NCERT Solutions Class 12 Biology Chapter 6 Evolution

In Class 12 Biology Chapter 6, Evolution, students learn how life on Earth has changed over millions of years through gradual and continuous processes. This chapter explains the origin of life, evidence supporting evolution, theories of evolution, modern ideas like genetic variation, adaptation, and speciation, etc., to help students understand how new species arise and how organisms become better suited to their environments.

To streamline your preparation, ALLEN offers expertly curated the NCERT Solutions that transforms complex theories and paleontological information into concise, easy-to-understand explanations that prioritize conceptual depth over rote memorization. These solutions are structured to help you develop a logical flow in your answers whcih is important for scoring well in descriptive board exam questions. By choosing ALLEN’s NCERT Solutions for Class 12, you are utilizing a study tool designed for accuracy, ensuring you remain ahead in both your school finals and competitive medical entrance tests.

1.0Download NCERT Solutions Class 12 Biology Chapter 6 Evolution : Free PDF

This chapter explains how organisms change and adapt over time through natural processes. The NCERT Solutions for Class 12 Biology Chapter 6 Evolution help students revise key theories, timelines, and examples easily. Download the free PDF now to study anytime and prepare confidently for exams.

2.0Key Concepts of Class 12 Biology Chapter 6 Evolution

The chapter evolution discusses a wide variety of topics. Some of the most important concerts discussed in the chapter include:

• Origin of Life: Early theories and experiments explaining how life may have begun on Earth.
• Evidences of Evolution: Studying fossil records, homologous and analogous organs, molecular similarities, etc., to prove that evolution is not fiction.
• Lamarck’s Theory: Learning what the inheritance of acquired characteristics is and the theory’s historical importance.
• Darwin’s Theory of Natural Selection: Understanding variation, struggle for existence, and survival of the fittest.
• Modern Synthetic Theory: Studying the role of genetics, mutation, recombination, and selection in evolution.
• Speciation: Understanding how new species form through reproductive isolation.
• Human Evolution: Learning about major stages in the evolution of humans.

3.0NCERT Class 12 Biology Chapter 6 Evolution : Detailed Solutions

1. Explain antibiotic resistance observed in bacteria in light of Darwinian selection theory. 

Ans:  According to Darwin’s theory of natural selection, populations show variation among individuals. In a bacterial population, some bacteria naturally possess genetic variations or mutations that make them resistant to a particular antibiotic.

When an antibiotic is introduced, the non-resistant (susceptible) bacteria are killed, while the resistant bacteria survive. These surviving bacteria then multiply rapidly by binary fission. This causes an increase in the proportion of resistant bacteria over successive generations.

Thus, the antibiotic acts as a selective pressure, and the resistant bacteria are selected for survival and reproduction. This leads to the development and spread of antibiotic-resistant strains.

2. Find out from newspapers and popular science articles any new fossil discoveries or controversies about evolution. 

Ans:

New fossil discoveries:

Jurassic Bird Fossil (China) — Baminornis zhenghensis

• Discovery of a Jurassic-age bird fossil with a short, fused tail suggests that capable flying birds existed earlier than previously believed.

Oldest Plant-Eating Dinosaur (Morocco) — Cerapodan dinosaur fossil

• A 168-million-year-old herbivorous dinosaur helps fill a gap in the early evolution of plant-eating dinosaurs.

Early Human Ancestors in Africa — Australopithecus and early Homo fossils

• Fossils show that different human ancestors lived in the same region at the same time, indicating a branching pattern of evolution.

Controversies

Early Origin of Birds

• The Jurassic bird fossil challenges the traditional timeline of bird evolution, raising debate about when true birds first appeared.

Petralona Skull (Greece)

• New dating suggests early humans and Neanderthals co-existed in Europe, which is controversial for human migration and ancestry models.

Hidden Branch in Human Evolution

• Some fossils suggest the presence of a previously unknown human lineage, questioning the idea of a simple, linear human evolution.

“Paradox Snake” Fossil

• A 37-million-year-old snake fossil does not fit known snake evolutionary patterns, creating debate about early snake adaptation.

3. Attempt giving a clear definition of the term species. 

Ans: A species is a group of similar organisms that can interbreed naturally among themselves and produce fertile offspring. They are reproductively isolated from other such groups. Members of a species share common structural, genetic, and behavioural characteristics and occupy a particular ecological category.

