSFER RNA (tRNA): A second class tRNA is called transfer RNA is ‘much smaller. Human cell contains more than 40 different kinds of RNA molecules. FUNCTION: During polypeptide synthesis (RNA molecules transport the amino acid into the ribosome for the synthesis of polypeptide chain 3. MESSENGER RNA (mRNA): Itis along strand of RNA that passes from the nucleus to the cytoplasm. EUNCTION: During polypeptide synthesis mRNA molecules bring information from the chromosome to the ribosomes to direct the assembly of amino acids into a poly peptide. GENE EXPRESSION AA gene performs its function by the following manner. 1. Amactive gene produces an mRNA which is attached with ribosome and directs the formation of a polypeptide chain. 2. Many polypeptide chains are combined to form a specific protein, 3. This protein forms a specific enzyme. 4. Then this enzyme produces different phenotypic effects. These effects are dt called “Gene expression”. ‘The process of gene expression occurs in two phases, 1. TRANSCRIPTION: The first stage of gene expression is production ofa RNA copy of the gene, with the help ofan enzyme RNA polymerase this process is known as Transcription. STEPS OF TRANSCRIPTION: ‘Transcription is initiated when a special enzyme called RNA polymerase binds to a particular sequence of nucleotide on one of the RNA strands, This strand is known as template strands ot Anti-sense strands, while the other strand is called coding or sense stand, + The sequence of nucleotide where the enzyme binds et that end of the edge of the gene. * Starting at the end of the gene the RNA polymerase proceed to assemble a single strand of RNA with a nucleotide sequence complementary to thet of the template strand. * When the enzyme arrives to a special stop signal at the far edge of the gene, it disengages from the DNA and releases the newly assembled RNA chain, 2. TRANSLATION: “The synthesis of a polypeptide by ribosomes, which use the information contained in and mRNA molecule to direct the choice of amino acids. This process of mRNA directed polypeptide synthesis by ribosomes is called Translation”. : :aaa BIOLOGY NOTES STEPS OF TRANSLATION: ® Translation begins when rRNA molecule within the ribosome binds to one end of mRNA strand, ‘+ When it has bound to the mRNA molecule a ribosome proceeds to move along the mRNA molecules in increments of three nucleotides. ‘© Ateach step it adds an amino acid to a growing polypeptide chain, It continues to do this until it encounters a “Stop” signal that indicates the end of the polypeptide. GENETIC CODES “The genetic codes are the sets of three nucleotide on mRNA to bring particular amino acids in ribosome for the formation of polypeptide chain”. ‘TYPES OF GENETIC CODES: CASE #1: Inthe form of single codon, ‘There will be only four types of genetic codes for 20 amino acids. AiG:c:U CASE#2: In the for of double codon, Then there will be 16 types of genetic codes. A [@ {c Tu A [AA |GA|CA [UA G_[ac [aa [ep [uc c [ac [ac [cc [uc u_|Au [Gu [cu [uu CASE #3: In the form of triple codon. In this condition 64 different types of codes will be present, AUG = Start (Methionine) UAA, UGA, UAG = stop. _ADAMJEE COACHING CENTRE-CLASS: Xi -102- BIOLOGY NOTES u © — x o eo ia uUA ca | UAA ett UGA cit 4) wo} vec VAG ex" vOG up 3 See ee et ee beer eee ae ees ee MUTATION “The abrupt change in the genetic material of an organisin is called Mutation”. TYPES OF MUTATION: There are two main types of mutation, 1. Chromosomal Mutation. 2. Gene Mutation, | CHROMOSOMAL MUTATION: ‘The change in amount, arrangement and the nature of genetic material on a chromosome is called chromosomal aberration. This mutation is visible under TYPES OF CHROMOSOMAL ABERRATION: There are following types of this mutation the microscope, DELETION: In deletion a small segment of a chromosome is missing, ABCDE ‘+ Deletion ABC4 | CLASS: XII =103- 1, PSEUDO-DOMINANCE: Deletion may cause pseudo dominance in 2, LETHAL EFFECT: If deletion takes place in both homologous then it has the lethal effect on the organism. DUPLICATIO! BIOLOGY NOTES. heterozygous. chromosomes ‘The repetition of a chromosomal segment on a chromosome is called duplication. Effects of duplication: ‘Due to the duplication different physiological and functions are disturbed. INVERSION: “When the arrangement of genes on a chromosome is ‘mutation is called inversion. JAABCDER Vinversion DEFABC Effects Of Inve Inversion reduced crossing over. TRANSLOCATION: The transfer of segment of chromosome to a non- chromosome is called translocation. ABCDE >< G@HIIK: ABCDGH EFIvKU EFFECTS OF TRANSLOCATION: ‘Translocation may give rise to varieties within species. GENE MUTATION ‘When one or few nucleotides are changed on DNA then called Gene mutation or Point mutation, ‘This mutation is invisible under the microscope, DNA DAMAGE; (CAUSES OF MUTATION) ‘There are three major important causes of DNA damage, they arc: + — Tonizing radiation Ultra violet radiation + Chemical Mutagens IONIZING RADIATION: morphological changed then the homologous the mutation is High energy radiation such as X-Rays and Gama rays are highly ‘mutagenic, Nuclear radiation is also of this sort * These radiations release unpaired electrons which are called free radical. «These free radicals are highly reactive chemically, reacting violently with the other molecules of the cell including DNA.CLASS: XIl -104- BIOLOGY NOTES ULTRA VIOLET RADIATION: © Ultra violet radiation is the component of sunlight. * When molecules absorb UV radiation a little damage is produce in these molecules. © Mostly certain organic ring compounds are affected by UV-radiation, CHEMICAL MUTAGENS: ) 2 ‘The chemicals that act on DNA fall into three classes. 1. Chemicals thet look like DNA nucleotides that pair incorrectly with the DNA molecule, 2.. Chemicals that remove the amino group from Adenine or Cytosine causing them to impair. 