SYLLABUS FOR RRB JE/SSE 2015
IMPORTANT NOTES
Atoms and Molecules
1. Law of conservation of mass :This law was stated by Lavoisier in 1744. It states that “In all physical and chemical changes, the total mass of reactants is equal to total mass of products.”
2. Law of constant proportions (or constant com-position) : This law was first stated by Proust in 1797. According to the law “a chemical compound is always found to be made up of the same elements combined together in the same proportions by weight” e.g. the ratio of hydrogen and oxygen in pure water is always 1: 8 by weight. This law is also called law of definite proportions.
3. Dalton’s Atomic theory : Postulates of Dalton Atomic Theory Matter is made up of extremely small indivisible particles called atoms. Atoms of the same substance are identical in all respects i.e., they possess same size, shape, mass, chemical properties etc. Atoms of different substances are different in all respects i.e., they possess different size, shape, mass etc. Atom is the smallest particle that takes part in a chemical reaction. Atoms of different elements May combine with each other in a fixed simple, whole number ratio to form compound atoms. Atoms can neither be created nor destroyed i.e., atoms are indestructible.
4. Atom : It is the smallest particle of an element which can take part in a chemical change. It may or may not be capable of independent existence.
5. Symbol: The abbreviation used for lengthy names of elements are termed as their symbols. The symbol of an element is the first letter or the first and another letter of English name or Latin name of the element. While writing a symbol, the first letter is always capital and the second is always small.
6. Molecule : It is the smallest particle of an element or compound that is capable of inde-pendent existence and shows all the properties of that substance. [The molecules of an element is made up of only one and same type of atoms, while the molecule of a compound is made up of dissimilar atoms]
7. Atomicity : The number of atoms present in a molecule of an element or a compound is known as its atomicity. e.g. the atomicity of oxygen is 2 while atomicity ozone is 3.
8. Ion : It is an electrically charged atom or group of atom. It is formed by the loss or gain of electrons by an atom. Ions are of two types : + + 2+ (i) Cation : It is positively charged ion and is formed by the loss of electron from an atom e.g. H , Na , Ca , Al , NH etc. (ii) Anion : It is negatively charged ion and is formed by the gain of electrons by an atom, e.g. Cl , O , C , F , CO PO etc.
9. Valency : The combining power (or capacity) of an element is known as its valency.
10. Formula of simple and molecular compounds Binary compounds are those compounds which are made up of two different elements e.g. NaCl, KBr, CaO etc. Following rules are to be followed for writing the formula. (i) The valencies or charges on the ions must be balanced. (ii) For a compound made up of a metal and a non-metal, the symbol of metal is written first. (iii) In compounds formed with polyatomic ions, the ion is enclosed in a bracket before writing the number to indicate the ratio.
11. Atomic mass of an element : The atomic mass of an element is the numerical number which indicates how many times an atom of an element is heavier than 1/12 of mass of an atom 12 of carbon-12. For example, the atomic mass of magnesium (Mg) is 24 which indicates that one atom of magnesium is 24 times heavier than 1/12 of a carbon-12 atom.
12. Gram atomic mass : The atomic mass of an element expressed in grams is known as gram atomic mass. (Gram atomic mass is also known as gram atomic weight)
13. Molecular mass : The number of times a molecule of a compound is heavier than the 1/12 of the mass of C-12 atom, is known as its molecular mass. The molecular mass is equal to the sum of the atomic masses of all atoms present in one molecule of the substance. For example H2 contains two atoms of hydrogen, so molecular mass of H is 2 (2 x 1 =2)
14. Formula unit mass : It is equal to the sum o atomic masses of all the atoms in a formula unit. In case of ionic compounds like NaCl formula mass is 58.5 (23 + 35.5 = 58.5)
15. Molecular Mass and Mole Concept : Mole the unit of a substance. It is a collection of 6.023 x 10 + + 2+ 3+ 4 + – 2- – – 3 2- 4 3- 2 23 particles. The mass of 1 mole particles is equal to its mas in grams. Thus 1 mole = 6.023 x 10 particles 1 mole atoms = 6.023 x 10 atoms 1 mole electrons = 6.023 x 10 electrons 1 mole protons = 6.023 x 10 protons 1 mole ions = 6.023 x 10 ions 1 mole molecules = 6.023 x 10 molecules
16. Avogadro’s constant or Avogadro’s number: The number of particles present in one mole (i.e. 6.023 x 10 particles) is called Avogadro’s number or Avogadro’s constant.
17. Mole 1 mole = 6.023 x 10 particles. = mass of 1 mole particles in grams = 22.4L of a gas at N.T.P. 1 mole atoms = gm atomic mass 1 mole molecules = gm molecular mass N.T.P. stands for normal temperature (0°C) and normal pressure (1 atmosphere or 76 mm of mercury.) Number of moles (in a substance) = Mass of substance in grams/grams molecular mass = Volume of gas in litre (at N.T.P.)/22.4
Structure of Atom
1. Sub-Atomic Particles Electrons: Electron was discovered in cath¬ode ray experiment. The term electron was coined by GJ Stoney Protons were discovered in anode ray experiment. Anode rays are also called posi¬tive rays or canal rays. Protons was discovered by Wilhelm Wien in 1902. It was identified by J.J. Thomson. Neutron was discovered by James Chadwick in 1932.
