Biology Short Notes PDF

Structure of Chromosomes, Cell Cycle & Cell Division Nucleus It controls all the cellular activities of cell. It consists of the following. a. Nuclear membrane – It has perforations called nuclear pores. b. Nucleoplasm c. Nucleolus Nucleolus is the site of ribosomal RN...

Structure of Chromosomes, Cell Cycle & Cell Division Nucleus It controls all the cellular activities of cell. It consists of the following. a. Nuclear membrane – It has perforations called nuclear pores. b. Nucleoplasm c. Nucleolus Nucleolus is the site of ribosomal RNA formation. Network of nucleoprotein fibres are called the chromatin. Chromatin contains DNA, histones (basic proteins), non-histone proteins, and RNA. Chromatin threads condense and organize to form chromosome. The primary constriction in the chromosome is called centromere. Based on the position of centromere, chromosomes are of four types: Metacentric: Centromere is located at the middle of chromosome. Sub-metacentric: Centromere is slightly away from the middle of chromosome. Acrocentric: Centromere is situated close to the end of chromosome. Telocentric: Centromere is located at the terminal end. A small chromosomal segment separated from the main body of the chromosome by a secondary constriction is called satellite. Structure of DNA It has a double-helix structure, similar to ladder. It is made up of nucleotides. Nuclotides are made of sugar, phosphate groups and nitrogen bases Components of DNA Sugar Phosphate groups Nitrogen bases Genes It is a unit of DNA. Located on Chromosomes. Controls the development of one or more traits. It is the basis of Inheritrance. It can acquire mutation leading to variation. Cell cycle It is defined as a series of events that takes place in a cell, leading to the formation of two daughter cells. The average duration of a cell cycle for a human cell is about 24 hours and for yeast cell, it is about 90 minutes Cell cycle is divided into two basic phases: Interphase and M phase Interphase Interphase involves a series of changes that prepares the cell for division. It involves the period of cell growth and DNA replication in an orderly manner. It is divided into three phases: G1 phase – It involves growth of cell and preparation of DNA replication. S phase – It involves DNA replication. The amount of DNA doubles, but the chromosome number remains the same. G2 phase – It involves protein synthesis and further growth of cell, which prepares it for division. G0 phase or quiescent phase – It is the stage when metabolically active cell remains quiescent for long period of time. Significance of Cell Division It is the mean of asexual reproduction in unicellular organisms. It is essential for the growth of a single celled zygote into a whole new multicellular organism. It helps in the repair of injuries and worn out tissues. It replaces dead cells of the body and thus is essential for growth of organism. In sexual reproduction, meiosis occurs. This type of cell division not only results in production of gametes, but also brings new combinations of genes, thus resulting in variations among a population. This also leads to evolution of a species. Mitosis It is a process of cell division where chromosomes replicate and get equally distributed into two daughter cells. Hence, it is also called equational division. The process of mitosis keeps the chromosome number equal in daughter as well as parental cell. Mitosis usually takes place in somatic cells. Mitosis involves four stages: Prophase It involves initiation and condensation of chromosomes.  Nucleolus and nuclear membrane disappear. Metaphase Chromosomal material condenses to form compact chromosomes that get aligned in the middle of nucleus at equatorial plate. Anaphase Centromere splits and chromosomes move apart towards two opposite poles due to shortening of spindle fibres Telophase Chromosomes finally reach their respective poles. Nuclear envelope assembles around each chromosome cluster. Nucleolus and other organelles reform. Karyokinesis and Cytokinesis Karyokinesis is the division of nucleus during mitosis or meiosis that is followed by cytokinesis. Cytokinesis involves the division of cytoplasm of a cell. Cytokinesis is achieved in animal cell by cleavage that deepens and divides the cell into two. It is achieved in plant cell by cell plate formation. When karyokinesis is not followed by cytokinesis, a multinucleate condition arises. This is called syncytium. Significance of mitosis It results in the formation of diploid daughter cells with identical genetic material. Mitosis plays a significant role in cell repair, growth, and healing. Meiosis It is a type of cell division that produces sex cells or gametes. It occurs in the reproductive organs. Significance of meiosis: Chromosome number is halved. It helps in mixing up of genes. Differences between Mitosis and Meiosis Mitosis Meiosis It occurs in the body cells It occurs in the reproductive cells during throughout the life. reproductive age. Parent chromosome and daughter Parent chromosome and daughter cell genes are cell genes are identical. randomly assorted causing genetic variation. It helps in growth and replacement. It helps in gamete formation. Full set of chromosome is passed. Only half of the total chromosomes is passed. Two daughter cells are formed. Four daughter cells are formed. Single nuclear division occurs after Double nuclear division occurs after duplication of duplication of chromosome. chromosome.  Genetics Genetics: It is the branch of science that deals with the principles of inheritance and its practices. Mendel was the first to carry out the study on the transmission of characteristics from parents to offspring. Mendel proposed that heredity is controlled by genes. Mendel’s law of inheritance Mendel experimented on garden pea plant (Pisum sativum) having many visible contrasting characters. He used seven contrasting pairs of characters or traits in garden pea. Trait Dominant trait Recessive trait Seed shape Round Wrinkled Seed colour Yellow Green Flower colour Violet White Pod shape Full Constricted Flower position Axial Terminal Stem height Tall Dwarf Pod colour Green Yellow Mendel crossed pea plants having these seven pairs of contrasting characters/traits and produced offspring from them. His experiments included three steps – Selection of true breeding plants Obtaining F1 plants by cross pollination  Self pollination of F1 plants to obtain F2 generation Important terms: Genes: Functional unit of heredity Alleles: Alternative forms of the same gene; for example, the gene for plant height in pea plant has two alleles T or t Phenotype: It is the physical expression of character; for example, tall and dwarf plants. Genotype: It is the genetic constitution of an organism; for example, TT or Tt is the genotype for tall plants while tt is the genotype for dwarf plants. Dominant: It is the character/trait that is able to express itself over another contrasting trait; for example, tall plant is dominant over dwarf plant. Recessive: It is the character/trait that is unable to express itself over another contrasting trait. Test cross: It is a cross between organisms with unknown genotype and recessive parents. This cross is used for determining whether the given individual has homozygous or heterozygous genotype. Monohybrid cross: It is a cross between two parents that have one pair of contrasting characters; for example, a cross between tall (TT or Tt) and dwarf (tt) plants. The phenotypic ratio obtained in monohybrid cross is 3:1 while genotypic ratio is 1:2:1. Based on observations on monohybrid crosses, two laws were proposed – 1. First law or law of dominance: It states that only one parental trait gets expressed in the F1 generation while both the traits get expressed in the F2 generation. 2. Law of segregation: It states that two alleles segregate from each other when characters are transferred from parents to offspring during reproduction. Dihybrid cross: It is the cross between two parents that have two pairs of contrasting characters; for example, the cross between round yellow seed and wrinkled green seeds. The phenotypic ratio obtained in dihybrid cross is 9:3:3:1.  On the basis of observation of dihybrid cross, the law of independent assortment was proposed. Law of independent assortment: It states that the members of different pairs of alleles assort independently into gametes. Incomplete dominance It is the phenomenon where one allele is incompletely dominant over the other member of the allelic pair. Both phenotypic and genotypic ratios are the same in the case of incomplete dominance, i.e., 1:2:1. Co-dominance It is the phenomenon where both the alleles of a gene are equally dominant and get expressed together in heterozygous condition; for example, ABO blood group in humans. Blood group ABO is an example of multiple alleles. Sex determination Female heterogamy: Presence of two kinds of sex chromosomes in the female; only one kind is present in the male; for example, birds (the female has ZW sex chromosome while the male has ZZ sex chromosome) Male heterogamy: Presence of two kinds of sex chromosomes in the male; only one kind is present in the female; for example, humans, Drosophila (the female has XX sex chromosome while the male has XY sex chromosome) In humans, the genetic make up of the sperm determines the sex of the baby. The genotype of male is XY and the genotype of a female is XX. Examples of sex linked Genetic Disorders Haemophilia – Sex-linked recessive disorder that affects the clotting of blood. Colour blindness – recessive X linked disease in which the person is not able to differentiate between reo colours – red and green Heredity- transmission of characteristics or traits from parents to offsprings.  