3. Chemicals that add hydrocarbon groups to nucleotide bases, also causing them to impair. HEREDITARY DISEASES DUE TO DNA DAMAGE: SICKLE CELL ANAEMIA : Sickle cell anaemia is a hereditary disorder in which the affected individuals are unabie to transport Oxygen to their tissues properly because the molecules with red blood cells that carry oxygen, molecules of the protein hemoglobin, are detective. EXPLANATION: ‘This disorder occurs due to the presence of abnormal hemoglobin (Glutamic acid is replaced by Valine in B-chain at Sth position). ‘The hemoglobin plays an important role to maintain the normal biconcave shape of red blood cells. But when the hemoglobin becomes abnormal the RBCs becomes sickle or crescent shaped. EFFECTS OE SICKLE CELL ANAEMIA: ‘The abnormal hemoglobin has low binding capacity with oxygen. ‘© These RBCs form clumps in blood vessel and cause their obstruction. This obstruction ‘may result in hemorrhage. : PHENYLKETONURIA: Phenylketonuria is a hereditary condition in which the affected individuals are unable to break down the amino acid Phenylalanine, In this condition Phenylalanine is instead converted to other chemicels that accumulate in the blood stream. : Although the accumulation of this amino acid is not harmful to an adult but it produces harmful effects in infants because the derivative of this amino acid interfere in the development of brain cells and infant with this disorder suffers severe mental retardation and affected individuals rarely live more than 30 years, Phenylketonuria is a recessive disorder caused by a mutant allele of the gene encoding the enzyme that normally breaks down phenylalanine, Only individual homozygous for the mutant allele developed the disorder.CLASS: Xil ~105- BIOLOGY NoTES CELL DIVISION: There are three types of cell division = Amitosis = Mitosis = Meiosis KARYOKINESIS: Division of nucleus is called karyokinesis CYTOKINESIS: Division of cytoplasm is called cytokinesis. AMITOSIS DEFINITION: ‘The cell division in which the nuclear spindle is not formed is known 2s amitosis, EXPLANATION: ‘Amitosis is also called the direct cell division. In this cell division first the nucleus of the * + cell becomes dumbbell shaped & finally it splits into two nuclei. In this way karyokinesis is completed. , ‘Then an invagination appears in the centre of the cell which becomes deep & at the end it divides the parent cell completely into the two daughter cells. EXAMPLES OF AMITOSIS: This type of cell division is found in bacteria, diseased tissues like cancer & tumor. CELL CYCLE DEFINITION: The cell undergoes a sequences of changes which involves period of growth , replication of DNA followed by cell division. This sequence of changes is called cell cycle. It comprises of two phases: (2) Interphase (2) Mitotic phase (mitosis) (1) INTERPHASE: The period of cell cycle b/w two consecutive divisions is termed as interphase. It may be divided into the following sub stages: - Gi (Gap-1) phase = $ (Synthesis) phase = Gr (Gap-2) phase G, PHASE: —+ Cell grows in size. — Specific enzymes are synthesized.CLASS: XI -106- BIOLOGY NOTES ——> DNA base unit are accumulated for DNA synthesis, —> Post-mitotic cell can exist a phase in which the cell may remain for weeks, days or in some cases (e.g., nerve cells & cells of the eye lens) even the life time of the organism. — > 25-50% of interphase S PHASE: — In this phase DNA synthesis takes place, —> Nuclear contents get doubled —> 35-40% of interphase. G, PHASE: - (PRE MITOTIC PHASE): —> _ Cell prepares itself for division e.g., energy storage for chromosomal movement, mitosis, specific proteins, RNA & microtubules sub-units (for spindle fibre) synthesis. Stages fe ceo 3 Gees gene aes eae ce esulcten coms one Bate ee SERRE DURATION FOR CELL CYCLE: —— > HUMAN CELLs: + 24 hrs (average time) for cell cycle. + Mitosis = 30 minutes ° 90 minutes are required for cell cycle. MITOTIC PHASE (MITOSIS) DEFINITION: The cell division in which the number of chromosome in the daughter cells remain equal to that of their parent cells is called mitosis. SUB STAGES OF MITOSIS: There are four sub stages of mitosis, — prophase —> metaphase — anaphase — telophase,CLASS: XII 107. BIOLOGY NOTES @ @ Gui) Gy) PROPHAS —> The chromatin-material is condensed by folding & the chromosomes appeat'as thin ‘threads (0,25 pm - 50pm) — The chromosomes become shorter & thicker. —> Each chromosome is infact a pair of fine threads called chromatids. The two chromatids of each chromosome are held together at Centromere (kinetochore) which is visible asa circular zone in each chromosome. > The spindle fibres start to appear. In animal cell the spindle fibres are produced by centriotes, —> All the spindle fibres collectively form a spindle shaped structure called nuclear spindle or mitotic apparatus which is composed of three types of fibres. Continuous spindle fibres: Running from pole to pole. Discontinuous Spindle fibr ‘Running from pole to equator. Astral fibres: Short fibres radiating from the centrioles only at poles. — Higher plants & some insects lack centrioles so the nuclear spindle develops without them. — Innate prophase the nucleolus & nuclear men frame disappear. —— In the spindle of animal cell astral fibres are present (amphiastral), while in a plant cell spindle does not contains astral fibres (an-astral). METAPHASE: —+ The nuclear spindle is fully developed & the chromosomes are arranged at the equatorial plane of the nuclear spindle, — Then cach chromosome is attached with the discontinuous fibres with the help of its centromere. —> Each Centromere gets two fibres each from opposite poles. —+ Due to the contraction of spindle fibres the Centromere divides & the chromatids of chromosome get separated. ANAPHASE: — Due to the contraction of discontinuous fibres, stretching of interzonal fibres & some cytoplasmic activities, one set of chromatids migrates towards each pole of the spindle. TELOPHASE: ——+ When the two sets of chromatids reach the opposite poles, the fibres of the spindle start diseppearing. — The nuclear membrane & the nucleolus start reappearing & new daugher nuclei are formed. —> This completes the process of karyokinesis. —+ Karyokinesis is then followed by cytokinesis.