The comprehensive approach in SCERT Class 8 Basic Science Textbook Solutions Chapter 8 Origin of Life, Origin of Living Things Important Questions ensure conceptual clarity.
Origin of Life, Origin of Living Things Extra Questions and Answers Class 8 Basic Science Chapter 8 Kerala Syllabus
Origin of Life, Origin of Living Things Class 8 Important Questions
Question 1.
Choose the correct answer.
Statement 1: Fossil studies also show that Pakicetus, the ancestor of the whales, had the physical characteristics of a wolf, as well as a body structure suitable for swimming.
Statement 2: The ancestor of the Whales was an ancient mammal called Pakicetus, which lived 60 million years ago.
(a) Statements 1 and 2 are correct.
(b) Statements 1 and 2 are wrong
(c) Statement 1 is true and Statement 2 is false
(d) Statement 1 is false and Statement 2 is true
Answer:
(c) Statement 1 is true and Statement 2 is false
Question 2.
Scientists who advanced the theory of chemical evolution
(a) Harold Urey, Stanley Miller
(b) Oparin, Haldane
(c) Sidney Fox, Joan Oro
(d) Watson, Crick
Answer:
(b) Oparin, Haldane
Question 3.
Complete the statement.
The ancestor of all whale species, including the blue whale, was an ancient mammal called …………………….
Answer:
Pakicetus
Question 4.
From the given below, select and write the one related to prokaryotes.
(a) Fewer organelles
(b) Organelles with membrane
(c) membrane bound nucleus
(d) membrane bound nucleus absent
(e) More organelles
Answer:
(a) and (d)
Question 5.
Identify and complete the word pairs. Also, write the relationship between the word pairs.
4 – 4.6 billion years : Origin of the Earth:: 2.5 – 541 million years : ……………………….
Answer:
Multicellular organisms, such as eukaryotes, timeline and animals
Question 6.
How did life originate on Earth?
Answer:
Scientists believe that life originated on Earth about 3.5 billion years ago.
Question 7.
What are the theories related to the origin of life?
Answer:
Theories related to the origin of life: Panspermia theory, Chemical evolution theory
Question 8.
What are the characteristics of prokaryotes?
Answer:
Few organelles, no membrane-bound organelles, and no membrane-bound nucleus.
Question 9.
Over time, complex organisms evolved into the plants and animals we see today.
(a) When is life thought to have originated on Earth?
(b) What conditions led to the formation of complex organisms?
Answer:
(a) Scientists believe that life originated on Earth about 3.5 billion years ago.
(b) Some of the simpler organisms released oxygen through photosynthesis, which led to the formation of more complex organisms.
Question 10.
Complete the list.
| Theory | Explanation |
| Panspermia hypothesis | …………..(a)………………… |
| …………….(b)…………… | Life emerged as a result of the chemical reactions that took place in the ocean under unique conditions on the early Earth. |
Answer:
(a) Life originated on another planet and arrived on Earth by chance as microorganisms or as particles. These tiny particles of life are called panspermia.
(b) Chemical evolution theory
Question 11.
The names of the scientists who made contributions that validate how the primitive cell was formed through the process of chemical evolution are given below. Write their contributions.
(a) Sidney Fox
(b) Joan Oro
Answer:
Sydney Fox: Demonstrated that molecules similar to proteins can be artificially produced
Joan Oro: The nitrogenous base adenine, one of the main building blocks of nucleic acids, was artificially produced.
Question 12.
List the statements given below.
(a) More organelles
(b) Organelles are not membrane-bound
(c) No membrane-bound nucleus
(d) There is a membrane-bound nucleus
| Prokaryotic cell | Eukaryotic cell |
Answer:
Prokaryotic cell: (b) and (c), Eukaryotic cell: (a) and (d).
Question 13.
Explain the theory of chemical evolution?
Answer:
The theory of chemical evolution explains that life arose as a result of the combination of chemicals in the ocean under unique conditions on early Earth. Although many theories have emerged over time to explain the origin of life, the theory of chemical evolution is the one that-is most supported by evidence and has received the most acceptance in the scientific world.
Question 14.
Observe the illustration and answer the questions below.
(a) Which process does the illustration indicate?
(b) Explain the process that the illustration indicates.
Answer:
(a) Formation of organelles found in cells.
(b) Eukaryotic cell engulfs small aerobic bacteria. Instead of digesting the small cell, it protects it. Gradually, these become mitochondria.
Eukaryotic cell engulfs small photosynthetic bacteria. Instead of digesting the photosynthetic bacteria, it – protects it. Gradually, these become chloroplasts.
Question 15.
The stages in which various living things evolved from prokaryotes are given below. Write them in chronological order.
(a) Dinosaurs
(b) Origin of the Earth
(c) Emergence of mammals, origin of humans
(d) Multicellular organisms called eukaryotes
(e) Unicellular prokaryotes with simple structures
(f) Plants and animals on land
Answer:
(b), (e), (d), (f), (a), (c)
Question 16.
