Class 07 Science NCERT

All organisms need food and utilise it to get energy for growth and maintenance of their body. Green plants synthesise food for themselves by the process of photosynthesis. They are autotrophs.

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

Our sense of touch is not always a reliable guide to the degree of hotness of an object. Temperature is a measure of the degree of hotness of an object. Thermometer is a device used for measuring temperature.

Acids are sour in taste. Generally, bases are bitter in taste and soapy to touch. Acid turns blue litmus red. Bases turn red litmus blue.

Changes can be of two types, physical and chemical. Physical changes are changes in the physical properties of substances. No new substances are formed in these changes. These changes may be reversible.

Respiration is essential for survival of living organisms. It releases energy from the food. The oxygen we inhale is used to breakdown glucose into carbon dioxide and water. Energy is released in the process.

In most animals the blood that circulates in the body distributes food and oxygen to different cells of the body. It also carries waste products from different parts of the body for excretion.

All organisms multiply or reproduce their own kind. In plants there are two modes of reproduction, asexual and sexual. There are several methods of asexual reproduction such as fragmentation, budding, spore formation and vegetative propagation.

The distance moved by an object in a unit time is called its speed. Speed of objects help us to decide which one is moving faster than the other. The speed of an object is the distance travelled divided by the time taken to cover that distance.

It is convenient to represent electric components by symbols. Using these, an electric circuit can be represented by a circuit diagram.

Light travels along straight lines. Any polished or a shining surface acts as a mirror. An image which can be obtained on a screen is called a real image. An image which cannot be obtained on a screen is called a virtual image.

We get various products from the forests surrounding us. Forest is a system comprising various plants, animals and micro-organisms.

Used water is wastewater. Wastewater could be reused. Wastewater is generated in homes, industries, agricultural fields and in other human activities. This is called sewage.