NCERT Class 12 Biology Biology: Chapter 6 — EVOLUTION
This chapter, Evolution, delves into the history of life on Earth, starting with the origin of life itself. It explores the vastness of the universe and the formation of stars and galaxies, leading to the creation of Earth approximately 4.5 billion years ago. The text discusses the early conditions of Earth, the role of UV rays, and the formation of oceans. It addresses theories on the origin of life, including Panspermia and the disproven theory of spontaneous generation, highlighting Louis Pasteur's experiments. The chapter introduces the Oparin-Haldane hypothesis, proposing chemical evolution from non-living organic molecules, supported by S.L. Miller's laboratory experiments simulating early Earth conditions. It touches upon the formation of amino acids and other organic compounds, suggesting similar processes occur in space. This foundational understanding of life's origins is crucial for comprehending biological evolution within the CBSE curriculum.
Quick info
| Board | CBSE / NCERT |
|---|---|
| Class | Class 12 |
| Subject | Biology |
| Book | Biology |
| Chapter | Chapter 6 — EVOLUTION |
| Language | English |
| PDF type | NCERT Textbook |
| Session | CBSE 2026 |
| Reading time | 4 minutes |
| Word count | 786 |
Learning outcomes
- Understand the concept of evolution and its study in biology.
- Learn about the origin of the universe and Earth.
- Explore theories regarding the origin of life, including spontaneous generation and chemical evolution.
- Recognize the contributions of scientists like Louis Pasteur and S.L. Miller.
- Understand the conditions on early Earth that may have led to the origin of life.
Vocabulary
| Word | Meaning |
|---|---|
| Evolutionary Biology | The study of the history of life forms on Earth. |
| Big Bang theory | A theory that explains the origin of the universe through a singular huge explosion. |
| Panspermia | The idea that units of life were transferred to Earth from outer space. |
| Spontaneous generation | The disproven theory that life could arise from non-living matter. |
| Chemical evolution | The formation of diverse organic molecules from inorganic constituents before the origin of life. |
| Amino acids | Organic molecules that are the building blocks of proteins. |
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Practice questions
- What is Evolutionary Biology? Answer: Evolutionary Biology is the study of the history of life forms on Earth.
- According to the Big Bang theory, how did the universe originate? Answer: The Big Bang theory suggests the universe originated from a singular huge explosion, followed by expansion and cooling.
- What was the theory of spontaneous generation? Answer: The theory of spontaneous generation proposed that life could arise from decaying and rotting matter.
- Who disproved the theory of spontaneous generation and how? Answer: Louis Pasteur disproved it by demonstrating that life only comes from pre-existing life through careful experimentation with sterilized flasks.
- What did Oparin and Haldane propose about the origin of life? Answer: They proposed that life originated from pre-existing non-living organic molecules through chemical evolution.
Practice MCQs
Q1. The universe is estimated to be approximately how old?
Explanation: The text states the universe is very old – almost 13.8 billion years old.
Q2. Which theory attempts to explain the origin of the universe?
Explanation: The Big Bang theory is mentioned as an explanation for the origin of the universe.
Q3. Early Greek thinkers believed units of life called ______ were transferred to planets.
Explanation: The text mentions 'units of life called spores' in the context of early Greek thinkers and Panspermia.
Q4. Louis Pasteur's experiments demonstrated that:
Explanation: Louis Pasteur's experiments proved that life originates from pre-existing life, disproving spontaneous generation.
Q5. The Oparin-Haldane hypothesis suggested that life arose from:
Explanation: Oparin and Haldane proposed that life was preceded by chemical evolution, forming diverse organic molecules from inorganic constituents.
Q6. S.L. Miller's experiment simulated early Earth conditions by creating:
Explanation: Miller created electric discharge in a closed flask containing CH4, H2, NH3, and water vapour at 800°C to simulate early Earth conditions.
Frequently asked questions
What is the main subject of Chapter 6 of NCERT Biology Class 12?
Chapter 6 of NCERT Biology Class 12 is titled 'Evolution' and discusses the history of life forms on Earth, including their origin and development.
How old is the universe according to scientific estimates?
The universe is estimated to be approximately 13.8 billion years old.
When is the Earth believed to have been formed?
The Earth is believed to have been formed about 4.5 billion years back.
What is the 'Panspermia' theory?
Panspermia is a theory suggesting that life originated elsewhere in the universe and was transferred to Earth, possibly in the form of spores.
Which scientist conclusively disproved the theory of spontaneous generation?
Louis Pasteur conclusively disproved the theory of spontaneous generation through his experiments.
What did S.L. Miller's experiment demonstrate?
S.L. Miller's experiment demonstrated the formation of amino acids under conditions simulating early Earth, supporting the theory of chemical evolution.
What is the significance of chemical evolution in the origin of life?
Chemical evolution is considered the precursor to the origin of life, involving the formation of complex organic molecules from simpler inorganic substances.
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NCERT Class 12 Biology — Biology — Chapter 6 — EVOLUTION. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.