2. Atomic Models : Models are the ideas about how things behave the way they do. Various Models of atom (a) Thomson Model or Water Melon Model or Plum pudding Model According to this model electrons are embedded in the positively charged mass distributed uniformly throughout the atomic sphere. This model was proposed by Joseph James Thomson in 1897. This model is also known as apple pie model. (b) Rutherford’s Model or Planetary Model: This model is based on experiments conducted by Rutherford. This model was given by Ernest Rutherford in 1911. According to this model all the positively charged particles are present in a small space in the centre of the atom. This small space is called nucleus. The electrons revolve around the nucleus just as the planets revolve around the sun. Due to this similarity, Rutherford’s model is called the planetary model or Solar model. Electrons (negatively charged) revolve around the nucleus in orbits with a high-speed to overcome the electrostatic force of attraction between positively charged particles (protons) present in the nucleus. Drawbacks of Rutherford’s Model The two deficiencies of this model are: It is possible to have infinite number of orbits. In practice it is not the case. The moving electron must continuously lose energy and fall into the nucleus. Actually it is not the case. (c) Bohr’s Atomic Model: This model was given by Neils Bohr in 1913. According to this model. an atom consists of heavy positively charged nucleus. The whole mass of the atom is concentrated in the nucleus. The electrons in an atom revolve around the nucleus in definite circular paths called orbits or energy level. Each energy level is associated with definite amount of energy. The change in energy takes place when electron jumps from one energy level to another energy level.
3. Arrangement of electrons in an atom : The arrangement of electrons in various shells (energy levels) of an atom of the element is known as Electronic configuration. The Maximum number of electrons that could be put in a particular shell (i.e., energy levels was given by Bohr and Bury. According to Bohr-Bury Scheme The maximum number of electrons that can be accommodated in any energy level is given by 2n where 11 = 1, 2, 3, 4, …. (for K, L, M, N…..) The maximum number of electrons in the outermost orbit will be 8 electrons even if it has capacity to accommodate more electrons. Electrons, are not accommodated in a given shell. Unless earlier shells are filled, that is stepwise filling of shells is followed.
4. Valency : The electrons present in the outer most shell of an atom are known as valence electrons. These electrons determine the valency of an atom. Valency is equal to the number of valence electrons. In case the number of valence electrons is close to its full capacity. Then, Valency =8— valence electrons If outermost shell is completely filled then 9. valency is zero. Valency is the combining capacity of an atom.
5. Atomic number (Z) : Atomic number of an element is equal to the number of protons present in the nucleus of an atom. Atomic number (z) = number of protons = number of electrons.
6. Mass number (A) : It refers to the total num¬ber of neutrons and protons, (i.e., sum of pro¬tons and neutrons) called collectively as nucleus, present in an atom. Mass number (A) = number of protons + number of neutron = number of nucleus
7. Isotopes : Atoms of the same element having same atomic number but different mass numbers are known as Isotopes eg.
8. Applications of Isotopes : Isotopes are used in, various fields. For example. 2 Isotope of uranium is used as a fuel in nuclear reactor Isotope of cobalt is used in treatment of cancer Isotope of iodine is used in treatment of goitre. 9. Isobars : Atoms of different elements having same mass numbers are known as Isobars, e.g K-40 and Ar-40
– Diversity in living Organisms
1. Thus different kinds of life forms show great diversity among themselves. For our convenience, we put them into different classes, groups and sub groups on the basis of similarities and differences among them. Eastern Ghats, Western Ghats, Tropical rain forests, Nilgiri mountain range and Himalayas are Biodiversity rich regions of India.
2. What is the Basis of Classification A whole hierarchy of mutually related characteristics is used for classification. Some important characteristics used for hierarchical classification are Presence and absence of nucleus in the cell. Body composed of single cell or group of cells. Autotrophs (producing own food) and heterotrophs (getting food from outside). Development and organisation of different body parts. These body design features are used to make sub groups among plants and animals.
3. Classification and Evolution (a) The life forms that we see today have arisen by accumulation of changes in the body design that help the ‘organisms to survive in a better way i.e through evolution. (b) Charles Darwin was a British scientist who gave the Theory of Evolution. He did his research work during a voyage on his famous ship HMS Beagle. He wrote the famous book “The Origin of Species”. (c) The idea of evolution was first given by Charles Darwin (1859) in his book “The Origin of Species”. Primitive organisms – They have ancient body design. Advanced organisms – They acquired changed body design recently. Older are simpler while younger are complex. The complexity in design comes during evolution.
