CBSE Class 12 Biology Biodiversity And Conservation Worksheet Set D

Question. Write the level of biodiversity represented by a mangrove. Give another example falling in the same level. 
Answer. Ecological diversity is found in mangrove. Rain forests also show same level of biodiversity.

Question. Name the type of biodiversity represented by the following:
(a) 50,000 different strains of rice in India
(b) Estuaries and alpine meadows in India.
Answer. (a) Genetic diversity
(b) Ecological diversity

Question. Name the type of biodiversity represented by the following:
(a) 1000 varieties of mangoes in India.
(b) Variations in terms of potency and concentration of reserpine in Rauwolfa vomitoria growing in different regions of Himalayas. 
Answer. (a) Genetic diversity (b) Genetic diversity

Question. Why is tropical environment able to support greater species diversity? 
Answer. Continuous favourable environment with little seasonal changes of temperature and moisture supports greater species diversity in tropical areas. Also, more solar energy is available in tropics, which promotes higher productivity and increased biodiversity.

Question. India has more than 50,000 strains of rice.Mention the level of biodiversity it represents.
Answer. When species show high diversity at the genetic level over its distributional range then the biodiversity is at genetic diversity level. The 50,000 strains of rice differ at genetic level.

Question. Eichhornia crassipes is an alien hydrophyte introduced in India. Mention the problems posed by this plant. 
Answer. Eichhornia crassipes, an alien hydrophyte introduced in Indian waters to reduce pollution has clogged water bodies resulting in death of aquatic plants and animals.

Question. Name the unlabelled areas ‘a’ and ‘b’ of the pie chart representing the global biodiversity of invertebrates showing their proportionate number of species of major taxa. 
Answer. (a) Insects, (b) Molluscs

Question. What does the term genetic diversity refer to? What is the significance of large genetic diversity in a population? 
Answer. Genetic diversity mean variation of genes within the species; the differences could be in alleles (different variants of same genes), in entire genes (the traits determining particular characteristics) or in chromosomal structures.
The genetic diversity enables a population to adapt to its environment and to respond to natural selection. The greater is the genetic diversity of a species, the higher is its eficiency to adapt. It also helps in speciation or evolution of new species. E.g., India has more than 50, 000 genetically different strains of rice and 1, 000 varieties of mango.

Question. Mention the kind of biodiversity more than a thousand varieties of mangoes in India represent. How is it possible? 
Answer. More than a thousand varieties of mango in India exhibit genetic diversity. Genetic diversity represents the diversity in number and types of genes as well as chromosomes and variations in the genes and their alleles in the same species. The reason for this genetic diversity is the occurrence of variations in environmental parameters and use of horticulture techniques like grafting, breeding etc.

Question. List four causes of biodiversity loss.
Answer. The four causes of biodiversity loss are – (i) Habitat loss and fragmentation
(ii) Over-exploitation
(iii) Alien species invasions
(iv) Co-extinctions.

Question. Where would you expect more species biodiversity– in tropics or in polar regions?
Give reasons in support of your answer.
Answer. Tropics have more species biodiversity than the polar regions because of favourable environmental conditions as compared to polar regions where harsh conditions are prevalent. The reasons behind the maximum biological diversity of tropical regions. are: (i) Prolonged evolutionary time : Speciation is
generally a function of time, unlike polar regions
subjected to frequent glaciations in the past, tropical latitudes have remained relatively undisturbed for millions of years and thus, had a long evolutionary time for species diversification.
(ii) High productivity : There is more solar energy available in the tropics, which contributes to higher productivity; this in turn might contribute indirectly to greater diversity.

Question. What is meant by ‘alien species’ invasion? Name one plant and one animal alien species that are a threat to our Indian native species.
Answer. Non-native or alien species are often introduced inadvertently by man for their economic and other uses. They often become invasive and drive away the local species. For example:
(i) Water hyacinth (Eichhornia crassipes) was introduced in Indian waters to reduce pollution but it turned out to be a problematic species. It has clogged water bodies including wetlands at many places resulting in death of several aquatic plants and animals.
(ii) Nile Perch (a predator fish) was introduced in lake Victoria of South Africa. It killed and eliminated ecologically unique assemblage of over 200 native species of small cichlid fish.
(iii) African catfish Clarias gariepinus introduced for aquaculture in India posses threat to indigenous catfishes.

Question. “Stability of a community depends on its species richness.” Write how did David Tilman show this experimentally. 
Answer. Communities with more species tend to be more stable than those with less species as it is able to resist occasional disturbance. This has been confirmed experimentally by David Tilman’s. He raised plots with different diversities in Minesota grassland and subjected them various stresses. He found that plots with more species showed less year to year variation in total biomass. He also showed that in his experiments, increased diversity contributed to higher productivity.