-CLASS: XIL -108- BIOLOGY NOTES CYTOKINESIS: The division of cytokinesis is called cytokinesis. There are two types of cytokinesis, CELL-PLATE FOMATION: In plant cells the division of cytoplasm begins with the formation of a structure called cell- plate at the equator. It grows outward dividing the mother cell into two daughter cells. FURROWIN In animal cells a furrow or cleavage appears in the cytoplasm at the outer side in the equatorial plane. It deepens inward, thus dividing the cel into two. SIGNIFICANCE OF MITOSIS s a cell division in which unchenged genetic information is transferred from erent cell to daughter cells. * The zygote develops into a complete individual by the process mitosis, * It is important for the replacement of broken cells like RBCS repairs of injured tissues, regeneration of organs, etc. * Growth takes place by mitosis, * Mitosis helps in asexual reproduction,BIOLOGY NOTES MEIOSIS DEFINITON: “The cell division in which the number of chromosomes in the daughter cells is reduced to half as compared to the parent cells called meiosis. ‘The process of meiosis is composed of following two divisions MEIOSIS-I: This division is also called first meiotic division, which is composed of the following stages, E ne PROPHASE METAPHASE-I ANAPHASE-I ‘ TELOPHASE-I 4 @ PROPHAS! q This is a very prolong phase & differs from the prophase ‘of mitosis, because in a this, chromosomes bebave as homologous pair, Prophase-I further consists of the following f stages. LEPTOTENE * ZYGOTENE 4 ‘+ PACHYTENE DIPLOTENE ‘+ DIAKINESISGLASS: XiL -110- BIOLOGY NOTES (a) LEPTOTENE: ‘The chromosomes become visible, shorten & thick, The size of the nucleus increases & homologous chromosomes start getting closer to each other (Each chromosome presents beaded appearance due to the presence of dense granules of chromomeres at irregular intervals along its entire length, (@) ZYGOTENE: ‘The homologous chromosomes come very close to each other & make their pairs. This pairing of chromosomes (homologous) is called Synapsis, The pairs of homologous chromosomes are called bivalents, (© PACHYTENE: % Each chromosome of a bivalent forms two sister chromatids. This is called duplication. + Now the bivalents are called tetrads. (® DIPLOTENE: ~The non-sister chromatids of a tetrad wrap around cach other é& then they are fused at one or more places called chiasmata, % Due to the chiasmata the homologous chromosomes exchange theit segments (genetic material). This process is called crossing over. ‘+ The paired chromosomes repel each other & begin separate. ‘However the separation is uncompleted because homologous chromosomes remain united by their points of interchange (chiasmata). @ DIA IS: + The separation process of bivalents remains continue by a process called terminalization. In this process the chiasmata move from Centro mere towards the end of the bivalent. The nuclear membrane & nucleolus start to disappear & the spindle fibres are formed. (i) ~~ METAPHAS ‘Nuclear membrane completely disappears, ‘Nuclear spindle develops é& the discontinuous spindle fibres are attached to the centromere of homologous chromosomes. (iii) ANAPHASE-I; + The spindle fibres contract & the homologous chromosomes move towards the opposite poles. ‘The two chromatids of each chromosome remain undivided & their movement to the opposite poles helps in removing the remaining chiasmata, ‘At the end of this phase the chromosomes are separated into two haploid sets, ‘one set being present at each pole, (iv) TELOPHASE-: 2 ‘Nuclear membrane reorganizes around each st at two poles. + Nucleoli reappear thus two nuclei each with haploid number of chromosomes are formed. ‘The spindle fibres usually disappear. + Cytokinesis may takes place & two daughter cells are formed.CLASS: XI BIOLOGY NOTES. MEIOSIS. ‘After telophase-I, two daughter cells pass through a small inter phase, but in contrast fo the terphase of mitosis, there is no replication of chromosomes. The ineiosis-II is almost similar to mitosis & induces the same stages. ‘> PROPHASE-II ‘» METAPHSE-IL ‘> ANAPHASE-IL o TELOPHASE-II () PROPHASE-II; The nuclear membrane disappears & the spindle is formed at right angles to the spindle of the 1* division. The chromosomes become short & thick. (i) -METAPHASE-II: “Nuclear spindle is formed + Chromosomes are arranged at the equatorial plane. ‘+ The discontinuous spindle fibres get attached to* centromere. Gi) ANAPHASE-II: % Each centromere divides & separates the two chromatids, which migrate to the opposite poles. (iv) TELOPHASE-1 % — “Annuclear membrane appears around each group of chromatids (now called chromosomes) forming a nucleus * This is followed by cytokinesis “Thus the two meiotic divisions result in the formation of four haploid daughter cells, SIGNIFICANCE OF MEIOSIS: ‘Meiosis is responsible for the formation of haploid gametes. % Crossing over during meiosis brings about re-shuffling of genes, resulting in new combinations of character in the offspring. ‘% Separation of homologous chromosomes & their random distribution into different cells also bring about genetic is variation which are the raw material for evolution, DIFFERENCE B/W MITOSIS & MEIOSI: : MITOSIS ; MEIOSIS The daughter cells receive the same | @ The daughter cells receive the half number of chromosomes. number of chromosomes. % It takes place in the somatic cells of 5 the body. % It takes place in the reproductive cells a of the body. a ‘The parent cell divides one time, + The parent cell divides two times. + Two daughter cells are formed. “> Four daughter cells are formed. ‘There is no crossing over, “> Crossing over takes place. MEIOTIC ERRORS: (NON-DISJUNCTION ‘Non-disjunction is an abnormality during meiosis in which chromosomes fail to separate during anaphase & telophase & does not finish with equal distribution of chromosomes among all the daughter nuciei,CLASS: XII -112- BIOLOGY NOTES MEIOTIC ERRORS: (SYNDROME) % Itis a condition, which produces multiple abnormalities in the offspring. “+ Down syndrome (mongolism) 4 Kline filter's syndrome (homosexual) % — Tumer’s syndrome DOWN’S SYNDROME: (MONGOLISM: Introduction: It is an autosamal non-disjunction in man, in which 21" chromosome fails to segregate, resulting in gametes with 24 chromosomes. This gamete fertlizes with normal gamete, so the new individual will have 47 chromosomes (2n+1). Non-disjunction appears to occur in the ova & related to the age of mother. Morphological & physiological abnormalities: ‘These individuals have flat, broad face, slant eyes with the skin fold in the inner comer & protruding tongue, mental retardation & defective development of central nervous system, KLINEFILTER’S SYNDROME: (HOMOSEXUAL) Introduction: ‘These individuals have additional sex chromosomes e.g. 47 chromosomes (44 autosomes + xxy). They are phenotypically male. Morphological & physiological abnormalities: ‘Testicular atrophy % Mental retardation “No spermatogenesis Nonfertile, TURNER’S SYNDROME: Introduction: ‘These individuals have one missing x chromosome with only 45 chromosomes (44 autosomes +x chromosome). These individuals have female appearance. Morphological & Physiological Abnormalit ‘Ovaries are totally absent. * Due to the absence of ovulation they are non-fertile. Short stature ‘Small nails, which are deeply seated in nail base, be oe CELL DEATH: J. NECROSIS: ‘The death of living cells duc to tissue injury is called necrosis. 