MOECDC Class 8 The Earth and Universe
MOECDC Class 8 Science and Technology | The Earth and Universe | Nepal Class 8 | Exercise | Question Answer
MOECDC Class 8 English Medium Science Chapter 11 The Earth and Universe Exercise Question Answer Solution.
|Board||Government of Nepal.|
|Subject||Science and Technology.|
|Chapter||The Earth and Universe|
|Topic||Exercise Solve / Question Answer / Notes.|
Exercise 1 :
(1) Choose the correct alternative from the given options :
(a) What is called the branch of science that deals with the study of minerals?
The branch of science that deals with the study of minerals is called – (iii) Mineralogy.
(b) Which mineral is necessary for the proper growth of plants?
(i) Nitrogen – is necessary for the proper growth of plants.
(c) Which of the following statement resembles the tidal hypothesis?
(i) Earth originated from the splashed mass due to the collision of two stars.
(ii) Earth originated from a hot lump of a star projected due to the strong force of gravitation when another giant star passed quickly by it.
(iii) Earth originated from nebular dust.
(iv) Earth originated from the explosion of a big heavenly mass.
(ii) Earth originated from a hot lump of a star projected due to the strong force of gravitation when another giant star passed quickly by it – resembles the tidal hypothesis.
(d) In which Era has the given organism evolved?
The given organism has evolved in – (ii) Paleozoic Era.
(2) Differentiate :
(a) Metallic minerals and Non-1netallic minerals
Metallic minerals and Non-metallic minerals:
(i) Metallic minerals are hard, but non-metallic minerals are light.
(ii) Metallic minerals are good conductors of heat and electricity, whereas non-metallic minerals are poor conductors of heat and electricity.
(b) Palaeozoic Era and Cenozoic Era
Paleozoic Era and Cenozoic Era:
(i) Paleozoic Era started 570 million years ago and ended 240 million years ago, whereas Cenozoic Era started about 65 million years ago and still running.
(ii) During Paleozoic Era, the evolution of varieties of multicellular animals and plants took place in water and some of them gradually dwelled on the land. Whereas during Cenozoic Era, all mammals including human beings and seed-making plants have envolved.
(3) Give reason :
(a) Minerals are said to be pure chemicals.
Minerals are said to be pure chemicals.
(b) Mesozoic Era is also called the era of coniferous.
Mesozoic Era is also called the era of coniferous because in this era, a coniferous forest of large gymnosperms like cycas, pines, ginkgo, juniper, ephedra etc. occupied almost all moist land.
(c) Living beings have evolved after a very long time on Earth’s evolution.
Living beings have evolved after a very long time on Earth’s evolution because at the beginning of formation, the earth was too hot for living beings and everything here was unstable.
(4) Answer the following questions :
(a) What is a mineral? Give examples
According to geology, a naturally made solid and pure substance is a mineral. Example – Coal, petroleum, limestone.
(b) What are the hypotheses about the origin of the earth? Explain any one of them.
The hypothesis about the origin of the earth are, Kant’s and Laplace’s Nebular hypothesis, George Buffon’s Planetesimal hypothesis, Chamberlin’s and Moulton’s Binary hypothesis and Jean’s and Jeffrey’s Tidal hypothesis.
Chamberlin’s and Moulton’s Binary hypothesis – The binary hypothesis was forwarded in 1905 by two American scientists Thomas Crowder Chamberlin and Forest Ray Moulton. According to this, our sun had a very big co-partner star of the binary system and they were revolving around each other. Once, the partner star, became very close to our sun and some solar mass was pulled out due to its strong gravitation. The binary star continued its way swiftly before the separated solar mass could fall on its surface. Later on, the separated solar mass started revolving sun, gradually cooled down, and became planets, satellites and other members of the solar system.
(c) Explain the importance of minerals for Nepal.
The importance of minerals for Nepal – More than 60 types of minerals are identified in Nepal among which 21 types are metallic, 23 types are related to chemical fertilizer and insulating material, 6 types are gems, 9 types of constructing material and 4 types of minerals are related to fuel and geothermal energy. Nepal has great potentiality. If proper research will done to explore such valuable minerals then it can uplift the economic status of the country more rapidly than any other resources.
