Galaxies are not stationary and are moving away from each other. This was first observed by Edwin Hubble. He also suggested that, the larger the distance between two galaxies, the faster they move away from each other. This led to the conclusion that the universe is expanding. . . .
When light travels from one transparent medium to another transparent medium, it bends from its original path. This phenomenon of bending of light is called refraction. Refraction i.e. bending of light takes place at the boundary of separation of the two media. Whenever light travels from a rarer medium to a denser medium, . . .
The photosphere lie the tenuous chromosphere and the corona (crown), which make up the thin solar atmosphere. This is where we see features such as sunspots and solar flares. Visible light from these top regions is usually too weak to be seen against the brighter photosphere, but during total solar eclipses, when the moon covers the . . .
Q. What is a species? Ans.- A species is a specific group of closely-related individuals which are all capable of interbreeding to produce fertile offsprings. Species is the lowest category in the hierarchy. . . .
Q. How do fish exchange gases? Ans.- Fish obtain oxygen dissolved in the water by muscle-powered movements such as forward motion of fish or the pumping actions of its mouth and throat force a flow of water over its gills. Gills are made up of thread like structures called filament. Each filament contains a number of capillaries that gives a large sur . . .
Q. How are plants classified according to their habitat? Give one example of each. Ans.- on the basis of habitat, plants may be of following types— (i) Hydrophytes- The plants which are adapted to grow in water are called hydrophytic plants, e.g. Lotus. (ii) Mesophytes-The plants which are adapted to grow in well-balanced moisture supply are ca . . .
Q. What is meant by higher levels of organization? Ans. Higher levels of organisation: There are some organisations which are above the level of organism. These are as follows: (a) Population (b) Community (c) Ecosystem (d) Biosphere (a) Population- We have a number of plants and animals around us. Each member of plants and animals belongs to a part . . .
Q. Who discovered cells, and how? Ans.- Cell was discovered by an English scientist, Robert Hooke. Hooke, in 1665, while observing a thin slice of cork, under his elude compound microscope, observedthat the Cork was I composed ofseveral box-like compartments, forming a honey-comb structure. He named the compartments as cells. . . .
Potential for Life The sun itself is not a place conducive to living things, with its hot, energetic mix of gases and plasma. But the sun has made life on Earth possible, providing warmth as well as energy that organisms like plants use to form the basis of many food chains. . . .
Science is a dynamic process of questioning, hypothesizing, discovering, and changing previous ideas based on what is learned. Scientific ideas are developed through reasoning and tested against observations. Scientists assess and question each other's work in a critical process called peer review. Defining the term Planet is important, beca . . .
CASE STUDY – GANGA RIVER Ganga is a sacred river of India. As it flows to different town and cities, it gets polluted because a large quantity of garbage, untreated sewage and industrial waste is thrown in it. At many places, the pollution level is so high that no aquatic life can survive. The river is virtually ‘dead’ at these plac . . .
CASE STUDY – AIR POLLUTION IN DELHI Some time back, Delhi was one of the most polluted cities in the world. It has a record number of automobiles running on petrol and diesel. The roads were chocked with fumes released from vehicles. A number of steps were introduced by government to reduce the pollution. These includes- Use of unleaded petr . . .
Petroleum Petroleum is a fossil fuel. It is dark coloured viscous and foul smelling liquid commonly called crude oil.it is always found trapped between two impervious rocks. It is derived from Latin word petra means rocks and oleum means oil. Thus, petroleum laterally means rock oil. Petroleum is a complex mixture of solid, liquid and gaseous hydr . . .
THE BRAIN The brain is the control centre of the body. It receives information from all parts of the parts through varies nerves. An adult human brain weighs about 1.4 kg. and contain millions of tiny cells.it is protected by hard bony skull. The space between skull and brain is filled with clear fluid known as cerebro-spinal fluid(CSF). It serves . . .
SOIL Soil is most important abiotic component of atmosphere that provide favourable condition to support life on earth. Soil contain many worms and micro-organisms that maintain the fertility of soil. Formation of soil Effect of heat, temperature, force of flowing water and wind and roots of plants causes the breaking down of rocks in . . .