Question. Alien species invasions is one of the causes of biodiversity loss. Explain with the help of an example.
Answer. Non-native or alien species are often introduced inadvertently by man for their economic and other uses. They often become invasive and drive away the local species. For example:
(i) Water hyacinth (Eichhornia crassipes) was introduced in Indian waters to reduce pollution but it turned out to be a problematic species. It has clogged water bodies including wetlands at many places resulting in death of several aquatic plants and animals.
(ii) Nile Perch (a predator fish) was introduced in lake Victoria of South Africa. It killed and eliminated ecologically unique assemblage of over 200 native species of small cichlid fish.
(iii) African catfish Clarias gariepinus introduced for aquaculture in India posses threat to indigenous catfishes.

Question. Justify with the help of an example where a deliberate attempt by humans has led to the extinction of a particular species.
Answer. Extinction of species due to human activities is known as anthropogenic extinction. Various human activities have led to extinction of particular species. The most common example is Nile perch, a large predator fish introduced in Lake Victoria for commercial purpose turned out to be a problematic species. It started feeding on the native fish cichlid fish, which results in extinction of ecologically unique assemblage of over 200 native species of small cichlid fish.

Question. Explain, taking one example, the effect of coextinction on biodiversity. 
Answer. Co-extinction means that when a species become extinct, the plant and animal species associated with it in an obligatory relation also become extinct. For example the case of a coevolved plant-pollinator mutualism like in Pronuba yuccaselles and Yucca where extinction of one invariably leads to the extinction of the other.

Question. How does over-exploitation of beneficial species affect biodiversity? Explain with the help of one example. 
Answer. Excessive exploitation of a species, whether a plant or animal, reduces size of its population so that it becomes vulnerable to extinction. For example, presently many marine fish population around the world are declining due to over harvesting results in endangering the continued existence of some commercially important species.

Question. In the biosphere immense biological diversity exists at all levels of biological organisation.
Explain any two levels of biodiversity.
Answer. Biological diversity means the variability among living organisms at all levels of biological organisation ranging from macromolecules within cells to biomes.
There are three levels of biodiversity are namely: (i) Genetic diversity
(ii) Species diversity
(iii) Ecological diversity 
Genetic diversity means variation of genes within the species; the differences could be in alleles (different variants of same genes), in entire genes (the traits determining particular characteristics) or in chromosomal structures. The genetic diversity enables a population to adapt to its environment and to respond to natural selection. The greater is the genetic diversity of a species, the higher is its efficiency to adapt. The greater the diversity the wider is the geographical distribution. E.g., India has more than 50,000 genetically different strains of rice and 1,000 varieties of mango.
The variety in the number and richness of the species of a region is known as species diversity. The number of species per unit area is called species richness and the number of individuals of different species represents species evenness. E.g., Western Ghats have greater amphibian species diversity as compared to Eastern Ghats.

Question. Giving two reasons explain why there is more species biodiversity in tropical latitudes than in temperate ones. 
Answer. The two reasons for more species biodiversity in tropical latitudes than in temperate ones are:
(i) Temperate region was subjected to frequent glaciations in the past, while tropical latitudes have remained relatively undisturbed for millions of years and thus, had a long evolutionary time for species diversification.
(ii) Tropical environments, unlike temperate ones, are less seasonal, relatively more constant and predictable. Such constant environments promote niche specialisation and lead to a greater species diversity.

Question. Sometimes alien species affect the indigenous organisms leading to their extinction.
Substantiate this statement with the help of any two examples.
Answer. Non-native or alien species are often introduced inadvertently by man for their economic and other uses. They often become invasive and drive away the local species. For example:
(i) Water hyacinth (Eichhornia crassipes) was introduced in Indian waters to reduce pollution but it turned out to be a problematic species. It has clogged water bodies including wetlands at many places resulting in death of several aquatic plants and animals.
(ii) Nile Perch (a predator fish) was introduced in lake Victoria of South Africa. It killed and eliminated ecologically unique assemblage of over 200 native species of small cichlid fish.
(iii) African catfish Clarias gariepinus introduced for aquaculture in India posses threat to indigenous catfishes.