Variations- difference among individuals of a species and also among offsprings of same parents. Variations are of two types- heritable and non-heritable. Basis of heredity- each trait is influenced by both maternal and paternal DNA. Mendel’s work Proposed- heredity is controlled by factors. Factors are now called genes. Performed experiments on garden pea (Pisum sativum) Used seven contrasting pairs of characters or traits to study heredity. Dominant trait- able to express itself over another contrasting trait Recessive trait-unable to express its effect in the presence of a dominant trait Mendel represented- dominant trait as upper case (e.g., T for tallness) and recessive trait as lower case (e.g., t for shortness) Homozygous- when the factors or genes of a trait are similar e.g., TT or tt Heterozygous- when the factors or genes of a trait are different e.g., Tt Genotype-genetic constitution of an organism e.g., pure tall- TT Phenotype-observable traits or characteristics of an organism e.g., tallness, shortness etc. Genotypic ratio-expected ratio of genotypes produced by a particular cross Phenotypic ratio-expected ratio of phenotypes produced by a particular cross Monohybrid cross-involves only one pair of contrasting characters Phenotypic ratio in monohybrid cross is 3:1 Dihybrid cross-involves two pairs of contrasting characters Phenotypic ratio in dihybrid cross is 9:3:3:1 Stages of Mendel’s experiment Selection of parents- true breeding with contrasting pairs of traits e.g., pure tall (TT) and pure dwarf (tt) pea plants were selected Obtaining F1 plants- F1 generation is the first filial generation, formed after crossing desirable parents e.g., crossing pure tall (TT) and dwarf (tt) plants gives heterozygous tall (Tt) F1 plants Self-pollination of F1 plants- involves crossing F1 plants to obtain F2 plants Dihybrid cross: It is the cross between two parents that have two pairs of contrasting characters; for example, the cross between round yellow seed and wrinkled green seeds. The phenotypic ratio obtained in dihybrid cross is 9:3:3:1. On the basis of observation of dihybrid cross, the law of independent assortment was proposed. Principles of Mendel Each characteristic in an organism is represented by two factors Two factors are - dominant and recessive Two contrasting factors when present in an individual do not blend When more than two factors are involved, they are independently inherited Heredity occurs at cellular level Inside the nucleus of a cell, heredity material is present in the form of DNA DNA associates with proteins to form chromosomes Every somatic (body) cell of the human body has 23 pairs (46) of chromosomes Monohybrid cross: It is a cross between two parents that have one pair of contrasting characters; for example, a cross between tall (TT or Tt) and dwarf (tt) plants. The phenotypic ratio obtained in monohybrid cross is 3:1 while genotypic ratio is 1:2:1. Based on observations on monohybrid crosses, two laws were proposed – 1. First law or law of dominance: It states that only one parental trait gets expressed in the F1 generation while both the traits get expressed in the F2 generation. 2. Law of segregation: It states that two alleles segregate from each other when characters are transferred from parents to offspring during reproduction. Dihybrid cross: It is the cross between two parents that have two pairs of contrasting characters; for example, the cross between round yellow seed and wrinkled green seeds. The phenotypic ratio obtained in dihybrid cross is 9:3:3:1. On the basis of observation of dihybrid cross, the law of independent assortment was proposed. Law of independent assortment: It states that the members of different pairs of alleles assort independently into gametes. Incomplete dominance It is the phenomenon where one allele is incompletely dominant over the other member of the allelic pair. Both phenotypic and genotypic ratios are the same in the case of incomplete dominance, i.e., 1:2:1. Co-dominance It is the phenomenon where both the alleles of a gene are equally dominant and get expressed together in heterozygous condition; for example, ABO blood group in humans. Blood group ABO is an example of multiple alleles. Sex determination Female heterogamy: Presence of two kinds of sex chromosomes in the female; only one kind is present in the male; for example, birds (the female has ZW sex chromosome while the male has ZZ sex chromosome). Male heterogamy: Presence of two kinds of sex chromosomes in the male; only one kind is present in the female; for example, humans, Drosophila (the female has XX sex chromosome while the male has XY sex chromosome). In humans, the genetic make up of the sperm determines the sex of the baby. Sex determination in honey bees Show a special mechanism of sex determination called the haplo-diploidy. Unfertilized eggs develop into males. Fertilized eggs develop into females. Sex-Linked Inheritance The appearance of a trait because of the presence of an allele either on X chromosome or Y chromosome is called Sex-linked Inheritance. Diseases observed in X-linked Inheritance Haemophilia Colour-Blindness Criss-Cross Inheritance The transfer of a gene from mother to son or father to daughter is called as criss-cross inheritance. For e.g. in X-chromosome linkage  Absorption by Roots Morphology It is the branch of biology which deals with the study of external structures of plants and animals. A plant consists of a root system (underground part) and a shoot system (above the ground parts). Roots are the parts of the root system; and stem, leaves, flowers, and fruits are parts of the shoot system. Roots It helps in anchoring plant and absorbing water and minerals. Developed from the radicle part of a cotyledon It consists of a region of meristematic activity covered by a root cap, a region of elongation, and a region of maturation having root hairs. Types of roots system: 1. Tap root system It consists of a primary root that grows deep inside the soil. It also bears lateral roots referred to as secondary and tertiary roots. Example- Dicotyledons (mustard) 2.Fibrous root system Primary root is short-lived and is replaced by a large number of secondary roots. Example- Monocotyledons (wheat) 3. Adventitious roots Roots arise from parts other than the radicle. Example- Banyan tree Root modifications Prop roots – Example: banyan tree Stilt roots – Example: maize and sugarcane Pneumatophores (that helps in respiration) – Example: Rhizophora Characteristics of Root for Absorbing Water Enormous surface area Root hairs containing cell sap at higher concentration Thin walled root hairs Translocation It is a biological process that involves the transport of dissolved material within a plant. It mainly occurs with the help of xylem and phloem. The transport of food from leaves to other parts of plant occurs by phloem. Movement of food in phloem is bidirectional. The conduction of water and minerals from soil to the rest of the plant occurs by xylem. Movement of water in xylem is unidirectional. Need of Water and Minerals for Plants Need of Water For photosynthesis For transpiration For transportation For mechanical stiffness Need of Minerals Needed as nutrients for the plants For the synthesis of a variety of compounds and enzymes Means of Transport Diffusion It is the spontaneous movement of molecules from a region of high concentration to a region of low concentration. It is a slow process and does not require any energy expenditure. It does not require a semi-permeable membrane and can take place through any membrane along concentration gradient. Rate of diffusion is affected by a. concentration gradient b. membrane permeability c. temperature d. pressure Facilitated diffusion It involves the movement of molecule from the region of higher concentration to lower concentration, mediated by a carrier (mainly protein) molecule. Movement of molecules across membrane occurs without expenditure of energy. Porins – They are large protein molecules that form pores in membranes of plastids, mitochondria, and some bacteria Porins allow the movement of small-sized proteins across membrane. Aquaporins are proteins, which form a water-permeable channel. Some protein molecules allow diffusion only if two molecules are present. Based upon the direction which is followed by both molecules, the path can be of three types. Symport – when both molecules cross the membrane in same direction Antiport – when both the molecules move in the opposite directions Uniport – when single molecule moves across a membrane independent of other molecule Active transport It involves the transport of molecules from a region of low concentration to a region of high concentration with an expenditure of energy. It is carried out by membrane proteins. Osmosis Osmosis is a special type of diffusion which involves the movement of water molecules from the region of high concentration to the region of low concentration through a semi-permeable membrane. Semi-permeable membrane = Selectively permeable membrane. Types of Osmosis: Endosmois Exosmosis Rate of osmosis is affected by (i) pressure gradient (ii) concentration gradient Osmotic pressure is the hydrostatic pressure produced by a difference in concentration between solutions on the two sides of a semi-permeable membrane. Tonicity : Relative concentration of solution and its surroundings. Isotonic solution: Solution that has the same salt concentration as the normal cells Hypotonic solution: Solution that has lower salt concentration than the normal cells Hypertonic solution: Solution that has higher salt concentration than the normal cells Important terms : Flaccidity, Turgidity, Plasmolysis, Deplasmolysis,Wall Pressure. Plasmolysis It is the contraction of cells within plants due to the loss of water through osmosis. When cells are placed in hypertonic solution, a cell tends to lose water to the surrounding solution due to exosmosis. The plasma membrane shrinks and the cell is said to be plasmolysed. When cells are placed in hypotonic solution, cells get deplasmolysed (turgid) due to movement of water into the cell from surrounding as a result of endosmosis. Deplasmolysis The opposite of plasmolysis. If not dead, the protoplasm absorbs water The cell swells up Difference between Diffusion and Osmosis Diffusion Osmosis 1 Movement of substances from higher concentration to lower Movement of selective substances thro concentration. membrane. 