NCERT Solutions Class 12 Biology
Chapter 15: Biodiversity and Conservation
Complete Question Bank with Detailed Solutions for CBSE Board Exams
1
Question
Name the three important components of biodiversity.
Answer
The three important components of biodiversity are:
- Genetic diversity - Variation in genes within species
- Species diversity - Variety of different species in an ecosystem
- Ecological diversity - Variety of ecosystems and habitats
2
Question
How do ecologists estimate the total number of species present in the world?
Answer
Ecologists estimate the total number of species present in the world through two main methods:
- Rate of discovery method: By estimating the rate of discovery of new species
- Statistical comparison method: By statistically comparing the temperate-tropical species richness in an exhaustively studied group (like insects) and extrapolating this ratio to other groups of animals and plants for a gross estimate
3
Question
Write any three hypotheses put forth by ecologists explaining the existence of greater biodiversity in tropical regions than in temperate regions.
Answer
Three hypotheses to explain greater biodiversity in tropical regions:
- Constant environment hypothesis: The constant environment in the tropics promotes niche specialization and increased species diversity
- Solar radiation hypothesis: Longer exposure to solar radiation in tropical regions leads to higher productivity and indirectly to greater species diversity
- No glaciation hypothesis: Absence of glaciation in tropical regions allowed undisturbed development and flourishing of species, resulting in more species diversity
4
Question
What is the significance of the slope of regression in a species-area relationship?
Answer
The slope of regression (regression coefficient Z) in a species-area relationship indicates:
- How species richness decreases as area decreases
- For most taxonomic groups or regions, Z ranges from 0.1-0.2
- For very large areas like continents, the slope is much steeper with Z values ranging from 0.6-1.2
5
Question
What are the major causes of species losses in a geographical region?
Answer
The four major causes of species loss, known as "The Evil Quartet," are:
- Habitat loss and fragmentation - Destruction of natural habitats
- Over-exploitation - Excessive use of natural resources
- Alien species invasions - Introduction of non-native species
- Co-extinctions - Extinction of species due to loss of other dependent species
6
Question
How is biodiversity important for ecosystem functioning?
Answer
Biodiversity is important for ecosystem functioning because:
- Stability: Communities with more species tend to be more stable than those with fewer species
- Productivity: Ecosystems with higher biodiversity show greater productivity than those with lower biodiversity
- Ecosystem health: Rich biodiversity is essential for ecosystem health and human survival due to the interlinked nature of species
- Resilience: Increased biodiversity provides resilience against natural or human-caused disturbances
7
Question
What are sacred groves? What is their role in conservation?
Answer
Sacred groves are forest patches designated for worship in parts of India where all trees and wildlife are venerated and wholly protected.
Role in conservation:
- They play a vital role in conservation by preventing any exploitation
- Tribal communities prohibit even cutting a single branch
- This results in preservation of ecosystems and their biodiversity
- Found in Khasi and Jaintia Hills (Meghalaya), Western Ghats (Karnataka and Maharashtra)
8
Question
Among the ecosystem services are control of floods and soil erosion. How is this achieved by the biotic components of the ecosystem?
Answer
Biotic components, particularly plants, achieve these ecosystem services through:
Control of Soil Erosion:
- Plant roots hold soil particles together, preventing loss from wind or water
- Plants increase soil porosity and fertility
Control of Floods:
- Plants retain water and prevent rapid runoff of rainwater
- Litter and humus act as sponges, allowing water to percolate and recharge groundwater
- This prevents surface flooding by controlling water flow
9
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 mainly because:
- Mobility advantage: Animals can move to escape predators and unfavorable environments, while plants are stationary and have limited adaptation mechanisms
- Advanced nervous system: Animals possess well-developed nervous systems that allow them to receive stimuli and respond to external factors, enabling better adaptation and survival
- Behavioral adaptations: Animals can modify their behavior to suit different environments, leading to greater ecological opportunities
10
Question
Can you think of a situation where we deliberately want to make a species extinct? How would you justify it?
Answer
A deliberate extinction may be justified for species harmful to humans, such as:
- Disease-causing pathogens: HIV virus, polio virus, smallpox virus
- Harmful bacteria: Those causing deadly diseases
Justification: These microorganisms are not part of any major food chain, so their removal would not significantly impact the ecosystem while benefiting human health and survival.
Multiple Choice Questions (MCQs)
11
Question
Biodiversity of a geographical region represents
Answer
Correct Answer: (b) The diversity in the organisms living in the region.
