Class XII – Biodiversity and its Conservation – PYQs

Ans. (i) Genetic diversity: A single species shows diversity at the genetic level over its distributional range. For example, the genetic variation showed by the plant Rauwolfia vomitoria growing in the different Himalayan ranges might be in terms of the potency and concentration of reserpine.

(ii) Species diversity: It is the diversity at the species level or the measure of the variety of species and their relative abundance with the region. For example, the Western Ghats have a greater amphibian species diversity than the Eastern Ghats.

(iii) Ecological diversity: It refers to the diversity at ecosystem level. It makes communities more productive and stable, e.g. India has a greater ecosystem diversity (in terms of variety of habitats in deserts, rainforests, mangroves, coral reefs, wetlands, estuaries and alpine meadows) than a Scandinavian country like Norway.

Ans. The different varieties of mangoes in India represent genetic diversity. It occurs because India lies within tropical latitudes where the environment is constant and predictable. Also more amount of solar energy is available which leads to higher productivity.

Ans. There are two methods to estimate and extrapolate the number of species on the earth.

(i) The primary method used by the scientists to extrapolate the number of species on earth is the estimation rate of discovery of new species.

(ii) Total number of species can also be extrapolated by the statistical comparison of the tropical and temperate species richness of exhaustively studied groups of insects.

The ratio is then extrapolated with existing species of plants and animals to predict the gross estimate of the number of species on the earth.

Ans. Species diversity decreases as we move toward the poles, because

(i) Temperature decreases and conditions become rough and harsh.

(ii) Both the amount and intensity of solar radiation decrease.

(iii) Vegetation decreases.

(iv) Less resources available to support species.

Speciation is generally a function of time and environmental stability, so if conditions are too harsh, it is difficult for the species to survive and adapt. This results in decrease in biodiversity towards the poles.

Ans. Importance of species diversity for the ecosystem are

(i) Ecologists for many years, believe that communities with species are more stable than those with less species.

(ii) A stable biological community does not show too much variation in production from year-to-year. It must be resistant or resilient to occasional disturbance and must also be resistant to invasions by alien species.

(iii) David Tilman’s long term ecosystem experiments using outdoor plots provided answers to stability of a biological community and species richness in that community. Tilman found that plots with more species showed less year-to-year variation in total biomass. He also showed in his experiments that increased diversity contributed to higher productivity.

Ans. India is one of the twelve megadiversity regions of the world with 8.1% of genetic resources of the world. Since, India is placed in the tropical part of the world it exhibits more species diversity than the regions of temperate zones. India with much of its land area in the tropical latitudes, has more than 1200 species of birds. Greenland, Norway is away from tropics, so it exhibits less biodiversity

Ans. Differences between genetic and species diversity are as follows

Ans. Three reasons are as follows

(i) Temperate regions were subjected to frequent glaciation in the past which had killed most of the species, but the tropics have remained undisturbed and hence, had evolved more species diversity.

(ii) Tropical environments are less seasonal, relatively more constant and predictable than temperate regions. Such constant environments have promoted niche specialisation and thus, lead to greater species diversity.

(iii) Resource availability is higher and rate of extinction is low in tropics.

Ans. Yes, there is more solar energy available in the tropics because

(i) As one moves from equator to the polar regions, the length of the day decreases and the length of the night increases.

 (ii) In the tropical regions, the length of the day is almost equal to the length of the night, hence it has more solar energy available.

Ans. Slope of regression represents the changes in the species richness with the area. Species richness decreases with the decrease in area. The value of ‘Z’ (regression coefficient) lies between 0.1-0.2, regardless of the taxonomic groups in the region. For very large areas like continents, the slope of the line becomes much steep with the Z values in the range of 0.6-1.

Ans. The characteristics/features that make a community stable are

(i) Less variation in productivity from year to year.

(ii) Resistance or resilience to occasional disturbances (natural or man-made).

(iii) Resistance to invasions by alien species.

Ans. The current species extinction rates are estimated to be 100-1000 times faster than in pre-human times.

