Evolution ncert solutions: Class 12th biology chapter 6 ncert solutions
| Textbook | NCERT |
| Class | Class 12 |
| Subject | Biology |
| Chapter | Chapter 6 |
| Chapter Name | Evolution class 12 ncert solutions |
| Category | Ncert Solutions |
| Medium | English |
Are you looking for Ncert Solutions for Class 12 Biology Chapter 6 Evolution? Now you can download Ncert class 12 biology chapter 6 questions and answers pdf from here.
Question 1: Explain antibiotic resistance observed in bacteria in light of Darwinian selection theory.
Solution 1: According to Darwin, environment selects organisms with favourable variations and these organisms are allowed to survive. When a bacterial population encounters a particular antibiotic, those sensitive to it die. But some bacteria having mutations become resistant to the antibiotic. Such resistant bacteria survive and multiply quickly as the competing bacteria have died. Some the resistance providing genes become widespread and entire bacterial population becomes resistant.
Question 2: Find out from newspapers and popular science articles any new fossil discoveries or controversies about evolution.
Solution 2: Recent fossil discoveries have generated exciting discussions in the field of evolution. For instance, researchers unearthed a 300,000-year-old fossil that may belong to an unknown species of archaic human, sparking interest in the complexity of human evolution.
Additionally, a new species of small reptile fossil from Brazil, dating back 237 million years, has been proposed as a precursor to dinosaurs, suggesting that the rise of these giants was a gradual process rather than a sudden event.
Moreover, a controversial “4-legged snake” fossil, believed to have been smuggled from Brazil, has ignited debates over fossil ownership and ethical practices in paleontology.
Question 3: Attempt giving a clear definition of the term species.
Solution 3: A species is typically defined as a group of organisms that can interbreed and produce fertile offspring under natural conditions. Members of a species share common characteristics and genetic similarities, which distinguish them from other groups.
This definition emphasizes reproductive isolation, meaning that species are reproductively independent from one another, preventing gene flow between distinct groups. In some contexts, species can also be identified based on morphological traits or genetic differences. Overall, the concept of species is fundamental to understanding biodiversity and the relationships among organisms.
Question 4: Try to trace the various components of human evolution (hint: brain size and function, skeletal structure, dietary preference, etc.)
Solution 4: Brain Size and Function
- Early Hominins: Early species like Australopithecus had relatively small brains (around 400-500 cc) similar to modern chimpanzees.
- Homo habilis: Showed an increase in brain size (about 510-600 cc), which correlates with more sophisticated tool use and social behaviors.
- Homo erectus: Had a larger brain (750-1,100 cc) and exhibited greater cognitive abilities, including the ability to control fire and create more complex tools.
- Neanderthals: Had brain sizes comparable to or slightly larger than modern humans, suggesting advanced cognitive abilities, as evidenced by their use of tools and symbolic artifacts.
- Homo sapiens: Have a brain size of about 1,300-1,400 cc, enabling advanced problem-solving, language development, abstract thinking, and social structures.
Skeletal Structure
- Bipedalism: The transition to upright walking is a crucial adaptation that influenced skeletal structure. Key changes include:
- Pelvis: The pelvis became shorter and broader to support bipedal locomotion.
- Spine: The curvature of the spine evolved to support an upright posture.
- Legs: Longer legs relative to arms improved efficiency in walking and running.
- Feet: The structure of the foot adapted to bipedalism, with arches for shock absorption and alignment for balance.
- Cranial Features: Changes in skull structure to accommodate larger brains included:
- Reduced Brow Ridge: A flatter face with less pronounced brow ridges in Homo sapiens.
- Skull Shape: A rounded cranium with a prominent forehead in modern humans compared to earlier species with elongated skulls.
Dietary Preferences
- Omnivorous Diet: Early hominins were likely omnivores, consuming a varied diet of fruits, nuts, leaves, and some meat.
- Tool Use: The development of tools allowed for more efficient food processing, including butchering meat and cracking nuts.
- Cooking: Control of fire by Homo erectus led to the ability to cook food, which made it easier to digest and allowed for the consumption of a wider variety of foods. This cooking process likely contributed to further brain development due to increased caloric intake.
- Agricultural Revolution: The shift to agriculture around 10,000 years ago led to changes in diet, with an increased reliance on cultivated crops and domesticated animals, influencing health, population density, and social structures.
Social Structures and Behavior
- Tool and Culture Development: The evolution of more sophisticated tools, from simple stone tools to complex instruments, reflects cognitive advances and social learning.
- Cooperative Behavior: Increased brain size may have facilitated complex social interactions, allowing for cooperative hunting and gathering, and later, agricultural practices.
- Language Development: Enhanced communication capabilities, possibly linked to increased brain size, fostered social cohesion and cultural transmission, allowing knowledge to be passed down generations.
- Art and Symbolism: The emergence of symbolic thinking is evidenced by cave art, ornaments, and burial practices, indicating complex cognitive and cultural evolution.
Genetic and Environmental Influences
- Genetic Variation: Genetic studies reveal interbreeding between Homo sapiens and other hominins, such as Neanderthals and Denisovans, contributing to modern human diversity.
- Environmental Adaptations: Humans adapted to various environments, leading to variations in skin color, body shape, and other traits influenced by climate and habitat.
