NCERT Solutions for Class 12 Science Biology Chapter 15 - Biodiversity And Conservation

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Due to the environment of South America, it is rich in high biodiversity. The large of South America consists of different ecosystems that together contain the World's largest biodiversity. It has approximately 5500 species of plant, 3000 fresh water fishes, and 700 mammalian species. It also contain several specie of birds and reptiles.

Hence, the correct answer is option a.

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Keeping animals in zoological parks is not a cause for loss of biodiversity. Zoological, botanical gardens and wildlife safari are ex-situ conservation method for biodiversity conservation. In this approach, the threatened plants and animal species are taken out from their natural habitat and placed in special setting where they can be protected and given special care.

Hence, the correct answer is option C.

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Cynodon is found in several tropical and sub-tropical regions including India and it is not an alien-species.

Hence, the correct answer is option b.

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The Pitcher-plant is found in the rainforest of North-East India. This plant is grow in a soil that contains less nitrate content and they obtain nutrients by trapping insects.

Hence, the correct answer is option a.

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Biodiversity hotspots are the regions that are characterised by the presence of large number of flora and fauna, abundance of endemic species and are mostly located in the tropics and temperate region. Their are no biodiversity hotspots in polar regions.

Hence, the correct answer is option d.

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Nepenthes is also known as the pitcher plant and is an insectivorous plant. While Psilotum is a pteridophyte and is used for medicinal purpose. Aconitum and Rouwolfia is a medicinal plant.
All these plants have different properties and are used prone to exploitation. This characteristics is common in all plants.

Hence, the correct answer is option d. 

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One-horned rhinoceros species are found in the Kaziranga National Park. It is an endangered species of rhinoceros.

Hence, the correct answer is option c.

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According to the IUCN regional red listing guide lines, 32% of amphibian species, 23% all mammals species, 31% of gymnosperms species in the world face extinction. They have highest percentage of endangered species and threats involves habitat loss, fragmentation and degradation, climate change, alien species invasion.

Hence, the correct answer is option c.

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Rauwolfia Serpentina, Santalum album, cycas beddonei all are endangered plant species of India. These plants are threat of extinctions because of their medicinal and commercial importance.

Hence, the correct answer is option d.

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Lantana, Eichhornia and African cat fish are neither indigenous species nor threatened species of India. All these three species are exotic species that are invasive results in the extinction of indigenous species.

Hence, the correct answer is option c.

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The extinction of passenger pigeon was due to over-exploitation of natural resources by humans.

Hence, the correct answer is option b.

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Steller's sea cow, and passenger pigeon are extinct due to over-exploitation of natural resources by humans.

Hence, the correct answer is option c.

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Coral reefs have the highest biodiversity with its microbiota that represents about 4-5% of the described global biota.

Hence, the correct answer is option c.

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The Amazon rain forest is also called 'Lungs of the planet'. It is a huge forest that harbour millions of plants and animal species.

Hence, the correct answer is option c.

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Rauwolfia Vomitoria produces an active chemical called reserpine.

Hence, the correct answer is option b.

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The tropical evergreen rain forest exhibit less seasonal variations. Maximum biodiversity on land is shown by the tropics and these regions have high productivity due to minimum temperature variation.

Hence, the correct answer is option a.

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The historic convention on biological diversity ('The Earth Summit') was held in Rio de Janeiro in 1992. This calls all the nation to take appropriate measures for the conservation of biodiversity and sustainable utilisation of its benefits.

Hence, the correct answer is option b.

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In-vitro fertilisation, cryopreservation and tissue culture all are ex-situ conservation method of biodiversity. The gametes of threatened plants and animal species can be preserved in viable and fertile condition for long periods by using cryopreservation techniques.
Eggs can be fertilised in vitro, and plants can be propagated by using tissue culture method. Seeds of different genetic strains of commercially important plants can be kept for longer period in seed banks.

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The characteristics that makes a community stable are as follows:

(i) Less or minimum variation in the productivity from year to year.
(ii) Resistance and resilience to the occasional disturbances that is caused either naturally or artificially.
(iii) Resistance to alien species invasions.

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The mass extinction of the species in the past occurred due to natural calamities such as flood, drought volcanic eruptions and so on. It can also be caused due to temperature change and fall all in sea level or alien species invasion.

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The greater ecological diversity in India is due to its deserts, rain forests, mangroves, coral reefs, wetlands, estuaries and alpine meadows. All these has a ecosystems diversity than a scondinavian country like Norway.

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Crop-field is a man-made ecosystem and has high primary productivity but have low diversity.

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The 'Red' colour in the IUCN Red list (2004) indicates the extinct endangered species.

