CBSE Revision Notes

CBSE Reaching the Age of Adolescence

• Human beings become capable of reproduction after the puberty sets in. The period of life when the body undergoes changes, leading to reproductive maturity, is called adolescence
• Between the age of 11 years and 19 years children are called adolescents.
• The human body undergo several changes during adolescence; these changes mark the onset of puberty
• The onset of puberty brings about growth of reproductive organs, hair grows at various body parts, breast develops in girls and moustache and beard in boys. Please refer Reaching the Age of Adolescence Class 8 Extra Questions for more information.

CBSE Reproduction in Animals

• Reproduction is the important process required for continuation of the species. There are two mode of reproduction: Sexual and Asexual.
• In sexual reproduction both male and female gametes fuses to form Zygote which develops into complete individual.
• Human follows sexual mode of reproduction in which female gamete (egg) fuses with male gamete (sperm) to produce zygote.
• Male reproductive organs in human consist of a pair of testes, two sperm ducts and a penis. Please refer Reproduction in Animals Class 8 Extra Questions for more information.

CBSE Cell Structure and Functions

• Cell is the building blocks of our life. Every living organism is made up of cells.
• Cells were first discovered by Robert Hooke through simple magnifying device. Presently, due to presence of high power microscope, study of cell and its component become easy task.
• Cells consist of different shapes and size, and vary in number depending on the organism. Unicellular organism consists of single cell, whereas, multicellular organisms contain number of cells. However, the cell of unicellular performs similar function as multicellular organism. Please refer Cell Structure and Functions Class 8 Extra Questions for more inforamation.

CBSE Conservation of Plants and Animals

• Plants and animals are our true friends; we must protect them as they provides us with lot of things
• For this purpose many national parks, wildlife sanctuaries and biosphere reserves had been made
• National parks, wildlife sanctuaries and biosphere reserves are names given to the areas meant for conservation and preservation wild life
• Biosphere reserves are the areas meant for conservation of biodiversity. Please refer Conservation of Plants and Animals Class 8 Extra Questions for more information.

CBSE Combustion and Flame Class 8 Extra Questions

• Fuels are of various types, and different types of fuels are used for different purposes like in industry, for running automobiles, for domestic uses etc.
• The chemical process in which a substance reacts with oxygen to give off heat is called combustion
• The substance which undergoes combustion is called combustible or fuel
• Fuel may be solid, liquid or gas. Please refer Combustion and Flame Class 8 Extra Questions for more information.

CBSE Coal and Petroleum Class 8 Extra Questions

• Natural resources can be broadly classified into inexhaustible natural resources and exhaustible natural resources
• Coal petroleum and natural gas are exhaustible natural resources
• Coal petroleum and natural gas are called fossil fuels because they are formed from dead remains of living organisms. Please refer Coal and Petroleum Class 8 Extra Questions for more information.

CBSE Materials: Metals and Non-Metals

• There are 92 elements occurring naturally, out of which 70 are metals and about 22 are non- metals some elements show properties of both metals and non-metals they are called metalloids
• Metals are solid, hard, malleable and ductile
• Metals have high melting and boiling points and are good conductor of heat and electricity.
• Non-metals may be solid, liquid or gas, and are not malleable and ductile.
• Non- metals have low melting and boiling points and poor conductor of heat and electricity. Please refer Materials: Metals and Non-Metals Class 8 Extra Questions for more information.

CBSE Synthetic Fibres and Plastics

• Fibres are used for making a large variety of household articles
• Natural fibres like cotton, wool, silk etc., are obtained from plants and synthetic fibres are made by human beings by chemical processing of petrochemicals
• Like natural fibres synthetic fibres and plastics are made of very large units called polymers, and polymers are made of many smaller units
• Synthetic fibres are used for making many household articles like ropes, buckets, container, furniture, etc., other applications involves in aircrafts, ships, space- crafts, healthcare, etc. Please refer Synthetic Fibres and Plastics Class 8 Extra Questions for more information.

CBSE Microorganisms: Friend and Foe Class 8 Extra Questions

• Microorganisms are too small that we cannot see them with unaided eye. They are found in air, water and inside the bodies of Plants and animals
• They can live in all kinds of environment ranging from very cold climate to hot springs and deserts to marshy areas
• They may be unicellular or multicellular
• Microorganisms are broadly classified into four major groups namely bacteria, fungi, protozoa, and some algae. Please refer Microorganisms: Friend and Foe Class 8 Extra Questions for more information.

CBSE Crop Production and Management Class 8 Extra Questions

We need to adopt certain agricultural practices in order to provide food to our growing population.

Plants of the same kind grown and cultivated at one place on a large scale for food, clothing, medicines, cosmetics, dyes, etc. are called crops. In India, crops are categorized into two types on the basis of seasons that is rabi and Kharif crops. Please refer Crop Production and Management Class 8 Extra Questions for more information.