Knowledge of Science

Nutrition in human beings- Human beings are heterotrophic omnivorous organisms. They obtain their food from plants, animals and their products by holozoic mode of nutrition. The essential components of human diet are  water, carbohydrates, fats, proteins, minerals and vitamins. Human Digestive system- The human digestive system consists of an alimentary canal and many digestive glands. So human digestive system is divided into two main parts the first one is the alimentary canal and the other one is different digestive glands associated with alimentary canal. (1) Alimentary canal (2) Digestive glands associated with alimentary canal (1) Alimentary canal- The alimentary canal is a long tube with muscular walls, glandular epithelial lining and varying diameter. It extends from the mouth to the anal opening (anus). When uncoiled, the alimentary canal measures nearly 9 metre long tube in which the ducts of several digestive glands open to secrete their respective digestiv

Carbohydrates- Importance- The carbohydrates are often termed as sugars are the 'staff of life' for most organisms. On the basis of mass, they are the most abundant class of biomolecules in nature. Carbohydrates are also known as saccharides (sakcharon = Sugars or sweetness) since many of those of relatively small molecular weight have a sweet taste, although this is not true of those with large molecules. They are widely distributed molecules (moles = mass) in both plant and animal tissues. They are indispensable for living organisms, serving as a skeletal structures in plants and also in insects and crustaceans. They also occur as food reserves in the storage organs of plants and in the liver and muscles of animals. In addition, they are an important source of energy required for the various metabolic activities of the living organisms; the energy being derived as a result of their oxidation. They also serve to lubricate skeletal joints, to provide adhesion  between cell

Reproductive system of human beings - Human beings are unisexual and the human reproduction is highly evolved. There is a distinct sexual dimorphism. Thus, the structures associated with reproduction are different in males and females. The structures associated with male reproduction constitutes the male reproductive system. similarly, The structures associated with female reproduction constituted the female reproductive system. The reproductive systems of males and females consists of many organs which are distinguishable into primary and secondary sex organs. Primary sex organs- The primary sex organs are gonads, which produce gametes and sacrete sex hormones. The gonads of the male are called testes which produce male gametes- sperms and the male hormone- testosterone . The gonads of the female are ovaries which produce female gamete- ova and female hormones -estrogen and progesterone. Secondary sex organs- The secondary sex organs include the genital ducts and glands which

Blood circulatory system    (Blood vascular system ) Blood circulatory system is regarded as a kind of vascular system and therefore, it is called blood vascular system. A vascular system is that which has tubes full of fluid to be transported from one place to another.  The blood vascular system comprises of heart, the organ which pumps and receives the blood, and blood vessels, which are tubes through which the blood flows.      Blood vessels- The blood vessels are elastic muscular tubes which carry blood. There are three kinds of blood vessels in human body.     They are of three types-(1)Arteries  (2)veins and  (3)capillaries. (1)Arteries- Arteries are the thick walled blood vessels which carry blood away from the heart for distribution to the body. The walls of arteries particularly those near the heart are thick that enables them to dilate but not rupture when the heart contracts and forces blood into them. Thus the blood passing through narrow lume

      Excretion in human beings Excretory system- Excretory system in human beings (also known as urinary system) consists of a pair of kidneys, a pair of ureters ,a urinary bladder and a urethra . The two kidneys are located towards the back of the lower part of the abdominal cavity, one on either side of the backbone. Left kidney is slightly larger and placed a little higher than the right kidney. The blood from aorta enters into kidneys via the renal arteries and returns to the posterior Vena cava via renal veins. Urine formed in the kidneys passes by a pair of ureters to the bladder where it is stored until it is released via the urethra. Structure and function of kidneys- There are two kidneys in humans each kidney is purplish- brown, slightly flattened and shaped somewhat like rajma Bean. It is about 12 centimetre long, about 6 CM thick and wait about 150 grams. Internally a kidney is made of numerous microscopic excretory units called nephrons. Single kidney contai

      Refraction of light The change in direction of light when it passes from one medium to another obliquely is called refraction of light.           In other words the bending of light when it goes from one medium to another obliquely is called refraction of light.           The  Refraction of light  takes place when light rays enter from air into glass , or from glass into air. The refraction of light takes place when light enters from air into water, or from water into air. And the refraction of light also takes place when light enters from water into glass or from glass into water.        The optical instruments like camera, microscope and telescope work on the the refraction of light through glass lenses.     The refraction (or bending ) of light takes place at the boundary between the two media. Causes of refraction- The refraction of light  is due to the change in the speed of light on going from one medium to another. Thus, when light goes from one medium to

Trichloromethane  (chloroform)       CHCl3  Trichloromethane is a trichloro derivative of methane. It is commonly called as chloroform. Methods of preparation-  It is prepared by the chlorination of methane in the presence of sunlight.          Sunlight CH4 -------------------> CH3Cl + HCl             +Cl2              Sunlight CH3Cl ---------------> CH2Cl2+ HCl                +Cl2              Sunlight CH2Cl2 ---------------> CHCl3+ HCl                  +Cl2 Properties- (1) colourless heavy liquid (2) sweet taste  (3) it is oxidised in the sunlight and form a harmful gas carbonyl chloride which is commonly called as phosgene.                     Sunlight 2CHCl3+O2 --------> 2COCl2 +HCl                                            Phosgene is a very poisonous gas. So it is not used in the anaesthetic purpose. Process of storage for chloroform- (1) For the prevent from sunlight chloroform is stored in coloured bottle. (2) for the prevent f

