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  1. A French scientist George Wofan put forward a hypothesis in 1749 AD. According to this hypothesis, the earth along with other planets and satellites were formed when a comet revolving around the universe struck the sun millions years ago.

  2. According to the tidal hypothesis, big star orbiting around the sun finally approached It. A large mass of gas ejected from the sun due to the tidal effect. In the course cooling, the tidal matter fragmented into small pieces forming planets, satellites, etc. As a result, the solar system was formed.

  3. According to this hypothesis, the whole solar system including other heavenly bodies was in the form of nebula. Slowly. the nebula began to contract due to its own gravity and the outermost ring was detached from the central core, which start to revolve around the central core. This central mass become the sun and other revolving bodies became planet & satellites including earth.

  4. The geological history is divided into four parts. They are:
            - Precambrian era.
            - Mesozoic era.
            - Cenozoic era.

  5. The largest duration of time of the geological time scale is called eon.
    The second longest duration of time of the geological time scale is called era.
            For example:    Mesozoic era, Cenozoic era.

  6. The duration of the Archean eon was from 4 billion years ago to 2.5 billion years ago.

  7. The time duration of Paleozoic era was between 570 million years ago and 250 million year ago.
    The main features of this era are:
            - Sedimentary rocks were formed.
            - Change in weather and atmosphere took place.
            - Fossils of different plants and animals were formed.
            - Aquatic & terrestrial vertebrate & invertebrate were formed.

  8. Mesozoic era:
    The time duration of this era was between (250-65) million years ago. A large number of reptiles were evolved on the land and sea. So, this era was also known as the golden era of reptiles. In the era, the climate condition was suitable for sustaining aquatic, terrestrial & aerial animals like dinosaurs, tortoises, toothed birds, etc.
    Cenozoic era:
    The time duration of this era is between (65-now) million years ago to now. In this ere, we human beings are evolved. The climatic condition was changing with decreasing temperature. As a result mountains peaks were covered with snow. Neanderthal man, toothed animals, gymnosperms and angiosperm were evolved. It is also known as recent era on the era of human beings.

  9. Mesozoic era is called the era of creepers because in this era, the climate condition was suitable to sustain aquatic, terrestrial and aerial animals like dinosaurs, tortoises, toothed birds, etc. In this era, evolution and extinction of huge reptiles took place.

  10. The dead bodies remains of animals and plants which are buried in the earth curst over long period of time are called fossils.
    Due to natural disasters like volcano, earthquake, foods, etc. the plants & animals may sink into the earth's ground. The delicate parts of organisms decay in the soil while hard part remains pressed down in the ground. The external morphology of those hard parts is formed in the soil, sand, etc. in the form of all impression. In this way, fossils are formed.

  11. Coal is a hard blaze minerals that is found below the ground and is burnt to produce heat.
    In ancient time, plants & animals were burnt under the earth curst due to the different geological phenoma like earthquake, food, etc. Then the remains were pressed under high pressure and temperature for long time. When whole or part of plant remains in swamp land in the form of a fossils for a long time, it is changed to cool. In this way coal is formed.
    Its importance are:
            - It is used as a fuel for railways, transportation, etc.
            - It is used to generate electricity for manufacturing petrol, coke, etc.
            - It is used for making various organic compounds.

  12. The oil that are formed in nature by the decomposition of parts of plants and animals that are burried under the earth's surface for a long period of time is called mineral oil.
    Any three importance of mineral oil are:
            - It is used as fuel in vehicles, industries, etc.
            - It is used for generating electricity, cooking, food, etc.
            - It is used for making various types of chemicals.

  13. The process by which fossils are formed is called fossilization. As we know that due to different natural disasters, the plants and animals may sink into the earth's ground. After that fossils are formed by the impression of preserved parts and skeleton after they are preserved by rocks. As a whole, this process is called fossilization.

  14. a.    Mesozoic era and Cenozoic era.

    Mesozoic era
    Cenozoic era
    It is the golden era of reptiles.It is the golden era of human beings.
    Formation of hills and mountains.Breaking and expansion of rocks.
    Coniferous plants were developed in this era.Toothed animals, gymnosperms and angiosperm were developed in this era.


    b.    Paleozoic era and Mesozoic era.

    Paleozoic era
    Mesozoic era
    Sedimentary rocks were formed in this era.Evolution of dinosaurs took place in this era.
    Change in weather and atmosphere took place in this era.Formations of hills and mountains took place in this era.
    Bryophytes and pteroidphytes were developed.Coniferous plants were developed.

  15. In Mesozoic era, dinosaurs evolved and became extinct.

  16. The fossils of dinosaurs is the evidence that there were dinosaurs on the earth in the past. 

  17. a.    Evolution of fishes.
            - Precambrican era
    b.    Evolution of horse.
            - Cenozoic era
    c.    Evolution of monkeys.
            - Cenozoic era
    d.    Dominance of reptiles.
            - Mesozoic era
    e.    Evolution of fern.
            - Paleozoic era
    g.    Development of conifers.
            - Mesozoic era
    h.    Dominance of human beings.
            - Cenozoic era

  18. We all know that, the earth was evolved about us billions years ago. At the time of evolution of the earth, it was very hot and there was no suitable environment for the evolution and survival of living beings. So, there were no life at the time of evolution of earth.

  19. We all know that, in Mesozoic era, there was the dominance of various types of large reptiles like dinosaurs, turtles, etc. on land and marine water. So, Mesozoic era is called the era of creepers.

  20. We all know that, petrol and diesel are formed when the dead plants and animals are burried under earth's surface and remained for long time there. It is formed by the process which is similar to fossilization. So, petrol and diesel are called fossil fuels.

  21. We all know that, fossils are the remained parts of dead animals that are burried long time ago under earth's surface. By studying the fossils, we can study about the geological history. Like about the organisms evolved before in past or age of something specific. So, study of fossils is important for human beings.

  22. We all know that, natural gas burns completely without leaving any residue. It burns with a smokeless flame and doesn't cause air pollution. It doesn't produce any harmful chemicals on burning. It has high calorific value viz 55kg/g. So, natural gas is considered as good as fuel.

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