NCERT Biology 12 Evolution chapter 7 – Exercise

Biology 12 Evolution chapter 7 – Exercise

Q 1. Explain antibiotic resistance observed in bacteria in light of Darwinian selection theory.
Ans 1. When a bacterial population encounters a particular antibiotic, those sensitive to it die. One or few bacteria having mutations which make them resistant to antibiotic, survive. Such resistant bacteria multiply quickly as the competing bacteria have died. Soon, the resistance-providing genes become widespread and entire bacterial population become resistant.
Q 2. Find out from newspapers and popular science articles any new fossil discoveries or controversial about evolution.
Ans 2. Fossils of dinosaurs have been unearthed to reveal evolution of reptiles in Jurassic period and further evolution of animals. i.e, bird and mammals. Recently, fossils of shark-toothed reptiles from Sahara Desert have been discovered. Also, fossil of flying bird with teeth in the jaws has been discovered. The latter reveals controversy about evolution.
Q 3. Attempt giving a clear definition of the term species.
Ans 3. Species are made up of populations of similar individuals differing from other species, which breed mostly among themselves (and rarely with other species), are reasonably stable ad yet are sufficiently flexible and plastic that they tend to change in the courses of many generations.
Q 4. Try ot trace the various components of human evolution (hint: brain size and function, skeletal structure, dietary preference etc.).

Ans 4. The order Primates, to which the humans belong, also includes the lemurs, Lorises, tarsiers, monkey and apes. Apes, monkeys and human are together called anthropoids. Humans are closer in phylogeny to the apes, which in turn, are closer to the old world monkeys than to the new world monkeys. The figure show the position of humans among the primates.

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Q 5. Find out through internet and population science articles whether animals other than man has self-consciousness.
Ans 5. Yes, animals other than man has self-consciousness but each animal has different level of consciousness. And recent studies gibbons are the nearest to human in this respect. Apes and orangutans came next. Among domestic animals, dog and other members of candidate family show subtle self-consciousness.

Q 6. List 10 modern day animals and form internet link them to corresponding ancient fossil. name both.

Ans 6. Modern-day animals                Ancient fossil

  1. Modern horse (equus)             (Down Horse) Eohippus
  2. Monkeys, apes and man         Tarseirs
  3. Man (homo sapiens)                Ramapithecus
  4. Camel (Camelus)                     Protylopus
  5. Modern elephant (elephas)      Moerithers
Q 7. Practice drawing various animals and plants.
Ans 7. You should practice it by yourself, Some animals and some plants.
Q 8. Describe one example of adaptive radiation.

Ans 8. The evolutionary process which produces new species diverged from a single ancestral from and adapted to new invaded habitats and to modes of life necessary there is known as adaptive radiation or divergent evolution.For example, revealing adaptive radiation, is based on locomotion in mammals a variety of mammals such as cheetah, mole, elephant, squirrel, sloth, seal, bat, flying squirrel.

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Q 9. Can we call human evolution as adaptive radiation?
Ans 9.  No.
Q 10. Using various resources such as your library or the internet and discussing with your teacher, trace the evolutionary stages of any one animal say horse.
Ans 10. Evolution of horse started with Eohippus, the dawn horse, about 6 crore years back in the Eocene. This horse was about the size of a fox terrier2, only 28 cm. high at the shoulders. It had short head and neck. It has four functional toes (2-5) and a splint of the first on each forefoot and three functional toes (2-4) and splints of the first and fifth on each hindfoot. Its molars were short-crowed and adapted for grinding.

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