2 It occurs in any medium It occurs in liquid medium. 3 It helps in equalising the concentration in the available space. It does not equalise the concentration 4 It does not depend on solute potential It depends on the solute potential. Imbibition: It is a special type of diffusion which involves water absorption through colloids causing tremendous increase in volume. For example: absorption of water by seeds and dry wood Water movement Root pressure It is the positive pressure that develops in the roots of plants by active absorption of nutrients from soil. It pushes the water up to small heights. Root pressure is linked to the phenomenon of guttation. Guttation: It involves the loss of water in the form of liquid droplets through the vein endings of the leaves. Guttation occurs early in the morning and late in the evening when evaporation is low and root pressure is high. Transpiration Pull Water transport in tall trees occurs by transpiration pull. Transpiration pull is generated by transpiration. It is also called cohesion - tension - transpiration pull model of water transport. The ascent of xylem sap is dependent on three physical properties of water: Cohesion Surface tension Adhesion  Transpiration Transpiration It is the loss of water in the form of water vapour through stomata. Types of Transpiration Stomatal transpiration- Occurs through stomata Cuticular transpiration- Occurs through surface of stem and leaves Lenticular transpiration- Occurs through lenticels Differences between Evaporation and Transpiration Evaporation Transpiration Loss of water from the surface in the form of water Loss of water from aerial parts of plants in the form of water vapours vapours Fast process Slow process A physical change controlled by temperature and A partially physical and vital process controlled by various pressure internal and external factors Factors affecting Transpiration External Factors: Light Wind Speed Humidity Temperature Atmospheric pressure Carbon dioxide Internal Factors: Water content of the leaves Adaptations in Plants To Reduce Excessive Transpiration Sunken stomata Less stomata Narrower leaves Loss of leaves Reduced exposed surface Thick cuticle Significance Of Transpiration Helps in ascent of sap Cools the internal temperature of plants Distribution of water and minerals in plants Experiments for Demonstration of Transpiration Cobalt chloride paper is used to check transpiration. It is a blue coloured paper which on exposure to moisture, changes its colour to pink. Measurement of Transpiration Two methods for measuring transpiration are : Weighing Method Potometer Method Potometer is a device used to measure water intake by a plant; this intake is equal to the water loss through transpiration. There are a number of designs of potometer that are used to measure transpiration. Some examples include Farmer's potometer and Ganong's potometer (to measure rate of water intake), Darwin's potometer (to demonstrate the suction force created by transpiration), Garreau's potometer (to demonstrate unequal transpiration from both the surfaces of a dorsiventral leaf), etc. Limitations of using potometer: Introducing the air bubble is not an easy task. The twig can die after sometime. Changes in outside temperature can affect the position of air bubble in the capillary tube.  Photosynthesis Green plants prepare their food by the process of photosynthesis. Photosynthesis is the process of synthesizing food from CO2 and water in the presence of sunlight. The equation for photosynthesis is Leaves are the sites for the synthesis of food. The green pigment called chlorophyll is present in leaves. Two phases of photosynthesis Photochemical Phase Biosynthetic Phase Reactions involved in Photolysis:- (i) (ii) (iii) (Phosphorylation) Biosynthetic Phase - The reactions that does not require light(happens during day time as well). Chlorophyll traps solar energy that is used to prepare food from CO2 and water. Thus, plants convert solar energy into chemical energy. Sun is the ultimate source of energy. Green plants absorb CO2 from atmosphere through tiny pores called stomata. Stomata are present on the surface of leaves. Water and minerals are absorbed by roots from soil and are transported to leaves via tiny vessel-like structures present in roots, stems, the branches and the leaves. Chlorophyll, sunlight, CO2 and water are essential raw materials for photosynthesis. Carbohydrates and oxygen are the end products of photosynthesis. The presence of starch in the leaves indicates the occurrence of photosynthesis. Photosynthesis Algae contain chlorophyll and prepare its own food by the process of photosynthesis. End Results of Photosynthesis Glucose Water Oxygen Site and phases of photosynthesis Photosynthesis takes place in chloroplasts. The light phase of photosynthesis takes place in grana. Light reaction is called so because the reaction is light driven. The dark phase of photosynthesis takes place in stroma part of chloroplast. Dark reaction is indirectly dependent on light as during dark reaction, the energy produced (during light reaction) is used. Factors affecting photosynthesis Several factors such as light, CO2, temperature, and water affect the process of photosynthesis. Law of Limiting Factors (Stated by Blackman) - The Blackman’s law of limiting factors states that when a chemical process is affected by more than one factor, then its rate will be determined by factor which is nearest to its minimal value (factor which directly affects the process if its quantity is changed). Light – There is a linear relationship between incident light and rate of photosynthesis at low light intensities. While the rate does not increase further at higher light intensities (as other factors become limiting).  Carbon dioxide – It is the major limiting factor. Concentration of CO2 upto 0.05% increases the rate of photosynthesis. However, beyond this value, it is harmful. Temperature – The rate is maximum at an optimum temperature, which differs in different plants. Water – Water is the main reactant in the process of photosynthesis and its scarcity affects a lot. 1. Sunlight is essential for photosynthesis Place a healthy green potted plant in a dark room for 1-2 days. This is done to ensure that the plant consumes all its reserve food and the leaves do not contain any starch. Then, cover a portion of a leaf of this plant on both sides with two uniform pieces of black paper, fixed in position with two paper clips. Now, expose this plant to bright light. After a few hours, remove the leaf and decolorized it with alcohol and test the presence of food (starch) with iodine solution. You will observe that the portion of the leaf covered with black paper does not show any presence of starch (food). 2. Chlorophyll is essential for photosynthesis Place a variegated plant (i.e. a plant which has both green and non-green areas, for e.g. croton or money plant) in a dark room for 2 − 3 days. This is done to ensure that all the reserve food (starch) is utilized. Place this plant in sunlight for six hours to allow photosynthesis to take place. Then, pluck a leaf from this plant and trace the green areas on a sheet of paper. Now, decolourize the leaf using alcohol and dip it in a dilute solution of iodine for a few minutes. Wash this leaf with water and compare it with the tracings of the leaf done earlier. It will be observed that only the green areas of the leaf could photosynthesize. Importance of Photosynthesis: Provides food Provides oxygen Carbon Cycle: A series of chemical reactions in which carbon as a chemical gets consumed by living organisms and again gets restored in the atmosphere by various means.  