Biodiversity and Conservation Question Answers: NCERT Class 12 Biology

Biodiversity is the variety of living forms present in various ecosystems. It includes variability among life forms from all sources including land, air, and water. Three important components of biodiversity are:

(a) Genetic diversity

(b) Species diversity

(c) Ecosystem diversity

Yes, there are various kinds of parasites and disease-causing microbes that we deliberately want to eradicate from the Earth. Since these micro-organisms are harmful to human beings, scientists are working hard to fight against them. Scientists have been able to eliminate small pox virus from the world through the use of vaccinations. This shows that humans deliberately want to make these species extinct. Several other eradication programmes such as polio and Hepatitis B vaccinations are aimed to eliminate these disease-causing microbes.

The diversity of living organisms present on the Earth is very vast. According to an estimate by researchers, it is about seven millions.

The total number of species present in the world is calculated by ecologists by statistical comparison between a species richness of a well studied group of insects of temperate and tropical regions. Then, these ratios are extrapolated with other groups of plants and animals to calculate the total species richness present on the Earth.

There are three different hypotheses proposed by scientists for explaining species richness in the tropics.

(1) Tropical latitudes receive more solar energy than temperate regions, which leads to high productivity and high species diversity.

(2) Tropical regions have less seasonal variations and have a more or less constant environment. This promotes the niche specialization and thus, high species richness.

(3) Temperate regions were subjected to glaciations during the ice age, while tropical regions remained undisturbed which led to an increase in the species diversity in this region.

The slope of regression (z) has a great significance in order to find a species-area relationship. It has been found that in smaller areas (where the species-area relationship is analyzed), the value of slopes of regression is similar regardless of the taxonomic group or the region. However, when a similar analysis is done in larger areas, then the slope of regression is much steeper.

Biodiversity is the variety of living forms present in various ecosystems. It includes variability among life forms from all sources including land, air, and water. Biodiversity around the world is declining at a very fast pace. The following are the major causes for the loss of biodiversity around the world.

(i) Habitat loss and fragmentation: Habitats of various organisms are altered or destroyed by uncontrolled and unsustainable human activities such as deforestation, slash and burn agriculture, mining, and urbanization. This results in the breaking up of the habitat into small pieces, which effects the movement of migratory animals and also, decreases the genetic exchange between populations leading to a declination of species.

(ii) Over-exploitation: Due to over-hunting and over-exploitation of various plants and animals by humans, many species have become endangered or extinct (such as the tiger and the passenger pigeon).

(iii) Alien species Invasions: Accidental or intentional introduction of non-native species into a habitat has also led to the declination or extinction of indigenous species. For example, the Nile perch introduced in Lake Victoria in Kenya led to the extinction of more than two hundred species of native fish in the lake.

(iv) Co­−extinction: In a native habitat, one species is connected to the other in an intricate network. The extinction of one species causes the extinction of other species, which is associated with it in an obligatory way. For example, the extinction of the host will cause the extinction of its parasites.

An ecosystem with high species diversity is much more stable than an ecosystem with low species diversity. Also, high biodiversity makes the ecosystem more stable in productivity and more resistant towards disturbances such as alien species invasions and floods.

If an ecosystem is rich in biodiversity, then the ecological balance would not get affected. As we all know, various trophic levels are connected through food chains. If any one organism or all organisms of any one trophic level is killed, then it will disrupt the entire food chain. For example, in a food chain, if all plants are killed, then all deer’s will die due to the lack of food. If all deer’s are dead, soon the tigers will also die. Therefore, it can be concluded that if an ecosystem is rich in species, then there will be other food alternatives at each trophic level which would not allow any organism to die due to the absence of their food resource.

Hence, biodiversity plays an important role in maintaining the health and ecological balance of an ecosystem.

Sacred groves are tracts of forest which are regenerated around places of worship. Sacred groves are found in Rajasthan, Western Ghats of Karnataka,and Maharashtra, Meghalaya, and Madhya Pradesh. Sacred groves help in the protection of many rare, threatened, and endemic species of plants and animals found in an area. The process of deforestation is strictly prohibited in this region by tribals. Hence, the sacred grove biodiversity is a rich area.

The biotic components of an ecosystem include the living organisms such as plants and animals. Plants play a very important role in controlling floods and soil erosion. The roots of plants hold the soil particles together, thereby preventing the top layer of the soil to get eroded by wind or running water. The roots also make the soil porous, thereby allowing ground water infiltration and preventing floods. Hence, plants are able to prevent soil erosion and natural calamities such as floods and droughts. They also increase the fertility of soil and biodiversity.

More than 70 percent of species recorded on the Earth are animals and only 22 percent species are plants. There is quiet a large difference in their percentage. This is because animals have adapted themselves to ensure their survival in changing environments in comparison to plants. For example, insects and other animals have developed a complex nervous system to control and coordinate their body structure. Also, repeated body segments with paired appendages and external cuticles have made insects versatile and have given them the ability to survive in various habitats as compared to other life forms.

