NCERT Solutions Class 12 Biology Chapter 15

NCERT Solutions for Class 12 Biology Chapter 15

Biology as a field has not only opened a plethora of options for students, but it has also considerably benefited individuals in improving their lives and the world around them. In addition, the potential for growth in the discipline of biology has attracted many students to pursue this course and a career as a biologist. Biology is concerned with human evolution, genetics, and cells, examining diverse species, the genesis of life, life-sustaining processes and elements, illnesses, diseases and many more.

Biodiversity and its Conservation is the 15th Chapter of Class 12 Biology. The Chapter discusses the term “biodiversity” and “conservation” refers to a wide range of components and features of Biodiversity, which has been identified as the essential component of an ecosystem for maintaining a healthy balance.

Class 12, a significant grade, is a crucial point for students, where they are under pressure to do well in their exams. It is convenient to keep notes on hand for last-minute revisions and clarify any remaining doubts of the chapters. Extramarks has recently come up with Chapter 15 Biology Class 12 NCERT Solutions which  presents detailed answers to the chapter end questions. This gives students a clear idea about the entire chapter. 

Apart from NCERT Solutions for Class 12 Biology Chapter 15, the Extramarks’ website is considered a one-stop solution for all the excellent study material. Extramarks contain material such as NCERT solutions, revision notes, CBSE sample papers, and CBSE past years’ question papers for all Classes for the student’s usage.

Key Topics Covered in NCERT Solutions for Class 12 Biology Chapter 15

All the key topics that are covered in NCERT Solutions for Class 12 Biology Chapter 15- Biodiversity and Conservation are mentioned below:

Levels of Biodiversity
India’s Mega Biodiversity
Patterns of Biodiversity
Importance of Biodiversity
Causes of Loss of Biodiversity 
Conservation of Biodiversity
How do we Conserve Biodiversity?

Let us look at Extramarks in-depth information on each subtopic in NCERT Solutions for Class 12 Biology Chapter 15- Biodiversity and Conservation.


NCERT Solutions for Class 12 Biology Chapter 15 explains that in 1985 , W.G. Rosen invented the word Biodiversity for the first time. It’s a condensed form of two words: “biological” and “diversity.”

The vast diversity of species and types of all living forms on Earth has typically termed Biodiversity or biological diversity. They include microbes, algae, fungi, plants, and animals that live on the planet in various environments, as well as the ecological systems and niches in which they exist.

Levels of Biodiversity

NCERT Solutions for Class 12 Biology Chapter 15 explains the three levels of Biodiversity in the following section:

Genetic Diversity

Genetic Diversity is defined as the amount as well as the type and of genes and chromosomes found in various species, along with the changes in genes as well as the alleles within the species.

A single species might show very high diversity at the genetic level. For e.g. A bacteriophage contains 100 genes on average, whereas Drosophila melanogaster has 13000 genes and Homo sapiens has 30,000–40,000 genes. 

The genetic variation shown by a plant can be in terms of the potency and the concentration of the active chemical that the plant produces. From genetic variety perspective, India has more than 1,000 varieties of mango, and 50,000 genetically different strains of rice.

Variation in a species’ genes rises as the habitat’s size and environmental conditions increase. Adapting to changes in ecological circumstances requires genetic variety. It helps in the formation of new species through speciation.

Species Diversity

It is the quantity and diversity of species in a given region’s diversity and variety. The count of species per unit of area is referred to as species richness. The number of individuals of different species in a particular region represents the species’ evenness or equitability.

NCERT Solutions for Class 12 Biology Chapter 15 says when roughly the same number of individuals represents species, those communities are said to be even. Dominance or unevenness can be seen in communities where one or more species has more members than others. Species diversity is the result of species richness, evenness, or equitability.

The diversity at the species level, for e.g, the Western Ghats have a greater amphibian species diversity as compared to the Eastern Ghats.

Ecological Diversity

Ecosystem diversity refers to the range of forms found in an ecosystem because of various factors such as niche diversity, trophic levels, and ecological processes such as nutrient recycling, food webs, energy flow, dominant species roles, and numerous biotic interactions.

Diversity helps in forming more productive and stable ecosystems that can withstand a variety of environmental challenges, including extended drought.