2. APOPTOSIS: Apoptosis is a type of orderly and preprogrammed cell death in which the cell responds to certain signals by initiating a normal response that leads to the death of cells. Mechanism: Apoptosis appears to be mediated primarily by the release of Ca++ ions and the activation of certain protein-Kinases and required activation of @ set of gene.CLASS: Xil oH BIOLOGY NOTES Example: During embryonic development, the growth of the cells in the spaces between the fingers; under apoptosis. CANCER CELLS: * In cancer cells the mitotic rate is not inhibited and the cells tend to pile up amitotically, forming irregular masses which are several layers deep, “ The cancer cells show less adhesion to the solid support and among themselves and motility is more pronounced. CAUSES OF CANCER: ‘ The cancer cells are developed by the mutation of cellular gene that controls cell growth and cell mitosis. “ The mutation of the above gene can be increased when a person is exposed to certain chemicals, physical or biological factors such as ionizing radiation, X-rays, gama rays and ultraviolet rays. ‘ In many families there is a strong hereditary tendency to develop a cancer. ‘% Some types of cancers may also develop due to certain type of viruses e.g, Leukemia. -ADAMJEE COACHING CENTRECLASS: XIL -114- BIOLOGY NOTES ‘The study of heredity, variations & environment is called genetics. Heredity: ‘Those characters which are transferred from the parents to their offsprings are called heredity. Inhei c The transmission of characters from the parents to the off spring is called inheritance. Variations: The differences between the two offsprings of the some parents are called variations. Genes: Genes are the unit of heredity which is located on the chromosomes. Allele: Pair of gene related to the same character is called alleles. Homozygous: If en individual has identical alleles of a character, then it is called homozygous. Heterozygous: -The individual having non identical alleles of a character is called heterozygous. Dominan The gene which masks the phenotypic expression of another gene is called dominant. OR The gene which expresses itself both in homozygous and heterozygous condition is called dominant. Recessive: ‘The gene which is unable to express itself in the presence of another gene is called recessive. OR The gene which can only express itself in homozygous condition is called recessive. Genotype: The makeup of genes in an individual is called its genotype. Phenotype: ‘The physical appearance of an organism is called its phenotype.CLASS: XI i -115- BIOLOGY NOTES GREGOR JOHANN MENDEL (182: 84 “Father of genetics” TRAITS DOMINANT | RECESSIVE Height of plaat Tall Dwarh Colour of seed | Yellow ‘Green (cotyledon) Shope of seed Round Winkied Colour of pod Green Yellow Shape of pod ‘Smooth Constristed Position of flowers | Axillary ‘Terminal Colour of seed coat | Coloured Colourless Q. Why did Mendel select pea plants for his experiments? Ans, Pea plants have the following favorable characteristics. ‘These plants can be cultivated in a pot or field, ‘The duration of the life cycle of this plant is very short. This plant has a variety of characters with their contrasting forms. Naturally this is a self pollinating plant. Cross pollination can be performed by some artificial methods This plant produces fertile hybrids. MENDEL’S LAWS OF INHERITANCE «Law of segregation Law of independent assortment 1, LAW OF SEGREGATION Statement: “The hybrids of F1, generation have both the characters of their parents in these characters one is dominant and the other is recessive. They may remain together for a long time but never mix with each other and always keep their identity. They are separated or segregated during the gametogencsis”.-CLASS: Xil -116- BIOLOGY NOTES. Ex) mation: (inheritance of a Mendel crossed pure or true breeding pea plants having yellow seeds (YY) with a true breeding pea plants having green seeds (YY). He termed this parental generation as Pl. generation. All the offsprings obtained in the next generation designated as F1 or first filial generation was having yellow seeds. The green seed character was not appeared in the Fl progeny. This held true whether the pollen grains came from the plants with yellow seeds or plants with green seeds, The yellow trait which found its expression in F, progeny was termed as dominant the green trait that was masked was termed as recessive. Mendel next allowed the FI plants with yellow seeds (Yy) to be self fertilized then F2 progeny was raised. In these progeny, unlike F1, some plants had yellow seeds like the original yellow seed parent and other having green seed like green seed parents. There was 3:1 ratio between yellow & green seeds plants, LAW OF INDEPENDENT ASSORTMENT: Statement: “When two contrasting pairs of traits are brought together in the F generation they first segregate and than assort alleles in each pair are independent of each other”. Explanation: (Inheritance Of Two Traits) Mendel crossed a pea plant having yellow and round seeds (YYRR) with a plant having green & wrinkled seeds (yy rr). All the Fl offsprings had yellow and round seeds (YyRr). Mendel allowed the F1 plants to self fertilize. The F2 plants consisted of not only the parental combinations but plants showing seeds with yellow-winkled & green round traits had also appeared. The F2 progeny appeared in the ratio of 9:3:3:1 for the four types. Yellow - Round = 9 Yellow — Winkled = 3 Green ~ Round 3 Green ~ Winkled 1 It demonstrated that the genes for seed colour & seed shape did not necessarily stay together in the same combination in which they occurred in the parental generation. Instead they assorted independent of each other. TEST CROSS Defi jon: A cross in which a phenotypically dominant individual is fertilized with a homozygous recessive individual is called test cross. Significance: This cross tells us about homozygosity and heterozygosity of a dominant character. Example: Phenotypically tall plants. Case 1: Phenotypically dominant individual is homozygous parents.