4. The Hierarchy of Classification – Groups : Ernst Haeckel (1894), Robert Whittaker (1959) and Carl Woese (1977) classified organisms into kingdoms. Whittaker divided them into 5 kingdoms, Monera, Protista, Fungi, Plantae and Animalia on the basis of their cell structure, mode and source of nutrition and body organisation. Various levels of classification are – Kingdom ->Phylum (animals)/ Division (plants) —> Class -> Order -> Family -> Genus -> Species. Species is the basic unit of classification. The 5 kingdoms of Whittaker are – A. Monera B. Protista C. Fungi D. Plantae– They are multicellular eukaryotes with cell walls. They have autotrophic mode of nutrition. All plants are included in this group. Plants are divided into following 5- groups (i) Thallophyta (ii) Bryophyta (iii) Pteridophyta Thallophytes, Bryophytes, Pteridophytes have naked embryos called spores. They are also called “Cryptogams” because reproductive organs are inconspicuous and there is no seed formation. “Phanerogams” have well-developed reproductive tissues. Seeds are formed. Phanerogams are divided into 2 groups – (a) Gymnosperms (naked seeded).: (b) Angiosperms (seeds enclosed in fruits). iv) Gymnosperms (v) Angiosperms E. Animalia — They are eukaryotic, multicellular and heterotrophic organisms that do not have cell wall. On the basis of extent and type of body design, they are classified as (i) PoriferaPorifera (ii) Coelenterata (iii) Platyhelminthes (iv) Nematoda (v) Annelida (vi) Arthropoda (vii) Mollusca (viii)Echinodermata (ix) Protochordata: Notochord is a flexible, rod — shaped body found in the embryos of all chordates. In vertebrates it is replaced by the vertebral column. Notochord helps in the development of nervous system. (x) Vertebrata : (i) Presence of notochord (ii) Presence of dorsal nerve cord (iii) Triploblastic (iv) Presence of paired gill pouches (v) Coelomic body. Vertebrates are divided into 5 classes : Pisces Amphibia Reptilia Ayes Mammalia
Properties of Fluids
1. Thrust and pressure : The force applied on a surface in a direction perpendicular (or normal) to the surface is called thrust. (i) When a body is placed on a horizontal surface, it exerts a thrust equal to its weight on the surface. (ii) A body resting on a horizontal surface will exert the same thrust irrespective of its orientation. The S.I. unit of thrust is newton (N). Pressure : Force per unit area of the surface acting in a direction perpendicular (or normal) to it is called pressure (P). If F is the force acting perpendicularly on a surface having an area A, then Pressure = (Force acting normally on the surface)/(Area A of the surface) P = F/A The S.I. unit of pressure is Newton per metre square (Nm ). Another name for the S.I. unit of pressure is pascal (Pa). 1 Pa = 1 Nm
2. Pressure in fluids : A substance which can flow is called a fluid. All liquids and gases are thus fluids.
3. Buoyancy : The tendency of a fluid to exert an upward force on a body immersed partly or wholly in it is called buoyancy.. The resultant upward force experienced by a body when immersed in a fluid is called buoyant force or upward thrust.
4. Apparent loss of weight of a body immersed in a liquid : If you weigh a body in air and next when it is immersed in water (or in any other liquid), then you will find an apparent loss in weight of the body. Loss in weight is equal to upward thrust of the liquid on the body, or Loss in weight = upthrust of the liquid
5. Principle of floatation : When the buoyant force on a body lowered in a liquid is equal to the weight of the body, the apparent weight of the body is zero and the body floats on the surface of the liquid. Submarines are also based on Archimedes’ Principle, are ships that can submerge in water and travel underneath.
6. Archimede’s principle : When a body is immersed fully or partially in a fluid, it experiences an upward force that is equal to the weight of the fluid displaced by it. Applications of Archimede’s principle : Archimede’s principle is applied for (a) determination of density and relative density of substances and -2 -2 (b) the design of ships and submarines
7. Relative Density : Relative density of any substance is its density relative to that of water. Mathematically, Relative density of a substance = (Density of the substance)/(Density of water) Relative density is a pure number. It has no units. We know, density of a substance = (Mass of the substance)/(Volume of the substance) So, we can write Relative density of a substance Relative density of a substance = (Mass of the substance/volume of the substance)/(Mass of water/volume of water) If the volume of the water is same as that of the substance Relative density of a substance (Mass of the substance/volume of the substance)/(Mass of water/volume of water) If the volume of the water is same as that of the substance = (Mass of the substance)/(Mass of same volume of water) Relative density of a solid can be determined by Archimecje’s principle
Work and Energy
1. Work : In physics work is defined if force applied on object displaces the object in direc¬tion of force. all three terms force, dis¬placement and direction of force are important W= Force x displacement (force in direction of displacement) Unit of work 1 Joule = 1 Newton. 1 metre 1 J= 1 Nm When a force of 1 Newton moves a body through a distance of 1 metre in its own direction the work done is 1 Joule. Other units of work 1 joule = 1 N x lm = 10 dyne x 10 cm = 10 erg
2. Work done by a force applied at an angle W = component of force in the direction of displacement *, magnitude of displacement W = Fcos0 S Work done by a force can be positive or negative according as the value of cos 0 is positive or negative. (therefore, F and s, being magnitudes, are always positive) W = +ve for 0 = acute angle W = —ve for 0 = obtuse angle work done by the force does not depend on the time taken in the displacement of point of action.
3. Energy : The energy may be defined as the capacity of a body to do work. – The SI unit of energy is joule (J). or 1 kJ = 1000 J Forms of energy : The various forms include potential energy, kinetic energy, heat energy, chemical energy, and light energy.
4. Kinetic Energy : Energy possessed by a body by virtue of its state of motion is called Kinetic energy. Kinetic energy is always positive and is a scalar. The fact, that moving bodies carry energy with them is proved by some, of the several happenings in day-to-day life. Kinetic Energy, K = 1/mv , when m is the mass and v is the velocity of body.