From the ecosystem perspective, India, with its rain forests, deserts, mangroves, wetlands, coral reefs,

estuaries, and alpine meadows has a much higher ecosystem diversity than any Scandinavian country.

India’s Mega Biodiversity

NCERT Solutions for Class 12 Biology Chapter 15 explains that India has achieved a unique distinction by being designated a mega diversity nation.

Although India consists of 2.4% of the global land area, our share of the global species diversity stands at an impressive 8.1%. This vast variety of species makes India one of the 12 mega diversity countries of the world. Almost 45,000 species of plants and around 90,000 species of animals have been recorded from India.

There are ten biogeographical regions in the nation. The biogeographical zones of India include the Trans Himalaya, Himalaya, Desert, Semi-arid, Western Ghats, Deccan Peninsula, Gangetic Plain, Coasts, North-East, and Islands.

There are 89 national parks in India and 492 animal sanctuaries, 14 biosphere reserves, 6 wetlands, and 5 world heritage sites. There are additional 27 tiger reserves in the nation.

The Deccan peninsula is the most significant biogeographical area, while the Western Ghats and northeast are the biogeographical zones with the most Biodiversity.

Endangered species include 33% of flowering plants, 10% of mammals, 36% of reptiles, 60% of amphibians, and 53% of freshwater fish. The Himalayas and the Western Ghats are the most prosperous areas. North-Eastern Hills and Indian Islands

There are many more species yet to be discovered. According to one of the estimate there are 

more than 1,00,000 plant species and more than 3,00,000 animal species yet to be discovered and described.

Patterns of Biodiversity

NCERT Solutions for Class 12 Biology Chapter 15 describes the two patterns of Biodiversity in the following section:

Latitudinal Gradient

At the poles, there was very little Biodiversity. On the contrary, temperate environments have higher Biodiversity, while tropical rainforests have the most. This is since tropical rain forests provide more appropriate circumstances for a broader range of creatures and fewer or no natural disasters. This has resulted in environmental stability and the development of more species.

In temperate places, severe circumstances prevail only during the winter. However, the polar areas experience highly tough circumstances for most of the year.

There are 118-236 vascular species per 0.1 hectares in tropical forests, while in temperate forests, there are 21-48 species per 0.1 ha. In arctic climates, their population would be 10/0.1 hectare.

Altitudinal Gradient

Due to a decline in temperature and increased seasonal fluctuation, species diversity decreases as we approach high mountains.

Importance of Biodiversity

NCERT Solutions for Class 12 Biology Chapter 15, in detail, explains the importance of Biodiversity in the following section.

  • Source of Food: Only 150 kinds of food plants have been marketed out of 3000. It can be shown that less than 20 species contribute 85 percent of the food output. Only three carbohydrate-rich crops, wheat, corn or maize, and rice, generate two-thirds of the world’s food.
  • Sources of fats and oil: Soybean, coconut, cottonseed, peanut, sunflower, sesame, safflower, mustard, and oil palm are the most common oilseed plants.
  • Fibres: Cotton, jute, flax, hemp, sun hemp, rosella, coir, and agave are the most common fibre sources. The search for new, better fibre-yielding plants is never-ending.
  • New varieties: By mixing domesticated commercial species with their wild cousins, several features, particularly disease resistance, have been enhanced.
  • Drugs and Medicines: Plant-based pharmaceuticals are used in a variety of medications. Thousands of native or wild plants are used in traditional medicine systems worldwide to cure various ailments. Plant chemicals are also known as botany chemicals, and they may be used to make a wide range of synthetic goods.
  • Cultural benefits: People have formed attachments to various plants and animals. Ocimum sanctum (Tulsi) variations flourish in gardens and pots in many Indian households. Ficus religiosa, also known as Peepal, and Prosopis cineraria, also known as Khejri, are sacred trees. They are also revered. Many birds are considered holy. Snakes are revered as well.
  • Ecosystem services: Biodiversity is necessary to survive and use many ecosystems’ and individual species’ products and services. Forest and marine systems regulate temperature and keep the atmosphere’s gaseous composition in check. The Amazon rain forests, which provide 28 percent of the world’s total oxygen, are known as the planet’s lungs. Biodiversity is necessary for natural pest management and the survival of diverse species’ populations.