Biodiversity encompasses the variety of all living organisms in a particular geographical area, including genetic, species, and ecological diversity.
12
Question
Which of the following countries has the highest biodiversity?
Answer
Correct Answer: (a) South America.
South America, particularly the Amazon rainforest region, has the highest biodiversity in the world due to its tropical climate and diverse ecosystems.
13
Question
Which one of the following is an example of ex situ conservation?
Answer
Correct Answer: (b) Seed bank.
Ex situ conservation involves preserving species outside their natural habitat. Seed banks preserve genetic material away from natural environments, while sanctuaries, sacred groves, and national parks are in situ conservation methods.
14
Question
Which one of the following is correct expanded form of the following acronyms?
Answer
Correct Answer: (d) IUCN = International Union for Conservation of Nature and Natural Resources.
IUCN is the global authority on the status of the natural world and measures needed to safeguard it.
15
Question
A collection of plants and seed having diverse alleles of all the genes of a crop is called
Answer
Correct Answer: (b) Germplasm.
Germplasm refers to the collection of genetic resources (seeds, plants) that contain diverse alleles representing the genetic diversity of a species or crop.
16
Question
The active chemical drug reserpine is obtained from:
Answer
Correct Answer: (b) Rauwolfia.
Reserpine is an important drug used to treat hypertension and is extracted from Rauwolfia serpentina (Indian snakeroot).
17
Question
Which of the following is not a cause for loss of biodiversity?
Answer
Correct Answer: (c) Keeping animals in zoological parks.
Zoological parks are conservation facilities designed to protect endangered species through ex situ conservation, not a cause of biodiversity loss.
18
Question
Where among the following will you find pitcher plant?
Answer
Correct Answer: (a) Rain forest of North-East India.
Pitcher plants (Nepenthes) are carnivorous plants found in the high-humidity environments of Northeast Indian rainforests.
19
Question
Which of the following statements is correct?
Answer
Correct Answer: (c) Steller's sea cow is an extinct animal.
Steller's sea cow was a large marine mammal that became extinct in 1768 due to overhunting, just 27 years after its discovery.
20
Question
Which one of the following is not a major characteristic feature of biodiversity hot spots?
Answer
Correct Answer: (d) Mostly located in the polar regions.
Biodiversity hotspots are characterized by high species richness, endemism, and are mainly located in tropical regions, not polar regions which have lower biodiversity.
21
Question
What is common to the following plants: Nepenthes, Psilotum, Rauwolfia and Aconitum?
Answer
Correct Answer: (c) All are prone to over exploitation.
These plants are vulnerable due to their medicinal or commercial value, making them targets for over-exploitation and requiring conservation efforts.
22
Question
The one-horned rhinoceros is specific to which of the following sanctuary?
Answer
Correct Answer: (c) Kaziranga.
Kaziranga National Park in Assam is famous for its population of one-horned rhinoceros and is a UNESCO World Heritage Site.
23
Question
Which one of the following pairs of organisms are exotic species introduced in India?
Answer
Correct Answer: (a) Lantana camara, water hyacinth.
Both Lantana camara and water hyacinth are invasive exotic species introduced to India that have caused ecological problems.
24
Question
Which of the following group exhibit more species diversity?
Answer
Correct Answer: (d) Fungi.
Fungi exhibit the highest species diversity among the given options, with over 100,000 known species and many more yet to be discovered.
25
Question
Which one of the following is not observed in biodiversity hot spots?
Answer
Correct Answer: (a) Lesser inter-specific competition.
Biodiversity hotspots have high species density, leading to greater inter-specific competition, not lesser competition.
26
Question
Amongst the animal groups given below, which one appears to be more vulnerable to extinction?
Answer
Correct Answer: (c) Amphibians.
Amphibians are most vulnerable to extinction due to their sensitivity to environmental changes, pollution, and habitat loss, particularly water pollution affecting their breeding.
27
Question
The historic convention on Biological Diversity held in Rio de Janeiro in 1992 is known as
Answer
Correct Answer: (b) The Earth Summit.
The Rio Earth Summit of 1992 was a landmark event that led to the Convention on Biological Diversity and other important environmental agreements.
28
Question
What is common to the techniques (i) in vitro fertilisation, (ii) Cryopreservation and (iii) tissue culture?
Answer
Correct Answer: (b) All are ex situ conservation methods.
These techniques preserve biological material outside their natural habitat in controlled laboratory or artificial environments.
29
Question
Which one of the following is an endangered plant species of India?
Answer
Correct Answer: (d) All of the above.
