NCERT Solutions for Class 12 Biology Chapter 7 - Evolution

Chapter 7 of Class 12 Biology focuses on the origin and evolution of life on Earth, exploring how diverse life forms have developed over millions of years. The chapter begins by discussing various theories about how life first appeared, such as the primordial soup theory and the theory of extraterrestrial origins. It emphasizes the importance of conditions on early Earth, like the presence of water and suitable chemicals, which helped create the first simple organisms.

The chapter also explains evolution, which is the process through which species change over time. Key mechanisms of evolution are introduced, including natural selection, genetic drift, and mutations. Natural selection, described by Charles Darwin, explains how organisms better adapted to their environment tend to survive and reproduce.

Moreover, the chapter highlights the concept of biodiversity, which refers to the variety of life forms on Earth. It stresses the importance of biodiversity for ecosystem health and stability. By understanding the origin and evolution of life, students gain insights into how all living beings are interconnected and how they adapt to survive in a changing world. This foundational knowledge is crucial for appreciating the complexity of life and the environment we live in.

Evolution NCERT Solutions Class 12 Biology Chapter 7: Question and Answers

Q 1. Explain antibiotic resistance observed in bacteria in light of Darwinian selection theory.
Answer: Darwinian selection theory suggests that the environment selects organisms with useful variation over those which do not have useful variations. It is mainly because, in a dynamic environment, these organisms are better adapted to survive. A well-defined example of Darwin's theory is antibiotic resistance in bacteria. When bacteria were grown on penicillin containing agar medium, all the bacteria died, however, the ones having variations conferring penicillin resistance survived. Later, the bacteria multiplied and increased their number. As a result of this, penicillin-resistant bacteria evolved and survived because of the environment that selected these over the others.

Q2. Find out from newspapers and popular science articles any new fossil discoveries or controversies about evolution.
Answer: A recent study suggests Ledum Hadi mafube is the fossil from South Africa that marked the beginning of gigantic dinosaurs. This 200 million-year-old dinosaur weighed around 12 tons, making it the earliest dinosaur to pass beyond the 10-ton threshold. Later, dinosaurs would become even bigger. But in its time, Ledumahadi mafube was a giant among dwarfs (Source- Business standard).

Q3. Attempt giving a clear definition of the term species.
Answer: The term species refers to a group of individuals that are similar in their characters and can interbreed among themselves and produce viable and fertile progeny.

Q4. Try to trace the various components of human evolution (hint: brain size and function, skeletal structure, dietary preference, etc.).
Answer: The various components of human evolution involve the age of appearance, brain capacity, posture, locomotion, height, body hairs, dietary preferences, skeletal structure, cranium structure, etc. A summary of human evolution ba ed on these components is as follows:

Q5. Find out through the internet and popular science articles whether animals other than man have self-consciousness.
Answer: Self-consciousness is the awareness of an animal towards its surroundings. Other than man the animals which show self-consciousness are dolphins, orangutans, gorillas, chimps, elephants, etc. Even dogs also show subtle consciousness.

Q6. List 10 modern-day animals and using the internet resources link them to a corresponding ancient fossil. Name both.
Answer: Some modern animals and fossils to which they can be linked are as follows:

Q7. Practice drawing various animals and plants.
Answer: With the help of your teachers try drawing various plants and animals. While drawing, you can draw comparisons between different structures of animals and plants.
Note- The answer to this question varies according to the students.

Q8. Describe one example of adaptive radiation.
Answer: Adaptive radiation refers to the process in which the individuals belonging to a rapidly diversifying group, diverge from their lineage to form new species. Adaptive radiation works on the theory of natural selection. One example of adaptive radiation is in Darwin's finches of Galapagos island. These finches were formed from a single diversifying species that came to this geographical region accidentally. The new species diversified and got adapted to the conditions present in this habitat. The different finches developed different eating habits and accordingly developed different beak structures. This further led to their evolution through adaptive radiation.

Q9. Can we call human evolution adaptive radiation?
Answer: No, human evolution cannot be called adaptive radiation because, in adaptive radiation, a single species diversifies into new different species, however, in the case of human evolution, the gradual evolution of a single species occurred with time.

Q10. 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.
Answer: The evolution of horses started during the Eocene period with eohippus, Oligocene period (mesohippus), Miocene period (merychippus), Pliocene period (pliohippus), and Pleistocene period (Eqqus). Eqqus is the modern horse.
The evolutionary changes were seen in a modern horse in comparison to eohippus:
-Their body side increased.
-Elongation of head and neck region.
-Increased in the length of limbs and feet.
-Gradual reduction of lateral digits.
-Enlargement of the third functional toe.
-Back strengthen.

Evolution Important Questions

Q1. What are the main theories of evolution that explain the origin of life?
Answer: The main theories include the primordial soup theory, which suggests life began in a warm, nutrient-rich ocean, and the extraterrestrial theory, which proposes life came from meteorites. Another idea is the hydrothermal vent theory, where life started near underwater volcanoes. Each theory explores how the first simple organisms emerged on Earth.

Q2. How does natural selection drive the process of evolution in different species?
Answer: Natural selection occurs when organisms with traits better suited to their environment survive and reproduce more successfully. For example, faster animals may escape predators, passing on their speed to offspring. Over time, these traits become more common in the population, leading to gradual changes in the species. This process helps create diverse life forms.

Q3. What role do mutations play in the evolution of organisms?
Answer: Mutations are random changes in an organism's DNA. They can introduce new traits, some of which may be helpful for survival. For example, a mutation could make a plant resistant to disease. If beneficial, these traits can spread through a population over generations, contributing to evolution and the development of new species.

Q4. How does genetic drift affect small populations and their evolution?
Answer: Genetic drift is a random change in the frequency of traits in a small population. It can lead to the loss of genetic diversity, as some traits may disappear entirely. This randomness can cause certain traits to become more common or rare by chance, influencing how species evolve, especially in isolated or small groups.

Q5. What is biodiversity, and why is it important for the survival of life on Earth?
Answer: Biodiversity refers to the variety of life forms in an ecosystem, including different species, genetic variations, and ecosystems. It is vital for the health of our planet because diverse ecosystems are more resilient and can adapt to changes. High biodiversity also provides resources like food, medicine, and clean air, supporting human well-being and survival.

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