Invasive species are also known as introduced, exotic or non- native species which are not native to an ecosystem and have the tendency to damage or affect the ecosystem. They are the second major cause of the loss of biodiversity. Some possible reasons are as follows that these species reduces the species diversity of an area:

1. They show rapid growth and reproduces fast and have the potential to cause harm. They are capable of causing extinction of native plants and animals by competing for the limited resources and altering habitat that leads to loss of biodiversity.
2. The sudden introduction of the invasive species to the particular given ecosystem leads to disastrous consequences for those species that are already present there, i.e. native species which also leads to loss of biodiversity.
3. For example: accidental introduction of an Atlantic comb jellyfish species to the Black sea.

Scientists or ecologists made a statistical comparison (by the use of statistics) of the species richness of exhaustively studied groups of insects of the temperate and the tropical regions and extrapolate this ratio to the other groups of animals and plants to calculate gross estimate of the total number of species existing on Earth.

Biodiversity provides several benefits for the human beings and these are as follows:

1. They provides ecosystem services.
2. Food: Biodiversity provides foodstuffs like fruits, nuts, honey, spices etc. 
3. Medicines: Biodiversity is rich in sources which is provided with the therapeutic properties. For example: quinine used for the treatment of malaria, taxol is an anticancer drug etc.
4. Industrial materials: they include building material, fibres, dyes, resins, gums, rubber, oil etc.

Other than anthropogenic causes (human activity), the loss of biodiversity occurs through natural causes like volcanic eruption, climate change, sea level change etc. and co- extinction of species. Co-extinction refers to that when species becomes extinct by any reason, the plants and the animal species which are bind to those species in the obligatory way, also becomes extinct.

Endangered species are represented by the symbol ER. Endangered species are those which are small in numbers and facing high risk of extinction. When the population reduction occurs 50- 70%, population size is <2500 of mature individuals and contains approximately 20% extinction rate in the 20 years in the wild; these are said to be endangered species.

Red panda, Snow leopard, one horned Rhinoceros and Black buck are some animal’s species which are said to be endangered. Baobab tree, Dragon tree, Baseball plant are some examples of endangered plant species.

Sacred grooves are one of the protected areas or natural habitat which have been set under the in situ conservation methods for the protection of wild flora and fauna. They are the sacred forest patches around the places of worship. Undistributed forest patches are surrounded by degraded landscapes. These types of sacred grooves are found in various places in India like Khasi, Jaintia hills of Meghalaya, Western Ghats of Maharashtra and Karnataka etc. Tribals built temples in these patches and they do not allow the cutting of a single branch of the tree from these sacred grooves. So, their flora and fauna are preserved naturally.   

Coral reefs are found scattered in the coastal zones above the continental shelves throughout the tropical and subtropical western Atlantic and Indo- Pacific Ocean. It is mainly divided into three major zones: Andaman and Nicobar Islands, Coral reefs of mainland, the coral reefs of Lakshadweep Island.

Mangroves are the group of shrubs which lives in the land- sea ecotone zone of tropical and sub- tropical latitudes. West Bengal has the highest diversity of the mangroves cover. For example: Sunderban in West Bengal.

Estuaries are the transition zone between the river and sea. Like in Kerala, Karnataka etc. where it can be studied.   

Yes, it is true that there are more solar energy or sunlight available in the tropics.

1. Sun’s rays are more intense or concentrated.
2. Tropical evergreen forests or rainforests are the dense forest which are covered by tall and straight evergreen trees that contains height of almost 60 m or more than that. So due to presence of dense forest of more solar energy in tropics, this area absorbs radiation and contribute higher productivity which leads to contribute greater biodiversity. 

Co-extinction refers to that when species becomes extinct by any reason, the plants and the animal species which are bind to those species in the obligatory way, also becomes extinct. For example: in case of plant- pollinator mutualism; the pollinators when feed on nectar it helps in growing the plant and helps in making the fruits in any way. If the pollinator become extinct then the plant will automatically become extinct and so as in case of plants.

Biodiversity refers to the sum total of all the variety of life in the particular area like in the terms of species, genetic and ecological diversity. Conservation is the protection, preservation, management or restoration of wildlife and natural resources like forests. By the conservation of biodiversity, the species and the habitat that are threatened can be protected. As an individual, it can be conserved with conservation methods that are as follows:

1. Conservation of habitat, ecosystem (flora and fauna) where organisms naturally occurs; protected by in- situ conservation method.
2. Hunting should be banned in all the areas.
3. Forest fire that leads to the elimination of various species should be prohibited.
4. Deforestation should be reduced or stop. It deprives the wildlife of cover and food.
5. People should share indigenous knowledge, innovative methods and practices related to the biodiversity.
6. Over- exploitation of the natural resources should be avoided so that future generation would meet the requirements of these resources.

