NCERT Solutions for Class 12 Science Biology Chapter 7 – Evolution
Here are simplified, step-by-step explanations of NCERT Solutions for Class 12 Science Biology Chapter 7 on Evolution. These solutions have gained popularity among Class 12 Science students for Biology Evolution. They prove useful for swiftly completing homework assignments and preparing for exams. All questions and answers from the NCERT Book of Class 12 Science Biology Chapter 7 are available here at no cost. Page No 142: Question 1: Explain antibiotic resistance observed in bacteria in light of Darwinian selection theory. ANSWER: Darwinian selection theory states that individuals with favourable variations are better adapted than individuals with less favourable variation. It means that nature selects the individuals with useful variation as these individuals are better evolved to survive in the existing environment. 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. This is because these bacteria had undergone chance mutation, which resulted in the evolution of a gene that made them resistant to penicillin drug. Hence, the resistant bacteria multiplied quickly as compared to non-resistant (sensitive) bacteria, thereby increasing their number. Hence, the advantage of an individual over other helps in the struggle for existence. Page No 142: Question 2: Find out from newspapers and popular science articles any new fossil discoveries or controversies about evolution. ANSWER: Fossils of dinosaurs have revealed the evolution of reptiles in Jurassic period. As a result of this, evolution of other animals such as birds and mammals has also been discovered. However, two unusual fossils recently unearthed in China have ignited a controversy over the evolution of birds.Confuciusornis is one such genus of primitive birds that were crow sized and lived during the Creataceous period in China. Page No 142: Question 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. Page No 142: Question 4: Try to trace the various components of human evolution (hint: brain size and function, skeletal structure, dietary preference, etc.) ANSWER: The various components of human evolution are as follows. (i) Brain capacity (ii) Posture 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, speech, etc. They cultivated crops and domesticated animals. Page No 142: Question 5: Find out through internet and popular science articles whether animals other than man have 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. Page No 142: Question 6: List 10 modern-day animals and using the internet resources link it to a corresponding ancient fossil. Name both. ANSWER: The modern day animals and their ancient fossils are listed in the following table. 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 Page No 142: Question 7: 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. Page No 142: Question 8: Describe one example of adaptive radiation. ANSWER: Adaptive radiation is an evolutionary process that produces new species from a single, rapidly diversifying lineage. This process occurs due to natural selection. An example of adaptive radiation is Darwin finches, found in Galapagos Island. A large variety of finches is present in Galapagos Island that arose from a single species, which reached this land accidentally. As a result, many new species have evolved, diverged, and adapted to occupy new habitats. 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. Page No 142: Question 9: Can we call human evolution as adaptive radiation? ANSWER: No, human evolution cannot be called adaptive radiation. This is 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. Human evolution is a gradual process that took place slowly in time. It represents an example of anagenesis. Page No 142: Question 10: Using various …
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