— CLASS: XI a7 BIOLOGY NOTES Case 2: i Phenotypically dominant individual is heterozygous parents. Conclusion: . If an individual is homozygous dominant, .then it forms all dominant individuals by the test cross. While in case of heterozygous dominant, 50% dominant and 50% recessive individuals are produced. : INCOMPLETE DOMINANCE Blending Inheritance) Definition: The condition which is found in heterozygotes in which the phenotypes is the intermediate form of two homozygotes is called incomplete dominance, Example: Colour of flowers in four O'clock (Mirabilus jalapa) plant when true breeding red flowers and true breeding white flowers of four O'clock plants are crossed, all the plants in F carry pink coloured flowers. The pink coloured flowers on self fertilization produce red, pink and white flowered plants in the ratio of 1:2:1. CODOMINANCE Definition: The condition found in heterozygotes where both the members of allelic pair contribute for the phenotype of individual is called codominance, Example: Coat colour in cattle. Explanation: In a cross between true breeding red cattle and true breeding white cattle, the off springs have roan colour. A close examination of the skin of roan coloured animal shows that the animal does not possess an intermediate shade of skin but it appears so because of mixture of red hair and white hair. It is that none of the two genes is dominant over the other. Such pairs of alleles of a gene to be codominent end the phenomenon as codominance. MULTIPLE ALLELE Three or more contrasting forms of a gene for a trait are called multiple alleles. Example: In human beings ABO blood group is a common exemple of multiple alleles. .CLASS: Xi 118. “ BIOLOGY NOTES ABO BLOOD GROUP SYSTEM: In 1902, Land Steiner classified the human blood into three groups on the basis of two types of antigens that are antigen A and antigen B. These blood groups are A-group, B-group & O-group. * Later on, two of Land Steiner's students Von De Castelli & Sturlli discovered a fourth group i.e., AB-group. Blood Genoty | Phenotype | Antig | Antibodl Group pe en__ | es ‘A= Group | IATA a x B homozygo TAT Ae x B heterozygo us B- Group | 1818 Be B x homozygo Ba B- B ry heterozygo O-Group it os AB (universal donor) ‘AB - Group | IATB ‘AB: AB o Ineterozygou 5 - Antibodies are such proteins which are found in plasma. Each antibody has the ability to destroy a specific antigen, A-GROUP: In this blood A-antigen is present on RBCs while B antibodies are found in serum. B-GROUP: In this blood the RBC contains B-antigen and the serum has A-antibodies. O- GROUP: In this blood RBCs have no antigen whereas the serum contains both A & B antibodies. Due to the absence of antigens, this blood can be given to any person. Therefore this blood is called universal donor, AB- GROUP: : The RBCs of this blood have both A & B antigens but the serum has neither A nor B antibodies. Due to the absence of antibodies this blood can accept all types of blood. Therefore it is called universal recipient. Agglutination: The reaction between antigen and antibody is called agglutination. In this reaction the antibody destroys the antigen. + During blood transfusion, agglutination takes place between the antigens of donor and the antibodies of recipient.i -CLASS: XII -119- BIOLOGY NOTES MR MRS ‘A (hetero) B (hetero) A (hetero) oO AB 0. B (homo) AB B (hetero) oO RH-ANTIGEN Weiner and Levine (1940) discovered a third antigen on RBCs of Rhesus monkey which is also related with the blood groups. This antigen is produced due to the presence of a dominent gene (Rh). Such a blood is called Rh positive when Rh gene is present in recessive form (rh), then Rh antigen does not develop on RBC. Such a blood is known as Rh negative 85% people have positive blood and 15% people have -ve blood. GENOTYPES: Rh Ra +ve (homozygous) Rh th = +ve (heterozygous) rh rh = “ve ERYTHROBLASTOSIS FOETALIS: * This is a disease which is found in new born babies which is caused when the mother is Rh -ve and the foetus is Rh +ve * In this disease Rh antibodies invade the fetus and attach is its red blood cells causing the child to be born severally anaemic. EPISTASIS:- (Genic Interaction & Modified Ratios’ The term “Epistasis” was introduced by Bateson, Epistasis is an interaction b/w the alleles of non homologous chromosomes. In this interaction one allele (epistatic) prevent the second allele hypostatic) to express itself due to this interaction the dihybrid phenotype ratio is modified. CONTINUOUSLY VARYING TRAIT (Polygenic Traits) Definition: Those traits which are controlled by two or more pairs of genes located on different pairs of chromosomes are called polygénic traits and the inheritance of these traits is known as polygenic inheritance. Example 1: Kernal colour in wheat Example 2: Milk production in cattle Example 3: Intelligence, height, colours of skin in human.CLASS: XII -120- BIOLOGY NOTES PLEIOTROPY Definition: The multiple effects of a single gene or allele are termed as pleiotropy. Example: Phenylketonuria in humans Symptoms of Phenylketonuria: + Light hair of light skin pigmentation * High level of phenylalanine in blood & urine. * In fruit fly, the recessive allele responsible for white eye colour also influences the colour of testes & even the shape of the sperm. + In cats, the genetic factor responsible for white & blue eyes also results in deafness. CROSS OVER Definition: The exchange of genetic material between homologous chromosomes in the form of small fragments of chromatids is called crossing over. Mechanism of crossing over This process is completed in following four steps:- > Synapsis > Duplication of chromosomes > Crossing over > Terminalization Synapsis: + Pairing of homologous chromosomes is called synapsis. + This process takes place in the zygotene stage of prophase-1. As a result of synapsis, the pairs of homologous chromosomes are called bivalents. Duplication of chromosomes: * After synapsis each chromosomes of a bivalent splits itself longitudinally to form two sister chromatids. * In this way the bivalents are converted into tetrads, Crossing over: * The process of crossing over between the homologous chromosomes always takes place in tetrad condition. + In this process small fragments of non sister chromatids of homologous chromosomes are separated by the activity of endonuclease enzyme (DNA cutter enzyme). * These fragments change their position & again connect with their chromosomes by the action of ligase enzyme. * In this process a bridge is formed between homologous chromosomes which are known as chiasma,CLASS: XIL 121 BIOLOGY NOTES Term’ This is a process by which the homologous chromosomes are separated after crossing over. * This is actually a specific type of movement of Chiasma in a zipper fashion away from the tetrad, + This process takes