All three species - Rauwolfia serpentina, Santalum album (Sandalwood), and Cycas beddonei are endangered plant species in India due to over-exploitation and habitat loss.
30
Question
Keystone species deserve protection because these
Answer
Correct Answer: (d) Play an important role in supporting other species.
Keystone species have a disproportionately large impact on their ecosystem structure and function, supporting many other species in the food web.
31
Question
Which of the following is not an invasive alien species in the Indian context?
Answer
Correct Answer: (b) Cynodon.
Cynodon (Bermuda grass) is a native species in India, while Lantana, Parthenium, and Eichhornia (water hyacinth) are invasive alien species.
Key Points to Remember
- Biodiversity has three components: genetic, species, and ecological diversity
- Tropical regions have higher biodiversity due to constant environment, more solar radiation, and no glaciation
- The Evil Quartet: habitat loss, over-exploitation, alien species, and co-extinctions
- Sacred groves are traditional conservation methods in India
- Ex situ conservation includes seed banks, tissue culture, and cryopreservation
- Keystone species play crucial roles in supporting ecosystem structure
Additional Information
This comprehensive question bank covers all aspects of NCERT Class 12 Biology Chapter 15 on Biodiversity and Conservation, providing:
Study Benefits
- Complete coverage of theoretical concepts and MCQs
- Detailed explanations for better understanding
- Perfect preparation for CBSE board exams and competitive tests
- Structured format for systematic learning
Understanding biodiversity and conservation is crucial for:
- Environmental science and ecology concepts
- NEET and other competitive examinations
- Building awareness about conservation issues
- Developing scientific thinking about ecosystem services
NCERT Solutions Class 12 Biology Chapter 15 - Questions 32-61
CBSE Class 12 Biology - Biodiversity and Conservation (Continued)
32
Question
Among the ecosystem mentioned below, where can one find maximum biodiversity?
- (a) Mangroves
- (b) Desert
- (c) Coral reefs
- (d) Alpine meadows
Answer
Answer: (c) Coral reefs
Coral reefs are the ecosystem among those listed where one can find maximum biodiversity. They are among the most diverse ecosystems on Earth, supporting numerous species of fish, invertebrates, and other marine life.
33
Question
Genetic diversity in agricultural crops is threatened by
- (a) intensive use of pesticides
- (b) extensive intercropping
- (c) intensive use of fertilisers
- (d) introduction of high yielding varieties
Answer
Answer: (d) introduction of high yielding varieties
Genetic diversity in agricultural crops is threatened by the introduction of high yielding varieties because they replace traditional varieties, leading to genetic erosion and loss of local cultivars.
34
Question
What is common to Lantana, Eichhornia and African catfish?
- (a) All are endangered species of India
- (b) All are keystone species
- (c) All are mammals found in India
- (d) All the species are neither threatened nor indigenous species of India
Answer
Answer: (d) All the species are neither threatened nor indigenous species of India
Lantana, Eichhornia (water hyacinth), and African catfish are all exotic/invasive species introduced to India. They are not native to India and are not threatened species.
35
Question
Which of the following forests is known as the lungs of the planet Earth?
- (a) Taiga forest
- (b) Tundra forest
- (c) Amazon rainforest
- (d) Rainforests of North East India
Answer
Answer: (c) Amazon rainforest
The Amazon rainforest is known as the lungs of the planet Earth because it produces about 20% of the world's oxygen and absorbs large amounts of carbon dioxide.
36
Question
Match the animals given in column I with their location in column II.
| Column I | Column II |
|---|---|
| A. Dodo | (i) Africa |
| B. Quagga | (ii) Russia |
| C. Thylacine | (iii) Mauritius |
| D. Stellars sea cow | (iv) Australia |
Choose the correct match from the following:
- (a) A-(i), B-(iii), C-(ii), D-(iv)
- (b) A-(iv), B-(iii), C-(i), D-(ii)
- (c) A-(iii), B-(i), C-(ii), D-(iv)
- (d) A-(iii), B-(i), C-(iv), D-(ii)
Answer
Answer: (d) A-(iii), B-(i), C-(iv), D-(ii)
The correct matches are: A-Dodo (iii) Mauritius; B-Quagga (i) Africa; C-Thylacine (iv) Australia; D-Stellars sea cow (ii) Russia.
37
Question
Assertion: Tropical rainforests are disappearing fast from developing countries like India.
Reason: No value is attached to these forests because they are poor in biodiversity.
Answer
Answer: (c) Assertion is correct but reason is wrong
The assertion is true - tropical rainforests are disappearing fast. However, the reason is wrong because tropical rainforests are actually rich in biodiversity, not poor.