5. Potential energy : Potential energy is energy. due to position. If .a body is in a position such that if it were released it would begin to move, it has potential energy. There are two common forms of potential energy, gravitational and elastic. (i) Gravitational Potential Energy : When an object is allowed to fall from one level to a lower level it gains speed due. to gravitational pull, i.e. it gains kinetic energy. Therefore, in possessing height, a body has the ability to convert its height into kinetic energy, i.e. it” possesses potential energy. If a mass m is at a height h above a lower level the P.E. possessed by the mass is (mg) (h). (ii) Elastic Potential energy : Same work has to be done to change the shape of a body. This work gets stored in the deformed body in the form of elastic potential energy. Elastic potential energy is never negative whether due to extension or to compression.
6. Law of Conservation of Energy : According to this law, energy can only be converted from one form to another: it can neither be created or destroyed. The total energy before and after the transformation remains the same. The law of conservation of energy is valid in all situations and for all kinds of transformations.
7. Power : The time rate of doing work is defined as power (P). More quickly work is done; power will be more. 2 Power= work/time 8. Unit of power : The unit of power is the joule per second and this is called the Watt . When large amounts of power are involved, a more convenient unit is the kilowatt (kW) where 1 kW = 1000W. 1 Megawatt = 10 watt 1 horse power = 746 watt The unit kilowatt-hour means one kilowatt of power supplied for one hour. It is, therefore, the unit of energy. 1 KWh = (1000 J/s) x 60 x 60s = 3.6 x 10 J
Periodic Classification of CLASSES Elements
1. Classification means identifying similar species and grouping them together.
2. Lavoisier divided elements into two main types known as metals and non-metals.
3. Doberiner’s Law of Triads: According to this law, “in certain triads (grout) of three elements) the atomic mass of the central element was the arithmetic mean of the atomic masses of the other two elements.” But in some triads all the three elements possessed nearly the same atomic masses, therefore the law was rejected. e.g., atomic masses of Li, Na and K are respectively 7, 23 and 39, thus the mean of atomic masses of I St and 3rd element is Limitations of Doberiner’s Triads: He could identify only a few such triads and so the law could not gain importance. In the triad of Fe, Co, Ni, all the three elements have a nearly equal atomic mass and thus does not follow the above law
4. Newland’s Law of Octaves: According to this law “the elements are arranged in such a way that the eighth element starting from a given one has properties which are a repetition of those of the first if arranged in order of increasing atomic weight like the. eight note of musical scale.”
Mendeleev’s Periodic Table : Mendeleev arranged 63 elements known at that time in the periodic table. According to Mendeleev “the properties of the elements are a periodic function of their atomic masses.” The table consists of eight vertical column called ‘groups’ and horizontal rows called ‘periods’. Merits of Mendeleev’s Periodic Table: (i) At some places the order of atomic weight was changed in order to justify the chemical and physical nature. (ii) Mendeleev left some gap for new elements which were not discovered at that time. (iii) One of the strengths of Mendeleev’s periodic table was that, when inert gases were discovered they could be placed in a new group without disturbing the existing order. Characteristics of the periodic table : Its main characteristics are : (i) In the periodic table, the elements are arranged in vertical rows called groups and horizontal rows called periods. (ii) There are eight groups indicated by Roman Numerals I, II, III, IV, V, VI, VII, VIII. The elements belonging to first seven groups have been divided into sub-groups designated as A and B on the basis of similarities. The elements that are present on the left hand side in each group constitute sub-group A while those on the right hand side form sub-group B. Group VIII consists of nine elements arranged in three triads. (iii) There are six periods (numbered 1, 2, 3, 4, 5 and 6). In order to accommodate more elements, the periods 4, 5, 6 are divided into two halves. The first half of the elements are placed in the upper left corners and the second half occupy lower right corners in each box.
Achievements of mendeleev’s periodic table (i) The arrangement of elements in groups and periods made the study of elements quite systematic in the sense that if properties of one element in a particular group are known, those of the others can be easily predicted. (ii) Prediction of new elements and their properties : Many gaps were left in this table for undiscovered elements. However, properties of these elements could be predicted in advance from their expected position. This helped in the discovery of these elements. The elements silicon, gallium and germanium were discovered in this manner. (iii) Correction of doubtful atomic masses : Mendeleev corrected the atomic masses of certain elements with the help of their expected positions and properties.
Limitations of mendeleev’s classification : (i) He could not assign a correct position of hydrogen in his periodic table, as the properties of hydrogen resembles both with alkali metals as well as with halogens. (ii) The isotopes of the same element will be given different position if atomic number is taken as basis, which will disturb the symmetry of the periodic table. (iii) The atomic masses do not increases in a regular manner in going from one elements to the next. So it was not possible to predict how many elements could be discovered between two elements.
6. Modern Periodic Law : This law was given by Henry Moseley in 1913. it states, “Properties of the elements are the periodic function of their atomic numbers”. Cause of periodicity : Periodicity may be defined as the repetition of the similar properties of the elements placed in a group and separated by certain definite gap of atomic numbers. The cause of periodicity is the resemblance in properties of the elements is the repetition of the same valence shell electronic configuration.