place in diekinesis of prophase LINKAGE Definition: The tendency of genes in a chromosome to remain together is called linkage. Example: Wings & colour of body in Drosophila SEX DETERMINATION & SEX CHROMOSOMES: SEX CHROMOSOMES: Definitio’ Those chromosomes in a cell by which the sex of an individual can be determined are called sex chromosomes. AUTOSOMES: Definitio: AIL the chromosomes in a cell except the sex chromosomes are called autosomes. SEX DETERMINATION MECHANISM There are two main types of sex determination mechanism. + Heterogametic male © Heterogametic female Heterogametic male: In these organisms the female organism has two x-chromosomes in addition with autosomes. Therefore it forms similar types of gametes having one chromosomes. Whercas, the male organism has only one x-chromosomes. Therefore it produces two types of gametes i.e. half gametes with an x chromosome and half gametes without an x chromosome. Such type of male is heterogametic. There ure two types of these organisms:- + XX-XO type © XX-XY type @. XX=XO TYPE: In these organisms the female organism has 2x chromosome: and male has only one x chromosome. In this way the female organism an additional chromosome as compared to the male,CLASS: Xi -122- BIOLOGY NOTES Example: Grasshopper Male (23 chromosome) Female (24 chromosome) (i) XX -XY TYPE: In this type male and female have equal number of chromosomes. The female contains two x — chromosomes while the male individual has one x one chromosome. Example: This condition is found in man, Drosophila, etc. Heterogametic Female: (Abraxas mechanism of sex determination) In many animals, the female organism has only one x-chromosome, Therefore, it is called heterogametic whereas the male individual contains two x- chromosomes. So it is called homogametic. In these cases x-chromosome is represented by z & y chromosome is denoted by W. ‘There are two types of these individual:- * ZO-ZZ Type © ZW-~ZZ Type ZO - 22 Type: In these organisms the male has an extra chromosome as compared to the female organism which indicates that male contains ZZ chromosomes and the female has only one Z chromosomes, Example: moth, butterflies, domestic chicken, ZZ-ZW TYPE: Tn this type the female organism has two non-identical sex chromosomes, One is called Z chromosome and the other is called W chromosome. Example: Certain insects, fishes, reptiles, birds SEX LINK INHERITANCE Definitio: If the genes of a trait are found on the sex chromosomes then the trait is called the sex linked trait and the inheritance of such trait is known as sex link inheritance. SEX — LINK INHERITANCE IN DROSOPHILA: In 1910, TH Morgan, discovered that colour of eyes is an example of sex linked trait in Drosophila, The red colour of eyes is dominant over white colour, Genotypes for colour of eyes: R= Red eyes r= White eyes Femal XE = red eyes (homo) xx! = white eyes eae = red eyes (hetero)CLASS: XII 212% BIOLOGY NOTES Mal, xRy = red eyes xy, = white eyes Male x Female 1. Red Red (hetero) f 2. White Red (hetero) 4 3. Red White i 4, White Red (homo) SEX —- LINKED INHERITANCE IN MAN * Colour blindness © Haemophilia COLOUR BLINDNES: Colour blindness is a sex linked hereditary disease. + A colour blind person is unable to distinguish between red & green colours. = The gene which is related with this trait is only found on x-chromosome, Therefore, this disease is common in males. Normal gene =N Colour blindness = n Genotypes: Females: E xe x" = Normal vision xt xe = Colour blind z X™X"= Normal vision (carrier) = E Males: a xy = Normal vision i xy = Colour blind i] Mr. x Mrs. 4 Colour blind. Normal i Normal Colour blind i Normal Normal (carrier) Colour blind Normal (carrier) a HAEMOPHILL ‘© Haemophilia is a sex linked hereditary disease. © In this disease, the human blood is unable to clot in case of external or internal injury. © The gene which is related with this trait is only found on x-chromosomes, Therefore, this disease is common in males. Normal gene = 4H Haemophilic = Genotypes: be Females: xt xt =. Normal _ADAMJEE COACHING CENTRE-CLASS; XII -124- _ BIOLOGY NOTES x" xh Normal (carrier) x® x* = haemophilic Males: xy Normal xy = haemophilic Mr. x Mrs. Haemophilic Normal Normal haemophilic Normal Normal (cerrier) Haemophilic Normal (carrier) DIABETES MELLITUS Introduction: Due to the deficiency or absence of insulin, the glucose level is increased in blood. This condition is called diabetes mellitus. * Insulin dependent diabetes. (Type — I) * Non insulin dependent diabetes. (Type - II) INSULIN DEPENDENT DIABETES: It is an auto immune disorder in which the immune system attacks on the cells of pancreas. This type of diabetes can be treated by insulin injections. NON-INSULIN DEPENDENT DIABETES: This diabetes is commonly produced by reduced responsiveness in target cells due to some change in insulin receptors. This diabetes cannot be treated by insulin injections. The only treatment of this diabetes is exercise and dietary control-CLASS: XiL BIOLOGY NOTES GENETIC ENGINEERING (DNA Recombinant Technology) Genetic engineering is the manipulation of genetic material for practical purpose. BIOTECHNOLOGY: Biotechnology is the manipulation of livitig organism or their components to perform practical task or provide useful products. haw aunee iS eahaa Avet-cancer Cone tierery 7] RECOMBINANT DNA TECHNOLOG' ‘The basic steps in recombinant DNA technology are: - ‘¢ Preparation of recombinant DNA (DNA) molecule. ‘© Insertion of (DNA into host cell. ‘+ Multiplication & production of numerous copies of host with rDNA in it Selection of Bacteria with required gene. PREPARATION OF RECOMBINANT DNA MOLECULE: ] The preparation of this type of DNA requires some basic tools: - i Q) Vector z (2) Restriction enzyme a (3) DNA ligase enzyme-CLASS: XII -126- BIOLOGY NOTES @) YECTOR: Itis ¢ DNA molecule into which a gene is inserted to construct a recombinant DNA molecule. It is capable of replication in host organism, It acts as a vehicle to transport (DNA into host cell. Examples: ‘Vectors used in this technology are bacterial plasmids & bacteriophage. @) RESTRICTION ENZYME: ‘This is @ group of enzyme, which is required fo cut a source DNA molecule into small pieces & to cut plasmid to make a gap where foreign DNA fits into it. @) DNA LIGASE ENZYME: DNA ligase is a key enzyme that seals the restriction fragment with sticky ends of vector, INSERTION OF DNA INTO HOST CELL: Usually the bacterial cells are used as host in recombinant DNA