Worksheet Solutions: The Origin and Evolution of the Earth | Geography Class 11 - Humanities/Arts PDF Download

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Q1: According to the Nebular Hypothesis, planets were formed from a rotating cloud of material associated with a young sun. Who revised Kant's hypothesis to propose this theory?
Ans: Otto Schmidt
Immanuel Kant, a German philosopher, presented an early argument related to the Nebular Hypothesis. However, Otto Schmidt, in collaboration with Carl Weizascar, revised Kant's hypothesis in 1950, leading to the Nebular Hypothesis as we understand it today.

Q2: Edwin Hubble provided evidence in 1920 that the universe is expanding; this evidence supports the _______ Theory.
Ans: Big Bang
The evidence provided by Edwin Hubble supports the "Big Bang Theory." Hubble's observations showed that galaxies are moving further apart as time passes, which is a key element of the Big Bang Theory.

Q3: The expansion of the universe can be visualized using a balloon analogy, but it is only partially correct because it implies that galaxies themselves are expanding, which is not supported by observations.
Ans: Balloon
The balloon analogy is used to help visualize the expansion of the universe. It represents the idea that points marked on an inflating balloon represent galaxies moving away from each other. However, it's important to note that the analogy is only partially correct because it may imply that galaxies themselves are expanding, which is not the case. Instead, it's the space itself that's expanding.

Q4: Stars are formed from dense gaseous clumps known as ________ in the process of star formation.
Ans: Planetesimals
In the process of star formation, stars are formed from dense gaseous clumps known as "planetesimals." These planetesimals are collections of gas and dust that gradually come together to form stars.

Q5: The Earth's lithosphere is made up of the Earth's ________.
Ans: Crust
The Earth's lithosphere is made up of the Earth's "crust." The lithosphere consists of the Earth's solid outermost layer, which includes the crust and the upper part of the mantle.

Q6: The process that led to the evolution of oxygen in Earth's atmosphere was ________.
Ans: Photosynthesis
The process that led to the evolution of oxygen in Earth's atmosphere was "photosynthesis." Photosynthesis is the biological process by which green plants and some other organisms use sunlight to convert carbon dioxide and water into oxygen and glucose.

Q7: The Moon is believed to have formed as a result of a ________ impact.
Ans: Giant
The Moon is believed to have formed as a result of a "giant" impact. This impact involved a Mars-sized object colliding with the early Earth, which resulted in the formation of the Moon.

Q8: The period between 4,600 million years and the present played a crucial role in the evolution of life on Earth's surface, with the evolution of life beginning around ________ million years ago.
Ans: 3,800
The period between 4,600 million years and the present played a crucial role in the evolution of life on Earth's surface, with the evolution of life beginning around "3,800" million years ago. This marks the emergence of early life forms on Earth.

Q9: The current composition of Earth's atmosphere is chiefly contributed by ________ and ________.
Ans: Nitrogen, Oxygen
The current composition of Earth's atmosphere is chiefly contributed by "nitrogen" and "oxygen." These two gases make up the majority of the Earth's atmosphere, with nitrogen being the most abundant.

Q10: The Earth's oceans are approximately ________ million years old.
Ans: 4,000
Earth's oceans are approximately "4,000" million years old. These oceans formed within the first 500 million years from the formation of the Earth, making them one of the planet's oldest features.

Assertion and Reason Based

Q1: Assertion: The Nebular Hypothesis suggests that planets formed from a rotating cloud of material.
Reason: Kant's hypothesis was revised by Otto Schmidt to propose the Nebular Hypothesis.
(a) Both assertion and reason are true, and the reason is the correct explanation of the assertion.
(b) Both assertion and reason are true, but the reason is not the correct explanation of the assertion.
(c) Assertion is true, but the reason is false.
(d) Assertion is false, but the reason is true.
Ans: (b)
In this case, both the assertion and reason are true. The Nebular Hypothesis indeed suggests that planets formed from a rotating cloud of material. Furthermore, it's accurate that Otto Schmidt revised Immanuel Kant's hypothesis to propose the Nebular Hypothesis, so the reason correctly explains the assertion.