Question 5: Find out through internet and popular science articles whether animals other than man has self-consciousness.
Solution 5: Apart from humans, there are many other animals that possess self-consciousness. One such example is the Dolphin. They are believed to have a high level of intelligence. Also, they have a sense of self and can identify themselves amongst others. They whistle, tail-slap and exhibit body movements to communicate with each other. Some other animals that exhibit self-consciousness are parrots, crows, gorillas, orangutans, chimpanzees, etc.
Question 6: List 10 modern-day animals and using the internet resources link it to a corresponding ancient fossil. Name both.
Solution 6: The list is as follows:
| Modern-Day Animal | Ancient Fossil | Description |
|---|---|---|
| 1. African Elephant | Mammuthus (Woolly Mammoth) | Mammoths were large, elephant-like creatures with long tusks, living during the last Ice Age. Their remains have been found in frozen tundras. |
| 2. Modern Horse | Hippotherium | An ancient horse-like creature that lived around 20 million years ago, showing early adaptations for grazing. |
| 3. Blue Whale | Basilosaurus | A prehistoric whale that lived around 40 million years ago, exhibiting elongated bodies and primitive features that predate modern baleen whales. |
| 4. Modern Bird (e.g., Crow) | Archaeopteryx | Often considered the first bird, Archaeopteryx lived about 150 million years ago and showcases features of both dinosaurs and modern birds. |
| 5. Crocodile | Deinosuchus | A giant prehistoric crocodile that lived about 80 million years ago, which could reach lengths of over 30 feet. |
| 6. Shark (e.g., Great White) | Megalodon | A giant prehistoric shark that lived around 23 million years ago, known for its massive size and powerful jaws, much larger than modern sharks. |
| 7. Modern Frog | Beelzebufo (Devil Frog) | An ancient frog that lived about 70 million years ago, known for its large size, with estimates suggesting it could weigh up to 10 pounds. |
| 8. Giant Ground Sloth | Megatherium | An extinct genus of giant ground sloths that lived during the Pleistocene, showcasing a size and morphology distinct from modern sloths. |
| 9. Modern Human | Homo neanderthalensis (Neanderthal) | An ancient relative of modern humans, Neanderthals lived in Europe and Asia until about 40,000 years ago and shared many traits with modern Homo sapiens. |
| 10. Giant Panda | Ailuropoda (Extinct Species) | Related to the extinct species Ailuropoda microta, ancient forms of giant pandas that lived millions of years ago, showcasing similar dietary adaptations. |
Question 7: Practise drawing various animals and plants.
Solution 7: Take cues from seniors and teachers for names of different plants and animals. Go through different science books, magazines, and encyclopedias to get an idea of different plant and animal species. To get further details, the internet serves as the ultimate option. There is a huge range of plants and animals from which you can pick the easiest one to begin with and practice them. Try tracing the outline first and then fill in the details.
Question 8: Describe one example of adaptive radiation.
Solution 8: Adaptive radiation is an evolutionary process in which a single ancestral species rapidly diversifies into a wide variety of forms to adapt to different environments and ecological niches. One classic example of adaptive radiation is the Darwin’s finches on the Galápagos Islands.
Darwin’s Finches
- Ancestral Species: The finches are believed to have descended from a common ancestor that arrived on the Galápagos Islands from the mainland.
- Diversity of Species: Over time, these finches adapted to the varying environmental conditions and available food sources on different islands. This led to the evolution of multiple species with distinct traits, including differences in beak size and shape.
- Beak Adaptations:
- Large Beaks: Some species evolved larger beaks to crack open hard seeds.
- Thin Beaks: Others developed thinner beaks to feed on insects or nectar.
- Medium-Sized Beaks: Some species adapted to consume a mixed diet of seeds and insects.
Question 9: Can we call human evolution as adaptive radiation?
Solution 9: Human evolution is not typically classified as adaptive radiation, although it exhibits some characteristics of the concept. Adaptive radiation refers to the rapid diversification of a single ancestral species into various forms that occupy different ecological niches.
In contrast, human evolution primarily follows a single lineage from early hominins to modern Homo sapiens, without the extensive branching seen in classic examples like Darwin’s finches. While different human populations have adapted to various environments, resulting in some morphological and cultural differences, these adaptations are not as pronounced or rapid as in typical adaptive radiation scenarios.
Additionally, many hominin species coexisted at various points in time but eventually went extinct, leaving Homo sapiens as the sole survivor. Therefore, while human evolution includes elements of adaptation to diverse environments, it does not fit the strict definition of adaptive radiation, which emphasizes rapid diversification and the emergence of multiple coexisting species.
Question 10: Using various resources such as your school Library or the internet and discussions with your teacher, trace the evolutionary stages of any one animal, say horse.
Solution 10: During the Eocene era, the evolution of the horse began with Eohippus and involved the following evolutionary phases:
Eohippus → Mesohippus →Merychippus → Pliohippus → Equus
Evolutionary traits observed were as follows:
(i) Increase in body size.
(ii) Elongation of neck.
(iii) Lengthening of limbs.
(iv) Enlargement of third digit.
(v) Increase in structural complexity of teeth for feeding on grass.