technology. Bacterial cells take up rDNA when they are treated with CaCl, to make them more permeable, MULTIPLICATION OF HOST WITH _rDNA: When the host cell divides & redivides, copies of the recombinant DNA molecules are passed to the progeny & further replication of vector takes place, After a large number of cell divisions, a colony or clone of identical host cells is produced. Each cell in the clone contains one ‘or more copies of rDNA molecules, APPLICATION OF GENETICALLY ENGINEERED BACTERIA: Genetically engineered bacteria can be used in the environment for serving in the field of agriculture. These bacteria can also be used to promote the health of plants to make them resistant towards insect as bioremediation (pollution cleaner), to synthesize organic chemicals, to detect ‘metals, to enhance genetic research to produce pharmaceutical products, Recombinany ‘DNA DNA a ct CGS"CLASS: XIL -127- BIOLOGY NOTES TRANSGENIC PLANTS: Free-living organisms in the environment that have a foreign genie inserted into tiem are 1 said to be transgenic organisms or genetically engineered organisms. The only plasmid for transgenic plant cell is Ti — plasmid (Ti = tumor inducing) transferred by a bacterium called Agro bacterium _tumefacians to many plants. The main aims for developing transgenic plants are: ~ . To cultivate more nutritious plants, Plants require less fertilizer, . Plants grow under unfavorable conditions. Agrobecterlum tumefaclens § CP) dNAconiaring 20 gene for desired tralt Plant cell a A) 2 Insertion of Ti plasmig ff Intro- geneinio ducllon plasmid bi of plant ‘ using rt = TOA estton ts Plant with enzyme and cure TONA new tralt Restriction DNA ligase carrying sile new gene . within plant ‘ chromasome ha & EXAMPLES: A number of transgenic plants have been developed which resist either insects, viruses or E herbicides. Crops of Soya bean, cotton, alfalfa & rice are genetically engineered. Plants are being i engineered to produce fructose, human hormones, clotting factors & antibodies in their seeds. TRANSGENIC ANIMALS Animal cells usually do not take plasmids. But itis possible to micro inject foreign genes into eggs before they are fertilized, This procedure has been used in fishes, chicken, cows, pigs, | rabbits & sheep. a EXAMPLES: ‘A transgenic calf has been produced that carries a gene for the production of human Tactoferin in cow milk (human lactoferin is 2 protein thet is involved in iron transport & has antibacterial activity.CLASS: XII -128- BIOLOGY NOTES Creating a transgenic antmat gene. ot sheiee seg graunese BPE TR ory NZ Gree Transgene is injected into'tite egg of an animal ce implanted ints a surrogate ISOLATION OF EUKARYOTIC GENES FOR TRANSGENESIS Eukaryotic gene or DNA cannot be cleaned directly from its genome because it often contains long non-coding region & bacterial cells are unable to express these genes. To avoid this problem an artificial gene can be made which lack introns. ‘+ In 1* step transcription of an intron containing gene in the cell nucleus produces a pre- RNA molecule. + In the next step intron RNA are removed & spliced the exon RNA together to produce mRNA. + This mRNA molecule is isolated from the cell & used as template to synthesize a complementary DNA (e DNA) strand. * This synthesis of CDNA on mRNA is the reverse transcription being catalysed by an enzyme reverse transcriptase obtained from Retro viruses, * The second DNA strand using is made by DNA molecule is synthesized which has no intron, ‘* This DNA is called complementary DNA (cDNA) GENE SEQUENCING Gene sequencing is a method of determining nucleotide sequence of a gene developed in late 1970s by Friedrich singer. DNA FINGER PRINTING: i About 30% of human DNA does uot code for protein & repeated frequently in genome of that individual. Each of such repetitive DNA sequences are of 20 - 40 bases long, These highly variable & usually unique lengih of non-functional DNA are passed onto the offsprings. The differences in DNA electrophorosis pattems among individuals are called restriction fragments length polymorphism (RFLP). Since RFLPs of each human are unique analogous to the finger prints which are used as ‘marks of identity so RFLPs can be termed as DNA finger prints,CLASS: XI -129- BIOLOGY NOTES Us ique is used to settle dispute are parentage & other relationships. (ii) It is also used to identify criminals from blood, semen, saliva, hair follicles etc. (iii) It is also used to detect hereditary diseases. GENOMIC LIBRARY It consists of copy of genetic information of a species in a preferred environment. This library provides easy access to a preferred geno for its further copying or manipulation. HUMAN GENOME PROJECT (HGP) This project was started in 1990 to discover all the estimated 30,000 to 35,000 human genes located on 23 pairs of chromosomes. Another project goal was to determine the complete sequence of 3 billion DNA sub units. In April 2003, the DNA sequence of 99.99% of human genes with 99% accuracy was accomplished. About 99.0% nucleotide sequence is the same in all humans. Significance of human genome project: 1 will reveal the methodology for early diagnosis better treatment & even prevention of genetic disease. ‘The genomic information of human & other species will greatly help to understand the genomic organization the control of gene expression, cellular growth & differentiation & evolutionany biology. DETECTION & TREATMENT OF SOME GENETIC DISEASES: ‘There are three types of genetic diseases: (Chromosomal abnormalities, (ii) Uni factorial defects, iil) Multi factorial defects, @ CHROMOSOMAL ABNORMALITIES: In the chromosomal defect (eg, Down's syndrome) a child is bom with structurally or numerically abnormal chromosomes. Gi), UNLFACTORIAL DEFECTS: Unifactorial diseases e.g. (Huntington's diseases, cystic fibrosis etc) are caused by a single defective gene or pair of genes, (iii) MULTI FACTORIAL DEFECTS: ‘Multi factorial disorders (e.g, asthma, insulin dependent diabetes) one caused by: the additive effects of several genes along with environmental factors. HUNTINGTON’S DISEASE (@._Itis due to an autosomal dominant ellele on chromosome 4 Gi). The affected individuals are almost certainly heterozygous for the defective gene.CLASS: Xi) -130- BIOLOGY NOTES (ii) Appearance of symptoms is usually delayed until the age of 40 to 50 years. Symptoms of Disease: (Progressive mental deterioration i) Involuntary muscle movements CYSTIC FIBROSIS Tt occurs due to an autosomal recessive