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Published on: 29/05/2021
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Download CBSE Class 12th Standard CBSE Biology question papers, sample papers, important questions, and previous year solved papers in PDF format. Get free study materials, NCERT solutions, and exam preparation resources for Class 12th Standard CBSE Biology
Questions + Answers key
Take MCQ Biology Test1.
Study-1. A forest that is rich in biodiversity seems to decline in animal population. The government declared it as a biodiversity hotspot and the forest regained its species richness in few years. Study-2. A lake that is rich in marine fishes seems to decline in its species population due to overexploitation. A wise man in the area decided to worship the lake. The species population f the lake again became normal.
(a) Which values are been promoted in the above studies.
(b) Suggest some ways by which you can contribute to this concern.
(c) What would be the effect if the forest was not declared hotspot?
2.
Alien species are threat to native species. Justify
3.
Loss of key species that drive major ecosystem functions is the most serious threat to species diversity found in any ecosystem. How is it explained by Paul Ehalich through the "rivet popper hypothesis" analogy.
4.
Conservation of bio-diversity is a collective responsibility of all nations. Mention the steps taken by various countries in this direction.
5.
Western Ghats & Srilanka, Indo-Burma and Himalaya are three hot spots of India. Why are these places named so? What are the criteria of determining hot spots?
6.
Categorize the following into in-situ and ex-situ approaches of biodiversity conservation.
i) Botanical gardens
ii) Wild life sanctuaries
iii) Gene bank
iv) Biosphere reserves
v) Sacred forests/lakes
vi) Pollen banks
vii) Tissue culture
viii) Cryo-preservation
7.
What is depicted by the following representation of species diversity? Why these estimates do not give any figure-for prokaryotes.

8.
Mention the major cause of air pollution in metro cities. Write any three ways by which it can be reduced.
9.
What is EI Nino effect? Explain how it accounts for biodiversity loss.
10.
Write a critical note on the following:
(i) Hotspots of biodiversity.
(ii) Ex-situ conservation.
(iii) India's effort in biodiversity
1.
(i) Biodiversity conservation, Ecosystem protection.
(iii) Educate people not to harm biodiversity.
(iii) Forest would be destroyed, many species of plants and animals lost.
2.
Alien species are species that have been introduced from another geographic region to an area outside its natural range. For example; Parthenium, Lantana and Eicchornia are invaded the native species of India and causes environmental damage. Introduction of African catfish Clarias gariepinus in India for aquaculture purpose is posing threat to many indigenous catfish.
3.
Details of rivet popper hypothesis emphasizing the loss of rivets on the wings of an aeroplane, less of key species that drive major ecosystem function is a serious threat.
4.
Earth Summit held at Rio de Janerio and World Summit on sustainable development held in 2002 in Johannesburg South Africa where 190 countries pledged their commitment to achieve by 2010, a significant reduction in the current rate of biodiversity loss at global, regional and local levels.
5.
Regions with high level of species richness, high degree of endemism.
6.
(i) Exsitu
(ii) Insitu
(iii) Exsitu
(iv) Insitu
(v) Insitu
(vi) Exsitu
(vii) Exsitu
(viii) Exsitu
7.
These represent global biodiversity of (a) invertebrates (b) vertebrates (c) plants. Conventional taxonomic methods are not suitable for identifying microbial species; many species are simply not cultural lab conditions.
8.
Vehicular pollution and Industrial pollution.
Three ways to check it are
(i) Use of catalytic converters in vehicles.
(ii) Use of CNG as an alternative to petrol/diesel.
(iii) Applications of Euro II norms for vehicles.
9.
(a) EI Nino. It is an abnormal warming of surface ocean waters in the eastern tropical Pacific. It is called the Southern Oscillation. The Southern Oscillation is the see-saw pattern of reversing surface air pressure between the eastern and western tropical Pacific; When the surface pressure is high in the eastern tropical Pacific it is low in the western tropical Pacific, and vice-versa. Because the ocean warming and pressure reversals are, for the most part, simultaneous, scientists call this phenomenon the EI Nino/Southern Oscillation or ENSO for short.

Unfortunately not all EI Nino's are the same nor does the atmosphere always react in the same way from one EI Nino to another. This is why NASA's Earth scientists continue to take part in international efforts to understand EI Nino events. Hopefully one day scientists will be able to provide sufficient warning so that we can be better prepared to deal with the damages and changes that EI Nino causes in the weather.
10.
(i) Hot spots of biodiversity. The concept of 'Hot-spots' was developed by Norman Myres (1988) to designate specific areas for in-situ conservation. The conservation the hot spots are the richest and most threatened reservoirs of plants and animal life on earth.
The criteria for determining hot spots are:
1. Number of endemic species.
2. Degree of threat which is measured in terms of habitat loss.
There are 25 hot spots in the world out of which two are in India. They are Western Ghats and eastern Himalayas.
Hot spot of Eastern Himalayas are active centres of evolution and rich in diversity of flowering angiosperms. Western Ghats have semi evergreen forests. Western Ghats include two main centres of biodiversity i.e. Agastyamalai hills and Silent valley.
(ii) Ex-situ conservation. It means maintenance of off site collections either in gardens by farmers, botanical garden for storing seeds, genes, pollen, tissue culture etc.
The rare plants have been found to flourish in large numbers under the care and protection of gardeners and nature lovers.
The farmers have been maintaining genetic diversity (enormous varieties) of crop plants since ancient times by saving seeds or other components for the next plantings.
Collection of samples of cultivated and wild varieties of plants and storing them in botanical gardens is another method of conservation of germplasm.
In seeds, the living meterial remains in metabolically suspened state. When the seeds are to be stores for longer periods, it is necessary to avoid conditions which favour respiration and enzymatic actions.
(iii) India's effort in biodiversity conservation. India has greatly contributed to conservation of biodiversity owing to its great utility and need for conservation. The following measures have been taken for this purpose:
1. Setting up bodies like Indian Board for Wildlife, Bombay Natural History etc.
2. observation of first week of October as national wildlife week.
3. Introduction of Wildlife Protection Act in 1972.
4. Setting up of sanctuaries, national parks and biosphere reserves.
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