The drawbacks of cutting trees are as follows:
(i) Due to cutting of trees, several species of wildlife are declining rapidly.
(ii) It is also leading to increasing natural disasters such as floods.
(iii) It will lead to increase in global warming.

A wide range of species is found in the mountains according to the variation in height. With the increase in height, temperature falls. At a height between 1500 meters and 2500 meters, most of the trees are conical in shape. These trees are called coniferous trees. Chir, pine and deodar are important trees of these forests. At the higher altitudes, temperate grasslands give way to Alpine vegetation.

The density of atmosphere varies with height. It is maximum at the sea level and decreases rapidly as we go up. Climbers experience problems in breathing at height due to decrease in the density of air.

Venus is the first celestial body to become visible in the sky at evening and is the last one to disappear from the sky at sunrise. That is why, it is called the Morning and the Evening star.

(i) Yes, two girls, Krishna and Ganga live in my locality who are named after a river.
(ii) The list of such names related to water are Ravi, Jhelum and Godavari.

Some of the depositional features are: moraines, levees, flood-plains and sand dunes.

The compass is very stable in areas close to the Equator, which is far from "Magnetic North". At some point close to the Magnetic Pole, the compass will not indicate any particular direction, but will begin to drift in a non-direction indicating manner. Also, the needle starts to point up or down when getting closer to the poles, due to the so called magnetic inclination. Cheap compass with bad bearings may get stuck due to this, thereby indicating a wrong direction.

The earth is called 'blue planet' because of excess of watery surface on it which is around 71 per cent of earth's surface.

On 21st March and 23rd September, the whole Earth experiences equal days and equal nights because neither of the poles is tilted towards the sun and the equator receives direct sun rays, this is called an equinox.

I visited Nehru planetarium at Delhi during vacation. I went there with my parents and elder brother. My experience of planetarium was fantastic and enjoying. I have learnt a lot after visiting there. I got to know about the movement of planet and satellites. I also came to know about the stars and constellations. I learnt about thefonctioning offollowing things by visiting the planetarium:
(i) Solar system: The live show about the structure and functioning of solar system revealed the arrangement of planets, satellites, asteroids and meteoroids. I also came to know about how the entire solar system is moving because of gravitation. It showed 'how sun emits light and heat'.
(ii) Structure of planets: The programme showed structure of each planet's surrounding and surface with 'how was it made'.
(iii) Structure of satellites: The show also revealed the structure and movement of satellites like moon and artificial satellites ete. The functioning of artificial satellites was shown.
(iv) Eclipse: Half an hour programme explained the cause that creates the condition of both solar and lunar eclipse.
(v) Stars: The short film

(i) In our Solar System, the time taken by each planet to complete a revolution around the Sun varies greatly.
(ii) Inner planets have much shorter orbits in distance and take lesser time than outer planets.
(iii) For example, Mercury, the closest planet to the Sun completes its orbital revolution around the Sun in 88 days, while the Earth takes 1 year to complete its revolution.
(iv) In addition, outer planets have slower average orbital speeds than inner planets.

Above picture depicts Rope Bridge and it is located in Arunachal Pradesh.

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(i) 23°30' N is value of the Tropic of Cancer.
(ii) Frigid zone is situated between 66030' and poles.

Galaxy A galaxy is a huge system of billions of stars and clouds of dust and gases. There are millions of galaxies in the universe. These galaxies altogether make the universe.
Akash Ganga or Milky Way is the example of galaxy. It appears as a river of light flowing in the sky, .
Universe Universe is the combination of millions of galaxies. The size of universe is very difficult to imagine and scientists still are working on it to know more about the universe.