Animal nutrition includes nutrient requirement, mode of intake of food and its utilisation in the body.

The breakdown of complex components of food into simpler substances is called digestion.

2.1 Different Ways of Taking Food

The mode of taking food into the body varies in different organisms. Bees and humming-birds suck the nectar of plants, infants of human and many other animals feed on mother's milk. Snakes like the python swallow the animals they prey upon etc. Continue Learning

Animal fibres − wool and silk

Wool

Wool comes from sheep, goat, yak and some other animals. These wool-yielding animals bear hair on their body. the hairy skin of the sheep has two types of fibres that form its fleece: (i) the coarse beard hair, and (ii) the fine soft under-hair close to the skin. The fine hair provide the fibres for making wool. Some breeds of sheep

possess only fine under-hair. Their parents are specially chosen to give birth to sheep which have only soft underhair. This process of selecting parents for obtaining special characters in their offspring, such as soft under hair in sheep, is termed ‘selective breeding’. Continue Learning

4.1 Hot and Cold

In our day-to-day life, we come across a number of objects. Some of them are hot and some of them are cold. Tea is hot and ice is cold.

A reliable measure of the hotness of an object is its temperature. Temperature is measured by a device called thermometer.

4.2 Measuring Temperature

The thermometer that measures our body temperature is called a clinical thermometer.

A clinical thermometer consists of a long, narrow, uniform glass tube. It has a bulb at one end. This bulb contain-s mercury. Outside the bulb, a small shining thread of mercury can be seen. Continue Learning

5.1 Acids And Bases

Curd, lemon juice, orange juice and vinegar taste sour. These substances taste sour because they contain acids. The chemical nature of such substances is acidic.

The word acid comes from the Latin word acere which means sour. The acids in these substances are natural acids.

If we rub its solution between fingers, it feels soapy. Generally, substances like these which are bitter in taste and feel soapy on touching are known as bases. The nature of such substances is said to be basic. Continue Learning

6.1 Physical Changes

Properties such as shape, size, colour and state of a substance are called its physical properties. A change in which a substance undergoes a change in its physical properties is called a physical change. A physical change is generally reversible. In such a change no new substance is formed.

6.2 Chemical Change

A change with which you are quite familiar is the rusting of iron. If you leave a piece of iron in the open for some time, it acquires a film of brownish substance. The substance is called rust and the process is called rusting.

A change in which one or more new substances are formed is called a chemical change. A chemical change is also called a chemical reaction. Continue Learning

7.1 Weather

The day-to-day condition of the atmosphere at a place with respect to the temperature, humidity, rainfall, windspeed, etc., is called the weather at that place.

The daily weather report carries information about the temperature, humidity and rainfall during the past 24 hours. It also predicts the weather for the day. Humidity, as you might know, is a measure of the moisture in air.

The weather reports are prepared by the Meteorological Department of the Government. This department collects data on temperature, wind, etc., and makes the weather prediction.

The temperature, humidity, and other factors are called the elements of the weather. The weather of a place changes day after day and week after week. Continue Learning

8.1 Air Exerts Pressure

While we have to fill air into the bicycle tube to keep it tight. Also, you know that a bicycle tube overfilled with air may burst. This experiences tell us that the air exerts pressure.

Due to the air exerts pressure that the leaves of trees, banners, or flags flutter when the wind is blowing. The pressure of air inside the can decreases than the pressure exerted by the air from outside the can.

8.2 High Speed Winds are Accompanied By Reduced Air Pressure Continue Learning

9.1 Soil Teeming with Life

Soil is one of the most important natural resources. It provides anchorage to the plants and supplies water and nutrients. So, we have learnt about the soil.

9.2 Soil Profile

Soil is composed of distinct layers. Perform the following activity to find out how these layers are arranged.

The rotting dead matter in the soil is called humus.

The soil is formed by the breaking down of rocks by the action of wind, water and climate and the process is known as weathering. Continue Learning

10.1 Why Do We Respire?

The process of breakdown of food in the cell with the release of energy is called cellular respiration. Cellular respiration takes place in the cells of all organisms. Breathing is a part of respiration.