38
Question
Assertion: Tropical rainforest are rich in flora and fauna along with microbes on this biosphere.
Reason: The low latitude humid tropics harbor the rainforest ecosystems.
Answer
Answer: (a) Both assertion and reason are correct statements and reason is correct explanation for assertion
Both statements are correct. Tropical rainforests are indeed rich in biodiversity, and this is because they are located in low latitude humid tropical regions.
39
Question
Assertion: Biodiversity is declining at an accelerated rate.
Reason: Exotic species cause extinction of endemic species.
Answer
Answer: (b) Both assertion and reason are correct statements but reason is not correct explanation for assertion
Both statements are correct, but exotic species are just one of many causes of biodiversity decline, not the primary explanation.
40
Question
Assertion: Tropical rainforest are rich in species diversity than temperate forest.
Reason: Frequent glaciation was quite common in temperate region in the past and absent in tropical rainforest.
Answer
Answer: (a) Both assertion and reason are correct statements and reason is correct explanation for assertion
Both statements are correct. Tropical rainforests have higher species diversity, and the absence of glaciation in tropical regions (unlike temperate regions) allowed continuous evolution and speciation.
41
Question
Assertion: IUCN maintains the red list of threatened species to assess conservation of different species.
Reason: Threatened species are those living species which are on the verge of extinction.
Answer
Answer: (b) Both assertion and reason are correct statements but reason is not correct explanation for assertion
Both statements are correct, but the reason doesn't explain why IUCN maintains the red list - it's maintained for conservation assessment, not just because species are threatened.
42
Question
Assertion: According to broadly utilitarian arguments, biodiversity needs to be conserved as it plays important role in many ecosystem services.
Reason: Species diversity at molecular and genetic levels are explored to obtain products of economic importance.
Answer
Answer: (c) Assertion is correct statement but reason is wrong statement
The assertion is correct about utilitarian conservation arguments, but the reason confuses species diversity with genetic diversity and doesn't accurately describe the utilitarian approach.
43
Question
Assertion: Species with high genetic variability are at greater risk of extinction than species with low genetic variability.
Reason: Species with low genetic variability are more vulnerable to predators and environmental challenges.
Answer
Answer: (d) Assertion is wrong statement but reason is correct statement
The assertion is wrong - species with high genetic variability are actually less at risk. The reason is correct - species with low genetic variability are more vulnerable.
44
Question
Assertion: Biodiversity loss of a region is only dependent on the human population around the region.
Reason: Overexploitation of a species reduces the size of its population and can eventually lead to its extinction.
Answer
Answer: (d) Assertion is wrong statement but reason is correct statement
The assertion is wrong - biodiversity loss has multiple causes beyond human population. The reason is correct about overexploitation leading to extinction.
45
Question
Assertion: Nile Perch introduced into Lake Victoria in east Africa lead to extinction of many species of Cichlid fish.
Reason: When alien species are introduced in a region, they become invasive and cause extinction of indigenous species.
Answer
Answer: (a) Assertion and reason both are correct statements and reason is correct explanation for assertion
Both statements are correct. The Nile Perch did cause extinction of many Cichlid fish species in Lake Victoria, and this is a classic example of how invasive alien species can cause extinction of indigenous species.
46
Question
Assertion: Traditionally, sacred groves acted as repository for various medicines.
Reason: In modern times, sacred groves have become biodiversity rich areas.
Answer
Answer: (b) Assertion and reason both are correct statements but reason is not correct explanation for assertion
Both statements are correct, but the reason doesn't explain why sacred groves traditionally acted as medicine repositories - they were always biodiversity rich, not just in modern times.
47
Question
The following graph shows the species-area relationship. Name the naturalist who studied the kind of relationship shown in the graph. Write the observations made by him.
Answer
Answer: Alexander von Humboldt
He observed that within a region, species richness increased with increasing explored area but only up to a limit. This relationship can be described mathematically as S = CAᶻ, where S is species richness, A is area, and C and Z are constants.
48
Question
Write the situations as discovered by the ecologists when the value of Z (slope of the line) lies between (a) 0.1 and 0.2 (b) 0.6 and 1.2. What does Z stand for?
Answer
(a) Z between 0.1 and 0.2: The slopes regression lines are similar when unaffected distribution in an area is analysed.
(b) Z between 0.6 and 1.2: The slope of regression is steeper when analysing species-area relationships among very large areas like entire continents.
Z stands for: The regression coefficient (slope of the line in the species-area relationship).
