Class 12 students can refer to Chapter 15 Biodiversity and Conservation notes given below which is an important chapter in the class 12 Biology book. These notes and important questions and answers have been prepared based on the latest CBSE and NCERT syllabus and books issued for the current academic year. Our team of Business Studies teachers has prepared these notes for class 12 Biology for the benefit of students so that you can read these revision notes and understand each topic carefully.

Biodiversity and Conservation Notes for Class 12 Biology

Case Based MCQs

Case I : Read the following passage and answer the questions from given below.
Within a region, species richness increases with increasing explored area, but only upto a limit.
The given graph explains this relationship.

Question. What does the given figure show?
(a) Rivet-popper hypothesis
(b) Species-area relationship
(c) Proportionate number of species of major taxa
(d) a-ecological diversity

Question. Who gave this concept of increase in species richness with increasing area?
(a) Humboldt
(b) Odum
(c) Edward Wilson
(d) Paul Ehrlich

Case II : Read the following passage and answer the questions from given below.
Biosphere reserves are multipurpose protected areas which are meant for preserving genetic diversity in representative ecosystems of various natural biomes and unique biological communities by protecting wild populations, traditional life style of tribals and domesticated plant/animal genetic resources. Each biosphere reserve has three zones-core, buffer and transition zone.

Question. Refer to the given figure representing different zones of a biosphere reserve and select the correct option regarding it.

(a) A-Limited human activity is allowed such as for research and education.
(b) B-An active co-operation occurs between reserve management and local people for activities like cropping, settlements, etc.
(c) C-No human activity is allowed.
(d) None of these

Question. Biosphere reserves differ from national parks and wildlife sanctuaries because in the former
(a) human beings are not allowed to enter
(b) people are an integral part of the system
(c) plants are paid greater attention than the animals
(d) living organisms are brought from all over the world and preserved for posterity.

Assertion & Reasoning Based MCQs

Two statements are given-one labelled Assertion and the other labelled Reason.
Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.

Question. Assertion : The rate of extinction of organisms have increased in recent years.
Reason : Human activities like deforestation, industrialisation, etc., have destroyed the natural habitat of plants and animals. 

Question. Assertion : Alpha diversity refers to species diversity present in a given community or habitat.
Reason : Alpha diversity is expressed by species richness and species evenness in a community or habitat.

Question. Assertion : Maximum biodiversity occurs in temperate areas.
Reason : Tropical areas have favourable conditions for speciation and for supporting variety and number of organisms.

Very Short Answer Type Questions

Question. What is an exotic species?
Answer : New species entering a geographical region are called exotic species.

Question. Eichhornia crassipes is an alien hydrophyte introduced in India. Mention the problems posed by this plant.
Answer : Eichhornia crassipes, an alien hydrophyte was introduced in Indian waters due to aesthetic value but it turned out to be a problematic species. It has clogged water bodies resulting in death of aquatic plants and animals.

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 Rauwolfia vomitoria growing in different regions of Himalayas. 
Answer : (a) Genetic diversity (b) Genetic diversity

Question. Sometimes introduction of an exotic species upsets native species of the ecosystem.
Substantiate the statement with two examples from India.
Answer : Exotic species often become invasive and drive away the local species. Water hyacinth was introduced in Indian waters due to its aesthetic value. However, it has clogged water bodies resulting in death of several aquatic plants and animals. Eupatorium odoratum has reduced the population of Tectona grandis in North-East.

Short Answer Type Questions

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

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 turn might contribute indirectly to greater diversity.

Question. Why are sacred groves highly protected?
Answer : Sacred groves are forest patches around places of worship, held in high esteem by tribal communities. They 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. “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. 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. 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 a 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.
(b) 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.

Question. Alien species are highly invasive and are a threat to indigenous species. Substantiate this statement with any three 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 due to its aesthetic value 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 East 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 possess threat to indigenous catfishes.

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. ‘In-situ’ conservation can help endangered/ threatened species. Justify the statement.
Answer : ‘In-situ’ conservation helps endangered and threatened species by protecting them in their natural habitats along with their ecosystem and its biodiversity. For example, National parks are the areas maintained by the government for better conservation of wildlife. It is a place where cultivation, grazing, forestry and habitat manipulation are restricted.
Sanctuaries are places where wild animals can take refuge without being hunted. Activities like collection of forest products, private ownership land, tilling of land, etc., are allowed but animal hunting is prohibited. Biosphere reserves are meant for preserving genetic diversity in representative ecosystems of various natural biomes and unique biological communities by protecting wild populations, traditional life style of tribals and domesticated plant/animal genetic resources.

 Long Answer Type Questions

Question. (a) Explain the species-area relationship using the graphical representation given below.

(b) Explain giving reasons why there is greater biodiversity in tropical regions of the Earth.
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.
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.
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.
Slope of line 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.
The equation of curve is S = CA^z where,
S = Species richness
C = Y – intercept
A = Area
Z = Slope of the line (regression coefficient).
The graph on species- area relationship shows that within a region, species richness increases with increasing explorable area, but only upto a certain limit. The relation between species richness and area for a wide variety of taxa turns out to be rectangular hyperbola.
(b) 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.
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. (a) According to ecologists, tropical regions in the world account for greater biological diversity. Justify.
(b) Why are habitat loss and alien species invasion considered as the causes of biodiversity loss? Explain with the help of an example of each.
Answer : (a) On the land, maximum primary productivity is found in tropical rainforest. Various factors which contribute to high productivity in tropics are discussed ahead. Maximum light is available in tropics. Due to this photosynthesis is maximum and net primary productivity is highest in tropics. Climate of tropics is warm and humid. Appropriate temperature, rain and humidity increase productivity of tropics. Moreover, ecosystem with higher biodiversity are more productive.
(b) Loss of habitat results in annihilation of plants, microorganisms and forcing out of animals which in alien lands die out after sometime due to unfavourable conditions. Fragmentation of habitats results in disruption of complex interactions among species and animals requiring large territories are badly affected. E.g., mammals and birds.
Alien species often become invasive and drive away the local species. They have proved harmful in both aquatic and terrestrial ecosystems. E.g., water hyacinth was introduced in Indian waters to reduce pollution. It clogged water bodies at many places resulting in death of several plants and animals.