Important Main Point in Class 7 Science Chapter 1

1. Mode of Nutrition in Plants

This part of the content gives you a fundamental idea about modes of nutrition which is usually required by different organisms. As we know, food is essential for all living organisms. The food contains some nutrients like, carbohydrates, Proteins, Fats, Vitamins, and Minerals which are required by our body for growth and development, called nutrition. We get food from plants and animals, as you know. But how do plants get their food? Remember, plants can make their food themselves, but humans and animals cannot. Autotrophs are the mode of nutrition in which organisms make their own food. That means plants are autotrophs. Here, we cannot make our food; we are dependent on plants for the readymade form of food. So, we are known as ‘Heterotrophs’. Therefore, it is clear that the plant uses the autotrophic mode of nutrition for its growth and development. Nutrition in Animals and most other organisms is heterotrophic mode of nutrition for growth and development.

2. Photosynthesis – Food Making Process in Plants

This part of the content focuses on the process of photosynthesis which is essential for the survival of all living organisms. Plants are the only organisms that can prepare food by using sunlight, water, carbon dioxide, and minerals. You are surprised to know that leaves are the food factories of plants. Therefore, all the raw materials must reach there. The leaves have a green pigment called chlorophyll which captures the energy of the sunlight. This light energy is used to prepare food. So, this process is known as ‘Photosynthesis’. The raw material, i.e. carbon dioxide taken from the air through the tiny pores of leaves, is called stomata. Water and minerals present in the soil are absorbed by the roots and transported to the leaves. The food produced by the process of photosynthesis is mainly carbohydrate which later gets converted into starch. During the process of photosynthesis, oxygen is released into the atmosphere. Thus, you can see how photosynthesis is essential for the survival of all living organisms.

3. Other Modes of Nutrition in Plants

There are some plants that do not contain chlorophyll in them and thus cannot prepare their food. They depend on other plants or organisms for food. Therefore, they are known as a parasite. You will be surprised to know that there are some plants that can trap insects and digest them. Such insect-eating plants are called insectivorous plants.

4. Saprotrophs

This part of the content introduces some other modes of nutrition which is usually essential for different organisms. You might have seen cotton-like threads spread on the rotten or wet piece of bread. These organisms are often known as fungi. The way they take their nutrients from dead or decaying matter is called ‘Saprotrophs’. Remember, the mode of nutrition in which organisms take their nutrients from decaying matter is called saprotrophic nutrition. Sometimes, two plants of different species live together and help each other in obtaining food and shelter. This association is called symbiosis, and such plants are called symbiotic plants. The association is significant for both of their survival.

5. How Nutrients Replenished in the Soil

You learned that plants absorb nutrients from the soil. Crops require much nitrogen to make protein. After the harvest, the soil becomes deficient in nitrogen. Plants cannot use the nitrogen gas available in the atmosphere directly. The action of rhizobium bacteria can convert this nitrogen into a soluble form but that bacteria cannot make its own food. In return, leguminous plants provide food and shelter to the rhizobium bacteria. Thus, they have a symbiotic relationship as you learn before. This association is significant for the farmer, as they do not need to add nitrogen fertilizers to the soil in which leguminous plants are grown. In this way, you can see that every living organization needs some energy and nutrient materials to ensure that the life processes go on smoothly.

Important Main Point in Class 7 Science Chapter 2

1. Different Ways of Taking Food

We have already studied nutrition in plants. This part of the content describes the nutritional needs and digestive system in human beings, along with other living beings. As we know that food is needed for every living organism. Plants can prepare their own food but animals cannot. But we know nutrition is required for every organism for energy. The food contains some nutrients like carbohydrate, protein, fat, vitamin, and minerals which are required by our body for growth and development, called ‘Nutrition’.

Generally, in the process of nutrition, food is taken as a complex substance and break down in simpler substances, called ‘Digestion’. After that, it is utilised by our body. You may have observed that different types of animals show different modes of nutrition. Such as, eagle tear flesh of prey, hummingbirds suck the nectar from the flower, mosquito and lice suck blood from other organisms. And amoeba capture and swallow tiny aquatic animals, snake-like python swallow others animal on the whole, human and many other animals feed on mother’s milk.