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Biodiversity hotspots are regions having high level of species richness. The protection of endangered species can reduce the current rate of extinction and such regions can be protected as national parks, sanctuaries and biological reserves.

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Species diversity is the diversity at species level. For example: Western Ghats have a greater amphibian species diversity than the eastern Ghats.
Ecological diversity is the diversity at ecosystem level. For example: Deserts, rain forests, mangroves, coral reefs, wetlands, estuaries and alpine meadows has a greater ecosystem diversity than a scandinavian country such as Norway.

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The genetic variation shown by the medicinal plant Rauwolfia Vomitoria growing in different himalayan ranges is due to the potency and concentration of the active chemical called resprine produced by this plant.

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The Red Data Book is a public document created in 2004 in order to record endangered and rare species of plants, animals, fungi as well as some local species that are present in a specific region. It provides complete information for research, studies and to monitor the programs on endangered species and rare species as well as their habitats.

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A gene pool is defined as the total genetic diversity present within a population or a species. A large gene pool represents great genetic diversity and has ability to withstand the challenges possessed by environmental stresses.

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Frugivorous are defined as the fruit-eating birds and mammals found in the tropical forests.

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IUCN stands for International Union for conservation of nature and natural resources.

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(i) Bioprospecting is the exploring molecular, genetic and species-level diversity to obtain products of economic importance.
(ii) Endemism: It is the ecological state of a species confined to a particular region and not found anywhere else.

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Both the plants are angiosperms flowering plants and an invasive weed species.

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Fig. A represents tiger that belongs to class mammalia.
Fig. B represents snake that belongs to class reptilia.
Both the animals belongs phylum chordata and they are characterized by the presences of a notochord, dorsal hollow nerve cord and paired pharyngeal gill slits.

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The earlier species extinction was due to natural causes such as volcanic eruption, fall in sea level, drought and soon. While extinction of species at present is due to anthrogenic causes.

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Habitat loss and fragmentation is main reason for the cause of extinction of plants and animals. It involves the habitat loss in tropical rain forests. Earlier, the tropical rain forests cover more than 14% of the Earth's land surface and now this forest only covers 6% of the Earth's land surface as it is destroyed fast.
The Amazon rain forest is called the 'lungs of the planet's that harbour millions of species. Now is being cut and cleared for cultivation of soya beans or for conversion of forest land to grasslands for raising beef cattles.
The survival of many species are also threatened by degradation of their habitats. When large habitats are broken into small fragments because of various human activities such as mammals and birds that requires large territories some animals have migratory habits are affected badly results in their population declines.

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Co-extinction involves the extinction of two mutually related or interrelated species. For example: extinction of host fish results in the extinction of all the parasites that are dependent on it for their nutrition. It can be explained with the help of another example: coevolved plant-pollinator mutualism where extinction of one invariably results in the extinction of the other.

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A large area requires more resources for the survival of species in this area by providing more food, space. It results in a large number of species that in a confined areas. This explains the steeper slope occurs when one can draw a species-area curve for a large area.

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No, this not possible to maintain a constant productivity and diversity of a natural resource over 100 years. This is due to increase in size of population results in the depletion of the available resources.

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The tropical regions are remain undisturbed during the course of evolution. These regions remains constant throughout the year. More solar energy is available in these regions that increases the productivity and sustains a diverse group of organisms such regions have less variable climatic conditions.
While temperate regions are more seasonal, less constant and unpredictable due to this, less species diversity are observed.

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Their are many bacteria that cannot be cultured under normal conditions. This creates a problem in their morphological and biochemical studies.
The morphological and biochemical characteristics along with other characteristics are used for the study of biodiversity of the bacteria.
Due to this, the conventional methods are not suitable for study of biodiversity of the bacteria.

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Following criteria should be used for the categorisation of species as threatened are:-
(i) The number of the members of the species are declining at an alarming rate.
(ii) The habitat of such species are either modified or destroyed.
(iii) Increase in the activity of predation.

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Amphibians are more vulnerable to extinction because of their habitat modification or destruction. As they require aquatic and terrestrial habitats for their survival. Threat to their habitat can affect population of amphibians. Change in climatic conditions results in the modification of aquatic habitats, that prevents the amphibians from spawning. Habitat fragmentation involves the isolation of few areas by habitat modification. Small population of amphibians that survive with these fragments are susceptible to inbreeding, genetic drift or extinction because of small fluctuations in the environments.

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Two methods are used for the estimation and extrapolate the number of species on Earth are follows:-
(i) The first or primary method used by the scientists is the estimation of rate of discovery of new species.
(ii) The total number of species are also extrapolated by the statistical comparison made between the tropical and temperate species richness of extinct studied groups of insects.
This ratio is then extrapolated with the existing plants and animal species in order to predict the gross estimation of the number of species present the Earth.