(d) Make a flowchart of minerals showing their types.
(e) Which Era was inappropriate for the evolution of life and why? Explain with an example.
The time before Cryptozoic Era was inappropriate for the evolution of life because at the beginning of formation, because of the collision of big boulders of rocks from every direction with tremendous velocity, the particular part of the earth had melted many times, everything here was unstable and the earth was too hot for living beings.
(f) When did mammoths with long tusks and fish with lungs evolve?
In Cenozoic Era, mammoths with long tusks and in first Cambrian period of Paleozoic Era, fish with lungs evolved.
(g) Make a list of places in Nepal for any five minerals with their uses.
Iron → Ramechhap = use for proper growth, greenery, and blooming of plants and also use to make iron rods.
Coal → Dang = use to generate very high temperatures.
Limestone → Udaipur = use to make images, idols, and stone inscriptions.
Marble → Lalitpur = use to decorate floors and other things.
Zinc → Ganesh Himal and surrounding = used in dry cells to generate electricity.
(h) Name the Era in the following organisms to be evolved:
Tree-fern, entelodon wild boar, dinosaur, frogs, monocot plants, bacteria, mosquito, trilobites, jellyfish.
Tree-fern → Paleozoic Era,
Entelodon wild boar → Cenozoic Era,
Dinosaur → Mesozoic Era,
Frogs → Paleozoic Era,
Monocot → Cenozoic Era,
Plants → Phanerozoic Era,
Bacteria → Cryptozoic Era,
Mosquito → Mesozoic Era ,
Trilobites → Paleozoic Era,
Jellyfish → Cryptozoic Era.
(i) Read the given passage and answer the following questions :
“Various types of minerals are found in Nepal. Recently. very precious uranium-like minerals are also reported to be found in Nepal. Some minerals like iron, copper, coal. gold etc. are being extracted and used traditionally but the effective exploring, extracting and commercial use of minerals is yet to be done. Such minerals are not being extracted sustainably.”
(i) What may be the reason that minerals are not being explored, extracted and utilized sustainably in Nepal?
(ii) Which minerals are being extracted traditionally in Nepal? What should be done to extract and use such minerals sustainably?
(a) Insufficient research may be the reason that minerals are not being explored, extracted and utilized sustainably in Nepal.
(b) Iron, coal, gold and copper are being extracted traditionally in Nepal. The sufficient and effective research of the minerals should be done to extract and use such minerals sustainably.
(i) Study the given figure and answer the following questions:
(i) In which Era did these animals evolve and extinct?
(ii) What are the reasons for their extinction?
(iii) If these animals were still roaming on earth, what impact, in your opinion would be occurred in biological balance?
(a) In Mesozoic Era, these animals evolved and were extinct.
(b) It is said that heavy meteor-shower took place on earth along with devastating volcanic eruptions which spread flames of fire and poisonous gas everywhere which led to their extinction.
(c) If these animals were still roaming on earth, then they killed other animals as they were dominant in all habitats and create a disturbance in biological balance.
Exercise 2 :
(1) Choose the correct alternative from the given options :
(a) Who put forward the concept of expanding the universe?
(ii) Lemaitre – put forward the concept of expanding the universe.
(b) Which comet was destroyed in Jupiter?
(i) Shoemaker-Levy – was destroyed in Jupiter.
(c) Which of the following statement represents the character of Trojans?
(i) They are in the Kuiper Belt.
(ii) They revolve around the sun along the orbit of Mars or Jupiter.
(iii) They will be destroyed by burning in the atmosphere.
(iv) They have a long bright tail.
(ii) They revolve around the sun along the orbit of Mars or Jupiter – represents the character of Trojans.
(d) What is ‘A’ shown in the figure made of?
(i) Rock, metal and dust particles
(ii) Ice, gas, and dust particles
(iii) Star, ice, and dark matter
(iv) Stars, nebular dust and cloud
‘A’ is shown in the figure made of – (iv) stars, nebular dust and cloud.