Ans. Human activities

Ans. To prevent sixth extinction to take place we would

(a) Preventing habitat loss and fragmentation

(b) Checking overexploitation

(c) Preventing alien-species invasion

(d) Preventing coextinction

(e) Conservation and preservation of species

Ans. The major causes of species losses in a geographical region are

(i) Habitat loss and fragmentation.

(ii) Overexploitation of natural resources.

(iii) Alien-species invasions that can cause decline or extinction of indigenous species.

(iv) Coextinctions, i.e. when a species become extinct, the plant and animal species associated with it in an obligatory way, also become extinct.

Ans. When Nile perch, a large predator fish was introduced in Lake Victoria, it started feeding on native fish, i.e. cichlid fish. As a result, cichlid fish become extinct and due to scarcity of food predator, Nile perch, died too.

Ans. Humans derive numerous economic benefits directly from diversity of organisms.

(i) Food products (cereals, pulses and fruits), firewood and fibre (cotton, jute from plants and silk, wool from animals).

(ii) Construction material (timber for making furniture, houses and sports goods), industrial products (tannis, lubricant, dyes, resins and perfumes) and products of medicinal importance (about 25,000 plants are used in traditional medicine).

There are huge indirect benefits that humans derive from the diversity of life. These are, pure oxygen, natural pollinators, flood and soil erosion control, nutrient replenishment, waste recycling by microbes and aesthetic pleasure and mental peace.

Ans. Biodiversity should be conserved for the following reasons

(i) The broadly utilitarian argument says that biodiversity plays a major role in many ecosystem services that nature provides.

(ii) The narrow utilitarian argument says that humans derive countless direct economic benefits from nature and products of medicinal importance.

(iii) The ethical argument for conserving biodiversity relates to what we owe to millions of plants, animal and microbe species with whom we share this planet

Ans. Practices that help to protect rare, threatened species are as follows

(i) In situ (on-site) conservation which involves protection of species in their natural habitat. It involves biosphere reserves, national parks, wildlife sanctuaries, sacred groves, etc.

(ii) Ex situ (off-site) conservation which involves placing of threatened animals and plants in special care units for their protection. Zoological parks, botanical gardens and wildlife safari parks serve this purpose.

Ans. In situ conservation involves the protection of species in their natural habitats. It helps in the conservation of threatened/endangered species via following means

(i) Biodiversity hotspots are regions with high levels of species richness and high degree of endemism (i.e. species confined to that region are not found anywhere else). These hotspots can reduce the ongoing mass extinctions by almost 30%.

(ii) Protected areas are ecologically unique and biodiversity rich regions. These are legally protected as biosphere reserves, national parks and sanctuaries. Hence, can help in conservation of endangered species.

(iii) Sacred groves are forest areas set aside, all the trees and wildlife within it are venerated and given total protection. These are religious and cultural places, which are protected for conservation of endangered species.

Ans. Endemism means when a species of plant or animal is confined to a particular region and are not found anywhere else, e.g. biodiversity hotspots and species are called endemic species.

Ans. India hosts 4 biodiversity hotspots, the Himalayas, the Western ghats, the Indo-Burma region and the sundaland (includes Nicobar group of Islands).

Ans. Sacred groves are small groups of trees with special religious importance in a particular culture.

They are found in Khasi and Jaintia Hills in Meghalaya, Aravalli Hills of Rajasthan, Western ghat regions of Karnataka and Maharashtra and the Sarguja, Chanda and Bastar areas of Madhya Pradesh.

Sacred groves help in the protection of many rare, threatened and endemic species of plants and animals found in area. The process of deforestation is strictly prohibited in these regions.

Ans. Six advantages of ex situ approach to conservation of biodiversity are as follows

(i) To conserve those animals that have become extinct in wild, but can be maintained in zoological parks.

(ii) To preserve gametes of threatened species in viable condition through cryopreservation.

(iii) To propagate threatened plants via tissue culture.

(iv) To grow plants with recalcitrant seeds in orchards where all possible varieties are maintained.

(v) To conserve seed of commercially important plants in seed banks.