7. Modern Periodic Table Moseley proposed this modern periodic table and according to which “the physical and chemical properties of elements are periodic function of their atomic number and not the horizontal rows called “periods”. The groups have been numbered 1, 2, 3 …. 18 from left to right. (ii) The elements belonging to a particular group make a family and usually named after the first member. In a group all the elements contain the same number of valence electrons. (iii) In a period all the elements contain the same number of shells, but as we move from left to right the number of valence shell electrons increases by one unit. The maximum number of electrons that can be accommodated in a shell can be calculated by the formula 2n2 where n is the number of the given shell from the nucleus.
8. Trends in Modern Periodic Table : The trends observed in some important properties of the elements in moving down the group (from top to bottom of the table) and across a period (from left to right in a period) are discussed below :
(i) Valency : Valency may be defined as the combining capacity of the atom of an element with atoms of other elements in order to acquire the stable configuration (i.e. 8 electron in valence shell. In some special cases it is 2 electrons).
(ii) Atomic size : It refers to the distance between the centre of nucleus of an isolated atom to its outermost shell containing electrons. The atomic radius decreases on moving from left to right along a period. This is due to an increase in nuclear charge which tends to pull the electrons closer to the nucleus and reduces the size of the atom. In a group atomic size decreases from top to bottom due to increase in number of shells.
(iii) Metallic and non-metallic properties : In a period from left to right metallic nature decreases while nonmetals character increases. In a group metallic character increases from top to bottom while non-metallic character decrease.
(iv) Electronegativity : The relative tendency of an atom to attract the shared electron pair of electrons towards itself is called electronegativity. In a period from left to right, the value of electronegativity increases while in a group from top to bottom the value of electronegativity decreases
Diversity in living Organisms
1. The production of new organisms from the existing organisms of the same species is known as reproduction.
2. Asexual Reproduction : Modes of sexual reproduction used are binary fission, multiple fission, Budding, spore formation, regeneration, vegetative propagation, tissue culture, fragmentation
3. Sexual Reproduction : In sexual reproduction, a male gamete (germ cells) fuses with a female gamete to form a new cell called ‘zygote’. This zygote then grows and develop into a new organism in due course of time. When male gamete and female gamete fuse, they form a zygote and the process is known as fertilization. Fertilization is of two types :– External fertilization and Internal fertilization.
4. Sexual Reproduction in Flowering Plants : Flower is meant essentially for sexual reproduction. Pollination is the process in which pollen grains are transferred from the anther to stigma of the carpel. It is of two types self pollination and cross-pollination. In the fertilization process primary endospermic nucleus is formed. After the fertilization process, ovary developes into the fruit whereas ovules into the seed.
5. Reproduction in Human Being : The sex organ in males are testes and ova in females. Male reproductive organ consist of a pair of testes, vasdeferens, a pair of epididymis, a pair of ejaculatory duct, urethra, pairs of accessory gland. Female reproductive part consist of a pair of ovaries, a pair of fallopian tube, uterus, vagina, external genitalia, mammary glands and accessory glands. Ovary produces the female gametes (eggs or ova) and female sex hormone (estrogen). If sperms are present, fertilization of ovum takes place in the upper end of the fallopian tube. Bleeding accompanied by discharge of soft tissue lining the reproductive tract is menstrual flow. It last for 3-5 days. Secretory phase lasts for 12-14 days. Fertilization process occurs in fallopian tube. In this process zygote is formed. In this process umbilical cord is produced which is attached to foetus. During this process two hormones are produced which are estrogen and progesterone. Progesterone stops menstruation and prevents ovulation. The placenta protects the body against diseases. Due to contraction of uterine muscles young one is expelled and the phenomenon is called parturition. If the egg is not fertilized, it lives for about one day. Since the ovary releases one egg every month, the uterus also prepares itself every month to receive a fertilized egg. After the age of 45-50 years menses stop and process is called menopause. Fertility control can be done chemically, mechanically or surgically.
6. Reproductive Health Barrier methods
(i) Mechanical barrier method:- They prevent contraception by preventing either sperms from entering uterus or preventing implantation if fertilization has occurred. The instruments are condom, cervical cap, diaphragm & ICDU method.
(ii) Hormonal method: They are used by women for suppressing the production of ovum. i.e. , oral pills, Implants morning after pills.
(iii) Chemical contraception: They are creams, jellies and foaming tables which are placed in vagina for killing the sperms at the time of coitus.
(iv) Surgical techniques:— (a) Vasectomy: — The two vasa deferential of the male are blocked by cutting a small piece of tying the rest. This prevents the passage of sperms from testes to semen. (b) Tubectomy:— A portion of both the fallopian tubes is excised to ligated to block the passage of ovum
7. Sexually Transmitted Diseases (STDs) It is a group of infections caused by different types of pathogens that are transmitted by sexual contact between a healthy person and an infected person. The sexually transmitted diseases are also called venereal diseases (VDs). Some 30 different types of STDs are known. Fol example : Gonorrhoea, Syphilis, Trichomonas, Genital warts, AIDS
Heredity and Evolution
1. The transmission of characters from parent to their offsprings is known as heredity. The study of heredity and variations is known as genetics. Clones are those organisms which are the carbon copies of one another. Variation in sexually reproducing organisms are caused due to the following factors like environment, crossing over and recombination of genes and mutation. The first study of inheritance was done by Gregor Mendel on garden pea. Paired condition of chromosomes is known as diploid. Unpaired condition of chromosomes is known as haploid. DNA (Deoxyribo Nucleic Acid), RNA (Ribo Nucleic Acid) is the genetic material in all organisms.
