NCERT Solutions for Class 12 Biology Chapter 7 - Evolution

Aakash NCERT Solutions for Chapter 7 of Class 12 Biology talks about the origin of life and the evolution of life forms or biodiversity on planet earth in a simple and easy language for the ease of students. Students will also learn about the mechanisms that cause evolution in nature.

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.

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