4. Try to trace the various components of human evolution (hint: brain size and function, skeletal structure, dietary preference, etc.) 

Ans: Human evolution involved gradual changes in brain development, skeletal structure, diet, and behaviour, which together led to the emergence of modern humans. SOme of the components of human evolution include:

Brain Size and Function

• Early hominins had a small-sized brain, but over time, there was a steady increase in cranial capacity. Example: Homo habilis (650-800cc), Homo erectus (900 cc) and Neanderthals (1400 cc)
• This allowed and led to the development of higher intelligence, memory, reasoning, and language skills.
• Advanced brain functions also supported tool-making, social organisation, and improved communication..

Skeletal Structure and Posture

• A major evolutionary change was the development of bipedal locomotion (walking on two legs).
• The pelvis became broader, the spinal column developed an S-shaped curve, and the foramen magnum shifted forward, helping maintain an upright posture.
• Limbs became adapted for efficient walking and running, while hands became free for grasping and tool use.

Facial Structure and Dentition

• The size of the jaw and teeth reduced over time, which also reflected the changes in diet and food processing.
• The face became flatter, and the brow ridges gradually decreased.

Dietary Preference

• Early humans were mainly plant eaters, but later became omnivorous, including meat in their diet.
• The use of fire and tools helped in cooking and processing food, making digestion easier and improving nutrition.

Tool Use and Culture

• There was a progressive improvement in stone tools, from simple hand axes to more refined implements.
• Development of social behaviour, art, language, and cultural practices marked advanced stages of human evolution.

5. Find out through internet and popular science articles whether animals other than man has self-consciousness.

Ans: A widely used method to test self-consciousness and self-awareness in animals is the mirror self-recognition test (MSR) where animals are marked in a way that they can only see the mark if they recognise themselves in a mirror.

Below are some examples of animals showing self-awareness while tested.

• Great apes: Chimpanzees, bonobos, and orangutans have consistently passed mirror tests where they use the mirror to groom parts of their bodies they cannot otherwise see.
• Dolphins: Bottlenose dolphins have displayed high levels of self-directed behaviour by inspecting marks placed on their bodies using underwater mirrors.
• Asian Elephants: A well-documented study showed an elephant repeatedly touching a "X" painted on its forehead while looking in a mirror.
• Eurasian Magpies and Cleaner fish: Surprisingly, these birds (members of the crow family) and sone fishes have passed the test, suggesting that self-consciousness is not restricted to mammals with large neocortexes.

6. List 10 modern-day animals and using the internet resources link it to a corresponding ancient fossil. Name both. 

Ans: Evolutionary connections between modern animals and ancient fossils illustrate how life has changed over millions of years. Some of the modern day animals that can be linked to their correspondig ancient fossils are given below:

7. Practise drawing various animals and plants. 

8. Describe one example of adaptive radiation. 

Ans: Adaptive radiation is the process by which a single ancestral species gives rise to many different species, each adapted to a different ecological niche.

Example: Darwin’s finches

Found on the Galápagos Islands, these finches are believed to have evolved from a common ancestral finch that originally migrated to the islands. Over time, as the birds spread to different islands and habitats, they encountered different types of food sources such as seeds, insects, and cactus flowers.

To survive in these varied environments, the finches developed beaks of different shapes and sizes adapted to serve their primary function. For example, some species developed strong, thick beaks essential for cracking hard seeds, while others developed slender, pointed beaks, which are beneficial for feeding on insects or nectar.

9. Can we call human evolution as adaptive radiation? 

Ans: Adaptive radiation is the process by which a single ancestral species gives rise to many different species, each adapted to a different ecological niche. By this definition, human evolution cannot be called adaptive radiation.

Human evolution shows a progressive and linear trend with a single evolutionary lineage. Different forms such as Australopithecus, Homo habilis, Homo erectus, and Homo sapiens represent successive stages in the evolution of modern humans rather than the formation of many species adapted to different niches at the same time

4.0Key Features and Benefits of Class 12 Biology Chapter 6 Evolution

• The solutions attempt to explain evolutionary theories clearly, helping students compare different ideas and understand their significance.
• The practice questions strengthen the understanding of evidence of evolution and the evolutionary timelines.
• Regular study and revision helps recall of scientific terms and concepts during the exam.
• During competitive exams like NEET, having strong fundamentals in these topics can be very supportive.
• Clear explanations help students connect the concept of evolution along with real-life biodiversity and adaptation.