2. Mendel’s laws of inheritance are (i) Law of Dominance (ii) Law of Segregation (Law of purity of gametes) (iii) Law of Independent Assortment
3. Genotype is the composition of genes present in an organism and the characteristic which is visible in an organism is called its phenotype.
4. When two parents cross (or breed) to produce progeny (or offsprings), then their progeny is called F1- generation (First Filial Generation) and when the first generation progeny cross among themselves to produce second progeny, then this progeny is called F2-generation or second Filial Generation. Mendel conducted his famous experiments on garden pea (Pisum sativum). He used a number of contrasting characters like round / wrinkled seeds, tall/ short plants, white/ violet flowers and so on.
5. During Monohybrid Cross When tall pea plants are crossed with short pea plants then in Fi generation only tall plants were obtained. F progeny ofFi tall plants are not all tall but one-quarter of them are short indicating that both tallness and shortness traits were inherited in F1 but only tallness trait was expressed due to dominance. In dihybrid cross two pairs of contrasting characters were considered. Tall plant with round seeds were crossed with short plant with wrinkled seeds. In Fi tall plants with round seeds were obtained. On selfing these F, plants with F produced tall plants with round seeds, short plant with wrinkled seeds and some new combinations (tall plant with wrinkled seeds and short plant with rounds seeds) 2 2 were also obtained. The tall/short trait and round wrinkled traits are independently inherited. The expression of a particular trait is controlled by gene.
6. DNA is the source of making protein in a cell. The section of DNA that provides information for one protein is called gene.
7. Physical and Chemical Basis of Heredity Mendel (1866) said that heredity was controlled by particles, called germinal units, or factors.
8 Sex determination is the process by which the sex of a person is determined. All human chromosomes are not paired. 22 pairs are called autosomes. Women have a perfect pair of sex chromosomes XX. But men have a mismatched pair XY.
9. Evolution It is the sequence of gradual changes which take place in the primitive organisms over millions of years in which new species are produced. A. The evidences of evolution are : i. Homologous organs, ii. Analogous organs, and Fossils B. Theories of Evolution Jean Baptiste Lamarck gave the first theory of evolution. Darwin’s Theory of Evolution Charles Robert Darwin (1809-1882) explained the evolutionary principle in his famous book “The origin of species”. The theory proposed by him is popularly known as theory of natural selection or Darwinsim. The main features of the theory of natural selection are as follows: (i) Over production (ii) Limited food and space (iii) Struggle for Existence (iv) Variations (v) Natural Selection or Survival of the Fittest
10. Speciation : The process by which new species develop from the existing species is known as speciation. The factors which leads to speciation are : Geographical isolation Genetic drift and Variations
11. Classification Evolutions are of three types :- (i) Convergent Evolution (ii) Divergent Evolution, and (iii) Parallel Evolution.
12. Fossils : The remains of dead plants or animals that lived in the remote past are known as fossils. Various kinds of fossils are : Ammonite, Trilobite and Dinosaur.
13. Evolution by Stages : Evolution of complex organs have taken place bit-by-bit over generations. For example eye, feathers of birds have evolved because of survival advantage of intermediate stages. Thus changes in DNA during reproduction are the main cause of evolution.
14. Human Evolution : All have beings belong to single speceis Homo sapiens, although there were many races of humans. They have originated in Africa, some ancestors left Africa and migrated to West Asia, Central Asia, Eurasia South Asia, East Asia, Indonesia, Australia, America, while others stayed there. Excavating, time-dating, studying fossils, determining DNA Sequences have been used for studying human evolution
Light (Reflection and Refraction)
1. Ray of Light : A line drawn in the direction of propagation of light is called a ray of light.
2. Beam of Light : A group of rays of light emitted by a source of light is called a beam of light. A light beam is of three types. (i) Parallel beam : A group of light rays parallel to each other is known as parallel beam of light. 7. (ii) Divergent beam : A group of light rays spreading out from a source of light is called divergent beam of light. (iii) Convergent beam : A group of light rays meeting at a point is called convergent beam 8. of light.
3. Reflection of Light : There are some surfaces which have ability to send the light back in the same medium when light strikes it. This 9. phenomena of sending the light back in the same medium by a surface is called reflection of light. (i) The incident ray, the reflected ray and the normal at the point of incidence, all lie in a same plane. (ii) The angle of incidence is always equal to the angle of reflection, ∠i = ∠r.
4. Image : When light rays meet or appear to meet after reflection from a mirror,then it is called an image. 1. Real Image : It is a kind of image which is formed by actual intersection of light rays after reflection. 2. Virtual Image : It is a kind of image which is formed by producing the reflected rays backward after reflection.
5. Plane Mirror : Plane mirror is a piece of glass whose one side is polished by using silver paint, which is covered by a coating of red paint to protect the silver layer.