Question. Name the sociobiologist who popularised the term biodiversity. Identify the levels of biodiversity in India represented by
(a) diversity among amphibians in Eastern and Western Ghats.
(b) 50,000 strains of rice in India.
(c) presence of deserts, mangroves and coral reefs in India. 
Answer. Edward Wilson popularised the term biodiversity.
(a) Species diversity
(b) Genetic diversity
(c) Ecological diversity

Question. The following graph shows the species-area relationship. Answer the following question as directed.
(a) Name the naturalist who studied the kind of relationship shown in the graph. Write the observation made by him.
(b) Write the situation as discovered by the ecologists when the value of ‘Z’ (slope of the line) lies between.
(i) 0.1 and 0.2
(ii) 0.6 and 1.2
What does ‘Z’ stand for?
Answer. (a) Alexander von Humboldt studied species- area relationship. He observed that within a region, the species richness increased with increasing area but upto a certain limit.
(b) (i) Ecologists have discovered that the value of Z lies in the range of 0.1–0.2 regardless of taxonomic group or region, i.e., whether it is plants in Britain, birds in California or molluscs in New York the slopes of the regression line are similar.
(ii) When the species-area relationship is considered for a very large area like a whole continent, regression coefficient Z or slope of the line become steeper with Z values in the range of 0.6 –1.2.
(c) Slope of line b, would become steeper when the value of Z ranges from 0.6 to 1.2 as for mammals of tropical forests of different continents, the slope is found to be 1.15.

Question. Since the origin of life on Earth, there were five episodes of mass extinction of species.
(a) How is the ‘Sixth Extinction’, presently in progress, different from the previous episodes?
(b) Who is mainly responsible for the ‘Sixth Extinction’?
(c) List any four points that can help to overcome this disaster. 
Answer. (a) Sixth extinction, i.e., the current species extinction is 100 – 1000 times faster than extinctions in pre-human times.
(b) Human activities like settlements, hunting, over exploitation and habitat destruction are mainly responsible for ‘Sixth extinction’.
(c) This disaster can be overcome by the following ways:
(i) Planting large number of trees on road sides and where space is available.
(ii) Avoid introduction of invasive alien species. (iii) Conserving biodiversity by maintaining National parks, zoos etc.
(iv) Deforestation and fragmentation of forested areas should be stopped.

Question. Explain giving three reasons, why tropics show greatest levels of species diversity. 
Answer. The two reasons for more species biodiversity in tropical latitudes than in temperate ones are:
(i) Temperate region was subjected to frequent glaciations in the past, while tropical latitudes have remained relatively undisturbed for millions of years and thus, had a long evolutionary time for species diversification.
(ii) Tropical environments, unlike temperate ones, are less seasonal, relatively more constant and predictable. Such constant environments promote niche specialisation and lead to a greater species diversity.

Question. Name and explain any two ways that are responsible for the loss of biodiversity.
Answer. The two ways that are responsible for the loss of biodiversity are alien species invasion and co-extinctions.

Question. Taking one example each of habitat loss and fragmentation, explain how are the two responsible for biodiversity loss. 
Answer. Loss of habitat through filling wet lands, polughing grasslands, cutting down trees, burning a forest and clearing some area of vegetation results in annihilation of plants, microorganisms and forcing out of animals which in alien land die out after sometime. Habitat loss deprives plants and animals of their homes and they get killed.
Fragmentation of habitat e.g., forest land surrounded
by crop lands, orchards, urban areas etc. disrupts complex interaction amongst species, annihilation of species restricted to deeper undisturbed parts of forest and decreased biodiversity.

Question. What are exotic species? Explain with the help of two examples how the exotic species disturb the native species of an ecosystem? 
Answer. Exotic species is an alien invasive or non- native species, which have been introduced by humans outside their native ranges.

Question. Write the importance of cryopreservation in conservation of biodiversity. 
Answer. Cryopreservation is ex-situ conservation technique in which tissues, organs, embryos, seeds etc. are stored at very low temperature of –196°C. At this temperature the living material can be stored indefinitely in compact, low maintenance refrigeration units. It can be revived as and when required. In order to prevent extinction, endangered organisms are being cryopreserved so that they can be revived to help in conservation.

Question. Why are sacred groves highly protected?
Answer. Sacred groves are forest patches around places of worship, held in high esteem by tribal communities. The are most undisturbed forest patches which are often surrounded by highly degraded landscapes. Not a single branch is allowed to be cut from these forests and as a result, many endemic species which are rare or have become extinct elsewhere can be seen to flourish here. E.g. Jaintia and Khasi hills in Meghalaya.

Question. List any four techniques where the principle of ex situ conservation of biodiversity has been employed. 
Answer. Four techniques where principles for ex situ
biodiversity conservation has been employed are:
(i) In vitro fertilisation – Egg are fertilised in
in vitro conditions.
(ii) Cryopreservation – Cells, embryos, tissues are preserved at – 196C.
(iii) Seed banks – Storing viable seeds at low temperature, and germinating them to obtain fresh seeds.
(iv) Tissue culture – Production of large number of plants through callus culture, pollen grain culture, embryoids etc.

