CBSE Class 12 Biology Biodiversity and Conservation Question Bank

CBSE Class 12 Biology Biodiversity and Conservation Question Bank. There are many more useful educational material which the students can download in pdf format and use them for studies. Study material like concept maps, important and sure shot question banks, quick to learn flash cards, flow charts, mind maps, teacher notes, important formulas, past examinations question bank, important concepts taught by teachers. Students can download these useful educational material free and use them to get better marks in examinations.  Also refer to other worksheets for the same chapter and other subjects too. Use them for better understanding of the subjects. 

Class 12 Biology: Chapter 15 Biodiversity and Conservation (Question Bank with Answer Key)

Why is India said to have greater ecosystem diversity than Norway? (1 mark)

Answer: India has a number of ecosystems such as deserts, rain forests, coral reefs, mangroves, wetlands, estuaries and alpine meadows; hence it has greater ecosystem diversity than Norway.

Write the importance of cryopreservation in the conservation of biodiversity. (1 mark)

Answer: Gametes of threatened species can be preserved in viable and fertile condition for long periods (at very low temperature, \(-196^\circ\)C in liquid nitrogen) using cryopreservation, and later used to revive the species.

The Amazon rain forest is referred to as 'the lungs of the planet'. Mention any one human activity which causes loss of biodiversity in this region. (1 mark)

Answer: Many trees are cut and the land is cleared for the cultivation of soya bean; the forest is also converted into grassland for raising beef cattle.

About 200 species of cichlid fish became extinct when a particular fish was introduced in Lake Victoria of Africa. Name the invasive fish. (1 mark)

Answer: The Nile perch. (The source question says 'about 20 species'; its own key says more than 200, which is the correct figure.)

What is the expanded form of IUCN? (1 mark)

Answer: International Union for Conservation of Nature and Natural Resources.

Why is genetic variation important in the plant Rauwolfia vomitoria? (1 mark)

Answer: Genetic variation in Rauwolfia is shown in terms of the potency and concentration of the active chemical (reserpine, used to treat high blood pressure and mental disorders) produced by the plant; so plants of high potency can be selected.

What is meant by 'alien species' invasion? Name one plant and one animal alien species that are a threat to our Indian native species. (2 marks)

Answer: Alien species invasion is the introduction of non-native species (deliberately or accidentally) which become invasive, compete with the native species and cause their decline or extinction. Plants: carrot grass (Parthenium), Lantana, water hyacinth (Eichhornia). Animal: the African catfish Clarias gariepinus, introduced for aquaculture, threatens the indigenous catfishes in our rivers. (The introduction of the Nile perch into Lake Victoria led to the extinction of more than 200 cichlid species.)

Why should biodiversity be conserved? List any two ethical arguments in support. (2 marks)

Answer: Biodiversity must be conserved as it plays an important role in many ecosystem services. Ethical arguments:

1. Spiritually or philosophically, every species has an intrinsic value, even though it may not be of any economic value to us at present.
2. Morally, we have a duty to care for the well-being of every species and to pass on our biological legacy in good order to future generations.

State the use of biodiversity in modern agriculture. (2 marks)

Answer:

1. Human beings obtain food, fibres, medicines and many industrial products from plants.
2. The wild relatives of our crops are useful as a source of disease resistance, pest resistance and many desirable characters; they are used in breeding to raise plants with desirable traits.
3. With increasing resources put into bioprospecting, i.e. exploring molecular, genetic and species-level diversity for economically important products, rich biodiversity will be beneficial.

Differentiate between in situ and ex situ approaches of conservation of biodiversity. (2 marks)

Answer:

Explain, taking one example, the effect of co-extinction on biodiversity. (2 marks)

Answer: Co-extinction leads to loss of biodiversity because when a species becomes extinct, the plant and animal species associated with it in an obligatory manner also become extinct. For example, in the case of co-evolved plant–pollinator mutualists, the extinction of one invariably leads to the extinction of the other.

In the biosphere, immense biological diversity exists at all levels of biological organization. Explain any two levels of biodiversity. (2 marks)

Answer:

1. Genetic diversity is the diversity of genes within a species, e.g. there are more than 50,000 genetically different strains of rice in India.
2. Species diversity is the diversity at the species level, i.e. the number of different species within a given region, e.g. the Western Ghats have a greater amphibian species diversity than the Eastern Ghats.
3. Ecological diversity is the variation of habitats, community types and abiotic environments present in a given area, e.g. India has a greater ecosystem diversity than Scandinavia.

(Any two of the above.)

What does the term genetic diversity refer to? What is the significance of large genetic diversity in a population? (2 marks)

Answer: Genetic diversity refers to the diversity of genes within a species. The greater the genetic diversity among the organisms of a species, the more sustenance (ability to survive) it has against environmental perturbations; genetically uniform populations are highly prone to diseases and harsh environments.

The sacred groves of Aravalli hills and the Ooty botanical garden, both aim at biodiversity conservation. How do they differ in their approaches? Explain. (2 marks)

Answer: The sacred groves are a part of in situ conservation: the plants and animals are protected in their natural habitat (the community protects the grove). The Ooty botanical garden is a part of ex situ conservation: plants are removed from their natural habitat and are maintained and protected under human care in a garden.

Alien species are highly invasive and are a threat to indigenous species. Substantiate this statement with any three examples. (3 marks)

Answer:

1. The Nile perch introduced into Lake Victoria in East Africa caused the extinction of more than 200 species of cichlid fish in that lake.
2. Parthenium (carrot grass), Lantana and Eichhornia (water hyacinth) caused environmental damage and are a threat to many native plant species in our country.
3. The illegal introduction of the African catfish Clarias gariepinus for aquaculture is posing a threat to the indigenous catfishes in our rivers.

