1. Root cells are in contact with water and minerals in the soil.
2. Water and minerals enter the cells on the root surface due to differences in concentration.
3. As a result, these cells become turgid.
4. These turgid cells exert pressure on the adjacent cells. This is called ‘root pressure’.
5. Under the effect of this pressure, water and minerals reach the xylem of the roots and to reduce this difference in concentration they are continuously pushed forward.
6. As a result of this continuous movement, a water column is formed, which is continuously pushed ahead.
7. This pressure is sufficient to lift the water up in shrubs, small plants and small trees.

1. Plants give out water in the form of vapour through the stomata on their leaves.
2. This is called transpiration.
3. Water is released into the atmosphere by leaves through the process of evaporation.
4. As a result, water level in the epidermal layer of the leaf decreases.
5. Water is brought up to the leaves through the xylem so as to compensate for the lost water.
6. Transpiration helps in absorption of water and minerals and distribution to all parts of the plant.
7. Whereas root pressure performs the important role of pushing the water up during the night time.

1. Special types of cells which conduct impulses from one place to another in the body are called neurons.
2. Neurons are the structural and functional units of the nervous system.
3. Nerve cells, the largest cells in the human the body, may measure up to a few metres in length.
4. Nerve cells have the ability to generate and conduct electrochemical impulses.
5. The cells that support the nerve cells and help in their functioning are called neuroglia.
6. Nerve cells and neuroglial cells together form the nerves.
7. All the information about our surroundings is collected by the ends or dendrites of the neuron.
8. The chemical process begins at those ends and electric impulses are generated which are conducted from the dendrites to the cell body, from the cell body to the axon and from the axon to its terminal.
9. These impulses are then to be transferred from this nerve cell to the next.
10. Now the impulse that reaches the terminal of an axon, stimulates the nerve cell to secrete certain chemicals.
11. These chemicals pass through a minute space, called the synapse, between two adjacent neurons and generate the impulse in the dendrites of next neuron.
12. In this way, impulses are conducted in the body and these impulses are finally conveyed by nerve cells to muscle cells or glands.

1. The organization of the brain is extremely delicate and highly evolved.
2. The brain is the main controlling part of the nervous system and it is safely located in the cranial cavity.
3. Cavities present in various parts of the brain are called ‘ventricles’.
4. Spaces between the meninges are filled with Cerebro-spinal fluid.
5. This fluid supplies nutrients to the central nervous system and protects it from shock.
6. The brain of an adult human weighs about 1300 – 1400 grams and consists of approximately 100 billion neurons.
7. The brain consists of the Cerebrum, Cerebellum and the Medulla Oblongata.
8. Cerebrum controls the voluntary movements, concentration, planning, decision-making, memory, intelligence, and intellectual activities.
9. Cerebellum coordinates the voluntary movements and maintains the balance of the body.
10. Medulla Oblongata controls the involuntary activities like the beating of the heart, blood circulation, breathing, sneezing, coughing, salivation etc.

1. An immediate and involuntary response given to a stimulus from the environment is called a reflex action.
2. Sometimes we react to an incident without any thinking on our part or control over the reaction.
3. This is a response given to a certain stimulus from the surroundings.
4. In such situations, proper control and co-ordination is achieved even without intervention of the brain.
5. The reflex actions are brought about through a reflex arc.
6. A reflex arc is formed by the nerves which detect pain (sensory neuron), the relay neurons in the spinal cord and the nerves which bring about the movement of the muscle (motor neurons).

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1. Several different organ systems function in multicellular organisms.
2. Their life goes on smoothly if there is co-ordination between the different organ systems or organs and the stimuli in the surrounding.
3. Systematic regulation of different processes can be called control.
4. Bringing about the different processes in the proper sequence can be called co-ordination.
5. If any activity in the body is to be completed successfully, proper co-ordination between different systems and organs participating at different steps of that activity is necessary.
6. For example, for oxidation of food and release of energy, there should be proper coordination between the respiratory and circulatory system.

1. The human excretory system consists of a pair of kidneys, a pair of ureters, the urinary bladder and the urethra.
2. The functional unit of the kidney that performs the basic function of filtration is called a nephron.
3. Each nephron has a cup-like, thin-walled upperpart called the Bowman’s capsule.
4. The network of capillaries in it is called a glomerulus.
5. The urea produced in the liver comes into the blood.
6. When the urea-containing blood comes into the glomerulus, it is filtered through its capillaries and urea and other similar substances are separated from it.
7. Water molecules and small molecules of some other substances can cross the semipermeable membrane of Bowman’s capsule.
8. The solution accumulated in the cavity of Bowman’s capsule passes into the tubular part of the nephron.
9. Here, molecules of water and some other useful substances are reabsorbed into the blood.
10. Urine is formed from the remaining solution which is full of waste materials.
11. The urine is carried by the ureters and stored in the urinary bladder.
12. Afterwards, urine is given out through the urethra.

1. Rubber is used to make tyres and synthetic fibres.
2. Tannin from the bark of acacia is useful to make ink and in tanning of leather.
3. Quinine from the bark of cinchona is used in treatment of Malaria.
4. Gum is used to make glue. It also has some medicinal properties.
5. Oxygen released during photosynthesis is useful for our respiration.
6. Some oils from the leaves of Eucalyptus, lemon, basil, sandalwood etc. have medicinal as well as cosmetic uses.

1. The food produced in leaves is transported to each cell in the plant body.
2. Excess food, except amino acids, is stored in roots, fruits and seeds. This process is called ‘translocation’ of materials.
3. It is carried out in both the upward and the downward directions by the phloem.
4. Translocation of materials is not a simple physical process; it requires energy. This energy is obtained from ATP.
5. Whenever food material like sucrose is transported towards a part of a plant via the phloem with the help of ATP, the water concentration decreases in that part.
6. As a result, water enters the cell by the process of diffusion.
7. The pressure on the cell wall increases due to the increase in cellular contents.
8. Due to the increased pressure, food is pushed into the neighbouring cells where the pressure is low.
9. This process helps the phloem to transport the materials as per the need of the plant.
10. During flowering season, the sugar stored in roots or stem is transported towards the floral buds to make them open and blossom.