Class 12 Biology Chapter 7 Evolution

Class 12 Biology Chapter 7 Evolution The answer to each chapter is provided in the list so that you can easily browse through different chapters Assam Board HS 2nd Year Biology Chapter 7 Evolution Question Answer.

Class 12 Biology Chapter 7 Evolution

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Also, you can read the SCERT book online in these sections Solutions by Expert Teachers as per SCERT (CBSE) Book guidelines. These solutions are part of SCERT All Subject Solutions. Here we have given Assam Board Class 12 Biology Chapter 7 Evolution Solutions for All Subjects, You can practice these here.


Chapter – 7


Very Short Answer Type Questions

Q.1. When does the earth originated? 

Ans : 600 million years ago. 

Q.2. What do you mean by ‘theory of spontaneous generation or abiogenesis? 

Ans : Aristotle and others believed that life originated spontaneously from inanimate objects and this is called the theory of spontaneous origin. 

Q.3. Who propounded the ‘theory of biogenesis’? 

Ans : Louis Pasteur. 

Q.4. What is protovirus? 

Ans : Primordial stage of evolution of virus. 

Q.5. What were the raw materials in Miller’s experiment?

Ans : CH₄, NH₃, and H₂,. 

Q.6. What were the earliest living beings? 

Ans : Bacteria and bacteria like organisms.

Q.7. Who wrote the book ‘origin of species’? 

Ans : Darwin.

Q.8. What is the term given to describe evolutionary history of organism? 

Ans : Phylogeny. 

Q.9. What is paleontology? 

Ans : The study of fossil to trace the history of evolution.

Q.10. Who proposed the theory of inheritance of acquired characters? 

Ans : Lamark. 

Q.11. What do yo mean by era? 

Ans : During the formation of the earth layers after layers of sedimentary rock had been deposited over the earth crust formed by igneous rock. There sedimentary layers of rocks have been divided into five distinct stratifications. The time taken for formation of each strata is called an era. 

Q.12.· How can you determine the age of a living tree? 

Ans : Using radioactive carbon or by making cross section of the main stem at the base and then by counting the annual rings. 

Q.13. How can you determine the age of a fossil? 

Ans : The sedimentary rock in which the fossil is discovered is tested for the percentage radioactive uranium and lead. 

Q.14. Define connecting link by giving example. 

Ans : The living organisms having the characters of two different taxonomic categories are called connecting links eg. Protopterus between the bony fish and amphibians, Duck bill platypus is the connecting link between mammals and reptiles. 

Q.15. What is atavism? 

Ans : It is reappearance or refunctioning of some ancestral organs which have either completely disappeared or are present as vestigial organs. eg. Birth of a human body with a small tail. 

Q.16. Give the alternative term of biogenetic law and define what it is. 

Ans : The alternative term of biogenetic law is biogenesis. This law states that life arises from pre existing life only. The idea was given by Fransisco Redi (1668).

Q.17. What do you meant by discontinuous distribution? 

Ans : When descendants of a common ancestor inhabit different geographical areas and differ from each other it is called discontinuous distribution. 

Q.18. What is gene pool? 

Ans : Total number of different genes present in all the individuals of a population is called gene pool. 

Q.19. When does a species becomes founders to cause founder effects? 

Ans : A species becomes a founder when it undergoes the variation process. 

(B). Fill Up The Blanks : 

Q.1. ___ and ___ tried to create an atmosphere in the laboratory which might have been existed in the primitive earth. 

Ans : Stanley Miller and Harold Urey. 

Q.2. Polymerization of amino acid results in the formation of _____ molecules. 

Ans : Protein. 

Q.3. The nictitating membrane or the third eyelid present at the inner corner of human eye is also a _____ organ. 

Ans : Vestigial organ. 

Q.4. ____ means the origin and development of new living organisms, both plants and animals, on the surface of the earth as a result of slow but continuous change. 

Ans : Evolution. 

Q.5. _____ provide the missing links in the evolution of the present day flora and fauna. 

Ans : Living fossil. 

Q.6. In plants, the thorn and tendrils of ___ and ____ represent homology. 

Ans : Duranta and Passion flower. 

Q.7. _____ is the example of adaptive radiation. 

Ans : Finches.

Q.8. Continuous _____ of an organ leads to its reduced efficiency and size and ultimately it disappears. 

Ans : Disuse .

Q.9. ____ brought forth the idea of mutation.

Ans : De vries.

Q.10. ____ and _____ one the two key concepts Darwinian theory of Evolution. 

Ans : Survival of the fittest, Natural selection. 

Q.11. Ontogeny ___ phylogeny.

Ans : Recapitulate.

Q.12. ____ is a connecting link between cartilaginous and bony fishes. 

Ans : Protopterus.

Q.13. Genetic drift causes change in gene frequency of_____

Ans : alleles.

Q.14. Atmosphere of the primitive was highly ____ while that of the present earth is highly _____ 

Ans : Hot, (gaseous), Cool (solid). 

(C). Select The True And False: 

Q.1. Life first originated on land surface. 

Ans : False. 

Q.2. Fossils do not form the evidence of evolution. 

Ans : False. 

Q.3. The most convincing morphological evidence of evolution is provided by the vestigial organ. 

Ans : True. 

Q.4. Lamarck wrote the book ‘Philosophic Zoologique’ in 1809. 

Ans : True. 

Q.5. Interspecific struggle occurs among individuals of same species living together. 