Q2: Assertion: The Big Bang Theory proposes the universe's initial existence as a tiny, singular atom.
Reason: Edwin Hubble provided evidence that galaxies move further apart as time passes.
(a) Both assertion and reason are true, and the reason is the correct explanation of the assertion.
(b) Both assertion and reason are true, but the reason is not the correct explanation of the assertion.
(c) Assertion is true, but the reason is false.
(d) Assertion is false, but the reason is true.
Ans: (b)
Both the assertion and reason are true. The Big Bang Theory does propose the universe's initial existence as a tiny, singular atom. Additionally, Edwin Hubble's evidence of galaxies moving further apart is a key piece of support for the Big Bang Theory, so the reason correctly explains the assertion.

Q3: Assertion: Star formation is a crucial process in the origin of planets like Earth.
Reason: Stars are formed from the collapse of dense clouds of gas and dust.
(a) Both assertion and reason are true, and the reason is the correct explanation of the assertion.
(b) Both assertion and reason are true, but the reason is not the correct explanation of the assertion.
(c) Assertion is true, but the reason is false.
(d) Assertion is false, but the reason is true.
Ans: (a)
In this case, both the assertion and reason are true. Star formation is indeed a crucial process in the origin of planets like Earth because planets are formed from the remnants of stellar formation. The reason also correctly explains the importance of star formation in the context of planet formation.

Q4: Assertion: The Moon played a significant role in the evolution of Earth.
Reason: The Moon is a giant star that emits light and heat.
(a) Both assertion and reason are true, and the reason is the correct explanation of the assertion.
(b) Both assertion and reason are true, but the reason is not the correct explanation of the assertion.
(c) Assertion is true, but the reason is false.
(d) Assertion is false, but the reason is true.
Ans: (c)
The assertion is incorrect. The Moon is not a star; it's Earth's natural satellite. While the Moon played a significant role in Earth's history, it is not a giant star. The reason is true because it correctly states the characteristics of a star.

Q5: Assertion: The Earth's lithosphere is responsible for the formation of mountains, earthquakes, and volcanic activity.
Reason: The Earth's lithosphere consists of solid, rigid plates that float on the semi-fluid asthenosphere.
(a) Both assertion and reason are true, and the reason is the correct explanation of the assertion.
(b) Both assertion and reason are true, but the reason is not the correct explanation of the assertion.
(c) Assertion is true, but the reason is false.
(d) Assertion is false, but the reason is true.
Ans: (a)
Both the assertion and reason are true. The Earth's lithosphere is indeed responsible for geological phenomena like mountains, earthquakes, and volcanic activity. The reason correctly explains this by stating that the lithosphere consists of solid plates floating on the semi-fluid asthenosphere, which allows for tectonic movements.

Very Short Answer Type Questions

Q1: What is the Nebular Hypothesis?
Ans: The Nebular Hypothesis suggests that planets were formed from a rotating cloud of material associated with a young sun.

Q2: How did Edwin Hubble contribute to our understanding of the universe's origin?
Ans: Edwin Hubble provided evidence that the universe is expanding, supporting the Big Bang Theory.

Q3: What is the significance of the Moon in Earth's evolution?
Ans: The Moon influenced Earth's rotation, tides, and axial tilt, which impacted its development and sustainability.

Q4: Explain the process of star formation.
Ans: Stars are formed from the collapse of dense clouds of gas and dust called nebulae.

Q5: What is the current composition of Earth's atmosphere?
Ans: Earth's atmosphere is chiefly composed of nitrogen and oxygen.

Q6: How old are Earth's oceans?
Ans: Earth's oceans are approximately 4,000 million years old.

Q7: What did Otto Schmidt and Carl Weizascar revise to propose the Nebular Hypothesis?
Ans: They revised Immanuel Kant's hypothesis.

Q8: What is the primary factor that led to the transformation of the initially barren, rocky, and hot Earth into a beautiful planet with ample water and a conducive atmosphere for life?
Ans: Certain events and processes over time.

Q9: Explain the process that led to the evolution of oxygen in Earth's atmosphere.
Ans: Photosynthesis led to the evolution of oxygen in Earth's atmosphere.

Q10: What process leads to the formation of stars in galaxies?
Ans: The gravitational collapse of planets.

Short Answer Type Questions

Q1: Explain the Big Bang Theory in detail, including the key events in the early universe.
Ans: The Big Bang Theory suggests that the universe began as a tiny, singular atom with infinite temperature and density. The key events include the rapid expansion of the universe, conversion of energy into matter, and the emergence of the first atoms.