6. Spherical Mirrors : It is part of hollow glass sphere whose one surface is polished. There are two types of spherical mirror. (i) Concave Mirror : It is a spherical mirror whose outer surface is polished and inner or concave side is reflecting surface. (ii) Convex Mirror : It is a spherical mirror whose inner is polished and outer side or convex side is the reflecting surface.
7.Principal Focus : A point on the principal axis of a spherical mirror where the rays of light parallel to the principal axis meet or appear to meet after reflection from the mirror.
8. Focal Length : The distance between the pole (P) and principal focus(F) of a spherical mirror is called the focal length of the mirror. It is denoted by f.
9.Uses of Concave Mirror : (i) It is used as a shaving mirror because when it is placed close to the face, it forms a large image. (ii) It is used in solar heating devices like solar cooker, because it converges Sun’s rays over a small area to produce high temperature. (iii) It is used for security checking purposes.
10. Uses of Convex Mirror : (i) It is used as rear view mirror in automobiles because it gives erect image as well as diminished due to which Pt has wider field of view. (ii) It is also used in street lights.
11. Mirror Formula : It is a relation between distance of object, distance of image from the pole of the mirror and it’s focal length, i.e., relation between ‘u’, ‘v and It is given by
12. Magnification : It is defined as the ratio of height of image to the height of the object. It is denoted by letter m.
13. Refraction of Light : The bending of ray of light when it passes from one medium to another is called refraction of light. Laws of Refraction : (i) The incident ray, the refracted ray and the normal at the point of incidence all lie in the same plane. (ii) When a ray of light undergoes refraction then the ratio of sine of angle of incidence to the sine of angle of refraction is constant.
14. The Refractive Index : The refractive index of medium 2 with respect to medium 1is given by the ratio of the speed of light in medium 1 and the speed of light in medium 2. This is usually represented by the symbol n . This can be expressed in an equation form as
15. Refraction by spherical lenses : Lens is a transparent medium which is formed by joining two pieces of spherical glass. There are two types of lenses. (i) Convex Lens : It is a lens which is thicker at the centre and thinner at the edges. (ii) Concave Lens : It is a lens which is thinner at the centre and thicker at the edges.
16. Terms related to a lens Optical Centre of Lens : It is the centre of the lens through which light can pass without any deviation. Principal Axis : It is the line passing through optical centre and is perpendicular to the line joining its edges. Principal Focus : It is a point on the principal axis where all light rays which are parallel to principal axis either converge or appear to diverge from, after refraction. 21
17. Lens formula :
18. Magnification : Magnification, m = h /h Ratio of height of image to the height of object. It is also given by v/u i.e., Ratio of distance of image to the distance of object.
19. Power of a lens : A beam of light parallel to principal axis either gets converged or diverged after refraction by a lens. Some lenses converge the beam of light to a small extent and some lenses converge it to a large extent. This ability of lens to converge or diverge a beam of light is known as the power of lens. Si unit of power of lens is dioptre : One dioptre is the power of a lens whose focal length is 1 m. Power of a combination of two or more lenses : If two or more lenses are placed together to form a combined lens then the power of this combined lens is equal to the sum of the powers of individual lenses. P = P + P + P + ……
The Human Eye and the Colourful World
1. The Human Eye It is a natural optical instrument which is used to see the objects by human beings. It is like a camera which has lens and screen system. (i) Retina : It is a light sensitive screen inside the eye on which image is formed. It contains rods and cones. (ii) Cornea : It is a thin membrane which covers the eye ball. It acts like a lens which refracts the light entering the eye. (iii) Aqueous humour : It is fluid which fills the space between cornea and eye lens. (iv) Eye lens : It is a Convex lens made of transparent and flexible jelly like material. Its curvature can be adjusted with the help of ciliary muscles. (v) Pupil : It is a hole in the middle of iris through which light enters the eye. It appears black because light falling on it goes into the eye and does not come back. (vi) Ciliary muscles : These are the muscles which are attached to eye lens and can modify the shape of eye lens which leads to the variation in focal lengths. (vii) Iris : It controls the amount of light entering the eye by changing the size of pupil. (viii) Optical nerve : These are the nerves which take the image to the brain in the form of electrical signals.
2. Accomodation power : The ability of eye to change the focal length of eye lens with the help of ciliary muscles to get the clear view of nearby objects (about 25 cm) and far distant objects (at infinity).
3. Colour blindness : Some people do not possess some cone cells that respond to certain specific colours due to genetic disorder.
4. Myopia (Short sightedness) : It is a kind of defect in human eye due to which a person can see near objects clearly but he can not see the distant objects clearly. Myopia is due to (i) excessive curvature of cornea. (ii) elongation of eye ball.
5. Hypermetropia (Long sightedness) : It is a kind of defect in human eye due to which a person can see distant objects properly but cannot see the nearby objects clearly. It happens due to (i) decrease in power of eye lens i.e., increase in focal length of eye lens. (ii) shortening of eye ball.
6. Presbyopia : It is a kind of defect in human eye which occurs due to ageing. It happens due to (i) decrease in flexibility of eye lens. (ii) gradual weakening of cilliary muscles.
7. Astigmatism : It is a kind of defect in human eye due to which a person cannot see (focus) simultaneously horizontal and vertical lines both.
8. Cataract : Due to the membrane growth over eye lens, the eye lens becomes hazy or even opaque. This leads to decrease or loss of vision. The problem is called cataract. It can be corrected only by surgery.