2. Digestion in Human

In this part of the content gives sufficient idea about the journey of food in human beings. As you learnt before in the process of digestion, food is breakdown in simple substances and after it is utilised by our body. The journey of our food starts from the buccal cavity (mouth) then it moves on food pipe or oesophagus and after it reaches to the stomach, small intestine and next to the large intestine and last the anus. Remember, tooth and digestive glands play an important role in our digestion.

3. Process of Digestion

As you know, food is taken through the mouth with the help of teeth food is breakdown. You must know that our mouth has salivary glands. It secrets a juice, called saliva. We use our tongue for talking beside it mixes saliva with the food and helps in swallowing food. The swallowed food passes into the food pipe and reaches into the stomach. You know digestive juices and acids are present in the stomach which helps the food to digest due to some of the physical and chemical changes. Partially digested food reaches the small intestine where intestinal juices complete the digestion. You are surprised to know that our small intestine is 7.5 metres long and highly coiled. Similarly, our large intestine is about 1.5 metre-long, and it helps to remove waste material time-to-time through the anus.

4. Digestion in Grass Eating Animals

You may have observed that cows, buffaloes and other grass-eating animals chewing continuously, even when they are not eating. They quickly swallow the grass and store it in a part of a stomach, called ‘Rumen’. Hence, they are called ruminants. You may know that partially digested food or grass present in the rumen of a cow is called ‘Cud’. When this cud is thoroughly chewed in the mouth of the cow and swallowed again and reaches small intestine for complete digestion and absorption of food.

5. Feeding and Digestion in Amoeba

Have you ever seen amoeba? Your answer will be ‘no’. Do you know amoeba cannot see by naked eyes? Amoeba is single-celled microscopic organisms which are found in pond, lakes and other water sources. The body of amoeba has a finger-like projection called pseudopodia or false feet. It captures food and helps in locomotion of amoeba. Then the captured food is break-down into simpler substances for digestion. This digested food is then absorbed and used for growth and maintenance by amoeba. In this way, you can see animals obtain their nutrients through a wide variety of feeding patterns. As nutrition is a must for a variety of reasons. Animals need the proper nutrition for growth, maintenance, transportation of materials and to provide energy for work and vital functions for their survival or existence.

Important Terms for Class 7 Science Chapter 3

1. Wool

Class 7 Science Chapter 3 describes the rearing and breeding of different animals and learns fibre production and its management. You have learnt about some fibres obtained from animals. You also learnt that wool and silk fibres are obtained from animals. Do you know where do we get wool? Wool is obtained from the fleece or hair of sheep. The hairy skin of the sheep has two types of fibres that form its fleece – the coarse type of beard hair and the fine soft hair close to the skin.

2. Animals that yield wool

Remember, fine hair provides the fibres for making wool. There are several breeds of sheep found in different parts of our country. However, the fleece of sleep is not the only source of wool. As Yak wool, Angora wool and Kashmiri wool is found in Tibet, Jammu and Kashmir respectively. The hair on the body of camels is also used as wool.

3. From fibres to wool

In this part of the content gives an idea about rearing and breading method of animals. As you know, wool mainly comes from sheep. It protects the sheep from the unfavorable climate and whether.

For obtaining wool, sheep are reared and breed in Jammu and Kashmir, Himachal Pradesh, Uttaranchal, Arunachal Pradesh, Sikkim, Haryana and many other parts of India. Rearing of sheep refers the shelter, food and taking care to provide to them. And breeding of sheep is done to obtain a good quality of wool in large quantities. Once, the reared sheep have developed a thick coat of hair, that hair is shaved off for getting wool.

4. Processing fibres into wool

In this part of the content introduced the step by step, the production method for getting fibre of wool. You will be surprised to know the wool which is used for knitting sweaters or for weaving shawls is the finished products of a long process. As you learn before, the fleece of sheep along with a thin layer of skin is removed from its body, called ‘Shearing’. Remember, shearing does not hurt the sheep. Then, sheared skin with hair is thoroughly washed in tanks to removed dirt and dust, called ‘Scouring’. After that, the hairy skin is sent to a factory for separating different hair, called ‘Sorting’. You may know a small fluffy fibre, called burrs are picked out from the hair. These are the same burrs which sometimes appears on our sweaters. And then, fibres are dyed in various colours. And lastly, fibres are straightened, combed and rolled into ‘Yarns’.