49
Question
When would the slope of the line b become steeper?
Answer
The slope of the line (b) becomes steeper if species richness is more, i.e., when Z is in the range 0.62–1.2. This typically occurs when analyzing very large geographical areas like entire continents.
50
Question
The following diagram shows global biodiversity distribution of major plant taxa. Which group of plants are most endangered?
Answer
Answer: Lichens
Lichens are the most endangered group of plants among major plant taxa shown in the global biodiversity distribution diagram, primarily due to their sensitivity to air pollution and habitat destruction.
51
Question
Why are mosses/ferns so few? Give reason.
Answer
Mosses and ferns are few because they need humid forest conditions that are fast disappearing. They require specific moisture conditions and are highly dependent on water for reproduction, making them vulnerable to habitat loss and climate change.
52
Question
How do fungi that are heterotrophs sustain themselves as a large population?
Answer
Fungi sustain themselves as a large population due to their wider adaptability to changing environmental conditions and their ability to grow on dead organic matter. As decomposers, they have abundant food sources and can survive in diverse habitats.
53
Question
Which group of plants is most advanced and which one is most primitive?
Answer
The most advanced group of plants is angiosperms (flowering plants), while the most primitive group is fungi (though technically fungi are now classified as a separate kingdom, not plants).
54
Question
What is the difference between endemic and exotic species?
Answer
Endemic species are native species restricted to a particular geographical region and found nowhere else in the world.
Exotic species are species that are introduced from other geographical regions into an area where they are not naturally found.
55
Question
Western Ghats have a greater amphibian diversity than the Eastern Ghats. What do you infer from the above two statements?
Answer
It can be inferred that the Western Ghats have a greater species diversity overall. The higher amphibian diversity indicates better environmental conditions, higher humidity, and more stable ecosystems that support greater biodiversity.
56
Question
India has more than 50,000 strains of rice. Mention the level of biodiversity it represents.
Answer
More than 50,000 strains of rice in India represent genetic biodiversity (or genetic diversity). This shows the variation within a single species at the genetic level.
57
Question
What are Ramsar sites?
Answer
Ramsar sites are conserved wetlands of international importance. They are designated under the Ramsar Convention for the conservation and sustainable use of wetlands.
58
Question
Name the type of biodiversity represented by the following:
- (i) 1000 varieties of mangoes in India
- (ii) Variations in terms of potency and concentration of reserpine in Rauwolfia vomitoria growing in different regions of Himalayas
Answer
(i) Genetic diversity - The 1000 varieties of mangoes represent variations within the same species.
(ii) Genetic diversity - The variations in reserpine potency and concentration in the same species growing in different regions represent genetic diversity.
59
Question
What are seed banks?
Answer
Seed banks are collections of seeds from many different genetic strains of commercially important plants, kept viable for longer periods. They serve as repositories for genetic diversity and are an important ex-situ conservation method.
60
Question
What is Red Data Book?
Answer
The Red Data Book is a compilation of data on species threatened with extinction, maintained by IUCN (International Union for Conservation of Nature). It provides comprehensive information about the conservation status of various species.
61
Question
Name the unlabelled areas a and b of the pie chart (given alongside) representing the global biodiversity of invertebrates showing their proportionate number of species of major taxa.
Note: Pie chart image referenced in original document
Answer
The unlabelled areas are:
- a – Insects
- b – Molluscs
Insects represent the largest group of invertebrates globally, while molluscs form another significant group in invertebrate biodiversity.
Key Points to Remember
- Coral reefs have the highest biodiversity among marine ecosystems
- High yielding varieties threat genetic diversity in crops
- Amazon rainforest is called the lungs of the Earth
- Species-area relationship was studied by Alexander von Humboldt
- Z value indicates the slope of regression in species-area relationships
- Endemic species are native to specific regions; exotic species are introduced
- Seed banks and Red Data Books are important conservation tools
- Insects represent the largest group of invertebrates globally
Additional Information
These questions (32-61) cover advanced topics in biodiversity and conservation biology, including:
Topics Covered
- Ecosystem diversity and species richness
- Conservation strategies (in-situ and ex-situ)
- Species-area relationships and mathematical models
- Threatened species and conservation status
- Global biodiversity patterns and distribution
- Assertion-reason type questions for deeper understanding
Understanding these concepts is crucial for:
- CBSE Class 12 Biology board examinations
- Competitive exams like NEET, JEE, and other entrance tests
- Building a strong foundation in ecology and conservation biology
- Developing environmental awareness and conservation ethics