Ans : False.

Q.6. Hugo de Vries was a Dutch botanist who coined the word mutation in 1901. 

Ans : True. 

Q.7. Homologous organs are structurally and ontogenetically similar due to common ancestry but have varied function.

Ans : False. 

Q.8. Vermiform appendix is not a vestigial organ. 

Ans : False. 

Q.9. From the protocells or provirus type of particles probably prokaryotic Monera like cells evolved in which organised nucleus was absent. 

Ans : False. 

Q.10. A. J. Oparin and JBS Haldone advocated the theory of chemical evolution of the origin of life.” 

Ans : True. 

Q.11. Atmosphere of earth became oxidising with the of cyanobacteria. 

Ans : False.

Q.12. Fins and flippers are homologous organs. 

Ans : True.

Q.13. Sickle cell anaemia is of selective advantage in malaria prone area. 

Ans : True.

Q.14. Amphibians have two chambered heart. 

Ans : False.

II. Question for 2 Mark : 

Short type Questions : 

Q.1. What do you mean by coacervates? 

Ans : In the ocean of the primordial earth there originated large molecules such as polysaccharides lipids, proteins, nucleic acids etc. There macromolecules combined in a complex situation to form a cell like structure which in course of further evolution gave rise to primitive cells. These cell-like substances are called coacervates. 

Q.2. ‘Archaeopteryx is considered as connecting link between reptiles and birds’. Explain. 

Ans : It happens that in the stages of evolution of two or more organisms no continuity is found and a result their evolutionary history remain inconclusive. But by chance if some intermediate form of each organism is discovered which give clue to the evolution of such organisms. These forms are called transitional forms. Archaeopteryx is one such form which shows evolutionary link between birds and reptile. Because it shows the certain characters of both. 

Q.3. How do Darwin’s finches illustrate adaptive radiation. 

Ans : All living organisms of today are descendent of some common ancestors. They have evolved differently due to the influence of climate, competition, reproductive isolation and so on. They have adapted according to climate, food, geographic location etc. The various finches species which Darwin had seen in Galapagos island were although different from the mainland all had originated from the main land stock, but evolved according to the local situation in the island. 

Q.4. What is ‘Theory of special Creation’? Describe briefly. 

Ans : People from the ancient time were curious about the origin of creatures. In the ancient time being unaware of scientific enquiry thought that all creatures have originated as they look like and had not gone through any change. This theory is called the Theory of Eternity. This theory is not much different from the theory of special creation. According to it God has created every species and these can never undergo any change. 

Q.5. What is the most widely accepted theory of origin of life who proposed it? 

Ans : Theory of Biogenesis. It means life originates from life. It over through the theory of special creation.or the theory of eternity. Louis Pasteur had proposed this theory.

Q.6. What are Fossils? 

Ans : Fossils are the remains of the past forms of life in parts or whole in which the organic molecules have been replaced by inorganic molecules rendering these indecomposable. Highly compressed form or their cast are found trapped between sedimentary layers of the earth they provide strong evidence of evolution. 

Q.7. What is geological time scale? 

Ans : The crust of the earth has been formed by deposition of sedimentary rocks formed layers after layers. These layers are called stratification. The geological time period at which these stratification have bcen formed has been determined. These time extends to millions of years in the past. For convenience of determining the age of these stratifications some time periods such as era, period, epoch have been determined. These are called geological time scale. 

Q.8. State any two vertebrate body parts that are homologous to human fore limbs. 

Ans : Wings of birds and forelimb of monkey. 

Q.9. ‘Adaptive ability is inherited’. Justify 

Ans : If separated from the main stock and migrate to places other than of its earlier one the organism try to adapt there. It may not be possible to adapt easily as the climate and the food may be different and the type of competition may also be different. Those who survive in the new condition after fully adapting to the changed situation may pass on the adapted character to their offsprings. If offsprings show these adaptive character then it means that the adaptive ability is inherited. 

Q.10. What is mutation? 

Ans : It means sudden change caused by change of structure of gene or chromosome various causes may be attributed to this. This is unlike slow and continuous change according to Darwin’s theory of evolution. This sudden change is also causes evolution if the change is transmitted to offsprings and is inherited. Generally most mutations are not stable. 

Q.11. Explain the term progressive and retrogressive evolution by giving suitable examples? 

Ans : Progressive evolution : In which the size of the organism increases eg. height of horse increases from the …. group. 

Retrogressive evolution : The evolution in which general degeneration and loss of organ takes place, is called retrogressive evolution. For eg. the number of functional digit reduced from 4 to 1 is known as retrogrennu evolution.

Q.12. What is spontaneous generation theory? Name the scientist who disproved this concept.

Ans : The spontaneous generation theory states that life originated biogenetically from non living decaying and rotting matter like straw mud etc. by spontaneous generation about 3.5 million years ago. This is proposed by Von Helmont (1577-1644).  

Q.13. Define biological species. 

Ans : The groups of organisms which are morphologically similar and can reproduce among themselves is called a biological species.

Q.14. Explain the term biogenesis? 

Ans : Biogenesis means life arises from pre existing life only (omne vivum ex vivo). 

Q.15. Mention the concept about mechanisms of biological evolution/speciation according to Devries. 

Ans : According to the mutation theory given by De Vries, evolution is a discontinuous and jerky process in which there is a jump from one species to another species so that new species arises from pre existing species in a single generation (macrogenesis). 

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