12 NCERT BIOLOGY SUBJECTIVE QUESTIONS

Q1. Mention the effect of global warming on the geographical distribution of stenothermals like amphibians. Solution Due to global warming, stenothermals like amphibians would either migrate or die due to change in the temperature. Q2. Write about the 3R technology in waste management. Solution We can follow the 3R approach - reduce, reuse and recycle - for effective waste management. Reduce: One can reduce the amount of solid waste at the source itself. Example: Use of less paper and less plastic carry bags. Reuse: One can use plastic bottles and jars, aluminium foils and plastic bags over and over again, before recycling or disposing them of. Recycle: Used and discarded materials like plastic, glass, paper and metal are sent to the respective industries, where they can be converted into other useful products. Q3. State the differences between biodegradable and non-biodegradable wastes. Solution Differences between biodegradab...

Q1. What is the function of National Bureau of Plant Animal and Fish Genetic Resources?  Solution The main function of National Bureau of Plant Animal and Fish Genetic Resources is to collect and conserve the germplasm of plants and animals in seed gene banks and field gene banks. Q2. Explain giving one example, how co-extinction is one of the causes of loss of biodiversity. List the three other causes also.  Solution When a species becomes extinct, the plant and animal species associated with it in an obligatory may also become extinct. This is called co-extinction. For example, when a host fish species becomes extinct, its unique assemblage of parasites also becomes extinct. Three other causes are- (a) Habitat loss and fragmentation (b) Over-exploitation (c) Alien species invasion Q3. (i) What is biodiversity? Why is it a matter of concern now? (ii) Satish heard about red data book in a TV programme on conservation of natu...

Q1. List the three parameters used for constructing ecological pyramids. Describe any one instance where the pyramid may look inverted.  Solution The three parameters used for constructing ecological pyramids are (i) Number of individuals in a trophic level. (ii) Biomass of individuals in a trophic level. (iii) Rate of flow of energy in a trophic level. The pyramid may look inverted in a tree ecosystem where the numbers of consumers are numerous depending on a single producer.  Q2. A food chain has only a few trophic levels. Justify. Solution In a food chain, about 80-90% of energy available with a trophic level is lost during its transfer from one trophic level to the next, so the amount of energy available decreases.  Q3. What are seral communities? Solution The whole series of changes in community characteristics from the pioneer stage to the climax stage constitute a sere. Q4. Describe the basic requirements of an ecosystem. Sol...

Q1. What does the sigmoid growth curve of a population mean?  Solution The sigmoid growth curve indicates rapid multiplication and then equilibrium of population. Q2. Egrets are often seen along with grazing cattle. How do you refer to this interaction? Give a reason for this association. Solution The interaction in egrets and grazing cattle is called commensalism. (i) In this association, egrets are found close to the grazing cattle. (ii) During movement, the cattle flush out various insects which may be difficult for the egrets to catch. (iii) The egrets are benefitted, but the cattle are neither benefitted nor harmed. Q3. What are the two types of population growth curves? What are the phases involved in both types of curves? Solution The two types of growth curve of a population are S-shaped and J-shaped. The phases of the S-shaped growth curve are lag phase, exponential phase and stationary phase. In the J-shaped growth...

Q1. For which variety of Indian rice was a patent filed by a USA Company? Solution Indian Basmati crossed with a semi-dwarf variety was claimed as a new variety, for which the patent was filed by a USA company. Q2. What is legally wrong in the US patent law? Mention the common items of biopiracy. Solution US patent law does not recognise technologies and methods in use to other countries as 'prior past'. The common items of biopiracy are soil micro-organisms plants, animals and their genetic material. Q3. How does a transgenic organism differ from the rest of its population? Give any two examples of such organisms for human advantage. Solution A transgenic organism contains functional foreign gene experimentally introduced into their genome by genetic engineering from another species. Hence, it differs from the rest of the population in having one or more extra genes apart from the gene pool of that population. Examples of ...

Q1. What are recombinant proteins? How do bioreactors help in their production? Solution The protein produced by genetically altered DNA (recombinant DNA) in a heterologous host is called recombinant protein. Bioreactors are vessels in which raw materials are biologically converted into specific products by microbes. It provides optimum growth conditions such as temperature, pH, substrate, vitamins, oxygen and salts for the production of recombinant proteins. Q2. For selection of recombinants, insertional inactivation of antibiotic marker has been superceded by insertional inactivation of a marker gene coding for a chromogenic substrate. Give reasons. Solution Selection of recombinants due to inactivation of antibiotic coding gene is a laborious process as it requires: (i) a vector with two antibiotic resistance markers (ii) preparation of two kinds of media plates, each with one type of antibiotic. Transformed cells are first plated on...

Q1. Explain in brief about the Yamuna Action Plan. Solution Most of the sewage water from urban as well as rural areas was discharged directly into the rivers resulting in their pollution. In order to protect the major rivers in India from sewage pollution, the Ministry of Environment and Forests has initiated development of sewage treatment plants under the National River Conservation Authority, e.g. Ganga Action Plan, Yamuna Action Plan etc. Under these plans, a large number of sewage treatment plants were built so that only treated sewage is discharged in the rivers. Importance of microbial treatment of sewage was then realized and more sewage treatment plants were established. Q2. Name the group of organisms and the substrate they act on to produce biogas. Solution Name of the group of organisms-Methanogens Substrate-Cellulosic material/cow dung/agricultural waste Q3. Which bacterium is involved in the production of Swiss cheese? What i...