1. It is a rich source of nutrients essential for plant growth. It makes the soil fertile.
2. It improves soil structure, texture aeration and water holding capacity and helps to prevent soil erosion.
3. It contains valuable vitamins, enzymes and growth regulator substances for increasing growth, vigour and yield of plants.
4. It enhances decomposition of organic matter in soil.
5. Vermicompost is free from pathogens and toxic elements.
6. Vermicompost is rich in beneficial microflora.

1. Yes, Chicken pox would not occur again for sanjay .
2. Because, once it occured, his body will derive immunity against that disease .
3. This kind of immunity is developed by our body, during the first infection of chicken pox pathogen .
4. The antibodies produced in the blood remain for a long period and kill the simile pathogens, whenever they enter the body.

i) Availability of more water than needed.
ii) Water current may damage the plant body.
iii) Water levels may change regularly.
iv) Maintain buoyancy in water.

1. The first four planets Mercury, Venus, Earth and Mars are relatively close together and close to the Sun. They form inner solar system and so they are called as inner planets .
2. They have a surface of solid rock crust and so are called terrestrial or rocky planets .
3. Their insides, surfaces and atmospheres are formed in a similar way and form similar pattern.

When an object travels at a speed higher than that of sound in air, it produces shock waves. These shock waves carry a large amount of energy. The air pressure variations associated with this type of shock waves produce a very sharp and loud sound called sonic boom or supersonic speed.

The number of vibrations (complete waves or cycles) produced in one second is called frequency. Its SI unit is hertz.

1. Use and throwaway plastics cause short and long term environmental damage.
2. Half of all the plastic items made today is used for throwaway plastic items.
3. They block drains and pollute water bodies .
4. One-time use plastic causes health problems for humans, plants and animals.
5. If these items are thrown away they can stay in our environment for over 1000 years causing plastic pollution for future generations.
6. Some examples are plastic carry bags, cups, plates, straws, water pouches etc.

It is easier to swim in the sea water as compared to river water, because sea water has dissolved salts in it, which increases the density of water and also increases its upthrust, so the body sinks less and we can easily swim in it as compared to the river water, because river water is less dense than sea water.

Biofertilizers are substances that contain living microorganisms which, when applied to
seeds, plant surfaces or soil, colonize the rhizosphere or the interior of the plant and promote growth by increasing the supply or availability or primary nutrients to the host plant.
Example:
Rhizobium:
It is a soil bacterium that colonize the roots of leguminous plants to form root nodules. The bacteria fix atmospheric nitrogen and convert them to ammonia.
Advantages of biofertilizers over other Fertilizers:
1. In addition to releasing nutrients biofertilizers improve the structure and texture of the soil and increases the ability to hold water and nutrients, over time, the soil and plants become healthy and strong.
2. Since it is technically living, it can symbiotically associate with plant roots involved microorganisms could readily and safely convert complex organic material into simple compounds, so that they are easily taken up plants.
3. Microorganism function is in long duration causing improvement of the soil fertility. It maintains the natural habitat of the soil.
4. It increase crop yield by 20 - 30% replaces chemical nitrogen and phosphorus by 30% and stimulates plant growth.
5. It can also provide protection against drought and soil borne diseases.

The immunization schedule indicates the age at which the vaccine should be administered to protect the children from infectious diseases.

Water recycling is reusing treated wastewater for beneficial purposes such as agricultural and landscape irrigation, industrial processes, flushing in toilets and ground water recharge.
Conventional waste water treatment involves the following stages:
Primary treatment:
Primary treatment involves temporary holding of the wastewater in a tank. The heavy solids get settled at the bottom while oil, grease and lighter solids float over the surface. The settled and floating materials are removed. The remaining liquid may be sent for secondary treatment.
Secondary treatment:
Secondary treatment is used to remove the biodegradable dissolved organic matter. This is performed in the presence of oxygen by aerobic microorganisms. The microorganisms must be separated from treated water waste by sedimentation.
After separating the sediments of biological solids, the remaining liquid is discharged for tertiary treatment.
Tertiary treatment:
It involves removal of inorganic constituents such as nitrogen, phosphorus and microorganisms. The fine colloidal particles in the sewage water are precipitated by adding chemical coagulants like alum or ferric sulphate.

