CBSE Class 12 Biology Biodiversity And Conservation Worksheet Set 03

Very Short Answer Questions

Question: India has more than 50,000 strains of rice. Mention the level of biodiversity it represents.
Answer. 50,000 strains of rice represent genetic biodiversity.

Question: What is mass extinction?
Answer. Due to natural calamities like volcanic eruptions, prolonged drought, heavy rains, earthquakes, asteroid collision, etc., a large number of species become extinct at the same time which is called mass extinction.

Question: Name the three important components of biodiversity.
Answer. The three important components of biodiversity are: genetic diversity, species diversity and ecological diversity.

Question: What is genetic diversity?
Answer. It is the measure of variation in genetic information contained in the organisms.

Short Answer Questions

Question: State how does ex-situ conservation help in protecting biodiversity.
Answer. Ex situ conservation (Off-site conservation)
QU This approach involves placing threatened animals and plants in special care units for their protection.
QU India has 35 botanical gardens and 275 zoological parks where animals which have become extinct in wild are maintained.

Question: Assess the effects of loss of biodiversity in a region. Mention any four such effects.
Answer. (i) Decline in plant production and animal species.
(ii) Lowered resistance to environmental perturbations such as drought.
(iii) Increased variability in certain ecosystem processes such as plant productivity/water use/pest and disease cycles.
(iv) Increased rate of species extinction.

Question: Differentiate between in situ and ex situ approaches of conservation of biodiversity.
Answer.

Question: Discuss one example, based on your day-to-day observations, showing how loss of one species may lead to extinction of another. 
Answer. In case a species becomes extinct, the plant and animal species associated within an obligatory way also become extinct. For example,
(i) When a fish species which is a host for a number of parasites becomes extinct, the parasite species which are uniquely dependent on the host fish will also become extinct.
(ii) The insects may be polyphagous (feed on more than one plant species) or monophagous (feed on only one particular plant species) in nature. The monophagous insect species are valuable and may become extinct if the plant species upon which it feeds becomes extinct.

Question: Narrowly utilitarian arguments are put forth in support of biodiversity conservation. Explain the other two arguments that are put forth in support of the same cause. 
Answer. Broadly utilitarian arguments
OU Biodiversity plays a major role in maintaining and sustaining supply of goods and services from various species as well as ecological systems.
OU The different ecological services provided are:
Ethical reasons
OU There are thousands of plants, animals and microbes on this earth which are not useless. Every one has some intrinsic value even if it is not of any economic value to us.
OU It is, therefore, our moral duty to ensure well-being of all the living creatures for the utilisation of future generations.

Question: The species diversity of plants (22 per cent) is much less than that of animals (72 per cent).
What could be the explanations to how animals achieved greater diversification?
Answer. Animals have achieved greater diversification than plants due to following reasons:
(i) They are mobile and thus can move away from their predators or unfavourable environments.
On the other hand, plants are fixed and have fewer adaptation to obtain optimum amount of raw materials and sunlight therefore, they show lesser diversity.
(ii) Animals have well-developed nervous system to receive stimuli against external factors and thus can respond to them. On the other hand, plants do not exhibit any such mechanism, thus, they show lesser diversity than animals.

Question: Alien species are highly invasive and are a threat to indigenous species. Substantiate this statement with any three examples.
Answer. Exotic species are defined as species that have been introduced from another geographic region to an area outside its natural range. For example,
(i) Parthenium, Lantana and Eichhornia are the exotic species of plants that have invaded the native species of India and caused environmental damage.
(ii) Introduction of African catfish Clarias gariepinus for aquaculture purpose is posing threat to many indigenous catfish.
(iii) Nile perch introduced into lake Victoria in East Africa led to the extinction of cichlid fish.

Question: How is biodiversity important for ecosystem functioning?
Answer. Importance of biodiversity for ecosystem functioning:
(i) Stability: Biodiversity is an important aspect for stability of an ecosystem. Ecologists believe that communities with more species tend to be more stable than those with less species.
(ii) Productivity: Ecosystem with higher biodiversity show more productivity than ecosystems with lower biodiversity. David Tilman’s long-term ecosystem experiments using outdoor plots provide confirmation.
(iii) Ecosystem health: Rich biodiversity is not only essential for ecosystem health but imperative for the survival of the human race on earth. Species are interlinked and so, killing or disappearance of one would effect the others also.
(iv) Resilience: Increased biodiversity provides resilience of the ecosystem against natural or man-made disturbances.

Question: Justify with the help of an example where a deliberate attempt by humans has led to the extinction of a particular species. 
Answer. When Nile perch, a large predator fish, was introduced in Lake Victoria, it started feeding on the native fish, Cichlid fish. As a result, Cichlid fish became extinct and Nile perch, not finding any food for itself, died too.

Question: Seeds of different genetic strains are kept for long periods in seed banks. Explain the conservative strategy involved in this process. 
Answer. The strategy is called Ex-situ conservation. In this technique, seeds are preserved in viable and fertile condition for long periods using cryopresrvation techniques.

Question: (a) Why should we conserve biodiversity? How can we do it?
(b) Explain the importance of biodiversity hotspots and sacred groves. 
Answer. (a) - Biodiversity is important for ecosystem health and for survival of human race on earth. There are
three main reasons for conserving the biodiversity which have been classified into the following categories:
(i) Narrowly utilitarian arguments
- Human beings derive direct economic benefits from nature, like food, firewood, fibre, construction material, industrial products (resins, gums, dyes, tannins, etc.) and medicinally important
products.
- More than 25 per cent of the drugs are derived from plants and about 25,000 species of plants are used by native people as traditional medicines.
(b) Conservation of Biodiversity
- Biodiversity can be conserved by protecting its whole ecosystem.
- There are two basic approaches for conservation of biodiversity.
(i) In situ conservation (On site conservation)
This approach involves protection of species in their natural habitat.