(2) Differentiate :
(a) Meteors and Meteorites
Meteors and Meteorites: The streak of light caused by falling meteoroids is called meteors, whereas remnants of fallen meteors are called meteorites.
(b) Galaxy and Constellation
Galaxy and Constellation: Organization of millions of stars, nebulas, remnants of nebulas, planetary system of many stars, dark matter and energy is called galaxy, whereas the region in the sky with some stars making a particular pattern is called constellation.
(c) Asteroids and Comets
Asteroids and Comets:
(i) The smaller masses of rocks without any specific shape that revolve around the sun along their orbits are called asteroids, whereas the smaller members of the solar system that appear with the long bright tail when coming closer to the sun are called Comets.
(ii) Asteroids are composed of rocks, minerals, metals, clay etc. Whereas comets are composed of ice, dust particles, fragments of rocks and gases.
(3) Give a reason :
(a) Near-earth asteroids are dangerous for our planet.
Near-earth asteroids are dangerous for our planet because sometimes, some of them fall into our planet earth and cause great devastation.
(b) Comets gradually lose their material when revolving around the sun many times.
Comets gradually lose their material when revolving around the sun many times because when they come closer to the sun, most of the substance present in them gets evaporated.
(c) Most of the meteors are completely destroyed after revolving some rounds around the sun.
Most of the meteors are completely destroyed after revolving some rounds around the sun because when they come closer to the sun, most of them gets evaporated.
(d) Galaxies are more important than other celestial bodies to study the universe.
Galaxies are more important than other celestial bodies to study the universe because galaxies are the organization of millions of stars, nebulas, remnants of nebulas, planetary system of many stars, dark matter and energy.
(4) Answer the following questions :
(a) What is the universe?
The aggregate form of limitless space, time, matter and energy is the universe.
(b) Describe the Big Bang theory in brief.
In 1927, a Belgium scientist George Lemaitre described that the universe is expanding continuously with a great speed and if this rate of expansion is imagined to be reversed, all the matter and energy of the universe, will crunch to be a single point after 13.8 billion years. It means the present universe has been initiated from the primeval atom 13.8 billion years ago. According to him, the unimaginable dense and pressurized primeval atom exploded 13.8 billion years ago. This explosion is called Big Bang.
(c) Mention the characteristics of asteroids.
The characteristics of asteroids:
(i) The orbits of asteroids around the sun are somewhat irregular.
(ii) Asteroids are composed of rocks, minerals, metals, clay etc.
(iii) Asteroids have various sizes and most of them are irregularly shaped.
(d) What is a comet? Explain its different parts with a suitable diagram
The smaller members of the solar system that appear with the long bright tail when coming closer to the sun are called Comets.
The center core of a comet is an icy solid called Nucleus. When they come closer to the sun, most of the substance present in them gets evaporated and makes a bright and spherical cloud around the nucleus which is called Coma. The thicker and whiter tail is composed of dust particles, called dust tail and another thinner and bluish tail is composed of ions, called ion tail.
(e) What are meteoroids? How are they turned into meteors?
Small irregular fragments of rocks and metals roaming randomly within the solar system are called Meteoroids.
Due to very high speed, meteoroids cause great friction with air particles in the mesosphere by which they burn to leave a streak of light behind within a few seconds. Such streak of light caused by falling meteoroids is called meteors and is seen only at night due to the absence of sunlight.
(f) Explain ‘meteor shower’ and ‘observable universe’.
Sometimes, many meteors fall at a particular region at a particular time and may cause devastation everywhere. This is called a Meteor shower.
The coverage of a powerful telescope is called the observable universe.
(g) Study the given figure and answer the following questions:
(i) Describe the special features of the celestial bodies shown in the figure.
(ii) Why are they important to study the celestial bodies?
(i) These celestial bodies are called constellation. Twelve of them lie in the ecliptic which are called zodiacs. They have a different number of stars, for example, there are 7 stars in Ursa Major and 5 stars in Cassiopeia. Crux is the smallest and Hydra is the biggest constellation.
(ii) The celestial bodies are important to study because an experienced one can easily predict the current time and the running season by the observation of these celestial bodies. Similarly, they also help to declare geographic direction from the position of any constellation in the sky.
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