                     Alcohols Hydrocarbons are the parents of other organic compounds. When One or more hydrogen atoms are replaced by the different types of atoms or group of atoms from hydrocarbons then different types of organic compounds are formed .            When hydrogen atoms are replaced from saturated aliphatic hydrocarbons by the hydroxyl group (-OH) ,then Alcohols are formed.   For example-                 -H   R-H ------------->    R-OH                                +OH Where R is the alkAl group.                    -H  CH3-H ------------->     CH3-OH                         +OH              (Methanol) So, Hydroxy derivatives of the aliphatic hydrocarbons are known as Alcohols. Classification of Alcohols- Hydroxy derivatives of the aliphatic hydrocarbons are known as Alcohols. The general formula of the alcohols are R-OH. Where R is the Alkyl group. Alcohols are classified on the basis of the number of the Hydroxyl groups (-OH) attached to

Nomenclature of Haloalkanes The name of the haloalkanes are given by two different ways- (1)Trivial or common system- In this system haloalkanes are known as Alkyl halide.        There nomenclature are performed by the adding halide word in the given alkyl group. In this system the name of the compound is written in the two different words.    For example-     CH3-Cl          (Methyl chloride) CH3-CH2-Br     (ethyl bromide)                     Prifixes of the different types of alkyl group- (a) prefix- n The means of prefix-n is normal. This is used in the straight chain of the Alkyl group.  For example-  CH3-CH2-CH2-Br                          (n-propyl bromide) (b) prefix- iso Prefix-iso is used for those Alkyl group in which methyl (--CH3) branch is present in the last of the chain. For example- CH3-CH-Br          |          CH3   (Isopropyl bromide) (c) prefix- neo Prefix-neo is used for those Alkyl group in which two methyl (--CH3) gro

      Haloalkanes and Haloarenes Haloalkanes-  The word Haloalkane is made up by the two words, -          Halo = halogen          Alkane= Aliphatic hydrocarbon (containing single bond only) So, Haloalkanes are those compounds which is formed when a hydrogen atom replaced by any halogen atom from the alkanes.                - H    R-H  -------------->      R-X                 +X Where ,   R  =  Alkyl group               X  = Halogen ( F,Cl, Br, I) For example-                                  - H          CH3-H  --------------> CH3-Cl                            +Cl Haloarenes-  The word Haloarene is made up by the two words, -          Halo = halogen    Arene= Aromatic hydrocarbon So, Haloarenes are those compounds which is formed when a hydrogen atom replaced by any halogen atom from the arenes.                - H    Ar-H  -------------->      Ar-X                 +X Where ,  Ar  =  Aromatic hydrocarbon               X  = Halogen ( F,Cl, Br,

  Allotropes of carbon  The various physical forms in which an element can exist are called allotropes of the element. The carbon elements exists in three solid forms called allotropes. The three allotropes of the carbon are - (1) Diamond (2) Graphite (3) Buckminster fullerene               (1) Diamond Diamond is a colourless transparent substance having extraordinary shining. Diamond is quite heavy. Diamond is extremely hard. It is the hardest natural substance known. Diamond does not cunduct electricity. Diamond burns on strong heating to form carbon dioxide. If we burn diamond in Oxygen , then only CO2 gas is formed and nothing is left behind. This shows that diamond is made up of carbon only. Structure of Diamond -  A Diamond crystal is a very big molecule of carbon atoms. Each carbon atom in the diamond crystal is linked to four other carbon atoms by strong covalent bonds. The four surrounding carbon atoms are at the four vertices of a regular tetrahedro

        Newton's laws of motion Newton has given three laws to describe the motion of bodies. These laws are known as Newton's laws of motion. The Newton's laws of motion give a precise definition of force and establish a relationship between the force applied on a body and the state of motion acquired by it. Newton's first law of motion - Newton's first law describes the behaviour of such bodies which are in a state of rest or of uniform motion in a straight line.          According to Newton's first law of motion -  A body at rest will remain at rest, and a body in motion will continue in motion in a straight line with a uniform speed, unless it is compelled by an external force to change its state of rest or of uniform motion.     It should be noted that by saying an external force, we mean a force from outside the body.      Let us take some examples to make the first law of motion more clear.     Suppose a book is lying on the table. It is at res

                         Cell  Cell -   The cell is the fundamental unit of life. All plants and animals are made up of cells. Cell is the microcosm (having a definite boundary with in) which constant chemical activities and flow of energy proceed. Cell is the structural and functional unit of all organisms.       The body of an organism may contain one cell as in Unicellular organisms. Each cell has the capacity to perform all vital activities like nutrition, growth, respiration, irritability, movement and reproduction etc. Discovery of cell - The cell was discovered by the scientist Robert Hooke in 1665, when he worked on the wooden cork. He cut the thin slices of wooden cork and see these thin slices of cork in the self made microscope. Then he saw the honey comb like structures . These structures are called cell by the scientist Robert Hooke in 1665. **  The cell which is discovered by the scientist Robert Hooke was a dead cell.  ** The first living cell (B

Real images and virtual images  (1) Real images-   The image which can be obtained on a screen is called a real image .  In a cinema hall , we see the images of actors and actresses on the screen. So, the images on a cinema screen is an example of real images. A real image is formed when light rays coming from an object actually meet at a point after reflection from a mirror ( or refraction through a lens ). A real image can be formed on a screen because light rays actually pass through a real image. Real images can be formed by a concave mirror. A convex lens can also form real images. (2) Virtual images-  The image which cannot be obtained on a screen is called a virtual image . A virtual image can be seen only by looking into a mirror ( or a lens) . The image of our face formed by a plane mirror cannot be obtained on a screen, it can be seen only by looking into the mirror. So the image of our face in a plane mirror is an example of virtual image. Virtual images are