Following are the scientific explanation for the direct relationship between diversity and stability of an ecosystem:

Imagine a forest area, where diversify species of flora are growing. Plants harbor a variety of insects on which a lot of bird species would depend for their food.

If a specific plant species dies then the related insect population will be affected in the obligatory way that would lead to food unavailability for the birds.

In addition, if the plant species was a nitrogen fixer then the death of these plants would mean no regain or fill up of soil with nitrogen. This will obviously affect the other plants as well. So, if the cycle continues, the whole habitat/ ecosystem will be negatively affected.    

The humans primarily evolved around 2.5 million years ago and agriculture began about thousands years ago. It is all started when then that humans have started to exploit the forest land for agriculture. Medical technology’s development has increased the lifespan or the natality rate of humans, decreased the mortality rate (death rate) of mother and child, further aggravating the problem of human population.

Along with this, the industrial revolution caused enormous consumption of earth’s resources but giving back nothing. The monument amount of waste is destroying the natural habitat of other species, either it aquatic or terrestrial, endangered or later caused extinction. That is how the human activities lead to the increase in conflict between humans and wildlife.

Ecosystem services are defined as the benefits that is obtained by the people from the ecosystem. According to the IPCC (Intergovernmental Panel on Climate Change), this process provides value to the individual and the society as well. For example: forest provides us pure air, water, cyclic nutrients, also provides aesthetic, cultural and spiritual values. Ecosystem services are divided into four major categories: 

For the maintenance and sustainable utilization of ecosystem services, biodiversity is very important. Various ecosystem services are important that are as follows:

1. Maintenance of various gases that is present in the atmosphere
2. Natural pest control
3. Formation and protection of soil
4. Conservation and purification of water
5. Nutrient cycling etc.

There should be no charge for the ecosystem services because they are provided naturally, i.e. by nature. But if they are used freely then we should take proper care of them and properly used so that our future generation also meets the requirements of these services. Every citizen or individual should be educated so that they can understand the value of ecosystem services. Prices of these services should also be available to the public so they can estimate properly, how it should be used or saved.     

Biodiversity provides several benefits for the human beings and conditions to drive the process that maintains the global economy and our survival. The consumptive use value of biodiversity as food, drugs and medicines, fuel and fibres are as follows:

1. Food: Several varieties of species of edible plants and animals are found. So by seeing the population increasement, man have developed many techniques to grow the crops in very fast rate and new varieties of food. Biodiversity provides foodstuffs like fruits, nuts, honey, spices etc. A number of varieties of plants like coconut, sunflower, mustard, soyabean are the sources of food and making oils. Some animal species are also used as making oil like fish oil etc.
2. Drugs and Medicines: Biodiversity is rich in sources which is provided with the therapeutic properties. For example: quinine used for the treatment of malaria, taxol is an anticancer drug, morphine used as an analgesic, drug Reserpine is obtained from the Rauwolfia serpentine which is used for the cure of high blood pressure patients for the control and used to treat the hypertension or relief of psychotic symptoms etc. Some significant portion of drugs are defined or derived directly or indirectly from the bioresources. Some Ayurvedic medicines are also used for the treatment of some diseases that are based on the plant products.
3. Fuel and fibres: Fossil fuels like petroleum are obtained from the fossils of organisms. Various plant species like cotton, flax, jute, Abacus etc. ate the major sources of obtaining fibres.

Species diversity decreases as we move from towards the poles, because

1. Temperature decreases and the conditions become excessive cold and harsh.
2. The amount and intensity of solar energy or sunlight decreases.
3. Vegetation get decreased because for the edible plants to grow they need proper sunlight and temperature.
4. Least resources are available for the survival of species.
5. If the conditions becomes too harsh then it will be difficult for the species to survive and adapt themselves in that condition. Thus it leads to the mortality of the species diversity as we move towards the poles.

Paul Ehrlich who is an Ecologist have developed rivet popper hypothesis that helps in the understanding of the contribution to species richness. He does comparison of each the species with rivet in the body of an airplane.

1. This hypothesis explains that ecosystem to be an airplane and the species to be the rivets joining all parts together.
2. If every passenger travelling in the airplane start taking rivets home (causing a species to become extinct), initially it may not affect flight safely (proper functioning of ecosystem), but over a period of time the plane becomes weak and dangerous (species become endangered and then they extinct).  

Alexander von Humboldt, a German naturalist and geographer, has observed that within the specific region, species richness increased with increasing explored area, but only upto the fixed limit. According to the relation between species richness and the area for a wide variety of taxa (like angiosperms, fishes, birds, bats) gives a rectangular hyperbola. Their relationship shows a straight line on a logarithmic scale which is described by the equation:

log S = log C + z log A

Where, S= species richness; A= Area; z = slope of the line; C= Y- intercept

The value of z lies between 0.1 to 0.2 in any case of the taxonomic group or the region. If the analysis of species- area relationship is done among large areas like continents etc. then the slope of line would be much steeper (here the value of z ranges from 0.6 to 1.2).