Chemical Coordination in Plants Plants respond to stimuli by showing movement. Examples of movements in plants When you touch a sensitive plant such as touch- me- not (Mimosa pudica), the plant folds its leaves and droops. When a seed germinates, the root grows down in the soil and the stem grows up in the air. In the first example, the plant shows movement by folding its leaves and there is no growth involved.So,it is a Growth-independent movement. In the second example, the seed germinates and shows directional movement. The movement of the seedling is caused by growth. If the seedling is prevented from growing, then it will not show any movement. Thus, it is a Growth-dependent movement Movement in Plants Plants show tropic movement and nastic movement. In tropic movement plant either moves towards or away from the stimulus. The movement could be phototropic (towards/away from light), geotropism (gravity stimulated), thigmotropism (touch stimulated) or hydrotropism (moisture stimulated) Nastic movements occur in response to environment stimulus but they are different from the tropic movements since the direction of response is not dependent on the direction of stimulus. Nastic movements may be classified as thigmonastic, thermonastic and photonastic. Tropic movement Directional movement of a specific part of the plant in response to an external stimulus Phototropism- response to light Geotropism- response to gravity Hydrotropism- response to water Chemotropism- response to chemicals Thigmotropism- response to touch Hormones in plants Growth and development in plants is possible because of plants hormones or phytohormones Auxin-growth of stem Gibberellin- promote stem elongation Cytokinin- promote cell division Abscisic acid- promotes seed dormancy Ethylene- regulates fruit ripening  The Circulatory System Need For transport Inside Our Body Digestive System Excretory System Endocrine System Respiratory System Blood Blood is a red-coloured fluid connective tissue. It helps in transportation of nutrients and oxygen from one organ to another. Functions of Blood Transportation by blood Transport of Digested Food Transport of Oxygen Transport of Carbon Transport of Excretory material Distribution of harmones from endocrine glands Distribution of heat throughout the body. Protection by blood Formation of Clot in cases of cut Preventing Blood loss Protecting body from bacteria Production of antitoxins and antibodies Haemoglobin : The chief constituent of RBCs.These are present inside stroma - a spongy body of RBCs. Carbon monoxide Poisoning-Haemoglobin has high affinity towards carbon monoxide as it forms a more stable compound carboxyhaemoglobin(HbCO). Blood comprises of plasma (55%) and formed elements (45%). Plasma is a straw-coloured viscous fluid. Protein contribution in plasma is about 6-8% and the rest about 90-92% is water. Three major proteins present in plasma are: fibrinogen, globulin and albumins – Maintain the osmotic balance of the body.  Plasma without the clotting factor is called serum. Formed elements: It comprises erythrocytes, leucocytes, and platelets. Erythrocytes (Red blood cells) o Healthy adult man has about 5.0 – 5.5 millions of RBCs/mm3 of blood. o It contains a pigment called haemoglobin that plays a role in transport of oxygen and carbon dioxide. Increased Efficiency Of RBCs The Mammalian red blood cells are more efficient as compared to others as they lack certain cell organelles. The factors that makes them more efficient are : Loss Of nucleus Loss Of mitochondria No endoplasmic reticulum Leucocytes (white blood cells) o Healthy adult man has about 6000 – 8000 WBCs mm-3 of blood. Platelets (Thrombocytes) o Blood contains about 1,500,000 – 3,500,00 platelets/mm3. o It plays a role in blood clotting. Functions of Leucocytes(WBCs) The basic function of white Blood Cells is body defence  Phagocytosis: This is a defence mechanism in which the WBCs engulfs the solid substances like bacterias. Inflammation: This occures with injury andinvasion of germs on them, these are taken care by the WBCs by destroying the disease causing germs(phagocytosis) Formation of Antibodies: These are produced by WBCs(lymphocytes) to kill or neutralise the germs and poison from them.These are stimulated by introducing weakned germs through vaccination. Lymph Lymph is a colourless fluid that does not contain RBCs. It transports nutrients from tissue cells to blood through lymphatic vessels. It is responsible for the immune responses as it has specialized lymphocytes. Blood Coagulation Clotting is required to prevent excessive loss of blood from the body. Blood clot − formed by threads of fibrin in which formed elements are trapped Prothrombin (inactive form) thrombin (active form) Fibrinogen (inactive form) fibrin (active form) Mechanism of coagulation is a cascade of reactions involving several clotting factors. Calcium ions play an important role in blood clotting mechanism. The clear liquid squeezed out of fabrin network is called Serum. Blood groups Human body contains four types of of blood groups – A, B, AB, and O. Antigens on Antibodies in Blood group RBCs plasma A A Anti – B B B Anti – A AB A, B Nil O Nil Anti – A, B Person with blood group AB is known as universal recipient. Person with blood group O is known as universal donor. Rh factor:  Rh is an antigen (antigen D) found on surface of red blood cells. Presence of Rh factor indicates Rh+ individual Absence of Rh factor indicates Rh- individual Rh-incompatibility can be observed between Rh-negative blood of mother and Rh-positive blood of foetus. The condition is known as erythroblastosis foetalis. Blood coagulation: Platelets contain chemicals that help in clotting. Clotting takes place through a series of linked enzymatic reactions called cascade process. Calcium ion is important for clotting. Circulatory System Human circulatory system Humans have a closed type of circulatory system. Human circulatory system consists of the heart, blood vessels, and circulating fluid i.e., blood. Blood vessels The three major types of blood vessels are:- Arteries that carry blood away from the heart. Veins that carry blood from tissues back to the heart. Capillaries that enable exchange of water and nutrients between blood and tissues. The capillaries can easily dilate called Vasodilation and easily contract called Vasoconstriction. Functions Of Capillaries: It allows the outward diffusion of Oxygen It allows the WBCs to squeeze out of capillary walls It allows inward and outward diffusion of urea, glucose, harmones etc. Differences between Arteries and Veins Arteries Veins 1. Carries blood towards organs and away Carries blood towards heart and away from from heart. organs. 2. Carries fully oxygenated blood Carries deoxygenated and Co2 enriched blood. Blood flows with low pressure and 3. Blood flows with high pressure and jerks,. smoothly. 4. Have no valves Have valves to prevent backflow of blood. 5. Walls are elastic. Walls are non-elastic. 6. Are Deeply placed. Are superficial. 7 Branched and decreases in size. Unites and increases in size 8. Can constrict and dilate Cannot constrict. 9. Have thick and muscular walls Have thin and less muscular walls. 10. Smallest artery is called arteriole Smallest vein is called Venules. Structure of Heart Heart Human circulatory system comprises of heart, blood, and blood vessels (arteries, veins, and capillaries). Human heart is myogenic. It is because in human heart, contraction is initiated by sino- atrial node (SA node). Heart has four chambers – two atria (auricles) and two ventricles. Tricuspid valve guards the opening between right atrium and right ventricle. Bicuspid valve guards the opening between left atrium and left ventricle. Semilunar valve guards the opening between right and left ventricles into pulmonary artery and aorta respectively. SA node initiates and maintains the auto-rhythmicity of heart. It is also known as pacemaker of heart. Flow of cardiac impulse: Heart beats 70 – 75 times per minute on an average of 72 beats per minute. Cardiac cycle: It is the complete cycle of events in heart that takes place between one heart beat to the next. It comprises three stages: 1. Atrial systole  2. Ventricular systole 3. Cardiac diastole Cardiac output is the amount of blood pumped out by ventricles per minute. Heart sounds 1. Lub is the first heart sound produced when tricuspid and bicuspid valves are closed. 2. Dub is the second heart sound produced when semi-lunar valves are closed. Human circulatory system Human circulatory system comprises of heart, blood, and blood vessels (arteries, veins, and capillaries). Human heart is myogenic. It is because in human heart, contraction is initiated by sino-atrial node (SA node). Heart has four chambers – two atria (auricles) and two ventricles. Tricuspid valve guards the opening between right atrium and right ventricle. Bicuspid valve guards the opening between left atrium and left ventricle. Semilunar valve guards the opening between right and left ventricles into pulmonary artery and aorta respectively. SA node initiates and maintains the auto-rhythmicity of heart. It is also known as pacemaker of heart. Flow of cardiac impulse: SA node AV node Bundle of His Purkinje fibres Heart beats 70 – 75 times per minute on an average of 72 beats per minute. Cardiac cycle: It is the complete cycle of events in heart that takes place between one heart beat to the next. It comprises three stages: Atrial systole Ventricular systole Cardiac diastole Cardiac output is the amount of blood pumped out by ventricles per minute. Heart sounds Lub is the first heart sound produced when tricuspid and bicuspid valves are closed. Dub is the second heart sound produced when semi-lunar valves are closed. Electrocardiograph (ECG) Electrocardiogram is the graphical representation of cardiac cycle produced by an electrocardiograph. P wave is of atrial origin. Q, R, S, T waves are of ventricular origin. Double circulation It is the process where blood passes twice through the heart during one complete cardiac cycle. It is seen in birds and mammals. It is an efficient process that supplies oxygen to all body cells. Blood is circulated to body tissues through systemic circulation and to the lungs through pulmonary circulation. Portal Vein : A vein that starts