NCERT Class 12 Biology Chapter 6: Evolution PDF Notes Download with Key Concepts

Chapter 6 of Class 12 Biology, titled Evolution, deals with the origin of life, the development of different life forms over millions of years, and the various theories and evidence supporting this process. It explains concepts like natural selection, speciation, adaptive radiation, and human evolution. Students often find this chapter both interesting and a bit

Chapter 6 of Class 12 Biology, titled Evolution, deals with the origin of life, the development of different life forms over millions of years, and the various theories and evidence supporting this process. It explains concepts like natural selection, speciation, adaptive radiation, and human evolution. Students often find this chapter both interesting and a bit philosophical because it touches upon how life began and how we, as humans, came into existence.

I am writing about this topic because it’s one of the most thought-provoking chapters in the NCERT Class 12 Biology book. Evolution is not just theory-based, it connects biology with history, geography and even geology. Many students prepare this chapter lightly, thinking it’s all theory, but it often has tricky conceptual questions in board exams and NEET. Understanding Darwin’s natural selection, differences between Lamarckism and Darwinism, and how fossils and molecular evidence support evolution is important to answer those questions confidently. That’s why I’ve explained the chapter in a simple way and also shared how to download the official NCERT PDF so you can study directly from the source.

Key Concepts of Evolution – Class 12 Biology

Let’s go through the main ideas and topics covered in Chapter 6 of the NCERT textbook.

Origin of Life

The Earth formed around 4.5 billion years ago
First life forms appeared nearly 500 million years later
Early atmosphere had methane, ammonia, hydrogen and water vapour
Oparin-Haldane theory: life originated from organic molecules in a “primordial soup”
Miller-Urey experiment (1953) supported this theory by creating amino acids in lab conditions

Theories of Evolution

Lamarckism: Proposed by Jean-Baptiste Lamarck. He believed that traits acquired during life could be inherited
Darwinism (Natural Selection): Proposed by Charles Darwin. Only those organisms which are better adapted survive and reproduce
Mutation Theory: Hugo de Vries said that mutations, not gradual changes, are responsible for evolution

Evidence of Evolution

Fossils: Help track changes in species over time (e.g. Archaeopteryx – link between reptiles and birds)
Homologous organs: Same structure, different function (e.g. forelimbs of humans and whales)
Analogous organs: Different structure, same function (e.g. wings of birds and insects)
Vestigial organs: Organs that no longer serve a function (e.g. human appendix)
Molecular Evidence: Similarity in DNA, RNA and proteins among different species

Mechanism of Evolution

Variation: Exists in every population
Mutation: Sudden change in genes
Genetic Drift: Random change in gene frequency
Gene Flow: Movement of genes between populations
Natural Selection: Favouring of traits that increase survival
Speciation: Formation of new species from existing ones

Adaptive Radiation

When a common ancestor gives rise to different species in different environments
Example: Darwin’s finches in Galapagos Islands with different beak shapes for different diets

Human Evolution

Humans and chimpanzees share a common ancestor
First human-like ancestors (e.g. Australopithecus) appeared about 4 million years ago in Africa
Modern humans (Homo sapiens) evolved about 200,000 years ago
Evolution involved changes in posture (bipedalism), brain size, tool use, and culture

Important Table – Differences in Evolution Theories

Feature	Lamarckism	Darwinism
Type of Change	Acquired traits	Inherited traits
Mechanism	Use and disuse of organs	Natural selection
Example	Giraffe’s neck growing longer	Giraffes with long necks survived
Acceptance	Discarded	Widely accepted

Download PDF – NCERT Class 12 Biology Chapter 6

To download the official and updated NCERT PDF for Chapter 6, follow the steps below:

NCERT Class 12 Biology Chapter 6

NCERT Class 12 English Vistas Chapter 6: Memories of Childhood PDF Download & Complete Summary

Memories of Childhood is Chapter 6 in the Class 12 English Vistas textbook by NCERT. What makes this chapter special is that it’s not a single story—it’s made up of two autobiographical excerpts written by two women, Zitkala-Sa and Bama. Both narrate incidents from their early lives that reflect the discrimination they faced because of

Memories of Childhood is Chapter 6 in the Class 12 English Vistas textbook by NCERT. What makes this chapter special is that it’s not a single story—it’s made up of two autobiographical excerpts written by two women, Zitkala-Sa and Bama. Both narrate incidents from their early lives that reflect the discrimination they faced because of their identity. While Zitkala-Sa was a Native American who suffered cultural oppression, Bama grew up as a Dalit in South India, dealing with caste-based discrimination. These two stories are placed together in the chapter to show that such issues exist in many parts of the world.

I decided to write about this chapter because it’s different from the others in the book. It’s not fiction, but a real account of how young children feel when they are treated unfairly just because of their background. When I first read Bama’s story, I couldn’t stop thinking about how common such behaviour still is in many Indian towns. These stories make us more aware and sensitive. As students, we need to understand not just grammar and vocabulary but also social realities. This chapter is an important step towards building that understanding.

What is “Memories of Childhood” About?

This chapter includes two short autobiographical narratives that focus on childhood memories shaped by discrimination and injustice.

Part One: The Cutting of My Long Hair by Zitkala-Sa

This section is written by a Native American woman who was taken to a missionary school where they tried to make her behave like a “white” child. She describes how humiliating it was when her long hair was forcibly cut, which in her culture was a sign of defeat. She feels powerless, angry, and alien in a place that tries to erase her identity.

Part Two: We Too Are Human Beings by Bama

Bama’s story takes place in a village in Tamil Nadu. She is a young Dalit girl who notices how upper-caste people treat her community with disrespect. She sees a man carrying food for his master without touching it, just because of his caste. When she narrates this incident to her brother, he tells her about caste discrimination and advises her to study hard to earn respect and equality.

Main Characters:

Zitkala-Sa – A Native American girl forced to give up her culture at a white-run school
Bama – A young Dalit girl who slowly becomes aware of social injustice

Key Themes:

Discrimination based on race and caste
Childhood trauma and awareness
Loss of identity
Education as a tool for change

Why This Chapter Matters for Students

Real stories: It helps students connect emotionally to real-life problems faced by children
Relevant to society: Topics like caste and cultural identity are still important in today’s India
CBSE exam favourite: Frequently asked in long and value-based questions
Builds empathy: Helps students look beyond textbooks and understand people around them better
Teaches resilience: Both writers turned their pain into power through education and awareness