Causes of Biodiversity Losses

NCERT Solutions for Class 12 Biology Chapter 15 states that the globe is seeing an increased pace of species extinction because of human meddling. There are four key reasons, sometimes known as the “evil quartet”:

Habitat loss and fragmentation

Every year, overpopulation, urbanisation, and industrialisation necessitate more land. Filling marshes, ploughing grasslands, chopping down trees, burning a forest, and removing some vegetation can result in the destruction or fragmentation of natural habitat. Large-territory animals are particularly vulnerable. Migrating animals would certainly get lost and many times they might not be able to survive in the new environment.


Excessive exploitation of a species, whether a plant or an animal, diminishes its population size, putting it at risk of extinction. Due to human overexploitation, three subspecies of Tiger, dodo, star sea cow, and passenger pigeon have been extinct in the past 500 years. Several marine fish populations are now falling down all around the world.

Alien species invasion

Inadvertently, non-native or alien species are frequently employed for commercial and other purposes. As a result, they often become invasive, suffocating the growth and survival of native species.

The most vulnerable ecosystems are those on islands. This is primarily due to their tiny size and limited species diversity.

Co- Extinctions

In nature, some mutualistic connections are required, such as between the Yucca moth and the Yucca flower. The extinction of one will result in the extinction of the other. All parasites located only on the host fish will extinct if the host fish extinct.

Conservation of Biodiversity

Biodiversity conservation is divided into three categories. NCERT Solutions for Class 12 Biology Chapter 15 explains these in the below section:

Narrowly Utilitarian

  • Nature provides us with several direct economic benefits.
  • Nature provides food, such as grains, pulses, fruits, fuel, fibre, and construction materials.
  • Natural goods also make industrial items, including tannins, lubricants, dyes, resins, and fragrances.
  • Medicinal products are also available.
  • Bioprospecting is a strategy for obtaining and developing economically important items by studying genetics and species diversity.

Broadly Utilitarian

  • During photosynthesis, Amazonian forests alone create roughly 20% of oxygen of the entire earth.
  • Pollinators include bees, bumblebees, birds, and bats, which pollinate the plant and allow it to generate the seed.
  • The aesthetic pleasure we derive from biodiversity protection.


  • Humans rely on the existence of all other species that live on or have lived on our planet.
  • The inherent worth of each species and variation is different.
  • It is our moral responsibility to protect and pass on the biological inheritance that has been bestowed on us.

How do we Conserve Biodiversity?

Conservation strategies are divided into two categories, NCERT Solutions for Class 12 Biology Chapter 15 explains them below: 

In Situ Conservation (on-site)

The entire ecosystem and its Biodiversity must be conserved and protected at all levels to safeguard vulnerable species. However, it is not economically feasible nor practically possible to protect all of its biological riches and ecosystems.

Ex Situ Conservation (off-site)

These are methods for preserving any chosen species or variant distant from its natural home. They are collections that are held off-site.

In botanical gardens, zoos, and other places, they are living collections of untamed and domesticated species. Captive breeding is used when the number of surviving individuals is so low that there is no realistic likelihood of in-place survival.

NCERT Solutions for Class 12 Biology Chapter 15 Exercise and Solutions

Extramarks website has become quite popular among students for its quality study material. Students can refer to study tools, including past years’  question papers, revision notes, extra question answers , and more, on the Extramarks’ website. Click on the below links to view NCERT Solutions for Class 12 Biology Chapter 15:

Students may access NCERT Solutions for Class 12 Biology Chapter 15 and other Chapters by clicking here. In addition, students can also explore NCERT Solutions for other Classes below.

By getting access to NCERT Solutions for Class 12 Biology Chapter 15, students can easily access to NCERT questions answers including all the concepts of Biodiversity and Conservation.