Question. Why is there a need to conserve biodiversity?
Answer. Conservation of biodiversity is the protection, uplift and scientific management of biodiversity so as to maintain it at its optimum level and derive sustainable benefits for the present as well as future strategies. The maintenance of a high level of biodiversity is important for the stability of ecosystem. The main reasons to conserve the biological diversity can be grouped in three categories :
– Narrowly utilitarian (useful products for humans like food, fibres, drugs and medicines etc.)
– Broadly utilitarian (ecosystem services like provision of pollination, climate regulation, flood and erosion control, ecological balance through nutrient cycling, microbial waste treatment, biological pest control, aesthetic and cultural values).
– Ethical utilitarian (every living species has an intrinsic value though it may not have any direct economic value, and also, every species has the right to live).

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

Question. White Bengal tigers are protected in special settings in zoological parks. Tiger reserves are maintained in Western Ghat.
(a) How do these two approaches differ from each other? Mention the advantages of each one.
(b) What is the significance of cryopreservation technique? 
Answer. (a) In Zoological parks, white Bengal tigers are protected outside their natural habitats. It is mode of Ex situ conservation. Animals are kept under human supervision and are protected against all adverse factors.
Western ghats are hot-spots, i.e., areas of high endemism and high level of species richness. It is a mode of in-situ conservation. Endangered species in Tiger reserves are conserved in their natural habitat. These are protected from predators.

Question. A particular species of wild cat is endangered.In order to save them from extinction, which is a desirable in situ or ex situ? Justify your answer and explain the difference between the two approaches. 
Answer. Endangered species of wild cat can be saved from extinction by ex situ conservation. In ex situ approach, endangered species are kept under human supervision, and are protected from all adverse factors. They are provided with all essentials and are also protected from predators. More offspring are produced by captive breeding and are released in their natural habitat to acclimatise, which helps in maintaining their population. 

Question. Many plant and animal species are on the verge of their extinction because of loss of forest land by indiscriminate use by the humans. As a biology student what method would you suggest along with its advantages that can protect such threatened species from getting extinct?
Answer. Conservation of biodiversity is protection, uplift and scientific management of biodiversity so as to maintain it at its optimum level and derive sustainable benefits for the present as well as future generations. There are two types of conservation strategies – in situ (on site) and ex situ (offsite).
In situ conservation is conservation and protection of the whole ecosystem and its biodiversity at all levels in their natural habitat in order to protect the threatened species. It involves hotspots and protected areas. Hotspots are areas of high endemism and high level of species richness. Protected areas are ecological/biogeographical areas where biological diversity along with natural and cultural resources is protected, maintained and managed through legal or other effective measures. Protected areas include national parks, sanctuaries and biosphere reserves. Ex-situ conservation is conservation of threatened plants and animals in places outside their natural homes under full protection and supervision. It includes offsite collections and gene banks.

Question. Compare narrowly utilitarian and broadly utilitarian approaches to conserve biodiversity,with the help of suitable examples.
Answer. There are a number of reasons to conserve biodiversity which can be grouped as:
(a) Narrow Utilitarian : Human derive a major part of their requirement from organisms. Their direct benefits are countless. Like (i) Food cereals : Pulses, fruits, vegetables, milk, egg, meat cones from plants and animals (ii) Fats and oils are obtained from plants and animal. (iii) Firewood as a source of energy for cooking and heating. (iv) Fibres, e.g., cotton, flax silk, wool. (v) Industrial products like tannins, lubricant dyes, resins, and perfumes. (vi) Drugs: Nearly 25% of drugs being used by us are directly coming from plants.
(b) Broadly Utilitarian : Biodiversity is fundamental to ecosystem services of nature. For example (i) Oxygen: Through their photosynthetic activity plants are replenishing oxygen of the atmosphere. Amazon rain forest is estimated to contribute 20% of it. (ii) Pollination: Bees, bumble bees, butterflies, moths, beetles, birds and bats are engaged in pollination of plants which is essential for formation of fruits and seeds. (iii) Climate regulation: Forest and oceanic systems regulate global climate. (iv) Aquifers: Plant cover is essential for retention of rain water, its percolation and storage in aquifers and reservoirs. (v) Flood and erosion control: Plant cover protects the soil from wind and water erosion. Run off of rain water is reduced so that flood water is rarely formed. (vi) Nutrient cycling : It is essential for continued availability of nutrients to plants without which there would be no photosynthetic activity.

