7th Class

       Classification of Motion   Motion, on the basis of covered distance has been classified into two groups.               Uniform Motion (Uniform = Alike) If a body covers equal distances in equal interval of time, the body is said to be in the uniform motion. (Interval of time: Time duration or time difference)     In the above picture, speed of the car is constant at different interval of time. Therefore, it covers equal distances in equal interval of time. Thus the above shown car is in uniform motion.   Graphical Representation of the Uniform Motion     The above graph shows that the body covers the distance 20 m in every 5 minute. It means, the more...

       Rest and Motion   As we know, in this universe nothing is fixed at a single place. The galaxies are moving away from each other and universe is spreading. Therefore, everything is changing its position with respect to the time. Rest and Motion is the branch of Physics that deals with the position of a body. We will study the two different physical quantities "motion and rest" to describe the position of a body. In our day to day life, we often come across the terms rest and motion. In actual, in this universe nothing is in the rest. Earth moves around the Sun; Sun moves around the centre of the galaxy. Galaxies are moving away from each other and so on. The objects, which we see as in rest, actual are in motion. As the Earth is moving around the Sun, more...

       Sexual Reproduction   A sexual reproduction requires two individual of opposite sexes (male and female). An egg or ovum is called female gamete and a sperm is called male gamete. In sexual reproduction,' a male gamete fuses with a female gamete, which results in the development of new organism.                Sexual Reproduction in Flowering Plants A sexual reproduction requires two opposite sex cells male gamete and female gamete. When a flowering plant is mature to produce new plants sexually, it produces flowers, which contain the sex organs of the plant. There are some flowers, which contain only one sex organ (either male sex organ or female sex organ), called unisexual flower. And some flowers contain both type of sex organ, called bisexual flower. In the plants, the male sex organ is more...

        Artificial Methods of Vegetative Propagation   We have developed many methods of vegetative propagation by which a new plant can be grown from a part of plant. There are three common methods of artificial vegetative propagation: Cutting Layering Grafting              Cutting In this method, a part of plant is cut and the cut portion is buried under the soil, which develops into a new plant.                Layering In this method, a branch of plant is pulled down and covered with soil in such a way that the tips of the branch remain exposed in air. After few days covered part develops roots and grows into new plants.   more...

       Mode of Reproduction   There are two types of reproduction: Sexual reproduction Asexual reproduction              Asexual Reproduction This type of reproduction has been continued since the beginning of life on earth. By asexual reproduction an organism alone can reproduce new offspring without the help of any sex partner. There are six different ways by which a life can alone give birth to young ones. These are: Fission Budding Spore formation Regeneration Fragmentation Vegetative propagation              Fission In this type of reproduction, body of a living organism divides into two or more than two, living organisms. When a living body divides into two new living bodies, it is called binary fission (bi means two). And, when a living body divides into more than more...

         Reproduction   Life appeared on the earth about 3.8 billion year ago and is still continuing. This continuation of life has been made possible only by reproduction. Reproduction not only increases the number of the organisms, but also opens the way for the coming up of new organisms. As a result, the earth is filled with new species of animals and life form has becomes more complex. The term reproduction is used to mean the development of new life from the existing one. In another word, reproduction is a method by which organisms increase their number in the nature.

     Movement of Substance   The two basic requirement of each and every cell are:

• Availability of life substances (glucose and oxygen)
• Removal of waste products

  Multicellular life may be made up of trillions of cells. All cells are not in direct contact with air so that they can get air directly and can make food for themselves. Therefore, a transport system is required for supplying all the cells with glucose and oxygen and for removing waste products out of the body. Transportation is one of the most important metabolic functions of the body, without which multicellular life is not possible..

          Need of Transport System in Plants   Plants are made up of mainly three parts, i.e. root, stem and leaves. Leaves develop in upper part of plants so that they remain in directly contact with atmosphere to trap \[C{{O}_{2}}\] and sunlight. Roots develop in lower part of plants and remain underground to absorb water and minerals from the soil. These raw materials, obtained by different parts of plant, need to be get together in the leaves for the process of photosynthesis. So for transporting these materials from one part to another part, plants need a transport system..

       Transport System in Plant   Inside the plant body, mainly three types of materials are transported. These are water containing minerals, digested food, and hormones. In plants two systems are involved in transportation, namely: Xylem Phloem                 Transportation of Water and Minerals The system, which is responsible for transportation of water and minerals is called xylem. Let us know about the xylem..                Xylem Xylem is responsible for transportation of water and minerals. Water and mineral absorbed by the roots of a plant is transferred to the leaves by xylem. The transport system, xylem, is made up of two kinds of elements: Xylem vessels Tracheids                Xylem Vessels Xylem more...

       Transportation of Food and Hormones   The system, which is responsible for transportation of food and hormones is called phloem. Transportation of food is called translocation.            Phloem Phloem is made up of living cells. Like xylem vessels its cells also joins end to end. But the cell walls at the joint are not broken completely although they form sieve plates, which have small holes in them to pass the food materials. Thus by connecting cells one by one, phloem tube is formed. Phloem tubes lie throughout the body. So food and hormones enter into it and reach to the required cells.