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Biodiversity serves as an important economic as well as ecological benefits for humans.
For example:- Water and natural resources provides health and nutrition to humans. Biodiversity helps to provide employment opportunities for many people. This also helps to ensure that the environment and its food chains are remain stable.

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The two major causes other than anthropogenic causes for biodiversity loss are as follows:-
(i) Alien species invasion:- Invasion of alien species results in the decline or extinction of indigenous species.
For example:- When the Nile Perch is introduced into Lake Victoria in east Africa led to the extinction of an ecologically unique assemblage of more than 200 species of cichild fish in the lake.
(ii) Co-extinctions:- When a species becomes extinct, the plant and animal species associated with it in an obligatory way also become extinct.
For example:- When a host fish species become extinct, its unique assemblage of parasites also become extinct.

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Endangered species are the population of organisms, that are facing a high risk of becoming extinct due to threatened by change in environmental conditions, threat of predator and decrease in their population.
Venus fly trap - Endangered plant species
Siberian tiger - Endangered animal species

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Sacred grows are defined as the traditionally protected patches of forests area around the places of worship. The local tribal communities are actively participating for the protection of these regions and not allow to cut the trees because of religious belief.
1. It helps in the protection of rare, endemic and endangered species.
2. Deforestation in these areas is strictly prohibited.

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For the study of coral reefs - Andaman and Nicobar islands
For the study of Mangrove vegetation - West Bengal (sunderban)
For the study of Estuaries - Coastal areas of Karnataka.

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It is true that maximum amount of solar energy is available in the tropics. This is because the sunlight directly falls at the tropics and duration of day is longer than at higher altitudes. Plenty of sunlight is available in the tropics. Availability of solar energy promotes high productivity and due to this tropics are rich in biodiversity.

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Co-extinction is the phenomenon in which a species becomes extinct, then the plants and animals that were dependent on it also becomes extinct.
For example:- When a fish becomes extinct, many parasites that are dependent on the fish also become extinct. Predators also become extinct as the fish serves as the main source of food.

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The introduction of alien species unintentionally or deliberately cause decline or extinction of indigenous species.
For example:- Nile perch introduced into lake victoria in east Africa led to the extinction of an ecologically unique assemblage of more than 200 species of cichild fish in the lake. Illegal introduction of the African catfish clarias gariepinus for aquaculture posing threat to the indigenous catfishes in the rivers. Species like carrot grass (Parthenium) Lantana and water hyacinth (Eicchornia) are invasive weed species that causes threat to the native species.

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Biodiversity involves different types of species, habitat ecosystem, gene, genepool in a specific place and different parts of the earth.
As an individual, this can be conserved with conservation strategies and management of abiotic and biotic resources.
Biodiversity conservation strategies are as follows:-
(i) Protection of animal and plant species in their natural habitats (in-situ conservation).
(ii) Preservation of critical habitats of endangered species such as feeding, breeding area and resting areas in order to promote their growth and multiplication.
(iii) Activities like hunting and porching should be banned or strictly prohibited.
(iv) Create awareness among people about the importance of biodiversity and its conservation.
(v) Need to avoid the over-exploitation of natural resources. 

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The scientific explanation for the direct relationship between diversity and stability of an ecosystem are as follow:-
In an forest area, a diverse variety of plants species are growing. Plants harbour different variety of insects and on them several varieties of birds are dependent for food.
If a particular species of insects die, then the related insect population will be also affected results in the unavailability of food for birds.
Hence, it means that if the ecosystem is rich in biodiversity, then the primary and secondary productivity is maintained at an optimum level and this helps in maintaining the stability in the ecosystem.

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The 'rivet popper hypothesis' was given by Paul Ehrlich. According to this hypothesis, ecosystem is just like an aeroplane, and all the parts of an aeroplane are joined together by using thousands of rivets (species). If every passenger travelling in its starts popping a rivet to take home (that causes a species to become extinct), then it may not initially affect the 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.
The rivet is removed may also be critical. Loss of rivets on the wings (key species that drive major ecosystem functions) is more serious threat to the flight safety than loss of a few rivets on the seats or windows inside the plane.

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Alexender Von Humboldt observed that within an region, species richness increases with the increasing explored area but only upto a certain limit.
The relationship between species richness and area for a large variety of taxa that includes angiosperm plants, birds, bats, freshwater fishes is turn out to be a rectangular hyperbola.
On an logarithm scale, the relationship between species-area is a straight line and is described with the help of given equation:-
log s = log c + zlogA
where 
S = Species richness
A = Area
Z = slope of line (regression coefficient)
C = Y-Intercept
So, the value of Z-lies between the range of 0.1-0.2 regardless of taxonomic group or the region. This process is called species-area relationship.