and ends with capillaries. A system of veins which collects blood from the digestive tract and passes it through capillaries in the liver is called hepatic portal system. Pulse The distension felt because of the contraction of heart, eveytime when blood passes through the arteries as they are elastic in nature is called Pulse. Blood Pressure The pressure exerted by blood through the arteries on their walls. There are two limits to the blood pressur: Systolic Pressure(upper limit) Diastolic Pressure(lower limit) The normal blood pressure for an adult is 120(systolic) and 80(diastolic)  The Excretory System Excretory system- The organ system that performs the function of excretion is known as the excretory system Excretion – It is the process of removing harmful waste products produced in the cells of living organisms. The excretory system in humans includes – a pair of kidneys, a pair of ureters, a urinary bladder and a urethra. Kidney- It is the main excretory organ of the human body. It plays an important role in the formation of urine. Human kidney produces about 1 – 1.8L of urine in a day. The urine consists of 95% water, 2.5% urea and 2.5% other waste products. It is divided into two layers - outer cortex and inner medulla. Nephrons are the basic filtering units of the kidneys. The main components of a nephron are the glomerulus, Bowman’s capsule, and a long renal tube. Ureter carries urine to the bladder. Urinary bladder collects and stores urine. Urethra carries urine out of the body. Dialysis- The process of removing wastes using an artificial kidney is called dialysis. Kidney is divided into outer cortex and inner medullary region. The cortical portion that projects between the medullary pyramids are known as columns of Bertini. Nephrons are basic functional units of kidney. Malpighian body or renal corpuscle comprises of Bowman’s capsule and glomerulus. Malpighian body, Proximal Convoluted Tubule (PCT), and Distal Convoluted Tubule (DCT) are located in the cortical region of kidney. Loop of Henle’s is found in the medullary region of kidney. Vasa recta – It is a loop of capillaries that runs parallel to Henle’s loop. Afferent arteriole: The arterioles that breaks into numerous capillaries to form glomerulus present inside the Bowman's capsule. Efferent arteriole: Emerging from the Bowman's capsule these capillaries combines together and travels a short distance and break up into the secondary capillary network. Urine formation It involves three process:  (i) Glomerular filtration - Filtration of water and dissolved substances out of the blood in the glomeruli and into Bowman's capsule (ii) Reabsorption - Reabsorption of water and dissolved substances out of the kidney tubules back into the blood. This process prevents substances required by the body from being lost in the urine. (iii)Secretion - Secretion of hydrogen ions (H+), potassium ions (K+), ammonia (NH3), and certain drugs out of the blood and into the kidney tubules, where they are eventually eliminated in the urine Glomerular filtration rate: It is the amount of glomerular filtrate formed in all nephrons of both kidneys per minute. It is about 125 mL/ minute in a healthy individual. Regulation of glomerular filtration rate is auto regulative. It is carried out by juxtaglomerular apparatus. About 99% of filtrate is reabsorbed by renal tubule. Glucose, amino acids, and sodium are actively absorbed. Nitrogenous wastes and water are reabsorbed passively from filtrate. Descending limb of Henle’s loop is permeable to water and impermeable to electrolytes. Ascending limb of Henle’s loop is impermeable to water. Distal convoluted tubule involves reabsorption of sodium ions. Counter current mechanism It is an adaptation for conservation of water. Two current mechanisms operating in kidney are – Henle’s loop and vasa rectae. They both help in maintaining a concentration gradient in the medullary interstitium. Regulation of Urine The posterior lobe of Pituitary gland controls the Diuresis (increases production of urine)and concentration of urine by water reabsorption with the help of antidiuretic hormone (ADH). Osmoregulation The process of regulation of water and salts by the kidney when removing wastes like urea is called osmoregulation. In other words the regulation of osmotic pressure of the blood is known as osmoregulation. Disorders of the excretory system There are certain disorders that affect the excretory system. These include kidney stones, urinary infections, presence of glucose or blood cells in the urine, etc.  The Nervous System Control and coordination Working together of various integrated body systems in response to changes in the surrounding for the maintenance of bodily functions is known as control and coordination Nervous system and endocrine system provide control and coordination in animals. Nervous system Neurons -functional units of the nervous system, conduct messages in the form of electrical and chemical impulses Neuron composed of cell body and dendrite, axon and nerve endings. Types of neuron:- Sensory neuron Motor neuron Relaying or intermediate neuron Nerve: A nerve is a collection of nerve fibres (or axons) enclosed in a tubular medullary sheath. This sheath acts as an insulation and prevents mixing of impulses in the adjacent fibres. Transmission of nerve impulse: Under normal conditions, the outer side of the nerve fibre consists of positive charge as more Na+ ions are present outside axon membrane. The neuron is then said to be in polarised state. On stimulation, the membrane becomes more permeable and Na+ ions move inside causing depolarisation. Such a region is known as excited region. The point of depolarisation behaves as stimulus for the neighbouring area and this goes on. In the mean time, the previous area becomes repolarised due to active transport (using ATP) of Na+ ions with the help of sodium pump. Synapse- a small gap between the axon of one neuron and the dendrite of the next neuron Parts of the nervous system Human nervous system divided into- central nervous system (CNS) and peripheral nervous system (PNS) CNS consists of the brain and spinal cord PNS consists of the nerves that connects the CNS to different parts of the body The Brain, spinal cord, and nerves are the important parts of the nervous system Brain The brain is enclosed in a bony box called the cranium and spinal cord is protected by vertebral column. The brain and spinal cord are externally covered by protective covering called meninges. It is made up of three layers namely duramater (outer layer), arachnoid (middle layer), piamater (inner layer). The space between meninges is filled by a watery fluid called cerebro- spinal fluid (CSF). Human brain is classified into- forebrain, midbrain, and hindbrain. Forebrain- It consists of cerebrum, thalamus, and hypothalamus. It has following functions: It is the thinking part of the brain. The forebrain has sensory regions that receive sensory impulses from various receptors.  It has motor regions that control the movement of various muscles (such as the leg muscles). Cerebrum controls intelligence, learning, memory, thinking, and speech. Hypothalamus contains many areas that control things such as body temperature, urge for eating and drinking, etc. Midbrain- It is mainly concerned with the sense of sight and hearing. Hindbrain- It consists of pons, medulla, and cerebellum. It has following functions: Most of the involuntary actions such as heartbeat, blood pressure, movement of food in the alimentary canal, salivation, etc., are controlled by the midbrain and medulla of the hindbrain. Cerebellum is responsible for voluntary actions and maintaining the posture and equilibrium of the body. Spinal Cord It is the continuation of the medulla oblongata and runs through the vertebral column. The spinal cord is made up of two similar halves fused together to form a central canal containing the cerebrospinal fluid. The outer portion of the spinal cord is known as the white matter, which consists of nerve fibres. The inner portion contains the cell bodies of neurons and is known as the grey matter. Autonomic Nervous System (ANS) ANS comprises of sympathetic as well as parasympathetic nervous system The general functions of the sympathetic division are concerned with preparing the body for emergencies (increased blood pressure and rate of heartbeat, increased release of stored nutrients, increased respiration rate, dilation of pupils), whereas the parasympathetic division is primarily involved with conserving energy and replenishing energy stores. Peripheral Nervous System (PNS) PNS comprises of cranial nerves and the spinal nerves. The details of cranial nerves are as follows Number Name Nature Major function 1. Olfactory Sensory Smell 2. Optic Sensory Sight 3. Oculomotor Motor Movement of eyeball 4. Trochlear Motor Rotation of eyeball 5. Trigeminal Mixed Sensation of touch and taste 6. Abducens Motor Rotation of eyeball Taste, facial expression saliva 7. Facial Mixed secretion, neck movement 8. Auditory Sensory hearing, equilibrium  9. Glosso-pharyngeal Mixed Taste, saliva secretion Gastric and pancreatic secretion, GI 10. Vagus Mixed movement visceral reflexes 11. Spinal accessory Motor Muscle movement visceral reflex 12. Hypoglossal Motor Tongue movement Spinal Nerves Spinal nerves are the nerves originating from the spinal cord by means of two roots- a dorsal root and a ventral root. All the spinal nerves are mixed nerves Man has 31 pairs of spinal nerves which are again put into five different categories 1. Cervical (8 pairs) 2. Thoracic (12 pairs) 3. Lumbar (5 pairs) 4. Sacral (5 pairs) 5. Coccygeal (1 pair) Three types of responses of the nervous system are- reflex action, voluntary action and involuntary action Reflex action Sudden movement or response to a stimulus Occurs in very short duration of time Does not involve will or any thinking of brain E.g. If we touch hot plate, we immediately pull our hand back. Voluntary action Actions such as writing, talking etc. that can be controlled consciously. Involuntary action Actions such as breathing, digestion etc. that cannot be controlled consciously. Reflex action – It is an automatic action or response provoked by a stimulus. Reflex pathway is comprised of the following: Receptor: It includes sense organs that receive stimulus. Sensory or afferent neuron: It conducts the nerve impulse from receptor to the spinal cord or brain. Association neuron: It helps to transmit nerve impulse from sensory neuron to motor neuron. Motor or efferent neuron: It transmits nerve impulse to the effector organs like muscles or glands.  