Photosynthesis is a process in which plants use water and carbon dioxide in the presence of sunlight to synthesize glucose and release oxygen. Plants synthesize their own food by photosynthesis. So, they are called autotrophs. During photosynthesis, oxygen is released as the life-sustaining gaseous component of the atmosphere while glucose or food is transported to all parts of the plant and used for growth. Here plants synthesize their own food through photosynthesis. So they are called autotrophs and the mode of nutrition is called autotrophic nutrition.

Food is very important for the sustenance of life. The digestive tract in humans starts from the mouth and ends at the anus. The human digestive system consists of the alimentary canal and secretory glands. It consists of the (i) buccal cavity,(ii) esophagus,(iii) stomach, (iv) small intestine, (v) large intestine, and (vi) anus. Nutrition is a complex process involving: (i) ingestion, (ii) digestion,(iii) absorption, (iv) assimilation and (v) egestion. The animal digestive system is different than the human digestive system and the bacteria living in the rumen of cattle can digest cellulose. We will also learn about the digestive system of the Amoeba.

The wool is obtained mainly from animals like sheep, yak, and goats. Wool is acquired from the fleece or hair of these animals. Wool is made from soft hair because of its fine quality. After removing hair, it is washed, cleaned, and dried. It is further sent to a factory wherein the sorting and dying of wool take place based on different textures and quality of the wool. Fibers are spun around bobbins, cones, etc. to make the yarn which is further used in making clothes. We will also understand the process of obtaining silk threads from the silkworm.

Temperature is the degree of hotness or coldness measured on a definite scale. The thermometer is a device used to measure temperature. Convection takes place when heated molecules move from one place to another, taking the heat with them. We will also learn about the convection of air which is when the air near the heat source gets heated up and rises up. The wind blowing from the sea towards the land is called Sea Breeze and the wind blowing from the land towards the sea is called the land breeze. We will also understand the science behind why black color absorbs more heat than white.

Litmus papers are basic indicators that indicate whether the solution or substance is acidic or basic. The acid converts blue litmus paper to red and the base converts red litmus paper to blue. We will also perform experiments through turmeric powder and understand this concept in detail. We will also understand how neutralization helps in indigestion. Neutralization is a process or a chemical reaction in which an acidic and basic substance is mixed with each other in order to neutralize their acidic and alkaline nature. The irritation of the skin due to ant bite is caused because of the presence of formic acid that the ant injects into the skin while biting. Hence we use a basic substance to neutralize the effect.

In a physical change, the chemical composition of a substance does not change. New substances are not created in a physical change. Chemical changes are complex changes that are mostly irreversible in nature. New substances are created in a chemical change. Iron is used in the making of bridges, ships, cars, truck bodies, and many other articles, and we see how rusting damages the iron. We will also learn that how metal is more reactive than the other reacts with the compound of less reactive metal, it replaces the less reactive metal in the compound and takes its place.

The average weather pattern taken over a long time, around 25 years, is called the climate of the place. Climate has a profound effect on all living organisms. The regions located in the extreme north and extreme south of the globe are called Polar Regions.  We will understand how an animal like a penguin or bear adapts to survive in the prevailing cold climate in a polar region. The tropical rainforest is located near the equator and receives most of the sunlight. We will learn how different animals have developed adaptations to survive in the unique conditions of a tropical rainforest.

Air exerts pressure from a higher density area to a lower density area of air. Fire extinguisher contains CO2 gas which stops the fire by eliminating the supply of oxygen. The fire extinguisher makes the layer over the fire. So, fire does not get oxygen, so the fire is extinguished. We will apply the same air pressure concept and understand how hot air balloons fly. We will also learn how wind currents on the earth are generated due to uneven heating on the earth. We will explore how the rainy season occurs further in the chapter.