Complete Explanation of CBSE Notes
The world as we know is largely known through senses and the sense of sight is one of the most important senses. It is only when the light from an object enters our eyes that we see it. The light might have been either emitted by the object or reflected by it. Please refer Light Class 8 Notes for more revision notes.
The class 8 science chapter 15 discusses natural phenomena: lightning and earthquakes, and the measures to be taken to minimize the destruction caused by these phenomena. Let us take a look at some important points discussed in the chapter. Please refer Some Natural Phenomena Class 8 Notes for more revision notes.
Chemical Effects of Electricity:
The passage of electric current through a conducting solution results in chemical reactions. Following are the chemical reactions that can occur:
Sound plays an important role in our life. It is through sound we know that a period in school is over or if someone is approaching you by just listening to the footsteps. Vibrating objects produce sound. Vibration is the to and fro or back and forth movement of an object. Sound needs a medium to travel. Hence, it cannot travel in a vacuum. Please refer Sound Class 8 Notes for more revision notes.
The class 8 science chapter 12 Friction, discusses friction and various factor affecting it. The force which opposes the relative motion between two surfaces in contact is known as friction. It acts on both the surfaces. Listed below are factors that affect friction. Please refer Friction Class 8 Notes for more revision notes.
In science, a push or pull of an object is known as force. The interaction between two objects arises force. Force has both magnitude and direction. The strength of a force is expressed in magnitude. Force brings about a change in the direction or state of motion of a body. Please refer Force and Pressure Class 8 Notes for more revision notes.
It is only after the puberty sets in, humans become capable of reproduction. The class 8 science chapter 10, discusses the various changes that hormones are responsible for making a child grow into an adult. The period in life where the body undergoes change resulting in the reproductive maturity is termed as adolescence. It generally begins at the age of 11 and lasts up to 18 or 19 years. Adolescence in girls starts a year or two earlier than boys. During adolescence, the human body undergoes several changes marking the onset of puberty. The class 8 science chapter 10 discusses the various changes undergone at puberty and the role of hormones in this. Please refer Reaching the Age of Adolescence Class 8 Notes for more revision notes.
Reproduction is vital for the continuation of species. There are two modes of reproduction in animals, they are:
The male reproductive parts in humans are comprised of a penis, a pair of testes and two sperm ducts. Male gametes known as sperms are produced by the testes. While the female reproductive organs include the uterus, oviducts (fallopian tube) and ovaries. Female gametes known as ova are produced by the ovary. Please refer Reproduction in Animals Class 8 Notes for more revision notes.
A cell is the basic structural unit of an organism. The cell was first discovered by Robert Hooke, until then very little was known about the cell. Cells are assembled to make the body of an organism. Organisms made of more than one cell are known as multicellular organisms while single-celled organisms are known as unicellular organisms.
The functions of organisms with a lesser number of cells are not affected by less number of cells. A single-celled organism like the amoeba respires, captures and digests food, grows, excretes and reproduces. Similar functions in a multicellular organism are carried out by groups of specialised cells forming different tissues. Tissues, in turn, form organs. A cell exhibits a variety of shapes and sizes. Please refer Cell Structure and Functions Class 8 Notes for more revision notes.
The government imposes methods, rules and policies to protect and conserve forest and wildlife. National parks, wildlife sanctuaries, biosphere reserves etc., are protected areas for the conservation of animals and plants present in an area.
We should save, recycle and reuse to save trees, water and energy. One should resort to reforestation which is the restocking of destroyed forests by planting new trees. Please refer Conservation of Plants and Animals Class 8 Notes for more revision notes.
CBSE Revision Notes