Q2: Describe the process of star formation and its significance in the cosmos.
Ans: Star formation occurs when dense clouds of gas and dust collapse under gravity, leading to the birth of stars. It is crucial because stars are the primary source of heavy elements needed for planet formation and life.

Q3: Discuss the stages in the development of planets from their formation as planetesimals to becoming full-fledged planets.
Ans: Planets form through stages:
(i) Gravitational force leads to the formation of a core and a rotating disc of gas and dust,
(ii) Matter condenses into small-rounded objects called planetesimals, and
(iii) Planetesimals accrete to form larger bodies.

Q4: How did the Earth's lithosphere evolve, leading to its current state?
Ans: The Earth's lithosphere evolved as the Earth cooled and solidified, leading to differentiation with denser materials sinking and lighter ones rising. This process created the Earth's crust and shaped its surface features.

Q5: Provide an overview of the evolution of Earth's atmosphere and hydrosphere.
Ans: The evolution of Earth's atmosphere and hydrosphere started with degassing and the release of gases from the interior. Continuous volcanic eruptions contributed water vapor and gases, leading to the formation of oceans.

Q6: Explain the role of photosynthesis in the evolution of Earth's atmosphere.
Ans: Photosynthesis played a role in the evolution of Earth's atmosphere by gradually contributing oxygen to the oceans, saturating them with oxygen over millions of years.

Q7: Describe the process of oxygen evolution in Earth's atmosphere.
Ans: Oxygen evolved in Earth's atmosphere due to the process of photosynthesis carried out by early life forms. As photosynthetic organisms released oxygen, it accumulated in the atmosphere.

Q8: How has the study of fossils contributed to our understanding of the history of life on Earth?
Ans: The study of fossils has contributed to our understanding of the history of life on Earth by providing a record of past life forms and their evolution over geological time. Fossils offer insights into the diversity and adaptations of ancient organisms.

Long Answer Type Questions

Q1: Discuss the Nebular Hypothesis and the contributions of Immanuel Kant, Laplace, Otto Schmidt, and Carl Weizascar in its development.
Ans: The Nebular Hypothesis suggests that planets were formed from a rotating cloud of material associated with a young sun. Immanuel Kant, a German philosopher, proposed an early argument related to this idea. Mathematician Laplace revised Kant's hypothesis in 1796, leading to the Nebular Hypothesis. In 1950, Otto Schmidt in Russia and Carl Weizascar in Germany made revisions to this hypothesis. They proposed that the sun was surrounded by a solar nebula composed mainly of hydrogen, helium, and dust. The friction and collisions of particles in the solar nebula led to the formation of a disk-shaped cloud, and planets were formed through the process of accretion.

Q2: Explain the concept of the Big Bang Theory and its implications for our understanding of the universe.
Ans: The Big Bang Theory suggests that the universe initially existed as a tiny, singular atom with infinite temperature and density. Approximately 13.7 billion years ago, a huge expansion, known as the Big Bang event, occurred, leading to the universe's formation. Some energy converted into matter during the expansion, and rapid expansion happened within fractions of a second after the Big Bang. Over time, the expansion slowed down, and the first atom began to form. The implications of this theory are significant, as it explains the origin of the universe, the formation of matter, and the evolution of galaxies and celestial bodies.

Q3: Discuss the process of star formation and its role in the universe.
Ans: Star formation is a fundamental process in the universe. It begins with the collapse of dense clouds of gas and dust known as nebulae. As these clouds collapse under their own gravity, they heat up and form protostars. The protostar continues to contract and heat up until nuclear fusion begins, resulting in the birth of a star. The leftover material in the surrounding disk can form planets and other celestial bodies. Star formation contributes to the creation of galaxies, and stars are essential for the universe's structure and energy generation.

Q4: Explain the evolution of Earth, including its early conditions, transformation, and the role of the Moon.
Ans: The Earth's early conditions were characterized by a barren, rocky, and hot surface with a thin atmosphere composed of hydrogen and helium. Over time, a series of events and processes transformed the Earth into its present condition. The Moon played a significant role in this transformation by influencing Earth's rotation, tides, and axial tilt. It stabilized the planet's conditions and allowed for the development and sustainability of life. The Earth's evolution occurred over billions of years, leading to its current state as a beautiful planet with ample water and a conducive atmosphere for life.