The VIDYANKER team has thoughtfully prepared the NCERT Solutions for Class 12 Biology Chapter 7, "EVOLUTION" These solutions are designed to help you tackle the NCERT textbook questions with ease. We recommend going through the chapter's theory before diving into the solutions for a deeper understanding. Feel free to share these NCERT Solutions for Class 12 Biology with others—learning is always better when shared!
Q1. Explain antibiotic, resistance observed in bacteria in light of Darwinian selection theory.
Ans: 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.
Q2. Find out from newspapers and popular science articles any new fossil discoveries or controversies about evolution
Ans: New fossil discoveries are as follows :
1. Recently, scientists have discovered some amber fly samples in El Sopalo cave, which is in Cantabria, Spain. According to the latest research study, appearing in scientific journal 'Current Biology', the specimens used nector, pollinating gymnosperm plants, 105 million years ago.
2. Research has recently been done in Japan that has revealed a very unusual new species of octocoral from a shallow coral reef in Okinawa, Japan. This new species can be regarded as "living fossil," and shows many relations with the rare blue coral.
3. The fossil found in the Bridger Formation in Wyoming is the first description of a new species, named Babibasiliscusalxiby the author, and may be the most primitive well-defined member of the lizard family Corytophanidae.
4. Neanderthals died out around 40,000 years ago but left their mark on the genes of present-day Eurasians to the tune of approximately one to three percent. After sequencing DNA from a 37-42,000 year old human mandible in Romania the researchers determined that six to nine percent of this individual's genome was comprised of Neanderthal DNA — more than any other sequenced modern human. A Neanderthal was in this person’s family tree as recently as four or six generations ago with large chunks of his chromosomes coming from that individual. This suggests that the first modern humans to enter Europe may have frequently interbred with Neanderthals.
Q3. Attempt giving a clear definition of the term species.
Ans: Species is population or group of individuals that have potential of interbreeding and are able to produce viable, fertile young ones but are reproductively isolated from members of other species.
Q4. Try to trace the various components of human evolution (hint: brain size and function, skeletal structure, dietary preference, etc.)
Ans:
| Name | Features |
| Dryopithecus | Ape like, canines large, arms and legs are of equal size, ate soft fruits and leaves |
| Ramapithecus | More man-like, canines were small while molars were large, walked more erect, ate seeds and nuts |
| Australopithecus | Man-like, canines and incisors were small, walked upright, hunted with stone weapons, ate fruits, brain capacities were between 400-600cc. |
| Homo habilis | First human like being, canines were small, first tool makers, did not ate meats, brain capacities were between 650-800cc. |
| Homo erectus | Used stone and bone tools for hunting games, ate meat, brain capacity 900cc. |
| Homo neanderthalnsis | Cave dwellers, used hides to protect their bodies, and buried their dead, brain capacity 1400cc. |
| Homo sapiens (Modern human) | Modern man with high intelligence, developed art, culture, language etc., cultivated crops and domesticated animals. |
Q5. Find out through internet and popular science articles whether animals other than man has self-consciousness.
Ans: Self-consciousness needs to be defined as the mental link or ones awareness of oneself as an individual or of one’s own being, actions, or thought. There are many other than humans, which have self-consciousness such as dolphins, crow, parrot, chimpanzee, gorilla, etc.
Q6; List 10 modern-day animals and using the internet resources link it to a corresponding ancient fossil. Name both.
Ans:
Animals | Fossils |
| Man | Homo Sapiens |
| Dog | Leptocyon |
| Chimpanzee | Dryopithecus |
| Elephant | Moerithers |
| Horse | Eohippus |
| Gorilla | Dryopithecus |
| Camel | Protylopus |
| Whale | Protocetus |
| Fish | Arandaspis |
| Octopus | Belemnite |
Q7. Practise drawing various animals and plants.
Ans: Draw variety of animals and plants from the chapter.
Q8.Describe one example of adaptive radiation.
Ans: Darwin's finches from the Galapagos Islands share common ancestors, but over time, their beaks have evolved into different shapes and sizes, each adapted to their specific food habits.
Q9. Can we call human evolution adaptive radiation?
Ans: Human evolution cannot be classified as adaptive radiation because adaptive radiation involves a single species diversifying into several distinct species. In contrast, human evolution represents the gradual development of a single species over time without branching into multiple different species.
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.
Ans: The evolutionary stages through which a horse passes are:
Eohippus: About 52 million years ago, during the Eocene period. It was somewhat the size of a fox at 0.4m, with a relatively short head and neck and springy back. It had 4 functional toes and splints of 1 and 5 on each hind limb and 1 and 3 in each forelimb.
Mesohippus: 40 million years ago, Mesohippus, living 40 million years ago during the Oligocene, was larger than Eohippus, about 0.6m. Its feet had three toes.
Merychippus: Flourishing during the Miocene period, the grazer Merychippus had grown to an approximate height of 1m. It still possessed three toes in each foot but could run on one toe, which was the middle toe with the other two toe not even touching the ground. The molars were adapted to copious grazing because of their special use in grass chewing.
Pliohippus: The first modern horse, Pilohippus, started coming into existence about the period of 12 million years ago known as Plioocene. It consisted of a single functional toe with splints of 2nd and 4th in each limb.
Equus: In this case, Pliohippus gave birth to the modern horse, Equus, which has one toe in each foot. There are incisors for cutting grass and molars for grinding food.