5. Silk

A fabric with a thousand years of history, silk is acclaimed for its smooth, lustrous texture that makes it comfortable to wear in both winter climates and warmer seasons. Do you know? Silk is a natural fibre which is obtained from an insect called ‘Silk Moth’.

Important Terms to be Covered in Class 7 Science Chapter 4

1. Hot and Cold

In this part of the content focuses on the effects of heat energy in different materials with practical activities which help you to better understanding the concept. 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. In winter we usually feel cool inside the house. If we come out in the Sun, due to effect of light, we feel warm. In summer, we feel hot even inside the house. How do we know whether an object is hot or cold? By using a reliable device for the measurement of the hotness of an object, is called a ‘Thermometer’.

2. Measuring Temperature

In this part of the content introduces the importance of thermometer in our life. Do you know that the thermometer that measures our body temperature is called ‘Doctor’s Thermometer’ or ‘Clinical Thermometer’? And a clinical thermometer consists of a long, narrow, uniform glass tube with a bulb at one end. This bulb contains mercury which is the main source of the measurement. You will also find two types of scale on Clinical thermometer. 35 to 40 degrees in ‘Celsius scale’ and 94 to 108 degrees in ‘Fahrenheit scale’. Do you know the normal temperature of the human body is 37 degrees Celsius, and it is the average body temperature of us? You will be surprised to know that different types of thermometers are used for different purposes. As maximum and minimum thermometer are used for the weather of a day. Clinical thermometer is used for human body temperature. How do we measure the temperature of other objects?

3. Laboratory Thermometer

In this part, we will learn about the process of getting the temperature of different objects. For measuring the temperature of different objects, we use ‘Laboratory thermometer’ for them. The range of a laboratory thermometer is generally from -10 degree Celsius to 110 degrees Celsius. Remember, we do not use a clinical thermometer for measuring the temperature of other objects and also not be use laboratory thermometer for the human body. In both cases, we use a separate device to measure the temperature. We can compare the temperatures of Water from different sources.

Transfer of Heat

In this part of the content helps you to understand the various methods of heat transfer with the help of different practical activities. You might have observed that frying pan becomes hot when kept on a flame. When the pan is removed from the flame, it slowly cools down. Do you know how it happens? Heat is a form of energy which spontaneously transferred from a hotter object to a colder object, called ‘Conduction’. The material which allows heat to pass through them easily is called ‘Conductors’. And those materials which do not pass heat through them are called ‘Insulators’.

 Convection and Radiation

You will be surprised to know the facts, how water is boiling. When water is heated, the water near the flame gets hot. Hot water rises and cold water moves down towards the source of heat. This water also gets hot, and rises and water from the sides move down again. This process continues until the whole water gets heated. This mode of heat transfer is known as ‘Convection’. When we come out in the sun, we feel warm. It cannot reach us by conduction or convection. Remember, from the sun, the heat comes to us by another process known as ‘Radiation’. The motion of heat by radiation does not require any medium. When we sit in front of a room heater, we get heat by this process.

 Clothes We Wear in Summer and Winter

You know that in summer we prefer light-coloured clothes and in winter we usually wear dark-coloured clothes. Do you know what the reason behind it is? The dark colour absorbs more heat, and therefore we feel comfortable with dark coloured clothes in winter. And light-coloured clothes reflect most of the light that falls on them and, therefore, we feel more comfortable to wear them in summer. As you know, in the winter we use woollen clothes. Wool is a poor conductor of heat.
Moreover, there is air trapped in between the wool fibres. This air prevents the flow of heat from our body to the cold surroundings. So, we feel warm. Uses of heat energy include but are not limited to: cooking, drying, heating, smoking, baking, water heating, cooling and manufacturing. Besides that, heat from the sun generates our weather patterns and gives energy to the growing green plants that provide the food and oxygen for life on Earth. Thus, the sun is the ultimate source of energy for all living organisms.

We use in our daily life a large number of substances such as lemon, tamarind, common salt, sugar, and vinegar. Do they have
the same taste? Let us recall tastes of some edible substances If you have not tasted any of these substances taste them now