Question. There are many animals that have become extinct in the wild but continue to be maintained in Zoological parks.
(a) What type of biodiversity conservation is observed in this case?
(b) Explain any other two ways which help in this type of conservation. 
Answer. (a) Zoological Parks represent ex situ conservation.
(b) Ex situ conservation, is conservation of endangered plants and animals outside their natural homes. It includes tissue culture and cryopreservation. Tissue culture is carried out through callus formation, embryoids, pollen grain culture and shoot tip culture for those plants which are either seedless, variable seed progeny or where clone is to be maintained. The method is useful in maintaining a large number of genotypes in small area, rapid multiplication of even endangered species and for hybrid rescue. Shoot tip culture maintains virus free plants. It is used for international exchange of germplasm in vegetatively multiplied cultivars, e.g., banana, potato.

Question. The sacred groves of Aravalli Hills and Ooty botanical garden both aim at biodiversity conservation. How do they differ in their approaches? Explain. 
Answer. Sacred groves are undisturbed forest patches, surrounded by highly degraded landscapes where not even a single branch of tree is allowed to be cut. As a result, many endemic species which are rare or have become extinct, seen to flourish here. While botanical gardens are areas where many species of plants, are conserved outside their natural habitats. They help to restore endangered species, whose chances of survival are very small. Thus, sacred groves of Aravalli Hills are sites of in-situ conservation, where endangered species are protected in their natural habitat whereas Ooty Botanical gardens are sites of ex situ conservation, where the endangered species are protected outside their natural habitats.

Question. What are the two types of desirable approaches to conserve biodiversity? Explain with examples bringing out the difference between the two types. 
Answer. Conservation of biodiversity is protection, uplift and scientific management of biodiversity so as to maintain it at its optimum level and derive sustainable benefits for the present as well as future generations. There are two types of conservation strategies – in situ (on site) and ex situ (offsite).
In situ conservation is conservation and protection of the whole ecosystem and its biodiversity at all levels in their natural habitat in order to protect the threatened species. It involves hotspots and protected areas. Hotspots are areas of high endemism and high level of species richness. Protected areas are ecological/biogeographical areas where biological diversity along with natural and cultural resources is protected, maintained and managed through legal or other effective measures. Protected areas include national parks, sanctuaries and biosphere reserves. Ex-situ conservation is conservation of threatened plants and animals in places outside their natural homes under full protection and supervision. It includes offsite collections and gene banks.

Question. Explain the importance of biodiversity hotspots and sacred groves. 
Answer. (i) Hotspots : ‘Biodiversity hotspots’ are the regions which are characterised by very high levels of species richness and high degree of endemism. India has three hotspots – Indo-Burma (North-East India), Himalayas, and Western Ghats. Importance of hotspots are as follows:
– Maintaining genetic diversity of all present species and varieties.
– Maintaining viable populations of native species, subspecies and varieties.
– Maintaining resilience in species/habitats/
ecosystems to adapt to environmental changes.
– Maintaining the various types of communities/ ecosystems/habitats both in number and distribution.
– Checking human aided introduction of alien/ exotic species.
(ii) Sacred forests or sacred groves are forest patches around places of worship which are held in high esteem by tribal communities. They are the most undisturbed forest patches (island of pristine forests) which are often surrounded by highly degraded landscapes. They are found in several parts of India, e.g., Karnataka, Maharashtra, Rajasthan (Aravali), Madhya Pradesh (Sarguja, Chanada and Bastar), Kerala, Meghalaya. Temples built by tribals are found surrounded by deodar forests in Kumaon region, Jaintia and Khasi hills in Meghalaya. Not a single branch is allowed to be cut from these forests. As a result, many endemic species which are rare or have become extinct elsewhere can be seen to flourish here. Bishnois of Rajasthan protect Prosopis cineraria and Black Buck religiously. Some water bodies are also held sacred in certain places. e.g., Khecheopalri in Sikkim. Their aquatic flora and fauna are naturally preserved.50.

Question. (a) Explain the narrowly utilitarian, broadly utilitarian and ethical arguments in favour of conservation of biodiversity.
(b) How is designation of certain areas as hotspots a step towards biodiversity conservation? Name any two hotspots in India.
Answer. Ethical human beings share the biosphere with over a million species of plants, animals and microbes. They have evolved just as we have evolved. Every living species has an intrinsic value though it may not have any direct economic value. It is therefore, our moral and ethical duty not to destroy them. Instead we should take care of their well being so as to pass the rich biological legacy to future generations.

Please click on below link to download CBSE Class 12 Biology Biodiversity And Conservation Worksheet Set D