NCERT Solutions for Class 12 Biology Chapter 7
Evolution Class 12
Chapter 7 Evolution Exercise Solutions
Exercise : Solutions of Questions on Page Number : 142
Explain antibiotic resistance observed in bacteria in light of Darwinian selection theory.
Find out from newspapers and popular science articles any new fossil discoveries or controversies about evolution.
Attempt giving a clear definition of the term species
Try to trace the various components of human evolution (hint: brain size and function, skeletal structure, dietary preference, etc.)
The various components of human evolution are as follows.
(i) Brain capacity
(ii) Posture
iii. Food / dietary preference and other important features
|
Name |
Brain capacity |
Posture |
Food |
Features |
1. |
Dryopithecus africans |
--- |
Knuckle walker, walked similar to gorillas and chimpanzees (was more ape-like) |
Soft fruit and leaves |
Canines large, arms and legs are of equal size |
2. |
Ramapithecus |
--- |
Semi-erect (more man-like) |
Seeds, nuts |
Canines were small while molars were large. |
3. |
Australopithecus africanus |
450 cm3 |
Full erect posture, height (1.05 m) |
Herbivorous (ate fruits) |
Hunted with stone weapons, lived at trees, canines and incisors were small |
4. |
Homo habilis |
735cm3 |
Fully erect posture, height (1.5 m) |
Carnivorous |
Canines were small. They were first tool makers. |
5. |
Homo erectus |
800-1100 cm3 |
Fully erect posture, height(1.5-1.8 m ) |
Omnivorous |
They used stone and bone tools for hunting games. |
6. |
Homo neanderthalnsis |
1300- 1600 cm3 |
Fully erect posture, height (1.5-1.66 m) |
Omnivorous |
Cave dwellers, used hides to protect their bodies, and buried their dead |
7. |
Homo sapiens fossilis |
1650 cm3 |
Fully erect posture with height (1.8 m) |
Omnivorous |
They had strong jaw with teeth close together. They were cave dwellers, made paintings and carvings in the caves. They developed a culture and were called first modern men. |
8. |
Homo sapiens sapiens |
1200- 1600 cm3 |
Fully erect posture, height (1.5-1.8 m ) |
Omnivorous |
They are the living modern men, with high intelligence. They developed art, culture, language, |
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speech, etc. They cultivated crops and domesticated animals. |
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Find out through internet and popular science articles whether animals other than man have self- consciousness.
List 10 modern-day animals and using the internet resources link it to a corresponding ancient fossil. Name both.
The modern day animals and their ancient fossils are listed in the following table.
Animal |
Fossil |
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1. |
Man |
Ramapithecus |
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2. |
Horse |
Eohippus |
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3. |
Dog |
Leptocyon |
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4. |
Camel |
Protylopus |
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5. |
Elephant |
Moerithers |
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6. |
Whale |
Protocetus |
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7. |
Fish |
Arandaspis |
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8. |
Tetrapods |
Icthyostega |
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9. |
Bat |
Archaeonycteris |
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10. |
Giraffe |
Palaeotragus |
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Practise drawing various animals and plants.
Describe one example of adaptive radiation.
Can we call human evolution as adaptive radiation?
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.
The evolution of horse started with Eohippus during Eocene period. It involved the following evolutionary stages.
(i) Gradual increase in body size
(ii) Elongation of head and neck region
(iii) Increase in the length of limbs and feet
(iv) Gradual reduction of lateral digits
(v) Enlargement of third functional toe
(vi) Strengthening of the back
(vii) Development of brain and sensory organs
(viii) Increase in the complexity of teeth for feeding on grass The evolution of horse is represented as
(i) Eohippus
It had a short head and neck. It had four functional toes and a splint of 1 and 5 on each hind limb and a splint of 1 and 3 in each forelimb. The molars were short crowned that were adapted for grinding the plant diet.
(ii) Mesohippus
It was slightly taller than Eohippus. It had three toes in each foot.
(iii) Merychippus
It had the size of approximately 100 cm. Although it still had three toes in each foot, but it could run on one toe. The side toe did not touch the ground. The molars were adapted for chewing the grass.
(iv) Pliohippus
It resembled the modern horse and was around 108 cm tall. It had a single functional toe with splint of 2nd and 4th in each limb.
(v) Equus
Pliohippus gave rise to Equus or the modern horse with one toe in each foot. They have incisors for cutting grass and molars for grinding food.