Effector: It includes muscles or glands where action takes place in response to stimulus. Sense Organs: Organs that helps us to be aware of our surroundings are known as sense organs. Receptors: Any cell or tissue sensitive to a selective stimuli are called receptors. Eye Composed of three layers: Outermost layer- sclera and cornea Middle layer- choroid, ciliary body, iris Innermost layer- retina, with rod cells and cone cells. Just behind the iris, a transparent, biconvex, and elastic structure called lens is present. Rods – Contain rhodopsin pigment that is highly sensitive to dim light Cones – Contain iodopsin pigment that is sensitive to high intensity light. Cones are also responsible for colour vision. Blind spot – Area where photoreceptors such as rods and cones are absent Fovea – Area that contains only cones. Vision is finest and sharpest in this zone. Aqueous chamber – Space between cornea and lens; contains aqueous humour. Vitreous chamber – Space between lens and retina; contains vitreous humour Pupil regulates the amount of light entering into the eyes. Specific abilities of eyes Power of Accommodation Stereoscopic Vision Common Defects of Eye Defect Characteristic features Myopia (short- In this, nearby things are visible clearly, but distant things become sightedness) blurred. Can be corrected using a concave lens Hypermetropia In this, the nearby objects appear blurred while the distant objects are (long- sightedness) clear. Can be corrected using a convex lens  Astigmatism Uneven curvature of the cornea is responsible for imperfect image of the objects. Glaucoma The aqueous humour is regularly supplied by arterial capillaries and reabsorbed by venous capillaries of ciliary body. Presbyopia In this, the lens loses its flexibility in older people and they are not able to see nearby objects clearly. This defect is corrected by wearing spectacles with convex lens. Cataract The protein fibres in the lens degenerate and the lens becomes opaque. The person loses clarity in the vision. Squint In squint, either both the eyes converge (cross eye) or diverge (wide eye). Colour blindness Person cannot differentiate between colours such as red and green. It occurs in the people with prolonged diabetes. The blood vessels of the retina may leak, close up or begin to grow due to diabetes. Diabetic retinopathy The blood may enter the clear jelly like fluid called vitreous humour and make it opaque causing blindness. Ear Organ for hearing and equilibrium 5/4/2020 Crista and macula are receptors of vestibular apparatus that are responsible for maintaining body balance and posture. Organ of corti is the main hearing structure of internal ear. It is located on basilar membrane that has hair cells. The middle ear contains three small bones – malleus, incus, and stapes (arranged from outside to inside). Mechanism of hearing Pinna collects sound waves and directs it towards ear drum ↓ Transmission of vibrations towards fenestra ovalis through ear ossicles ↓ Generation of sound waves in lymph ↓ Ripple created in basilar membrane bends the hair cells (of organ of corti) against tectorial membrane ↓ Sound waves converted into nerve impulses ↓ Impulse carried to cortex of brain ↓ Impulse analyzed and sound is recognized Role of Ear in balancing Body When we turn our head fluid inside the semicircular canals moves pushing against the sensory hair cells sending nerve impulse to brain -->via auditory nerve cells present in the semicircular canals are highly sensitive to dynamic equilibrium. we are able to balance our body. Nose It is the sense organ of smell. Sensory receptors are present in the nasal cavity. Sends impulses through olfactory nerve. Skin It is the sense organ for the sense of touch and feel. Also protects the body. Has two layers, epidermis and the dermis. Has sweat glands, oil glands and hair follicles. Tongue It is the sense organ of taste. Have taste buds to recognize tastes like sweet, sour, bitter and salty.  Sense Organs Sense Organs: Organs that helps us to be aware of our surroundings are known as sense organs. Receptors: Any cell or tissue sensitive to a selective stimuli are called receptors. Eye Composed of three layers: Outermost layer- sclera and cornea Middle layer- choroid, ciliary body, iris Innermost layer- retina, with rod cells and cone cells. Just behind the iris, a transparent, biconvex, and elastic structure called lens is present. Rods – Contain rhodopsin pigment that is highly sensitive to dim light Cones – Contain iodopsin pigment that is sensitive to high intensity light. Cones are also responsible for colour vision. Blind spot – Area where photoreceptors such as rods and cones are absent Fovea – Area that contains only cones. Vision is finest and sharpest in this zone. Aqueous chamber – Space between cornea and lens; contains aqueous humour. Vitreous chamber – Space between lens and retina; contains vitreous humour Pupil regulates the amount of light entering into the eyes. Specific abilities of eyes Power of Accommodation Stereoscopic Vision Mechanism of vision: Light rays falls on retina ↓ Dissociation of retinal from opsin  ↓ Structure of opsin changes ↓ Permeability of membrane changes ↓ Generation of action potential in ganglionic cells ↓ Transmission of impulse to cortical region of brain ↓ Image formed on retina Ear Organ for hearing and equilibrium Crista and macula are receptors of vestibular apparatus that are responsible for maintaining body balance and posture. Organ of corti is the main hearing structure of internal ear. It is located on basilar membrane that has hair cells. The middle ear contains three small bones – malleus, incus, and stapes (arranged from outside to inside).  Mechanism of hearing Pinna collects sound waves and directs it towards ear drum ↓ Transmission of vibrations towards fenestra ovalis through ear ossicles ↓ Generation of sound waves in lymph ↓ Ripple created in basilar membrane bends the hair cells (of organ of corti) against tectorial membrane ↓ Sound waves converted into nerve impulses ↓ Impulse carried to cortex of brain ↓ Impulse analyzed and sound is recognized Role of Ear in balancing Body When we turn our head fluid inside the semicircular canals moves pushing against the sensory hair cells sending nerve impulse to brain -->via auditory nerve cells present in the semicircular canals are highly sensitive to dynamic equilibrium. we are able to balance our body.  Endocrine Glands Hormones Hormones are chemical messengers that regulate the physiological processes in living organisms. These act upon specific target cells/tissues and organs. Differences between Hormonal Control and Nervous Control Hormonal Control Nervous Control Transmitted electro-chemically through nerve Transmitted chemically through blood fibres Transmitted slowly Transmitted rapidly Affects different organs Affects specific organs Is not affected by previous experience Is affected by previous experience Has both long lasting and short lasting Has short lasting effect effects Glands Exocrine glands – Glands that discharge their secretions into ducts Examples: salivary gland in buccal cavity, sebaceous gland in skin Endocrine gland– Glands that do not discharge their secretions into ducts, but directly into blood These are also called ductless glands. Examples: pituitary gland, thyroid gland, adrenal gland, etc. Human Endocrine System Pituitary, pineal, thyroid, adrenal, pancreas, parathyroid, thymus, and gonads are the organised endocrine glands in our body. In addition, GI tract, liver, kidney, heart also produce hormones. Adrenal gland It is divided into: Adrenal medulla – It secretes adrenaline (epinephrine) and noradrenaline (norepinephrine). These are collectively called as catecholamines. These hormones are also called emergency hormones. Adrenal cortex – It secretes hormone called corticoids. Corticoid such as glucocorticoid regulates carbohydrate metabolism. Example includes cortisol. Corticoid such as mineralocorticoid maintains the sodium potassium level in blood and tissue. Example includes aldosterone. Hyposecretion : Less secretion from adrenal cortex. Disease caused is called Addison's disease. Hypersecretion: Excess of secretion from adrenal cortex Disease caused is called Cushing's Syndrome. Pancreas The islets of Langerhans have two types of cells: α – cells – secrete glucagon 1. β – cells – secrete insulin Insufficient Secretion of Insulin Disease caused: Diabetes mellitus Over- Secretion of insulin Disease caused: Hypoglycemia  Hyperglycemia – Increased blood glucose level Glucagon is a hyperglycaemic hormone. Hypoglycaemia – Decreased blood glucose level Insulin is a hypoglycaemic hormone. Diabetes mellitus – Abnormal high glucose level in blood, which results in release of sugar in urine and formation of toxic ketone bodies Testis Leydig cells (Interstitial cells) – Secrete androgens, mainly testosterone Testosterone plays a role in spermatogenesis and development of male secondary sexual characters. Ovary It secretes two hormones. Estrogen – Secreted by Graafian follicle, it regulates the development of female secondary sexual characters. Progesterone – Secreted by corpus luteum, it acts on mammary glands and helps in milk secretion. Human endocrine system Hypothalamus: Contains neurosecretory cells that produce hormones Hormones regulate the synthesis and secretion of pituitary glands. Two types of hormones are released. Releasing hormones – Stimulate pituitary gland to release hormones Inhibiting hormones – Inhibit pituitary gland from releasing hormones Pineal gland  It secretes a hormone called melatonin. It also regulates the rhythm of body. Thyroid gland It secretes two hormones: Tetraiodothyronine or thyroxin (T4) Triiodothyronine (T3) Deficiency of iodine results into Hypothyroidism. The disease is known as goitre Creatinism Myxodema High level of iodine results into hyperthyroidism. Thyroid hormone plays a role in carbohydrate, fat, and protein metabolism in the body. It also secretes thyrocalcitonin, which lowers the calcium level in blood plasma. Parathyroid gland: It regulates calcium level in body. It increases the reabsorption of calcium ions by renal tubules and digested food. Pituitary gland (i). Adenohypophysis is further divided into two regions: Pars distalis (anterior pituitary): Growth hormone – It is involved in growth and development of the body. Low secretion of growth hormone results in dwarfism and acromegaly (extra  growth of bones in jaws, hands or feet) Prolactin – It helps in growth of mammary gland and milk formation. Thyroid stimulating hormone – It helps in secretion of thyroxine from thyroid glands. Adreno-corticotrophic hormone – It helps in secretion of glucocorticoid hormone from adrenal cortex. Gonadotrophic hormone – It includes the following. Luteinizing hormone – It helps in secretion of androgen from testis. It also induces ovulation from Graafian follicles. Follicle stimulating hormone – It maintains the growth and development of Graafian follicle. Pars intermedia: It secretes melanocyte-stimulating hormone (MSH), which maintains skin pigmentation. (ii). Neurohypophysis (posterior pituitary): – It contains pars nervosa region. Pars nervosa region secretes two hormones: Oxytocin – It helps in contraction of uterus and milk ejection. Vasopressin (Anti-diuretic hormone) – It stimulates reabsorption of water by distal convoluted tubules.Deficiency causes Diabetes Insipidus. Thymus This gland is degenerated with the age. Thymus produces a hormone called thymosins. Thymosins produce T-lymphocytes that protect the body against infectious agents. It provides cell-mediated immunity and also humoral immunity. Endocrine glands  Hormones are secreted by endocrine glands such as the pituitary gland, thyroid gland, adrenal gland, pancreas etc. Major endocrine glands in humans are Pituitary Hypothalamus Pineal Thyroid Thymus Pancreas Adrenal Testis in men /ovary in women A feedback mechanism (positive and negative) regulates the action of the hormones. Characteristics of hormones: Hormones act as chemical messengers. They are secreted by living cells/tissues or organs called glands. They are secreted in very small quantities by glands. They act upon specific cells, tissues, or organs called the target sites. They are generally slow in action, but have long lasting effects. They either accelerate or inhibit a reaction.  The Reproductive System Reproduction: It is a biological process through which living organisms produce offsprings similar to themselves. Modes of reproduction: Sexual and asexual reproduction. Sexual reproduction It involves the fusion of male and female gametes. Male gametes are called sperms and female gametes are called ova. The type of reproduction, which involves only a single parent and the new individuals are formed without fusion of gametes, is known as asexual reproduction. Male and Female Reproductive Systems Reproductive events in humans – Male reproductive system: It includes 1. A pair of testes 2. Accessory glands and ducts 3. External genitalia Testes are located outside the abdominal cavity, within the scrotum. Scrotum acts as temperature regulator. Testes contain seminiferous tubules that contain two types of cells. 1. Spermatogonia (male sperm cell) 2. Sertoli cells, which provide nutrition to spermatids (sperm) Outside seminiferous tubules, there are Leydig cells. Leydig cells are also known as interstitial cells. They secrete the male hormone, testosterone. Male sex accessory ducts are 1. Rete testis 2. Vasa efferentia 3. Epididymis 4. Vas deferens Male external genitalia include the penis. It facilitates insemination.  Male accessory glands are 1. Seminal vesicles 2. Prostate gland 3. Bulbourethral gland Female reproductive system: It consists of 1. A pair of ovaries 2. A pair of oviducts (fallopian tube) 3. Uterus 4. Vagina 5. External genitalia 6. A pair of mammary glands Female accessory ducts are oviduct, uterus and vagina. The fallopian tube is divided into isthmus, amphulla and infundibulum. Structure and Function of Female Reproductive System Female reproductive system: Consists of 1. A pair of ovaries 2. A pair of oviducts (fallopian tube) 3. Uterus 4. Vagina 5. External genitalia 6. A pair of mammary glands  Female accessory ducts are oviduct, uterus and vagina. The fallopian tube is divided into isthmus, ampulla and infundibulum. Ovaries are the primary female sex organ. The ovarian stroma is made up of peripheral cortex and inner medulla. Menstrual cycle Menarche: First occurrence of menstruation at puberty Menopause: End of the menstrual cycle, at around 50 years of age Events during the menstrual cycle – Menstruation phase: It involves the process of menstruation. If the egg does not get fertilised, the endometrium breaks down and is released out from the vagina in the form of blood. Follicular/proliferative phase: It involves increase in levels of FSH and LH hormones. Release of the FSH hormone stimulates the primary follicle to change into the matured Graafian follicle. Release of the LH hormone induces release of the ovum. Ovulatory phase: It is characterised by ovulation or release of the ovum from the Graafian follicle due to high level of LH hormone. Luteal phase: It is characterised by the rupture of the Graafian follicle in the corpus luteum.  In the absence of fertilisation, the corpus luteum degenerates. The corpus luteum secretes progesterone. Progesterone is important during pregnancy as it prepares the endometrial wall of the uterus for implantation. Fertilisation and implantation Fertilisation takes place in the ampullary–isthmic junction. Binding of the sperm with the zona pellucida layer of the ovum changes the membrane permeability and blocks the entry of any other sperm. Sex of the baby is determined by the type of the male gamete (X or Y) that fuses with the female gamete (X). A diploid zygote undergoes several mitotic divisions to form the blastocyst. Zygote →Blastula →Morula (8 to 16 cell stages) →Blastocyst The blastocyst is implanted in the endometrium of the uterus. Pregnancy After implantation, the trophoblast forms finger-like projections called chorionic villi, surrounded by the uterine tissue and maternal blood. The chorionic villi and the uterine tissue get integrated to form the placenta. Placenta: It is the structural and functional unit between the embryo and the maternal body. It is connected to the embryo through the umbilical cord.Placenta acts as a permeable membrane and allows diffusion of substances through it. Moreover it does not allow the germs to pass through. Substances that passes through placenta: From Mother to Foetus Oxygen Nutrients(gucose, amino acids, vitamins, mineral ions) From Foetus to Mother CO2 Urea and other wastes Functions of the placenta:  Umbilical cord helps in transportation of substances between the mother and the foetus. Provides nutrients to the embryo Removes waste products produced by the foetus It releases several hormones that are essential for pregnancy – Human chorionic gonadotropin (hCG). Human placental lactogen (hPL) Oestrogens Progestogens Relaxin is secreted by the ovary. Relaxin, hCG and hPL are released only during pregnancy. After nine months of pregnancy, the foetus is ready for delivery. Parturition: It is the process of expulsion of the full term foetus out of the uterus. It is induced by the hormone oxytocin. Lactation: It the process of producing milk after the birth of the baby. The hormone involved in lactation is prolactin.  