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Showing posts from October, 2019
                         Lymphoid organs of the body Lymphoid organs :  These are the organs where origin and or maturation and proliferation of lymphocytes occur. (a)   The primary lymphoid organs are bone marrow and thymus where immature lymphocytes differentiate into sensitive lymphocytes. (1) Bone marrow : Bone marrow present in bones is the main lymphoid organ where all bllod cells including lyphocytes are produced. Bone marrow provides the microenvironment for the development and maturationof B lymphocytes. (2) Thymus  : Thymus is a lobeled organ located near the heart and beneath the breast bone. Thymus is quite large at the time of birth but keeps reducing withg age and by the time puberty is attained ity atrophies to a very small size. It provides microenvironment for the development and maturation of T- lymphocytes. (b)  Secondary lymphoid organs : The lymphocytes after maturatio...
                      The Human Eye It is a sensitive sense organ that acts like a camera, enable us to capture the colourful  pictures of the surroundings. It forms a real image on it's light sensitive surface retina.                       Parts of Human Eye Cornea  :  It is a thin membrane through which light enters. It forms the transparent bulge on the front of eyeball. Most of the refraction occurs at the outer surface of the cornea. Eyeball :  It is approximately spherical in shape, with a diameter of 2.3 c.m.  Iris :  It is a dark muscular diaphragm that controls the size of pupil. It is behind the cornea. Pupil :  It regulates and control the amount of light entering in the eye . It is the black opening between aqueous humour and lens. Crystalline Eye lens :  Provide the focussed real and inv...
                  Electrolysis  of  water Electrolysis of water is an example of decomposition reaction in which waterr breaks up into it's constituents. Let perrform an activity to demonstrate electrolysis of water.                                  Activity Take a plastic mug. drill holes at it's base and fit rubber stoppers in these holes. insert carbon electrodes in these rubber stoppers . Connect these electrodes to a 6 volt battery. Fill the mug with water such that the electrodes are immersed. Add a few drops of dilute sulphuric acid to the water. Take two test tubes filled with water and invert them over the two carbon electrodes. switch on the current and leave the apparatus undisturbed for some time. you will observe the formation of bubbles at both the electrodes. These bubbles displace water in the test tubes. Is the volume...