Key Features of NCERT Solutions for Class 12 Biology Chapter 15

The NCERT Solutions from Extramarks include all answers to the in-text and end-text questions of the chapter. Through these students can also understand important concepts. . Therefore, students are suggested to read NCERT Solutions provided on the Extramarks’ website to perform well in upcoming board examinations. But, you might wonder, why Extramarks? Well,  this is why:

  • These solutions guide students in understanding concepts through detailed answers of the chapter end questions. By this, they also get a fair idea of how to attempt questions in exams and how to manage time efficiently
  • All subject matter experts have created these solutions.
  • Extramarks’ experts have a wealth of experience, so they know exactly what a student needs to understand in a  chapter. As a result, they provide authentic study material which students can rely upon.   

Q.1 Name the three important components of biodiversity.

Our biosphere is immensely diverse or heterogeneous not only at the species level but all levels of biological organization. Edward Wilson popularised the term biodiversity and explained the three important components of the biosphere:

  1. Genetic diversity: A single species showing a high level of diversity at the genetic level.
  2. Species diversity: The variations that exist at species levels.
  3. Ecological diversity: Large varieties of ecosystems like deserts, mountains, grasslands.

Q.2 How do ecologists estimate the total number of species present in the world?

It is a very difficult task to estimate the total number of species present in the world. According to a study, 1.5 million different kinds of species of plants and animals have been reported however, there is no idea about the numbers that have not been identified yet. More work has been done in temperate regions as compared to tropical regions, thus inventories in temperate regions are more complete and exhaustive for many taxonomic groups. The insect species have been largely studied in both regions. Ecologists use the statistical means of analysis and comparison of the temperate-tropical species richness of this largely studied group of insects and then try to extrapolate this information/ratio to other plants and animals of tropical regions. This allows them to come up with a gross estimate of the total number of plant and animal species present across the world. Some estimates that have been made by this method range from 10 to 50 million different species.

Q.3 Give three hypotheses for explaining why tropics show greatest levels of species richness.

It is well known fact of ecology that species diversity is not uniform across the globe but shows latitudinal diversity. It means that as we move from equator towards the pole, with very few exceptions, tropics ( latitudinal range of 23.5° N to 23.5° S) harbor more species diversity than temperate or polar regions. Given below are three different hypotheses by ecologists for this:

  1. In the past, temperate regions were subjected to frequent climatic changes such as glaciations. However, tropical regions have remained relatively undisturbed for millions of years. This constant environment allowed species to diversify over millions of years without any environmental disturbances.
  2. Tropical regions are less seasonal, relatively more constant and predictable in terms of the environment. This helps in greater species diversification over time.
  3. Tropical regions receive more solar energy throughout the year. This significantly contributes to higher productivity and thus, greater diversity.

Q.4 What is the significance of the slope of regression in a species–area relationship?

The slope of regression depicts the relationship between the number of species present in a given area. One of the most fundamental ecological relationships is that, as the area of region increases, so does the number of different species encountered. It has been found that in smaller areas, where the study is being done, the value of slopes of regression is similar regardless of the taxonomic group or the region under study e.g. the slope of regression for smaller areas remains same across various taxonomic group or region (whether it is the plants in Britain, birds in California or molluscs in New York). However, when a similar analysis is done in larger areas like entire continent (e.g. fruit-eating birds or mammals in the tropical forest across different continents), then the slope of regression is much steeper which means that with the increasing area, the number of species does not increase proportionately.

Q.5 What are the major causes of species losses in a geographical region?

The large varieties of plant and animal species that constitute our biosphere are dwindling at an alarming rate. With passing time, the number of species present across the globe is going down or becoming extinct. This is largely due to human activities and interventions with natural phenomenon. The four major causes of species losses in a geographical region are:

  1. Habitat loss and fragmentation: This has been the most important cause for the loss of species in a geographical region. Human activities have been largely responsible for habitat loss and fragmentation of existing habitats resulting in a very sharp decline in biodiversity. The rain forests, which harbour the maximum variety of species across the globe, are being cut at a very rapid pace due to human needs resulting in the mass extinction of many species of plants and animals, many of which never came to our knowledge as well.
  2. Over-exploitation: With time, the dependence of the human race over natural resources is steadily increasing. Our population is growing at an alarming rate, thereby putting increased pressure on the availability of natural resources. The ‘need’ for natural resources has turned into ‘greed’ with time. All these factors have resulted in over-exploitation of available resources and thus, resulted in the extinction of the species or some species being pushed on the verge of extinction. E.g. overhunting of tigers for skin has made them endangered species across the world.
  3. Alien species invasion: When an alien species is introduced in an ecosystem intentionally or unintentionally, at times, it turns invasive. This invasive property results in the decline or extinction of original species. E.g. great threat is posed on the native species because of invasion of weed species like water hyacinth, Lantana, etc.
  4. Co-extinctions: Many species of plants and animals are interdependent on each other for a living. Extinction of one automatically leads to extinction of the dependent species. E.g. with the extinction of the host fish, the parasites associated with the fish also vanish automatically.

