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Reproductive processes give rise to new individuals that are similar, but subtly different. Some amount of variation is produced even during asexual reproduction. The number of successful variations are maximised by the process of sexual reproduction.

Organisms look similar because their body designs are similar. If body designs are to be similar, the blueprints for these designs should be similar. Thus, reproduction at its most basic level will involve making copies of the blueprints of body design.

In animals, control and coordination are provided by nervous and muscular tissues.

The biological process involved in the removal of these harmful metabolic wastes from the body is called excretion. Different organisms use varied strategies to do this.

Blood transports food, oxygen and waste materials in our bodies. Blood consists of a fluid medium called plasma in which the cells are suspended. Plasma transports food, carbon dioxide and nitrogenous wastes in dissolved form.

The food material taken in during the process of nutrition is used in cells to provide energy for various life processes. Diverse organisms do this in different ways - some use oxygen to break-down glucose completely into carbon dioxide and water, some use other pathways that do not involve oxygen.

When we walk or ride a bicycle, we are using up energy. Even when we are not doing any apparent activity, energy is needed to maintain a state of order in our body.

The maintenance functions of living organisms must go on even when they are not doing anything particular. Even when we are just sitting or even if we are just asleep, this maintenance job has to go on. The processes which together perform this maintenance job are life processes.

On the morning of 14 July 1789, the city of Paris was in a state of alarm. The king had commanded troops to move into the city. Rumours spread that he would soon order the army to open fire upon the citizens.

Acids are sour in taste and change the colour of blue litmus to red, whereas, bases are bitter and change the colour of the red litmus to blue.

Whenever a chemical change occurs, a chemical reaction has taken place.

Sound is a form of energy which produces a sensation of hearing in our ears.

Two conditions need to be satisfied for work to be done: (i) a force should act on an object (ii) the object must be displaced. If any one of the above conditions does not exist, work is not done.

A force is needed to change the speed or the direction of motion of an object. An object dropped from a height falls towards the earth. All the planets go around the Sun. The moon goes around the earth.

A force can be used to change the magnitude of velocity of an object (to make the object move faster or slower) or to change its direction of motion. A force can change the shape and size of objects.

To describe the position of an object you need to specify a reference point called the origin. Motion is a change of position. It can be described in terms of the distance moved or the displacement.

All living organisms are made of cells. In unicellular organisms, a single cell performs all basic functions. For example, in Amoeba, a single cell carries out movement, intake of food, gaseous exchange and excretion.

The fundamental organisational unit of life is the cell.

Atoms and molecules are the fundamental building blocks of matter. The existence of different kinds of matter is due to different atoms constituting them.

Ancient Greek philosophers, Democritus and Leucippus suggested that if we go on dividing matter, a stage will come when particles obtained cannot be divided further. Democritus called these indivisible particles atoms.

All living organisms need food. Food supplies proteins, carbohydrates, fats, vitamins and minerals. Both plants and animals are major sources of food. We obtain most of this food from agriculture and animal husbandry.

Mixtures are constituted by more than one kind of pure form of matter. Dissolved sodium chloride can be separated from water by the physical process of evaporation. However, sodium chloride is itself a pure substance and cannot be separated by physical process into its chemical constituents.

Matter is made up of small particles. The matter exists in three states - solid, liquid and gas. The forces of attraction between the particles are maximum in solids, intermediate in liquids and minimum in gases.

While there are billions of planets in the universe, Earth is the only one where life, as we know today, exists and thrives in all its forms.

The living beings are termed as the biotic components and non-living things as the abiotic components of a habitat.

The bright portion of the Moon decreases from a full circle to a half circle in about a week.

Spherical mirrors are a common type of curved mirrors which are shaped like a part of a hollow glass sphere. Mirrors, whose reflecting surfaces are spherical are called spherical mirrors.

When salt and sugar are mixed with water, a uniform mixture is formed, whereas when chalk powder or sand, or sawdust is mixed with water, the components are not evenly distributed. Such mixtures are known as non-uniform mixtures.

When two or more substances are mixed, where each substance retains its properties, it is called a mixture. The individual substances that make up a mixture are called its components.

A constituent particle is the basic unit that makes up a larger piece of a substance or material. The spaces between the particles are known as interparticle spaces.

When we carry a bag, we feel its weight because of the force of gravity acting on our shoulders. The weight of the bag with narrow straps acts on a smaller area of our shoulders, whereas the weight of the bag with broad straps is spread out over a larger area of our shoulders.

In everyday life, we come across many situations where a force is applied, for example, opening a drawer, stretching a rubber band, a fielder stopping a ball, kicking a football, applying brakes on a moving bicycle, rolling a chapati, or turning the steering handle of an auto rickshaw.

When the current flows, the compass needle gets deflected from its original direction. When the current stops, the needle returns to its original direction.

There was a boy called Mario who loved to have lots of friends. He showed off a lot, always talking about how many friends he had at school, and how he was so friendly with everyone.

May my friendships always be
The most important thing to me.

Gajaraj, the elephant, lived in the best booth of the royal stables. The king was fond of Gajaraj, and he had ordered that the elephant should be well looked after.

Mr Raven was perched upon a limb,
And Reynard the Fox looked up at him;
For the Raven held in his great big beak,
A morsel the Fox would go far to seek.

Rama Natha was the son of a rich landlord. His father left him large tracts of land when he died. But Rama Natha did not spend even one day looking after his land.

As per the World Health Organization (WHO), health is defined as a state of complete physical, mental, and social well-being, and not merely the absence of disease.

The human eye can only see objects that are above a certain size. For a long time, many tiny things around us remained unknown.

The Earth spins (or rotates) on its own axis in space. The Earth’s axis of rotation passes through its geographic North Pole and the South Pole. The Earth completes one rotation in about 24 hours.

The Sun gives out or emits its own light and is the main source of natural light on the Earth. Stars, lightning, natural fire, and certain animals also emit their own light.

plants require both sunlight and water for their growth.

Life processes such as nutrition, circulation, respiration, excretion, and reproduction are essential for the survival of living beings. These processes are collectively called life processes.

Humans got interested in keeping track of time long ago. They started noticing that many events in nature repeat themselves after definite intervals of time.

There are three ways in which heat is transferred from one place to another - conduction, convection, and radiation.

The journey of life of a human can be divided into different stages - infancy, childhood, adolescence, adulthood, and old age. Each person experiences these stages at their own pace, and the duration of each stage may vary from one individual to another.

The changes could be in the size, shape, smell, or other property of the substance or object.

Metals are generally hard, lustrous, malleable, ductile, and good conductors of heat and electricity.

Electricity is generated in multiple ways - by windmills, by using wind energy, by solar panels capturing the Sun’s energy, by falling water and by using natural gas or coal. The electric supply from these sources reaches homes and factories via wires.