allele. Symptoms: It is characterized by a tendency to chronic lung infection & inability to absorb fats & other nutrients from food. Treatment: Most patients can be helped by daily physiotherapy for their lung problems. ROLE OF BIOTECHNOLOGY IN THE DIAGNOSIS OF DISEASE: ‘The use of PCR & DNA probes is providing an excellent tool for the diagnosis of genetic diseases even before the on set of symptoms. Medical scientist can non diagnose more than 200 genetic diseases using such technologies. GENE THERAPY: One of the potential benefits of genetic engincering is to treat genetic diseases in an individual, Example: Severe combined immunodeficiency disease (SCID) SCID This disease is characterized by a very poor immune system so the victim cannot resist infections & consequently dies due to infections like pneumonia, influenza etc. + In this condition the cells of the bone marrow cannot produce an enzyme called adenosine deaminase (ADA) ‘Treatment of SCID: Tn the treatment of SCID, the defective bone marrow cells are removed from the patient & the normal gene for the ADA enzyme is inserted into these cells & then these cells are again inserted into the patient's bone marrow. In this way the patient’s bone marrow starts to synthesize ADA itself. AMNIOCENTESIS: tis a diagnostic procedure in which a small amount of amniotic fluid is with drawn from the amniotic sac. The amniotic fluid contains cells & chemicals from the fetus that can be analyzed to detect fetal abnormalities such as Down's syndrome, hemophilia ete. Tt is usually performed between the sixteenth & eighteenth week of gestation. TISSUE CULTURE Introduction: ‘Tissue culture is a test tube method used to create and clone novel plant varieties, Haberlandt (1902) is called the father of tissue culture.CLASS: XI 2133. BIOLOGY NOTES Chapter 10 DEFINITION I: ¢ gradual development of something is called Evolution.” EXAMPLE: Evolution of Earth, Evolution of Man, Evolution of Plant etc. DEFINITION II; “The evolution of living organism is called Organic Evolution.” DEFINITION II: ‘According to Zimmerman (1953) “Evolution is the transformation of the form and mode of existence of an organism. In such a manner that the descendants differ from their ancestors.” THEORIES OF EVOLUTION: 1- THE THEORY OF SPECIAL CREATION: INTRODUCTION: This theory was put forward by Father Suarez (1548-1613), Spanish Priest. STATEME! “God created all animals & plants. All living things came into existence in their present form especially & specifically created by nature & no change has occurred.” SUPPORTERS OF THE THEORY OF SPECIAL CREATIO! ‘Carolus Linnaeus (1707 — 1778) was also believed in this theory. People believed in this theory till the middle of 19" century. NATURE OF EARLIEST ORGANISMS:- ‘The Holy Quran provides evidence for the formation of earliest organisms. “ Allah hath created every animal of water. Of them is (a kind) that gocth upon its belly & (a kind) that goeth upon two legs & (a kind) that goeth upon four Allah createth what he will, Lo! Allah is Able to do all things. “ (Sura Al-Nur, Ayth 45) * It is believed thot life may have begun deep in the water especially in hot spring called hydrothermal vents. A group of bacteria called Archaebacteria that tolerate temperature upto 120°C. * The Eukaryotic cell might have evolved when a large anaefobic amoeboid prokaryote ingested small aerobic bacteria & stabilized them instead of digesting them. * ILis believed that the prokaryotes may have arisen more than 1.5 million years ago. * Another hypothesis for the evolution of Eukaryotic cells proposed that the prokaryotic cell membrane folded inward to enclose copies of its genetic material. + This imagination resulted in the formation of membrane-bounded organelles in a single cell. Ill-__ THEORY OF ORGANIC EVOLUTION:-CLASS: XII -134- BIOLOGY NOTES According to this theory species are not immutable but once the life appeared on earth, it slowly evolved icc. a species may slowly changes into new species. INTRODUCTION: This concept is called Organic Evolution, Following are the theories, which explained the process of organic evolution, (@® Lamarck’s theory. (Inheritance of acquired characters) Gi) Darwin's theory. (Theory of Natural selection). ii) Weismann’s theory. (Germinal continuity theory). (iv)De Vries, () LAMARCK’S THEORY:- Introduction:~ This theory uses coined by a French Zoologist Jean Baptiste de Lamarck (1774 - 1829) in 1809. POSTULATES OF LAMARCK’S THEOR! His theory was based on following postulates: (1). Effects of environment. 2). Use & disuse of organs, @). Inheritance of acquired characters. a EFFECTS OF ENVIRONMENT:-When some animals under changed condition of environment require new needs & as such acquire new characters (new organs) to better meet with the changed situation of food habit, physiology or shelter secking, Prep. By = Raza Mehdi 2) USE OR DISUSE OF ORGANS:. In the new environment these organisms use some organelles constantly & disuse others so the efforts of an individual of greater use & total disuse of organs strengthens & develop an organ & disuse result in its degeneration & ultimate disappearance. Lamarck believed that such small changes through successive generation promote the origin of new organs & characters which are transmnitted to its off spring in the next generation this is called “ Inheritance of acquired characters”, @) INHERITANCE OF ACQUIRED CHARACTERS: Due to the inheritance of acquired character for ' many generations, such organism started to develop, which are totally different from their ancestors therefore they I are considered as the new species.CLASS: XIL 213+ BIOLOGY NOTES. Totipoteney: Plant cells are totipotent i.e., a cell with full genetic potential of organism. In 1950 a carrot was produced by Fredrich Steward from a single carrot phloem cell, which was grown in nutritive medium containing sugar, minerals & vitamins with coconut milk. Ss TIC EMBRYOS © Cultured plant of certain plants gives rise to embryo like structure that is small & simple than plantlets. ‘They are called somatic embryos because they are derived asexually from somatic cells, ANTHER CULTURE Another type of tissue culture in which anthers are cultured in an artificial medium is called anther cutture, In this method the haploid tube cell within the pollen tube divide producing pro-embryos consisting of as many as twenty to forty cells, Finally the pollen grains rupture releasing haploid embryos, which develop into haploid plant.