4th Class

     Introduction   Every organisms living on this earth is unique in itself. This uniqueness of each living individual is the basis of the great differences or diversity of the living world. The type of living organism found in one place is entirely different from organisms found in another place. For example, animals found in plains is different from the animals found in mountains or hilly regions. In fact different places, in different part of the world have their own typical kind of living Organisms. The degree of diversity in the living world is endless.                                               Different Types of Animals With such vast differences and large number, it is very difficult to study each and every living organism separately, at more...

     Animals and Their Habitat   Animals are found everywhere on the earth. They are found on the highest of mountains and in the deepest of the sea. They are found in the hottest deserts or in the cool poles (Antarctica). Animals live in the wild and even in our homes. They live in air too. The surrounding or the environment in which an animal lives and survive is called its habitat. Animals develop certain features, which help them to survive in their specific environment, or habitat. If they are not properly adapted to their surrounding, they either die or they move to places where they are better suited and can adjust in a much better way for survival and growth. The process of developing special features in order to adjust to the changes in the surrounding or the habitat of an animal is more...

     Food of Animals   We all need food to live and grow. Animals cannot prepare their own food like plants. Hence they have a heterotrophic form of nutrition. The large and the diverse groups of animals living in this world have different food habits. It is for this difference that all the forms of life are surviving. Can you guess what will happen if all the animals eat the same type of food? Different animals eat different kind of food and their body parts are accordingly adapted. Adaptability and availability are the two main reasons for an animal to have a specific food habit. Based on the type of food that an animal eats, they have been divided into five major groups.              Herbivores Plants i.e. herbs, bushes, leaves, grasses, fruits or seeds more...

     Adaptation for Protection   The living world is full of challenges. Organisms have to adopt all the harsh conditions of the environment, in order to live and reproduce. Apart from the harsh environmental conditions like high and low temperature, little or lots of water etc., a major struggle of the animals is for food. Many of the animals are the food for other animals. Mostly the carnivores or omnivores hunt herbivores for their requirement of foods. However, many of the animals have adopted special features that help them to protect themselves from enemies. Let us look and understand at some of the special adaptive features of animal have evolved specially for their protection against their enemies.            Large Size Huge sizes of some animals are enough to scare away their enemies. For example, bear, more...

     Reproduction in Animals   Like any other living thing, animals are born, grow, give birth to their own kinds, get old and die. The ability to produce more of their own kind is known as reproduction. Reproduction is very essential for the continuation of a species or a group of animal. It ensures the continuation of similar kind of individuals (animals) generation after generation. Animals have mainly two different ways of reproduction. Animals, which give birth to their young one, the baby develops inside the body of the mother. Second group of animals are those which lays eggs, baby hatches out from the egg. Now let us understand these two ways of reproduction in detail.                                                    Reproduction       more...

     Introduction   To do any kind of work we have to apply force and to apply force we require energy. It shows that these three terms (Work, Force and Energy) are related and dependent on one another. Work                                     Force                                     Energy Done      <—————            Applied       <—————      Needed Thus we can say that work is only done, when we have the energy to apply force.          Force Think of the normal activities like catching a ball, throwing a ball, pulling or pushing a chair. Have you ever thought, why a chair moves when we push it or pull it? The chair moves because we apply a force on it.                 Force is push or pull acting more...

    Types of Force   In this chapter, we will study about two types of forces: (i) Frictional force (ii) Gravitational force            Friction Friction is a type of force exerted when two surfaces are in contact with each other. Lets us understand it in a simpler way with an example.   A bicycle gradually slows down and finally stops, when we stop pedaling. A ball that you have rolled, gradually slows down and then comes to rest. When you push your toy, it moves for some distance and then slow down and finally stops after some time. These are few of the events that most of you have experienced. Can you guess why the moving object comes to rest automatically?   In all the above cases there is no more...

     Work   When force is used to move an object from its position, we say that work is done. To move a table from its one positions to another, we require to apply force on the table. You must have pushed a chair many a times. Why the chair moves? The chair moves because of the force applied by you. You apply the force on the chair and move it from its original position to a new position of your choice. This is the process of doing work.       Work done by moving an object   Work is always done by a force. We often name the agent that has applied this force and say that the agent has done work. When a girl pushes a notebook on the table, we say that the more...

     Types of Energy   There are two major types of energy. The energy present in a resting body is the potential energy and the other is the kinetic energy, which is present in the objects in motion.             Potential Energy Potential energy is the energy of an object due to the position of its body. The S.I. unit of potential energy is     When a rubber band is stretched to the left, it exerts a force to the right so as to return to its original un -stretched position. When a mass is lifted up, the force of gravity on the object brings it back to the ground. Roller coaster climbs a hill, it has maximum potential energy at the top of the hill. When the Roller more...

     Sources of Energy   Any system from where energy is tapped is called a source of energy. Sun is the ultimate source of almost all energy. Energy that the earth receives from the sun is in the form of heat and light. Some of the main sources from where we get energy are as follows:        Different source of Energy                Solar Energy Solar energy is the energy that we get from the sun. It is in the form of heat and light. The green plants use this solar energy to make food for all living things on the earth. Animals eat the food made by the plants and get energy to do work. Animals can't use the solar energy directly. We depend more...