1. Artificial satellites are made to revolve in an orbit at a height of few hundred kilometers. At this altitude, the friction due to air is negligible.
2. The satellite is carried by a rocket to the desired height and released horizontally with a high velocity, so that it remains moving in a nearly circular orbit.
3. The horizontal velocity that has to be imparted to a satellite at the determined height so that it makes a circular orbit around the planet is called orbital velocity.
4. The orbital velocity of the satellite depends on its altitude above Earth.
5. Nearer the object to the earth, the faster is the required orbital velocity.
6. The orbital speed and distance permit the satellite to make one revolution in 24 hours. Since earth also rotates once in 24 hours, a satellite stays in a fixed position relative to a point on earth's surface. Because the satellite stays over the same spot all the time, this kind of orbit is called 'geostationary'.
Orbital velocity can be calculated using the following formula.
V = \(\sqrt {\frac {GM }{R + h }}\)
Where
G - gravitational constant (6.673 x 10^-11 Nm² kg^-2)
M - Mass of the earth (5.972 x 10²⁴kg)
R - Radius of the earth (6371 km)
h - height of the satellite from the surface of the earth.

1. When a vibrating body moves forward it pushes and compresses the air in front of it creating a region of high pressure. This region is called Compression. This compression starts to move away from the vibrating object.
2. When a vibrating body moves backwards, it creates a region of low pressure called rarefaction. As the object is in a to and fro movement or oscillates rapidly a series of compressions and rarefactions is created in the air.
3. This makes the sound wave to propagate in the air.
4. compressions are the regions where particles are crowded together creating high pressure region. And rarefactions are the regions, where the particles are spread apart creating low pressure region.

Hydrometer is based on the principle of floatation. The weight of the liquid displaced by the immersed portion of the hydrometer is equal to the weight of the hydrometer

1. It is a direct reading instrument used for measuring the density or relative density of the liquid.
2. It consists of a cylindrical stem having a spherical bulb at its lower end, and a narrow tube at its upper end.
3. The lower spherical bulb is partially filled with lead shots or mercury. This helps hydrometer to float or stand vertically in liquids.
4. The narrow tube has markings so that relative density of a liquid can be read directly.
5. The liquid to be tested is poured into the glass jar. The hydrometer is gently lowered into the liquid until it floats freely.
6. The reading against the level of liquid touching the tube gives the relative density of the liquid.

a) Both assertion and reason are true and reason is the correct explanation of assertion.

b) Both assertion and reason are true but reason is not the correct explanation of assertion.

Time taken by a satellite to complete one revolution round the earth is called time period.
Time period T = \(\frac { Distances covered }{ Orbital velocity }\)

The Sun and celestial bodies which revolve around it form the solar system.

Treatment of certain diseases by destroying the invading organism without damaging the cells of the host, by the use of certain organic compounds is known as Chemotherapy. It is widely used for treating cancer.

Friedrich Wohler

Wood piece of mass 100g floating in water, it will experience an upthrust due to water displaced by the immersed part of the wood.
For a floating body, upthrust will be equal to the weight of the body. Therefore the apparent weight of the body will be zero.
(ie. the weight of the body in air - upthrust)

No we can't recharge the batteries used in watches, because they are primary cells. The primary cells can't be recharged again. So it is not possible to recharge them again.

1. In the Biosphere all the living things are made up of carbon compounds.
2. All the fossil fuels are also made up of carbon like hydro carbon.
3. In biogeochemical cycle carbon is exchanged among biosphere, geosphere; hydrosphere and atmosphere of the Earth.
4. It is the main compound of nitrogen cycle, water cycle. So, it is mostly in combined state.