(vi) To save endangered or threatened plant that needs urgent measure to save it from extinction in botanical gardens.

Ans. Three ways to conserve plants and animals are as follows

(i) Seed banks: The storage of different genetic strains of commercially important plants in the form of seeds is one of the most widespread and valuable ex situ approaches of the conservation strategy.

(ii) Tissue culture: Plant tissue culture is widely used to produce clones of a plant in a method known as micropropagation. This method is useful in maintaining a large number of genotypes in small area, rapid multiplication of even endangered species and for hybrid rescue, e.g. banana and potato.

(iii) Cryopreservation: It is a method of in vitro conservation in liquid N2 at temperature of -196°C (–130°F) in a controlled rate freezer for vegetatively propagated crops and storing other biological materials.

Ans. Differences between in situ and ex situ conservation are as follows

Ans. As a biology student, I would suggest ex situ conservation approach for such animals. It involves placing the threatened animals and plants in special care units for their protection. It includes off-site collections (botanical gardens, zoological parks, etc.) and gene banks (seedbank, tissue culture, etc). Advantages of ex situ conservation are

(i) Off-site collection can be used to restock depleted population, reintroduce species in the wild and restore degraded habitats.

(ii) It is useful in maintaining a large number of genotypes in small area, rapid multiplication of even endangered species, through tissue culture, etc.

Ans. According to Av Humboldt, a German scientist, ‘within a region, species richness increases with increase in explored area (only upto a limit)’. Accordingly, the relation between species richness and area for a wide variety of taxa (birds, bat, angiosperms, aquatic fishes) turns out to be a rectangular hyperbola. The relationship depicts a straight line on a logarithmic scale described by the following equation

Log S = log C + Z log A

Where, ‘S’ stands for species richness, ‘A’ is area and ‘Z’ and ‘C’ are slope of line (regression coefficient) and y intercept, respectively.

Ans. Biodiversity is very important for ecosystem functioning. More diverse ecosystems are considered more stable. Stable communities are resilient and resistant to change. Hence, diversity stabilises the community and also helps in increasing the productivity. Higher the biodiversity of an ecosystem, higher the number of species and therefore, lower is the rate of extinction. While in case of low biodiversity, there are higher chances of extinction. Extinction of even one or two key species has negative impacts on the entire ecosystem.

Thus, the diversity ensures the stability and proper functioning of the entire ecosystem as explained via the ‘Rivet popper hypothesis’.

•  According to this hypothesis, ecosystem is like an aeroplane and all its parts are joined together using thousands of rivets (species).
•  If every passenger, travelling in it, starts popping a rivet to take home (causing a species to become extinct), it may not affect flight safety (proper functioning of the ecosystem), but as more and more rivets are removed the plane becomes dangerously weak over a period of time.
•  Moreover, which rivet is removed is also crucial, e.g. loss of rivet on the wings (key species that drive major ecosystem functions) is a more serious threat than loss of rivets on seats or windows inside the plane.

Ans. Biological resources are the basis of life forms on our planet. The countries with maximum biodiversity possess better potential to compete with the rest of the world.

Biodiversity has great economic importance to mankind due to its many uses.

Some of the uses with consumptive value are as follows

(i) Food is obtained from biodiversity sources like livestock, forestry and fish. Biodiversity in modern agriculture is beneficial as a source of new crops, e.g. cereals crop like wheat, rice and maize account for about 55% of protein and 60% of calories in humans.

(ii) Drugs such as morphine (Papaver somniferum), quinine (Cinchona ledgeriana), reserpine (Rauwolfia vomitoria), belladonna (Atropa belladonna), aconite (Aconitum napellus), wintergreen and birth bark (Gaultheria procumbens) are derived from plants.

(iii) Fuel and fibre Plants like Chorchorus, Gossypium are sources of fibre while Jatropha is a source of biofuels. Fossils fuels are obtained from fossils of organisms.

Ans. Biodiversity is the occurrence of different types of species, habitat, ecosystem, gene, gene pool in a particular place and various parts of earth. As an individual biodiversity can be conserved with conservation strategies and management of both biotic and abiotic resources.