CBSE ADDA

All   blood cells   are produced in the   bone marrow . As children, most of our bones produce blood. As we age this gradually diminishes to just the bones of the spine (vertebrae), breastbone (sternum), ribs, pelvis and small parts of the upper arm and leg. Bone marrow that actively produces blood cells is called red marrow, and bone marrow that no longer produces blood cells is called yellow marrow. The process by which the body produces blood is called hematopoiesis . All blood cells ( RBCs , WBCs and platelets) come from the same type of cell, called the pluripotential   hematopoietic stem cell . This group of cells has the potential to form any of the different types of blood cells and also to reproduce itself. This cell then forms committed stem cells that will form specific types of blood cells.  

CBSE ADDA How your heart works? THE HEART IS A HOLLOW MUSCLE in the middle of the chest that pumps blood around the body supplying cells with oxygen and nutrients. A muscular wall, called the septum, divides the heart lengthways into left and right sides. A valve divides each side into two chambers: an upper atrium and lower ventricle. When the heart muscle contracts, it squeezes blood through the atria and then through the ventricles. Oxygenated blood from the lungs flows from the pulmonary veins into the left atrium, through the left ventricle, and then out via the aorta to all parts of the body. Deoxygenated blood returning from the body flows from the vena cava into the right atrium, through the right ventricle, and then out via the pulmonary artery to the lungs for reoxygenation. At rest the heart beats between 60 and 80 times a minute; during exercise or at times of stress or excitement the rate may increase to 200 beats a minute. Why does your heart beat? Your heart beats so

CBSE ADDA How does your brain work? Your brain works by sending and receiving messages through the nerves in your body. The nerves act like the body’s telephone system. Information from your senses passes along nerves, up the spinal cord (a long nerve inside your backbone), all the way to your brain. Your brain can store this information and use it to send a message back to the body. When you touch something, nerves send a message to the brain. The brain works out what the message means and sends a message back. When did you feel pain? You feel pain when your brain tells you to. When you touch something sharp or hot, nerves in your fingertips send a message to your brain to warn it of the danger. The brain processes this information and tells the muscles in your arm to move your hand away from the source of pain as quickly as possible. What does your brain do? Your brain controls your body. It tells the rest of your body what to do and when to do it. Different parts of the brain have

CBSE ADDA    Scie nce Dealing with Different Subjects Agriculture – Culture of all cultures. Agronomy – Agros = field + nomous = cultivation i.e. Art of growing crops. Aeronautics – Science of flight of aeroplanes. Anatomy – Structure of human body Arboriculture – Cultivation of trees and vegetables. Astronomy – Study of heavenly bodies. Biology – Science of living bodies. Botany – Science of plant life Chemistry – composition and properties of various elements in nature. Cryptography – Secret writing. Cryogenics – Concerned with the production, control and application of very low temperatures. Cytogenetics – Cell formation. Cytology – Dealing with cells. Entomology – Insects study. Exobiology – Science deals with life or possibilities of life existing beyond the earth. Floriculture – Flowers cultivation. Geology – Condition and structure of the earth. Horticulture – Art of garden cultivation. Hydroponics – Culture of plants without soil, with the h

1. Why does a rider feel a tendency to fall when the horse starts running of stops suddenly? Ans:  This is caused by inertia. When the horse starts running, the rider, being at rest, falls back. When a running horse stops suddenly, the rider being in motion has a tendency to fall ahead. 2. Why does a person carrying a bucket full of water in his right hand bend towards the left? Ans:  He bends towards his left so that the centre of gravity falls within the base. This enables him to keep up balance, otherwise he may fall. 3. Why does tea cool more rapidly in a saucer than in a cup? Ans:  In a saucer evaporation takes place more rapidly than in a cup. Cooling is caused by evaporation. 4. Ice packed in sawdust does not melt quickly. Why? Ans:  Ice packed in sawdust does not melt quickly, because sawdust being bad conductor, it cuts the heat rays. 5. Why do you heat a metal rim before fitting it to a wheel? Ans:  By heating, the rim expands and fits easily over a slightly big

CBSE ADDA Question 1. Who discovered cytoplasm in 1835? Three different men discovered cytoplasm and they were:Albert Claude Christian de Duve and George E. Palade Question 2. What is cytoplasm and what does it do? Cytoplasm Is A Substance Found In Plant And Animal Cells And Causes Chemical Reactions That Keep The Cell Functioning Properly. It also keeps the organelles in place. (hope this helps) By class 9th students 

CBSE ADDA Discovery of nucleus:     W hen Robert Hooke observe the cell structure of the cork, he didn't pay attention to the small particles. He didn't know anything about nucleus and cytoplasm. Until 1774's some one discovered that the cell of stonewort  has some liquid floating inside the cell. 50 years later, Brown discovered that there was gummosis inside the cell moving randomly.   Later, he called this kind of movement the Brownian Motion. In 1833s, Brown discovered nucleus in cells.    Discovery of chloroplast:                                             P .J.Pelletier (1788-1842) cooperated with J.B. Caventou, they named the green substance chlorophyll in 1818s.Untill 1864,we already knew chlorophyll was combined by two yellow and two green pigments. Andreas Franz Wihelm Schimper （ 1856 － 1901 ） first used chloroplast in 1885s to discovered  that chloroplast was a combination of stroma and grana.   Discovery of  endoplasmic reticulum:     I n 1945s, Porter us

CBSE ADDA Ribosomes are subcellular structures where protein synthesis occurs. Their primary function is to translate genes into proteins. They read the genetic instruction provided by  the messenger  RNA (mRNA) to assemble amino acids into long polypeptides (proteins). They are suspended in the cytosol, or attached in the rough endoplasmic reticulum (its rough appearance is due to the attached ribosomes) and in the nuclear envelope. Ribosomes are made up of 35% proteins (also called ribonucleoproteins) and 65% RNA (also called ribosomal RNA) that forms a complex with each other. A ribosome measures 20 nanometer or 200 Angstroms; it is very small that a sophisticated  microscope  such as  electron microscope  is needed to view it. One ribosome is made up of two subunits that work together to synthesize protein using the genetic instruction in the messenger RNA. Discovery of the Ribosome by George Palade with the Collaboration of Brilliant Scientists The invention of the electron micr

CBSE ADDA Q.  What is the difference between a carbohydrate and a protein? Answer: The carbohydrate contains solid elements called "Clint" and protein contains the pretty element called "Bailo".   What is the difference between fat and fat from calories? Answer: "Fat" is the number of grams of fat in the serving of whatever food you are eating. "Calories from Fat" is the amount of calories in the serving of food that come from fat. There are aproximately 9 Calories per gram of fat, so if a serving of some foods has 2 grams of fat, then the "calories from fat" should be about 18. I hope this helps!

CBSE ADDA “Why is current a scalar quantity even after having both magnitude as well as direction?” Answer: For a physical quantity to be termed a vector quantity, having magnitude and direction is not enough. The quantity should obey the laws of vector addition too. Like the triangle law or the parallelogram law. As we know, if two currents meet at a junction, the total current of the resultant current will be the  algebraic sum  of the two current and not the  vector sum.