7th Class

       Transpiration   Plant use only 5% - 10% of the water, which is absorbed by the plant roots. Rest of the water is evaporated in the atmosphere through stomata. Evaporation of water through stomata is called transpiration. Transpiration actually helps in reducing pressure in the upper part of xylem. Reduction of pressure in the upper xylem pulls water in upward direction. Thus transpiration helps in water transportation.              Water is absorbed by the roots, which are in the lower part of the plant. This water needs to be transported to the leaves of the plant, which is in the upper part of the plant. For absorption of water from lower to the upper part a force more...

         Transport System in Animals   Plants have evolved in such a way that their root system remains in contact with soil and shoot system remains in contact with atmosphere. Thus plants get all the required material from a single place and need not have to move. But animals have to move from place to place in order to get food and shelter. Movement in animals demands an improved transport system. When animals move fast, rate of their energy consumption increases by great extent. For the fast production of energy in the cells, cells required a fast transportation of required materials. Therefore, animal body requires a more efficient and evolved transport system, whose rate of transportation can be increased or decreased according to the body requirement.

       Transport System in Human Being   Human body also need a transport system as varieties of substances like oxygen, carbon dioxide, water, food, hormones, enzymes, etc. are needed to be transported form one part to another. In human being, the work of transportation is carried out by circulatory system. Circulatory system is made up of blood vessels and a heart. Blood vessels are the tubular path through which blood keeps on circulating. There are three types of blood vessels, that is, arteries, veins, and capillaries. Together they form a net of blood vessels, which reaches every part of the body, making the blood to reach every parts. Blood, for reaching from heart to other parts of the body and for returning into heart from other parts of the body, use two different vessels system. more...

     Lymphatic System   There is one more system that helps in the work of transportation, known as Lymphatic System. Lymphatic system consists of lymph capillaries, lymph node and lymph. When blood passes through blood capillaries, blood plasma containing glucose and water leaks around the body cells through the walls of capillaries, since walls of capillaries are very thin. Here exchanges of substances occur between the cell and this leaked fluid (tissue fluid). The tissue fluid receives waste materials from the cells and seep back into blood capillaries. Tissue fluid also receives protein molecules, fragment of dead cells, germs etc., which cannot enter into blood capillaries because of their larger size. Therefore, they enter into lymph capillaries through the pores present in their wall. Lymph capillaries by joining together form lymph vessels. Lymph vessels contain lymph nodes, which have lymphocytes. Lymphocytes fight against the more...

       Introduction   Often a question arises in our mind, why does our body take food, air and water? What does our body do with these substances? Our body takes food, water, and air to serve mainly the following purposes: (a) To full fill the energy requirement of the body; (b) For growth of the body; (c) To repair the damaged parts of the body; (d) To fight against the pathogens.          Respiration Respiration can be termed as the production and utilization of energy. It fulfills the energy requirement of the living body. In winter days, you might have seen people burn woods to get heat energy to keep the body warm. Similarly our body burns glucose inside the cell to get energy, which is required to perform various functions. Our body performs many metabolic procedures. more...

     Human Respiratory System   As we know our body cells require oxygen for survival. Therefore, our body has evolved a tubular path so that oxygen can reach to the body cells from the atmosphere. This path (consists of many organ) is called respiratory path or respiratory system, as the path is specialized for respiration. This path begins from the nose and ultimately leads to the body cells through lungs and heart. Nose is an outer organ of respiratory system, which can be called as the gate of respiratory path, as air enters through it. It has been evolved in hollow tubular shape so that air can enter through it automatically. This air reaches the lungs through nasal cavity, pharynx and wind pipe, where it enters into another system called as circulatory system. Circulatory system is a net of blood vessels, which are laid more...

     Respiration in Plants   Plants have evolved themselves in such a manner that their every part may get air from atmosphere individually. Therefore, they do not need a respiratory system like animals. All parts of plants like roots, stem, and leaves perform respiration individually. Root has root hair for exchange of respiratory gasses. Root hairs lie in-between the soil particles, where air is trapped and receive air through the process of diffusion and send to the cells of root. Older plants have a pore called lenticels instead of root hair for exchanging respiratory gasses. Stem also have lenticels to get required air. Leaves have a pore on its lower surface called stomata through which exchange of respiratory gasses takes place.   Look at the Following Picture of Respiration in Plants           more...

     Respiration in Animals   In respiration, oxidation of food inside the cell in almost all animals and plants are somewhat similar. But the transportation of respiratory gasses (\[{{O}_{2}}\]and\[C{{O}_{2}}\]), essential for respiration inside the cell and outside the cell, is different in different animals, as different animals live in different type of habitat. Therefore different animals have evolved different body shapes according to the environment they live in and to transport respiratory gasses from the environment. For example, earthworm lives in soil. So it has developed moist skin for the exchange of respiratory gasses. Fishes live in water and have to absorb oxygen dissolved in water. So they have developed gills for respiratory purpose. Land animals like human, dog, lion etc. have developed different respiratory system as they live on land. Hence, we see that different types of respiratory system have been evolved in more...

     Structure of the Earth   The internal and outer structure of the Earth is layered. Denser and heavier materials (iron and nickel) are present in the core. The layer between the inner core and mantle is outer core. The outer core of the Earth is in liquid form and is composed of iron and nickel.   Look at the following picture of the Inner layer of the Earth                 The mantle layer of the earth is mainly composed of elements like, magnesium, iron, silicon and oxygen. Temperature of the mantle layer is about 3000°C Outer mantle of the Earth is thinner than the inner mantle. The upper layer (crust) is made up of rocks, which are again made up of amino silicates. more...

       Soil Profile and Formation   Soil profile is the layer of soil on the surface of the Earth. The colour of the soil is dark brown. There are three soil profiles, namely. A, horizon, B horizon and C horizon. The upper layer of soil is called/^ horizon or top soil. A horizon provides nutrition to living organism. The layer below the A horizon, is B horizon. Horizon C is below the horizon B. Some part of minerals from horizon A is transported through horizon B to horizon C. There are various kinds of insects and bacteria that live on the soil and these are essential for plants. The organic matter (humus) is found in the soil. Soil profile looks different in the different part of the earth.   Look at the following picture of the soil profile more...