When breakdown of glucose occurs with the use of oxygen it is called aerobic respiration and Food can also be broken down, without using oxygen is known as anaerobic respiration.

Glucose in the presence of oxygen/heat → carbon dioxide + water + energy Continue Learning

11.1 Circulatory System

We have learnt earlier that all organisms need food, water and oxygen for survival. They need to transport all these to various parts of their body.

Blood

Blood is the fluid which flows in blood vessels. It transports substances like digested food from the small intestine to the other parts of the body. It carries oxygen from the lungs to the cells of the body. It also transports waste for removal from the body. Continue Learning

The production of new individuals from their parents is known as reproduction.

12.1 Modes of Reproduction

There has the different mode of reproduction based on the category of organism. Plant has different mode of reproduction as compared with human, as different with animals etc.

In plant the flowers perform the function of reproduction in plants. Flowers are the reproductive parts.

There are several ways by which plants produce their offspring. These are categorised into two types: (i) asexual, and (ii) sexual reproduction. Continue Learning

13.1 Slow or Fast

It is very common experience that we see the motion of some objects is slow while that of some others is fast.

The distance moved by objects in a given interval of time can help us to decide which one is faster or slower. The distance covered by you after 5 minutes would be much smaller than that covered by any object.

13.2 Speed

The most convenient way to find out which of the two or more objects is moving faster is to compare the distances moved by them in a unit time. Thus, if we know the distance Continue Learning

14.1 Symbols of Electric Components

Some common electric components can be represented by symbols. when an bulb has electric current passes it will glow.

14.2 Heating Effect of Electric Current

The wire gets hot when an electric current passes through it. This is the heating effect of the electric current.

An electric room heater or an electric heater used for cooking. All these contain a coil of wire. This coil of wire is called an element. You may have noticed that when these appliances are switched on after connecting to the electric supply, their elements become red hot and give out heat. Continue Learning

15.1 Light Travels Along a Straight Line

15.2 Reflection of Light

The candle, which appears behind the mirror, is the image of the candle formed by the mirror. The candle itself is the object.

When we see a mirror changes the direction of light that falls on it, the change of direction by a mirror is called reflection of light.

15.3 Right or Left!

When we see in the mirror the ‘right’ appears ‘left’ and the ‘left’ appears ‘right’. Note that only sides are interchanged; the image does not appear upside down. Continue Learning

If you have water, you can think of the future

16.1 How Much Water is Available

We are aware that about 71% of the earth's surface is covered with water. Almost all the water on the earth is contained in the seas and oceans, rivers, lakes, ice caps, as groundwater and in the atmosphere.

16.2 Forms of Water

The water on the earth has been maintained for millions of years by various processes which make the water cycle.

The solid form, snow and ice, is present as ice caps at the poles of the earth, snow-covered mountains and glaciers. Liquid water is present in oceans, lakes, rivers, and even underground. The gaseous form is the water vapour present in the air around us. Continue Learning

17.1 Visit to a Forest

While we visit any forest we'll be surprised because we could not see any land The different treetops had formed green cover over the land. However, the cover was not uniformly green. The environment was peaceful and a cool breeze was blowing.

The forest floor provides favourable conditions for them to germinate and develop into seedlings and saplings. Some grow up into trees. The different horizontal layers in the forest. These are known as understoreys Giant and tall trees constituted the top layer followed by shrubs and tall grasses, and herbs formed the lowest layer. Continue Learning

Rich in lather, mixed with oil, black−brown water that goes down the drains from sinks, showers, toilets, laundries is dirty. It is called wastewater.

18.1 Water, Our Lifeline

Clean water is a basic need of human being. Clean water that is fit for use is unfortunately not available to all. It has been reported that more than one billion of people have no access to safe drinking water. This accounts for a large number of water-related diseases and even deaths.

Cleaning of water is a process of removing pollutants before it enters a water body or is reused. This process of wastewater treatment is commonly known as “Sewage Treatment“. It takes place in several stages. Continue Learning