List the reasons that account for the greater biological diversity in the tropics. (3 marks)

Answer:

1. Speciation is a function of time: the temperate regions were subjected to frequent glaciation in the past, while the tropics have remained relatively undisturbed for millions of years, so they had a longer time to evolve more species diversity.
2. Tropical environments are less seasonal, relatively more constant and more predictable than the temperate environments; such constant environments promote niche specialisation and lead to greater species diversity.
3. More solar radiation is available in the tropics, which contributes directly to higher productivity and indirectly to greater species diversity.

Explain, giving one example, how co-extinction is one of the causes of loss of biodiversity. List the three other causes also (without description). (3 marks)

Answer: Co-extinction is a phenomenon in which, when a species becomes extinct, the plant and animal species associated with it in an obligatory manner also become extinct. Examples:

1. In the case of a co-evolved plant and its pollinator, if one of them becomes extinct, the other also invariably becomes extinct.
2. If a host fish becomes extinct, the unique parasites depending on it also become extinct.

The three other causes are: (i) habitat loss and fragmentation, (ii) over-exploitation, (iii) invasion of alien species.

Explain the 'Rivet popper hypothesis'. Name the ecologist who proposed it. (3 marks)

Answer: It was proposed by the ecologist Paul Ehrlich.

1. In an airplane all parts are joined together using thousands of rivets.
2. If every passenger travelling in it starts popping a rivet to take home, it may not affect the flight safety initially, but as more and more rivets are removed, the plane becomes dangerously weak over a period of time.
3. Further, which rivet is removed may also be critical: the loss of rivets on the wings (the key species that drive major ecosystem functions) is obviously a more serious threat to flight safety than the loss of a few rivets on the seats or windows.
4. In the same way, the species of an ecosystem are the rivets: the loss of a few species may not be noticed at first, but the loss of many species, especially the key (keystone) species, makes the ecosystem collapse.

What are the two types of desirable approaches to conserve biodiversity? Explain with examples, bringing out the difference between the two types. (5 marks)

Answer: The two desirable approaches to conserve biodiversity are (1) in situ conservation and (2) ex situ conservation.

(a) Taking one example each of habitat loss and fragmentation, explain how the two are responsible for biodiversity loss. (b) Explain two different ways of biodiversity conservation. (5 marks)

Answer:

(a) Habitat loss is the primary cause for extinction. The tropical rain forests initially covered about 14% of the land surface of the earth, but now they cover only about 6% of the land area; the Amazon rain forest is being cleared for soya cultivation and cattle ranching. The total loss of a habitat deprives many animals and plants of their homes and they face extinction.

Fragmentation: when a large habitat is broken into small patches (for example by roads, farmland or dams), animals requiring large territories and those with certain migratory habits start decreasing and disappear from the small patches.

(b) The two ways of conservation are in situ and ex situ conservation:

The Isha Upanishad says 'let no one species encroach over the rights and privileges of other species. One can enjoy nature by giving up greed'. But human activities have accelerated the rate of extinction of species in recent times. (a) Name any four such activities. (b) Describe how each of these activities leads to loss of biodiversity. (c) What value is taught by the Upanishad? (5 marks)

Answer:

(a) The major causes of loss of species are: (i) habitat loss and fragmentation, (ii) over-exploitation, (iii) invasion of alien species, (iv) co-extinction.

(b)

1. Habitat loss and fragmentation is the primary cause of extinction. The tropical rain forests initially covered 14% of the land surface of the earth, but now they cover only 6%. The total loss of a habitat deprives many animals and plants of their homes and they face extinction. When a large habitat becomes fragmented, animals requiring large territories and those with certain migratory habits start decreasing.
2. Over-exploitation: when nature is over-exploited by man for natural resources, many species become extinct (e.g. Steller's sea cow and the passenger pigeon).
3. Invasion of alien species: alien species become invasive and compete with native species and cause the extinction of indigenous species.
4. Co-extinction: when a species becomes extinct, the plant and animal species associated with it in an obligatory manner also become extinct.

(c) The Upanishad teaches that we have no right to destroy other species: live and let others live, and enjoy nature by giving up greed (co-existence and non-exploitation).

During an excursion to a botanical garden, the teacher shows an old tree which was on the verge of extinction. As soon as the teacher advanced with the students, some enthusiastic students climbed up the tree and started cutting the branches, collecting its leaves as a precious collection. Rajesh instead took photographs of the tree from various angles. The boys mocked Rajesh while the teacher appreciated him. (a) What values did Rajesh possess? (b) Why should we conserve biodiversity? (c) How can biodiversity be conserved? (4 marks)

Answer:

(a) Rajesh possessed respect for nature, a scientific attitude and a vision of the future (concern for the environment).

(b) We should conserve biodiversity because it provides us:

1. the main source of food;
2. economically important fibres (cotton, flax, hemp, jute, etc.);
3. plant and animal products (gum, resin, dye, fragrance, waxes, wool, leather, honey, lac, pearl, ivory, silk, horns);
4. drugs and medicines;
5. sports and recreation, aesthetic and cultural value;
6. material for scientific research, and many ecosystem services.

(c) In situ conservation: sacred groves, biosphere reserves (terrestrial and marine), national parks and wildlife sanctuaries, etc. Ex situ conservation: sacred plants and home gardens, seed banks, gene banks and cryopreservation, botanical gardens, zoological gardens, aquaria, etc.