NCERT Solutions for Class 12 Biology Chapter 7 – Evolution – FREE PDF Download
NCERT Solutions for Class 12 Biology provided by CoolGyan are available online in PDF form to help students with their exam preparation. NCERT Solutions for Class 12 Biology Chapter 7 – Evolution solved by Expert Teachers as per NCERT (CBSE) textbook guidelines. All Chapter 7 – Evolution Exercises Questions with Solutions to help you to revise complete Syllabus and boost your score more in examinations.
Revision Notes Class 12 Biology
NCERT Solutions Class 12 Biology
Answers of Biology NCERT Chapter 7 – Evolution
Solution:
As per Darwin’s observation, the environment selects entities with favorable variations, these entities are capable of surviving. When a population of bacteria is attacked by a specific antibiotic, sensitive bacteria tend to perish, while other bacteria possessing favorable mutations turn resistant even in the presence of antibiotics and these survive, thriving, and rapidly multiplying as the other competing bacteria have died out. Thus, the number of bacteria is on the rise. In addition to this, they mass transfer these genes, resistant to bacteria, to other bacteria. Consequently, bacteria resistant to antibiotic widely spread across making the entire population to become antibiotic-resistant.
Solution:
Fossil discover of dinosaurs had some interesting revelations. It conveys about the evolution of reptiles in the Jurrasic era. This revelation gave rise to the discovery of evolution of other animals such as mammals and birds. Two unfamiliar fossils recently unearthed in China exploded a controversy over the evolution of birds. One such genus of primitive birds were Confuciusornis. These were crow-sized and thrived during the Creataceous era in China.
Solution:
Species is a group or population of individuals having the potential to interbreed and produce sustainable and fertile offsprings.
Solution:
Human evolution can be based on different components, namely:
- Size of the brain
- Body posture
- Food habits/dietary preferences
- Characteristics/features
The following table depicts the same:
| Human evolution stages | Size of the brain | Body posture | Food preferences | Features |
| Dryopithecus africans | – | Knuckle-walking, ape-like walk | Leaves and tender fruits | Equal sized arms and legs, large canines |
| Ramapethicus | – | Semi-erect posture | Nuts and seeds | Large molars, small canines |
| Australopithecus africanus | 450 cm3 | Completely erect posture, around 1.05m tall | Fruits (herbivorous) | Inhabited trees, stone weapons for hunting, incisors &canines are smaller |
| Homo habilis | 735cm3 | Completely erect posture, around 1.5m tall | Carnivorous | Small canines, first to make tools |
| Homo erectus | 800 cm3 to 1100 cm3 | Completely erect posture, around 1.5m – 1.8m tall | Omnivorous | For hunting used bone and stone tools |
| Homo neanderthalnsis | 1300 cm3 to 1600 cm3 | Completely erect posture, around 1.5m – 1.66m tall | Omnivorous | Inhabited caves, buried their deads, hid their bodies for protection |
| Homo sapiens fossils | 1650 cm3 | Completely erect posture, 1.8m | Omnivorous | Possessed strong jaw with teeth closely placed, inhabited caves, made carvings and paintings in caves. Developed a culture and were referred to as the first modern men |
| Homo sapiens sapiens | 1200 cm3to 1600 cm3 | Completely erect posture, around 1.5m – 1.8m tall | Omnivorous | Possess high intelligence quotient, referred to as the living modern men, Developed language, speech, culture, art, language. Cultivation of crops and domestication of animals observed. |
5. Find out through internet and popular science articles whether animals other than man has self-consciousness.
Solution:
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 oneself amongst others. They whistle, tail-slap and exhibit body movements to communicate with each other. Some other animals that exhibit self-consciousness are parrot, crow, gorilla, orangutan, chimpanzee etc.
6. List 10 modern-day animals and using the internet resources link it to a corresponding ancient fossil. Name both.
Solution:
The list is as follows:
| Name of the animal | Name of the fossil |
| Horse | Eohippus |
| Man | Ramapithecus |
| Elephant | Moerithers |
| Whale | Protocetus |
| Fish | Arandaspis |
| Giraffe | Palaeotragus |
| Dog | Leptocyon |
| Camel | Protylopus |
| Tetrapods | Icthyospega |
| Bat | Archaeonycteris |
7. Practise drawing various animals and plants.
Solution:
Take cues from seniors, teachers for names of different plants and animals. Go through different science books, magazines, encyclopedia to get an idea of different plant and animal species. To get further more details, 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 up the details.
8. Describe one example of adaptive radiation.
Solution:
When members of a single assemblage or lineage, deviate evolutionarily into a range of different forms, it is adaptive radiation. These are the forms that are governed by natural selection and the usage of resources or habitats. The Darwin’s finches of the Galapagos islands had shared or common ancestors whereas now, we have different sorts of modified beaks based on their food preferences. In order to suit their feeding habits, these finches have adopted different eating preferences and varied beak types. From a single seed-eating finch ancestor, different finch-species with varied dietary habits have evolved such as the blood-sucking, insectivorous entities etc.
9. Can we call human evolution as adaptive radiation?
Solution:
No, human evolution can be referred to adaptive radiation as adaptive radiation is an evolutionary process which gives rise to new species from a single common ancestor but in the case of human evolution, although we share a common ancestor, we humans have undergone an eventual but progressive alteration in the eating preferences, structure of body etc. The evolution of human does not include diversification and radiating into different species which in fact is a distinguishing feature of adaptive radiation.
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:
During the Eocene era, the evolution of horse began with Eohippus and involved the following evolutionary phases:
Eohippus → Mesohippus →Merychippus → Pliohippus → Equus
Evolutionary traits observed were as follows:
- Increase in the size of body
- Elongated neck
- Expansion of the third digit
- Enhanced structural composition of the teeth to feed on grass
- Broadening of the limbs
- Eventual decrease in the lateral digits
- Strengthened back
- Sense organs and brain development