12 NCERT BIOLOGY MOST IMPORTANT QUESTIONS

Q1. Strontium-90 accumulates in the 1) Bone 2) RBCs 3) Brain 4) WBCs Solution Strontium-90 accumulates in the bone and may cause bone cancer. Q2. The figure below shows the relative contribution of four greenhouse gases to global warming.       (i) Identify the gases A and C. (ii) Why are these four gases called greenhouse gases? Solution (i) A recent survey has revealed 60%, 20%, 14% and 6% of warming effect of CO 2 , CH 4 , CFCs and N 2 O. So, according to the figure, Gas A is carbon dioxide (C0 2 ) and Gas C is chlorofluorocarbon (CFC). (ii) These gases in the atmosphere are transparent to sunlight but can trap heat and keep the Earth’s surface warm. They are responsible for the greenhouse effect and are therefore ca...

Q1. While going to Nainital during summer vacations, Amitabh saw a board indicating the direction to Jim Corbett National Park. He asked his uncle, who happened to be a forest officer, about national parks. He explained that national parks are maintained by government solely for the welfare of entire wild life in it. Read the above passage and answer the following questions: (a) How is wild life maintained in a national park? (b) Name two other national parks. (c) What value is displayed by Amitabh’s uncle? Solution (a) In a national park, some land is allowed for wildlife conservations and habitat manipulation is not permitted in this zone. Cultivation and grazing is also not allowed. (b) Two national parks are Bandipur National Park and Hazaribagh National park. (c) Amitabh’s uncle had a sound knowledge of wildlife conservation that he provided to his nephew, which is important for our life. Q2. What is the function of National Bur...

Q1. The common nitrogen-fixer in paddy fields is 1) Rhizobium 2) Frankia 3) Azospirillum 4) Oscillatoria Solution Azospirillum is the common nitrogen-fixer in paddy fields. Q2. The pyramid of energy in an aquatic ecosystem is 1) None of the above 2) Always inverted 3) Always upright 4) Bell-shaped Solution The pyramid of energy in an aquatic ecosystem is always upright because at each transfer about 80-90% of the energy available at a lower trophic level is used up to overcome its entropy and to perform metabolic activities. Only 10% of the energy is available to the next trophic level. Q...