Q.6 How is biodiversity important for ecosystem functioning?

An ecosystem which is more diverse is more stable and more productive because of the delicate balance that is maintained between various species existing in that ecosystem. Each one of them is dependent on the other for some of the other need and this balance is very complicated. In an ecosystem which is not very diverse, even a slight disturbance here and there results in the fall out of the entire ecosystem. The food chains working in the ecosystem are the best example of the interdependence of different trophic levels and suggests how each one of them is connected with each other. Any disturbance in the food chain at any level results in the non-functioning of that food chain affecting the balance of the ecosystem e.g. if snakes are killed and wiped off from the area, rat population will drastically increase in that area. This, in turn, will not only affect the insect species but also will have large impact on agriculture and food storage. However, in a diverse ecosystem, where each trophic level of the food chain has large varieties of plants and animals, a single fall out will not affect the food chain and the balance will be maintained.

The diverse nature also imparts stability to the ecosystem under changing environment and does not affect the productivity of the ecosystem. One species might be more productive under a given climatic condition as compared to the other, so in an ecosystem, where both are present at the same time, the productivity will remain the same under different climatic conditions.

Q.7 What are sacred groves? What is their role in conservation?

Sacred groves are tracts of forests that have been set aside based on the religious and cultural importance of that area and community. All the trees and wildlife within such sacred grooves are given total protection by the community. Thus, it forms important repositories of forest diversity and provides shelter to many plant and animal species that require protection otherwise. India has well over 13,000 documented ‘Sacred Groves’. This allows automatic protection of the wildlife even in the absence of any law. Such grooves are found in Khasi and Jaintia Hills of Meghalaya, Aravali Hills of Rajasthan, Western Ghat regions of Karnataka and Maharashtra. In Meghalaya, sacred grooves are the last refuges for a large number of rare and threatened plant species.

Q.8 Among the ecosystem services are control of floods and soil erosion. How is this achieved by the biotic components of the ecosystem?

Plants form one of the major biotic components of the ecosystem. They play a very big role in the control of floods and soil erosion. When the rainwater falls on the earth, it usually gets soaked into the ground and recharges the groundwater. The root of plants keeps the soil locked and also makes the soil more porous, thereby, allowing more water to seep into the earth. However, with depleting green cover, and more of concrete cover, the rainwater does not enter the earth but runs over the surface, eroding the topsoil and causing floods.

Q.9 The species diversity of plants (22%) is much less than that of animals (72%). What could be the explanation to how animals achieved greater diversification?

The species diversity of plants is much less as compared to that of animals possibly due to the following reasons:

  1. Animals could relocate to different places when the conditions became unsuitable in a particular area, unlike plants which remain at one place. This ability to move to a new geographical condition requires diversification. Plant species either remained in one place or became extinct.
  2. Animals developed more complex body structures, like segmented body or complex nervous system, unlike plants which allowed them to diversify much more under changing environmental conditions.

Q.10 Can you think of a situation where we deliberately want to make a species extinct? How would you justify it?

The viruses, parasites and other disease-causing microorganisms that cause lethal diseases in humans have been targeted for eradication from this world by humans. Major examples of such disease-causing microorganisms are small pox virus and polio virus. Since large populations were affected by these diseases, they were of huge concern to the scientific and medical community. However, with well planned programmes, the smallpox virus was eradicated way back in 1977. World has also become relatively polio-free with massive immunisation programmes except for in few countries like Pakistan and Afghanistan. This deliberate eradication of a living species can be justified by the fact that they played no useful role, at least not any known to humankind, in the ecosystem. Instead, they were harmful to the mankind causing large scale suffering and deaths. Their eradication by no means has affected or will affect the ecological balance.

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