NCERT Class 12 biology chapter 7 evolution solutions

NCERT Class 12 Biology chapter 7 evolution


Hello students today we are going to discuss about NCERT Solutions for Class 12 biology chapter 7 Evolution textbook solutions.  In this article we collected all the questions and answers of NCERT Biology Class 12 Chapter 7 Evolution with simple answers.

So before starting the questions and answers of NCERT solutions Class 12 Biology chapter 7 solutions just rewise it with the important points to remember ......

Important points to remember
  1. The origin of life on earth can be understood only against the background of origin of universe especially earth. Most scientists believe chemical evolution, i.e., formation of biomolecules preceded the appearance of the first cellular forms of life.
  2. The subsequent events as to what happened to the first form of life is a conjectured story based on Darwinian ideas of organic evolution by natural selection.
  3. Diversity of life forms on earth has been changing over millions of years. It is generally believed that variations in a population result in variable fitness. 
  4. Other phenomena like habitat fragmentation and genetic drift may accentuate these variations leading to appearance of new species and hence evolution. 
  5. Homology is accounted for by theidea of branching descent. Study of comparative anatomy, fossils and comparative biochemistry provides evidence for evolution. 
  6. Among the stories of evolution of individual species, the story of evolution of modern man is most interesting and appears to parallel evolution of human brain and language.



1. Explain antibiotic resistance observed in bacteria in light of Darwinian
selection theory.
Answer :
  1. Darwinian selection theory states that individuals with favourable variations are better adapted than individuals with less favourable variation. 
  2. It means that nature selects the individuals with useful variation as these individuals are better evolved to survive in the existing environment. 
  3. An example of such selection is antibiotic resistance in bacteria. When bacterial population was grown on an agar plate containing antibiotic penicillin, the colonies that were sensitive to penicillin died, whereas one or few bacterial colonies that were resistant to penicillin survived. 
  4. This is because these bacteria had undergone chance mutation, which resulted in the evolution of a gene that made them resistant to penicillin drug.
  5. Hence, the resistant bacteria multiplied quickly as compared to non-resistant (sensitive) bacteria, thereby increasing their number. 
  6. Hence, the advantage of an individual over other helps in the struggle for existence.



2. Find out from newspapers and popular science articles any new fossil
discoveries or controversies about evolution.
Answer : Fossils of dinosaurs were found that have revealed the evolution of reptiles in Jurassic period. Two unusual fossils recently found in China which brings the controversy over the evolution of birds. Confuciusornis lived during the Cretaceous period in China is the genus of the primitive bird.


3. Attempt giving a clear definition of the term species.
Answer : Species can be defined as a group of organisms, which have the capability to interbreed in order to produce fertile offspring and do not breed with members of other species.


5. Find out through internet and popular science articles whether animals
other than man has self-consciousness.
Answer : Self consciousness is defined as the awareness of oneself. Other than man there are some animals which are self-conscious. These include dolphins, elephants, chimpanzees, apes and monkeys. Self-consciousness in animals can be studied using the mirror test. When chimpanzees were exposed to the mirror for the first time they were threatened. However on repeated exposure they started looking into the mirror and grooming, picking their nose, making faces, etc.


6. List 10 modern-day animals and using the internet resources link it to
a corresponding ancient fossil. Name both.
Answer :
Human - Ramapithecus.
Elephant - Moerithers.
Gorilla - Dryopithecus.
Horse - Eohippus.
Bat - Archaeonycteris.
Fish - Arandaspis.
Octopus - Belemnite.
Dog - Leptocyon.


7. Practise drawing various animals and plants.
Answer :



8. Describe one example of adaptive radiation.
Answer:
  1. The process of evolution of different species in a given geographical area starting from a point and literally radiating to other areas of geography (habitats) is called adaptive radiation.
  2. Darwin’s finches represent one of the best examples of this phenomenon.
  3. Another example is Australian marsupials. A number of marsupials, each different from the other evolved from an ancestral stock, but all within the Australian island continent. When more than one adaptive radiation appeared to have occurred in an isolated geographical area (representing different habitats), one can call this convergent evolution. 
  4. Placental mammals in Australia also exhibit adaptive radiation in evolving into varieties of such placental mammals each of which appears to be ‘similar’ to a corresponding marsupial (e.g., Placental wolf and Tasmanian wolf-marsupial). 



9. Can we call human evolution as adaptive radiation?
Answer :
  1. No it cannot be calledadaptive radiation because adaptive radiation is an evolutionaryprocess that produces new species from a single, rapidly diversifying lineage, which is not the case withhuman evolution. 
  2. Human evolution is a gradual process that took place slowly in time.
  3. In biology, evolution is the change in the characteristics of a species over several generations and relies on the process of natural selection. 
  4. The theory of evolution is based on the idea that all species are related and gradually change over time.



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.
Answer : 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 evolution of horse
(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.