Free NCERT Solutions for Class 12 Biology Chapter 7 : Evolution Free PDF Download

Question 1:Explain antibiotic resistance observed in bacteria in light of Darwinian selection theory.

Ans:
According to Darwin, environment selects organisms with favorable variations and these organisms are able to survive. When a bacterial population encounters a particular antibiotic, those sensitive to it die. But some bacteria that have favorable mutations become resistant to the antibiotic. Such resistant bacteria survive and multiply quickly as the competing bacteria have died. Thus, their numbers increase. Additionally they may also pass on the genes imparting resistance to other members of the population. Therefore, antibiotic resistance become widespread and entire bacterial population becomes resistant.

Question 2: Find out from newspapers and popular science articles any few fossil discoveries or
controversies about evolution.

Ans:
Chimps are more evolved that humans (The Times of India):
A study suggests that chimpanzees are more evolved than humans. There is no doubt that humans are the more advanced species. But a comparison of 14,000 human and chimpanzee genes shows the forces of natural selection have had the greatest impact on our ape cousins. The researcher’s discovery challenges the common assumption that our large brains and high intelligence were the gifts of natural selection. Humans and chimps followed different evolutionary paths from a common ape ancestor about 5 million years ago. Both underwent changes as the fittest survived to pass their genes on to future generations. But the US study shows that humans possess a ‘substantially smaller’ number of positively-elected genes than chimps.

Question 3: 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 and fertile young ones.

Question 4: Try to trace the various components of human evolution (hint: brain size and function, skeletal structure, dietary preference, etc.)

Ans:
The various components of human evolution are:

1. Human-Brain Volume
2. Skeletal structure
3. Posture
4. Dietary preference
5. Behavioral features

Question 5: Find out through internet and popular science articles whether animals other than man has self-consciousness.

Ans:
Self-awareness is the capacity for introspection and the ability to recognize oneself as an individual separate from the environment and other individuals. It is a measure of intelligence in the animal kingdom and yet most living species do not possess it. Of the many animals tested few animals other than humans have shown this capacity. They are orangutans, chimpanzees, gorillas, bottlenose dolphins, elephants, orcas, bonobos, Rhesus macaques and European Magpies.. Among domestic animals, dog and other members of Canidae family show subtle self consciousness.

Question 6: List 10 modern-day animals and using the” internet resources link it to a corresponding ancient fossil. Name both

Serial Number	Animal	Fossil
1	Man	Ramapithecus
2	Horse	Eohippus
3	Dog	Leptocyon
4	Camel	Protylopus
5	Elephant	Moerithers
6	Whale	Protocetus
7	Fish	Arandaspis
8	Tetrapods	Icthyostega
9	Bat	Archaeonycteris
10	Giraffe	Palaeotragus

Question 7: Practice drawing various animals and plants.

Ans:
Select few plants and animals that you find relatively easy to draw and label and practice to make these diagrams perfect. You can take suggestions from teachers, parents or even look up in the internet for simple animal and plant figures

Question 8: Describe one example of adaptive radiation.

Ans:
Adaptive radiation is when members of a single group or lineage evolutionarily diverge into a variety of different forms. These forms are dictated by natural selection and the use of habitats or resources. Darwin’s finches of the Galapagos islands had common ancestors but now have different types of modified beaks according to their food habits. These finches have developed different eating habits and different types of beaks to suit their feeding habits. The insectivorous, blood sucking, and other species of finches with varied dietary habits have evolved from a single seed eating finch ancestor.

Question 9: Can we call human evolution as adaptive radiation?

Ans:
No, human evolution cannot be called adaptive radiation. Adaptive radiation ca be defined as evolutionary process that produces new species from a single common ancestor. In case of human evolution, while we share a common ancestor we have undergone gradual but progressive modification in our body structure, eating habits, etc. Human evolution does not involve diversifying and radiating into different species which is characteristic of adaptive radiation.

Question 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.

Ans:
The evolution of horse started with Eohippus during Eocene period. It involved the following evolutionary stages.
Eohippus – Mesohippus – Merychippus – Pliohippus – Equus.
Evolutionary trend:
(i) Increase in body size.
(ii) Elongation of neck.
(iii) Lengthening of limbs.
(iv) Enlargement of third digit.
(v) Gradual reduction of lateral digits
(vi) Increase in structural complexity of teeth for feeding on grass
(vii) Strengthening of back
(viii) Development of brain and sensory organs