What is the Cosmic Calendar?
Answer:
The cosmic calendar is a depiction of the chronology from the creation of the universe to the emergence of man in an easy-to-understand way. If a calendar were prepared assuming the age of the universe to be just one year, one second in that calendar would be equivalent to approximately 438 years.
Question 17.
Choose and write the correct pairs.
(a) 4 – 4.6 billion years ago: Origin of the Earth
(b) 3.5 – 2.5 billion years ago: Multicellular organisms called eukaryotes
(c) 541 – 252 million years ago: Plants and animals on land
(d) 252 – 66 million years ago: Single-celled prokaryotes with simple structures
(e) 66 million years ago to the present: Emergence of mammals, origin of humans
Answer:
(a), (c), (e).
Question 18.
Observe the illustration and answer the questions below.
(a) Who performed the experiment shown in the illustration?
(b) What is the source of energy in this experiment?
(c) How does this experiment validate the theory of chemical evolution?
Answer:
(a) Harold Urey and Stanley Miller
(b) Electric spark
(c) This experiment was conducted by artificially recreating the conditions of the primitive Earth in the laboratoiy. This experiment was able to produce amino acids, which are organic molecules. This experiment proved that organic molecules can be formed from inorganic components under suitable conditions.
Question 19.
Observe the illustration and answer the questions below.
(a) Which theory related to the origin of life is indicated in the illustration?
(b) Explain the theory.
(c) Complete the illustration.
Answer:
(a) Chemical evolution theory
(b) The chemical evolution theory explains that life emerged as ,a result of the combination of chemicals in the ocean under special conditions on the early Earth.
(c) A – Sunlight, lightning, ultraviolet rays, volcanic eruptions B – The complex molecule called nucleic acid and the lipid envelope are formed.
Question 20.
Complete the list.
| Scientist | Contributions |
| …………..(a)………….. | They together proved that the fundamental units responsible for the origin of life can form from simple gases. |
| Sidney Fox | …………..(b)………….. |
| Joan Oro | …………..(c)………….. |
Answer:
(a) Harold Urey, Stanley Miller
(b) Proved that molecules similar to proteins can be synthesised artificially.
(c) Adenine, one of the key building blocks of nucleic acids, was artificially synthesised.
Question 21.
Observe the picture and answer the questions below.
(a) Which cell is indicated in the figure?
(b) What are the characteristics of this cell?
Answer:
(a) Eukaryotic cell
(b) More organelles, membrane-bound organelles, and a membrane-bound nucleus.
Question 22.
Arrange based on the cosmic calendar
| Land plants, eukaryotes, mammals, vertebrates, humans, dinosaurs |
Answer:
Eukaryotes, vertebrates, land plants, dinosaurs, mammals, humans
Question 23.
Explain the evolutionary history of the whale.
Answer:
The ancestor of whales, including the blue whale, was an ancient mammal called Pakicetus, which lived 50 million years ago. Fossil studies show that this creature had the physical characteristics of a wolf, as well as a body structure suitable for swimming. As its descendants spent more time in the water, their legs evolved to resemble paddles. The evolutionary history of whales is evidence that organisms change as part of their adaptation to changing conditions. All living things, including humans, have a fascinating history of this kind of evolution.
Question 24.
Who are the scientists who made contributions that validate the formation of the primitive cell through the process of chemical evolution?
Answer:
Harold Urey, Stanley Miller: They together proved that the fundamental units responsible for the origin of life can form from simple gases.
Sydney Fox: Proved that molecules similar to proteins can be synthesised artificially.
Joan Oro: Adenine, one of the key building blocks of nucleic acids, was artificially synthesised.
Question 25.
Explain the Harold Urey and Stanley Miller experiments.
Answer:
Among the many experimental evidence supporting the theory of chemical evolution, the most notable is the Urey-Miller experiment. This experiment was conducted in a laboratory by artificially recreating the conditions of the primitive Earth. This experiment was able to produce amino acids, which are organic molecules. This experiment proved that organic molecules can form from inorganic components under suitable conditions.
Question 26.
What changes occurred in the primitive cell?
Answer:
The primitive cell is composed of nucleic acids capable of self-replication and a lipid membrane that surrounds it. Cells such as bacteria evolved from this primitive cell. These first, simple organisms are called prokaryotes.
Question 27.
How did complex organisms evolve from primitive cells?
Answer:
About 3.8 billion years ago, primitive cells evolved from molecules in Earth’s oceans. Prokaryotic cells evolved 3.5 billion years ago. About 2.5 billion years ago, photosynthesis began, bringing oxygen to the atmosphere. Later, eukaryotic cells with organelles such as mitochondria and chloroplasts evolved. Then came simple multicellular organisms, and about 800 million years ago, more complex organisms had formed.