Lesson Archives

  1. Page No 7: Question 1: Discuss the central problems of an economy. Answer: Every economy faces three central problems due to scarce availability of resources. This scarcity challenges the best possible usage of these available resources to fulfil the unlimited demands. The three central problems of an economy are as follows: What to produce and […]
  2. Page No 286: Question 1: What are the various constituents of domestic sewage? Discuss the effects of sewage discharge on a river. Answer: Domestic sewage is the waste originating from the kitchen, toilet, laundry, and other sources. It contains impurities such as suspended solid (sand, salt, clay), colloidal material (fecal matter, bacteria, plastic and cloth […]
  3. Page No 268: Question 1: Name the three important components of biodiversity. Answer: Biodiversity is the variety of living forms present in various ecosystems. It includes variability among life forms from all sources including land, air, and water. Three important components of biodiversity are: (a) Genetic diversity (b) Species diversity (c) Ecosystem diversity Question 2: How do ecologists […]
  4. Page No 256: Question 1: Fill in the blanks. (a) Plants are called as_________ because they fix carbon dioxide. (b) In an ecosystem dominated by trees, the pyramid (of numbers) is _________ type. (c) In aquatic ecosystems, the limiting factor for the productivity is _________. (d) Common detritivores in our ecosystem are_________. (e) The major reservoir of carbon on earth […]
  5. Page No 239: Question 1: How is diapause different from hibernation? Answer: Diapause is a stage of suspended development to cope with unfavourable conditions. Many species of Zooplankton and insects exhibit diapause to tide over adverse climatic conditions during their development. Hibernation or winter sleep is a resting stage where in animals escape winters (cold) […]
  6. Page No 215: Question 1: Crystals of Bt toxin produced by some bacteria do not kill the bacteria themselves because − (a) bacteria are resistant to the toxin (b) toxin is immature: (c) toxin is inactive: (d) bacteria encloses toxin in a special sac. Answer: toxin is inactive: In bacteria, the toxin is present in an inactive form, called […]
  7. Page No 205: Question 1: Can you list 10 recombinant proteins which are used in medical practice? Find out where they are used as therapeutics (use the internet). Answer: Recombinant proteins are obtained from the recombinant DNA technology. This technology involves the transfer of specific genes from an organism into another organism using vectors and […]
  8. Page No 189: Question 1: Bacteria cannot be seen with the naked eyes, but these can be seen with the help of a microscope. If you have to carry a sample from your home to your biology laboratory to demonstrate the presence of microbes under a microscope, which sample would you carry and why? Answer: […]
  9. Page No 178: Question 1: Explain in brief the role of animal husbandry in human welfare. Answer: Animal husbandry deals with the scientific management of livestock. It includes various aspects such as feeding, breeding, and control diseases to raise the population of animal livestock. Animal husbandry usually includes animals such as cattle, pig, sheep, poultry, […]
  10. Page No 164: Question 1: What are the various public health measures, which you would suggest as safeguard against infectious diseases? Answer: Public health measures are preventive measures which are taken to check the spread of various infectious diseases. These measures should be taken to reduce the contact with infectious agents. Some of these methods […]