Human Evolution Origin of life Evolutionary biology is the field of science that deals with the study of evolutionary development of life forms on earth Big-bang theory explains the origin of the universe. Scientists believed that life originated through chemical evolution. Formation of biomolecules → First life form According to Oparin and Haldane, the primitive atmosphere was reducing as it lacked oxygen. The atmosphere was rich in methane, water vapour, ammonia and carbon dioxide. The temperature was high and volcanic eruptions were frequent. Urey and Miller experimentally confirmed that formation of life was preceded by chemical evolution. Branching descent and natural selection are the key concepts of Darwin’s theory. Evidences of evolution - Fossils Homologous organs Analogous organs Vestigial organs Comaprative anatomy and morphology Embryological evidences Molecular evidences The slow and gradual process of change of one organism into another is known as Organic Evolution. The occurrence of evolution has been supported by various theories put forth by biologists. In 1809, Jean Baptiste Lamarck a French zoologist put forth the theory of inheritance of acquired characters; also known as Lamarckism. He stated that according to their need, organisms put some organs in their bodies to maximum use while some of the organs were not used. The part of the body put to maximum use will have the tendency to grow larger and stronger while the part less used will become less prominent and ultimately disappear  altogether. Thus, the organisms acquired new characters. For example, giraffe have developed long necks as a result of attempts to eat leaves high up on trees. Darwinism According to Darwin, evolution took place by natural selection. Another aspect of natural selection is the survival of the fittest, where nature selects the individuals, which are most fit, to adapt to their environment. Evolution of man  Population Population It is a group of organisms inhabiting a given area. Attributes of population are – Birth rate Death rate Sex ratio Age distribution Age pyramid: It shows the age distribution pattern for a population. Age pyramid for human population shows – Expanding population: Has a broader base, representing more number of individuals in pre-reproductive (young individuals) age group Stable population: Has almost equal number of individuals in the pre- reproductive and reproductive age groups, converging at the post-reproductive age group Declining population: Has lesser number of individuals in the pre-reproductive group and greater number of individuals in the reproductive age group Demography The Statistical study of human population considering the following factors: Distribution of population Size and Density of population Birth rate Death rate Growth rate of population Reasons Behind the Population Explosion Rapid rise in population has been observed in past few decades and some of the reasons behind it are: Industrial Revolution New Discoveries in Medical Science Factors responsible for population explosion in India Consequences of population explosion Environmental pollution Problem of poverty and unemployment Price hike Sanitation problem in congested areas Pressure on natural resources like water mineral resources, food, forests and fossil fuels. Sustainable Use of Resources: Using the resources in such a manner that it is available for the future generation as well as there is no ill effect on the resource. Sustainable Development can be achieved by: Optimum utilisation of resources Recycling and reusing Using renewable resources Need for adopting control measures as it creates a lot of problems: Per capita income is decreasing Health of population is affected Over utilisation of natural resouces Contraceptive methods include Intrauterine devices: Non-medicated IUDs (e.g., Lippes loop), Copper- releasing IUDs (e.g., CuT, Cu7), and hormone-releasing IUDs (e.g., LNG 20). Oral administration: Mainly used in the form of pills. Example: saheli Sterilisation technique: It includes surgical methods. Tubectomy: It involves the cutting and tying of the fallopian tube in females. Vasectomy: It involves the cutting and tying of the vas deferens in males. It is essential to educate the people about populatiuon explosion and its adverse effects by creating awareness and educating people about advantages of small families.  Pollution Global warming - The rise in overall temperature of the earth because of the green house effect is referred as global warming. Air pollution The layer of air present around the earth is called atmosphere. Atmosphere is composed of 78% of nitrogen, 21% of oxygen, and 1% percent other gases such as carbon dioxide, ozone, water vapour, methane, etc. The phenomenon of contamination of air with unwanted substances so that it becomes harmful for living organisms and non-living substances is known as air pollution. The substances, which cause air pollution, are called air pollutants. Sources of air pollution are Power plants Factories Automobiles Burning of firewood Types of air pollutants Carbon monoxide It is a colourless poisonous gas. It is produced from incomplete burning of fossil fuels. Smog It is made up of smoke and fog. Sulphur dioxide It is produced from combustion of fuels. Nitrogen dioxide It is produced from incomplete burning of fuels. Chlorofluorocarbons (CFCs) They are released from refrigerators, air conditioners, and aerosol sprays. They cause damage to the ozone layer resulting in the formation of ozone hole.  Suspended particulate matter It comprises of tiny particles, which remain suspended in air for a long time. They are produced during burning of fossil fuels in power plants, mining, steel making, and other industrial processes. Ozone depletion Ozone can be classified as good ozone and bad ozone. Good ozone is present in the stratospheric region of the atmosphere while bad ozone is produced by the interaction between the various primary pollutants in the tropospheric layer. The thickness of ozone is measured in terms of Dobson units (DU). The thinned layer of ozone over Antarctica region is referred to as the ozone hole. Chlorofluorocarbons or CFCs have caused damage to the stratospheric layer, leading to the formation of the ozone hole. High dose of UV-B radiations causes corneal cataract and inflammation of cornea in human beings. The inflammation of cornea is known as snow blindness or sunburn of cornea. Montreal Protocol is an international treaty signed for controlling the emission of ozone-depleting substances. It was signed in the year 1987. Water pollution The common sources of water pollution are domestic sewage, industrial effluents, thermal wastewater discharge. Eutrophication: It is the natural ageing process of a water body due to nutrient enrichment. It increases the ecosystem’s primary productivity. Domestic sewage is rich in nitrogen and phosphorus. These compounds act as nutrients for the growth of algae in contaminated water bodies. This accelerates the rate of eutrophication in the water bodies. Oil Spills - The accidental discharge of oil or petroleum in water bodies is called oil spills. This results in the death of a lot of marine lives. The algal bloom causes the microbial population to increase, which consumes larger amount of oxygen dissolved in the water bodies. As a result, the level of dissolved oxygen in the water bodies decreases, and biological oxygen demand of the water bodies increases.  Industrial effluents contain inorganic toxic substances, which may undergo biomagnification. Thermal wastewater discharge involves release of heated water from thermal power plants that increase the temperature of the water body. It causes damage to the indigenous biodiversity of the water body. Biological magnification: It is the increase in the concentration of pollutants or harmful chemicals with the increase in each trophic level. DDT shows the phenomenon of biomagnification. Integrated wastewater management is the possible solution for controlling water pollution. In this approach, the water is first treated by conventional means such as filtration, sedimentation, and chlorine treatment, followed by bioremediation. Sources of soil pollution: Industrial Wastes Commercial and Domestic Waste Chemical Fertilizers Biomedical Wastes Pesticides Solid waste can be categorised into into two types: Biodegradable Waste Non- biodegradable Waste Preventive measures to reduce soil pollution: Treating the waste products before disposal Reducing the use of polythene bags Minimizing the use of products made of plastic Minimizing the use of pesticides Sources of radioactive pollution Mining of radioactive ores (such as uranium and thorium) Nuclear power plants accidents Nuclear explosions  Industrial emissions from nuclear reactors Use of X rays in medicine Effects of radioactive pollution Radiations have the ability to penetrate into the body tissues and can bring the cellular damage. It leads to various diseases such as skin cancer, eye cataract, etc. Radioactive substances, when penetrate into the soil, result in soil pollution. They destroy the fertility of the soil. Radioactive substances can get transported into the plants through roots. It leads to genetic mutation and hampers the normal functioning of plants. Measure to prevent radioactive pollution The safety measures during the handling of radioactive substances should be strictly enforced. Careless handling of radioisotopes and leakage from nuclear reactors must be avoided. The radioactive wastes must be carefully and efficiently dispose off from the environment. Industrial wastes carrying radioactive substances must be adequately treated before being discharged into the environment. Unpleasant sound is called noise. Noise pollution – Presence of unwanted and excessive sound in the environment Noise pollution may cause many health related problems. Measures to control noise pollution: Moving noise producing industries away from residential area. Minimizing the usage of loud speakers. Avoiding unnecessary usage of horns Planting more and more trees.