We have compleed the NCERT/CBSE Solutions chapter-wise for Class 12 Biology Chapter 7 Evolution with Answers by expert subject teacher for latest syllabus and examination. Prepare effectively for the exam taking the help of the Class 12 Biology NCERT Solutions PDF free of cost from here. Students also can take a free NCERT Solutions of Evolution. Each question has right answer Solved by Expert Teacher. Download the Biology NCERT Solutions with Answers for Class 12 Biology Pdf and prepare to help students understand the concept very well.
NCERT Solutions for Class 12 Biology
Page No. 142
Q1. Explain antibiotic resistance observed in bacteria in light of Darwinian selection theory.
Answer: According to the Darwinian selection theory.
When the bacteria are grown in culture that have a certain antibiotic, most of the bacteria are killed but some of them develop a mutation which provides resistance against the antibiotic . With time the bacterial population having antibiotic resistance will increase and outgrow the population of the non-resistant bacteria. Thus a new species that has antibiotic resistance will be selected against the original one.
Q2. Find out from newspapers and popular science articles any new fossil discoveries or controversies about evolution.
Answer: Chimps are more evolved than humans (The Times of India): Chimpanzees are more evolved than humans, a study suggests. 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 and the greatest impact on our ape cousins.The researchers’ 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-selected genes than chimps.
Q3. Attempt giving a clear definition of the term species.
Answer: Species is a group or population of individuals having the potential to interbreed and produce sustainable and fertile offsprings.
Q4. Try to trace the various components of human evolution (Hint : Brain size and function, skeletal structure, dietary preference, etc.).
Answer: Human evolution shows the following trends:
A. Brain size: It increased gradually along with evolution. The brain capacity of Australopithecus africanus – 500 cc, Homo habilis – 700 cc, Homo eredus – 800 – 1300 cc, Homo sapiens sapiens – 1450 cc.
- Ramapithecus had jaws and teeth like humans (small canines and large molars), prognathous face, and walked on legs
- Australopithecus africanus had erect posture, human-like teeth, was without chin, with brow ridges, and had a prognathous face.
- Homo habilis walked nearly erect, had human-like teeth, with brow ridges face was slightly prognathous.
- Homo erectus had an erect posture, prognathous face, with projecting brow ridges, small canines, and large molar teeth and had a small chin.
- Homo sapiens had four curves in the vertebral column, orthognathous face (without projecting jaw), forehead broad, chin well developed, walked on the sole.
Q5. Find out through internet and popular science articles whether animals other than man has self-consciousness.
Answer: There are many animals other than humans, which have self consciousness. An example of an animal being self conscious is dolphins. They are highly intelligent. They have a sense of self and they also recognize others among themselves and others, They communicate with each other by whistles, tail-slapping, and other body movements. Not only dolphins, there are certain other animals such as crow, parrot, chimpanzee, gorilla, orangutan, etc., which exhibit self-consciousness.
Q6. List 10 modern-day animals and using the internet resources link it to a corresponding ancient fossil. Name both.
Q7. Practise drawing various animals and plants.
Answer: Ask your teachers and parents to suggest the names of plants and animals and practice drawing them. You can also take help from your book to find the names of plants and animals.
Q8. Describe one example of adaptive radiation.
Answer: 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.
Q9. Can we call human evolution as adaptive radiation?
Answer: No, human evolution cannot be called adaptive radiation because adaptive radiation is an evolutionary process that produces new species from a single, rapidly diversifying lineage, which is not the case with human evolution.
Q10. 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: 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:
- 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 developmen
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