9. Dispersion of white light by a glass prism : The phenomenon of splitting of white light into its seven constituent colours when it passes through a glass prism is called dispersion of white light. The various colours seen are Violet, Indigo, Blue, Green, Yellow, Orange and Red. The sequence of colours remember as•VIBGYOR. The band of seven colours is called spectrum.
10. Composition of white light : White light consists of seven colours i.e., violet, indigo, blue, green, yellow, orange and red.
11. Monochromatic light: Light consisting of single colour or wavelength is called monochromatic light, e.g., sodium light
12. Polychromatic light : Light consisting of more than two colours or wavelengths is called polychromatic light, e.g. white light.
13. Recombination of white light : Newton found that when an inverted prism be placed in the path of dispersed light then after passing through prism, they recombine to form white light.
14. Formation of rainbow : The water droplets act like small prisms. They refract and disperse the incident sunlight, then reflect it internally, and finally refract it again when it comes out of the raindrop. Due to the dispersion of light and internal reflection, different colours reach the observer’s eye.
15. Atmospheric Refraction : The refraction of light caused by the earth’s atmosphere (having air layers of varying optical densities) is called atmospheric refraction.
16. Why, the duration of day becomes approximately 4 minutes shorter if there is no atmosphere on earth : Actual sun rise happens when it is below the horizon in the morning. The rays of light from the sun below the horizon reach our eyes because of refraction of light. Similarly, the sun can be seen about few minutes after the actual sun set. Thus the duration of, day time will increase by 4 minutes.
17. Scattering of light : According to Rayleigh’s law of scattering the amount of scattered light α/(wavelength ) So that the wavelength of violet, blue and indigo is small as compared to the rest of the colours. So sky appears blue in colour.
18. Colour of the Sun at sunrise and sunset : At noon, the light of sun travels relatively shorter distance through earth’s atmosphere thus appears white as only a little of blue and violet colours are scattered. Near the horizon, most of the blue light and shorter wavelengths are scattered and sun appears red
Our Environment
The environment includes our physical surroundings like air (or atmosphere), water bodies, soil (land) and all the organisms such as plants, animals, human beings and micro organisms like bacteria and fungi (called decomposers). The waste materials produced by the various activities of man and animals are poisonous to some extent and can be divided into two main groups : 1. Biodegradable wastes, and 2. Non-biodegradable wastes. Ecosystem An ecosystem is a self-contained unit of living things (plants, animals and decomposers), and their non-living environment (soil, air and water). e.g. a forest, a pond, a lake, a greenland etc. There are two components of an ecosystem : biotic component and abiotic component. Biotic component : It includes three types of organisms: Producer Consumer Decomposer/saprophyte Abiotic component Consumers can be further divided into three groups : herbivores, carnivores and omnivores. Planktons are very minute or microscopic organisms freely floating on the surface of water in a pond, lake, river or ocean. Planktons are of two types : Phytoplanktons and Zooplanktons. The microscopic aquatic plants freely floating on the surface of water are called phytoplanktons. The microscopic aquatic animals freely floating on water are called zooplanktons. The freely floating protozoa are an example of zooplankton. The micro-organisms which break down the complex organic compounds present in dead organisms like dead plants and animals and their products like faeces, urine, etc. into simpler substances are called decomposers. Food Chains and Webs The sequence of living organisms in a community in which one organism consumes another organism to transfer food energy, is called a food chain. A food chain is unidirectional where transfer of energy takes place in only one direction. In aquatic ecosystem of the biosphere, like fresh water ponds, lakes or sea, the food chain starts with microscopic free-floating plants (phytoplankton) The various steps in a food chain at which the transfer of food (or energy) takes place are called trophic levels. The inter-connected food chains operating in an ecosystem which establish a network of relationships between various species, is called a food web. How do our activities affect the environment Global Warming The addition of certain pollutants like the carbon dioxide gases increases the temperature of the earth. The reduction in the forest cover also contributes to the heating of earth. This is called global warming. Ozone Layer formation and importance Ozone (O ) is a molecule formed by three atoms of oxygen. Ozone, is a deadly poison. It shields the surface of the earth from ultraviolet (UV) radiation from the Sun. This radiation is highly damaging to organisms. Ozone at the higher levels of the atmosphere is a product of UV radiation acting on oxygen (O ) molecule. The higher energy UV radiations split apart some molecular oxygen (O ) into free oxygen (O) atoms. The deplation of ozone layer is due to CFC (chloro fluorocarbons). SOME
IMPORTANT POINTS
Flow of materials in an ecosystem is cyclic but flow of energy is unidirectional.
There is a continuous transfer of energy from one trophic level of organisms to the next in a food chain.
Ten percent law states that only 10 percent of the energy entering a particular trophic level of organisms is available for transfer to the next higher trophic level.
The increase in concentration of harmful chemical substances like pesticides in the body of living organisms at each trophic level of a food chain is called biological magnification. The disposal of waste should be done in a scientific way. There are different methods of waste disposal. The method to be used depends on the nature of the waste. Some of the important modes of waste disposal are : (i) Recycling (ii) Preparation of compost (iii) Incineration (iv) Landfill (v) Sewage treatment.
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