NCERT Solutions Biodiversity and Conservation class 12 notes PDF

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biodiversity and Conservation class 12 notes, Biodiversity and Conservation, in situ and ex-situ conservation of biodiversity, biodiversity and conservation class 12, biodiversity and conservation class 12 notes,


biodiversity and Conservation class 12 notes 


Class12th 
Chapter No15
ProvidingQuestions And Answers, Notes & Numericals PDF
Chapter NameBiodiversity and Conservation
BoardCBSE
Book NCERT
SubjectBiology
Medium English
Study MaterialsFree VVI Study Materials are Available
Download PDF biodiversity and its conservation pdf

biodiversity and Conservation class 12 notes


1. Biodiversity is the term used to describe the total variety of biological organisations at all levels. The diversity is seen at all levels from organic molecules to ecosystems to biomes. The three most important levels of biodiversity are

NCERT Solutions Biodiversity and Conservation class 12 notes PDF e1689326308834 1024x614 1

(i) Genetic diversity A single species might show high diversity at the genetic level in terms of the number of chromosomes (or genes) and variation in genes (allelic forms) even in different members of the same species, e.g., The human, Homo sapiens-30000-40000 Number of genes in an E. coli-4000 In fruit fly, Drosophila melanogaster- 13000

(a) The genetic variation (in terms of allelic forms of the same gene) is expressed by the medicinal plant Rauwolfia vomitoria growing in different Himalayan ranges in terms of the potency and concentration of the active chemical (reserpine) that the plant produces.

(b) India has more than 50000 genetically different strains of rice and 1000 varieties of mango. 

(c) Genetic diversity affects the adaptability and capability of a species to survive in diverse habitats. It may help in speciation (evolution into new species).

(ii) Species diversity refers to the number and distribution of species in an area.

(a) It is expressed in terms of the number of species per unit area’ and also as the number of individuals of different species in an area. 

(b) e.g., the Western Ghats have a greater amphibian species diversity than the Eastern Ghats. Species diversity is the trait of a community and influences the interactions and stability of the community. 

(iii) Ecological diversity refers to the diversity at the ecosystem br level. This can include a variety of habitats, trophic levels, food webs, ecological processes and biotic interactions, etc. Ecosystem diversity makes communities more productive and stable.

now e.g., India has a greater ecosystem diversity (in terms of variety of habitats in deserts, rain forests, mangroves, coral reefs, wetlands, estuaries and alpine meadows) than a Scandinavian country like Norway.

2. According to the IUCN (2004), more than 1.5 million species have been recorded in the world and there might be about 6 million species on Earth waiting to be discovered and named. 

(i) Out of the total animals recorded, 70 % are insects. It means that out of every 10 animals on this planet, 7 are insects.

(ii) The group fungi has more species than all the vertebrate species (fishes, amphibians, reptiles and mammals) combined.

(iii) Nearly 45000 species of plants and about 90000 animals have been recorded from India. It is one of the 12 mega-diversity countries of the world. (iv) It is interesting to know that the diversity of microbial species alone might run into millions.

3. Patterns of Biodiversity The diversity of plants and animals, throughout the world, is not evenly distributed and shows some interesting patterns of distribution.

(i) Latitudinal gradients mean that species diversity decreases as we move away from the equator towards the poles.

(a) Generally, the tropics (latitudinal range of 23.5°N to 23.5°S) have more species than temperate or polar areas.

(b) The largely tropical Amazonian rain forest in South America has the greatest biodiversity on the Earth with more than 40000 species of plants, 3000 fishes, 1300 birds, 427 mammals, 427 amphibians, 378 reptiles and more than 125000 invertebrates.

(c) Some hypotheses proposed by scientists to explain the rich biodiversity in the tropics and less in temperate regions are:

The temperate regions were subjected to frequent glaciations in the past, whereas tropical latitudes have remained relatively undisturbed for millions of years and thus, had a long evolutionary time for species diversification.

Tropical environments provide continued favourable seasons that are relatively more constant and predictable. Such a constant environment promotes niche specialisation and leads to a greater species v diversity.

Availability of more solar energy in the tropics, boda contributes to higher productivity; this in turn might contribute indirectly to greater diversity.

(ii) Species-area relationships A German naturalist and geographer Alexander von Humboldt observed that within a region species richness increased with the increasing available area, but only up to a limit. 

(a) The relation between species richness and area, for a la wide variety of taxa (angiosperm plants, birds, bats, freshwater fishes) is a rectangular hyperbola. On a logarithmic scale, the relationship is a straight line described by the equation log Showing a species-area relationship. 

Note that on a log scale, the relationship becomes linear

where, S = species richness, A= area, Z = slope of the line (regression coefficient) and C=Y-intercept. 

(b) But, the ‘species-area’ relationships among very large areas like the entire continents, will give a much steeper slope of the line (Z values in the range of 0.6 to 1.2), e.g., for frugivorous (fruit-eating) birds and mammals in the tropical forests of different continents, the slope is found to be 1.15.

4. The Importance of Species Diversity to the Ecosystem Species diversity is important in terms of the following:

(i) Stability Communities with more species diversity, generally, tend to be more stable than those with less bo in species. This is because such communities are more resistant or resilient to occasional disturbances (natural or

man-made) and to invasions by alien species. 

(ii) Productivity Ecosystems with higher species diversity are much more productive, e.g., tropical forests. David Tilman’s long-term ecosystem experiments showed

that increased diversity contributed to higher productivity. 

(iii) Ecosystem health No species can exist independently Interactions among species ensure good health and stability,

5. Ecologist Paul Ehrlich gave an analogy rivet popper hypothesis to help understand the species. He compared each species with each rivet in the body of the aeroplane. 

(i) This hypothesis explains that the ecosystem is an aeroplane and the species are the rivets joining all parts together. 

(ii) If every passenger travelling in the aeroplane starts taking rivets home (causing a species to become extinct), initially it may not affect flight safety (properly removed, over some time, the plane becomes weak. 6. Loss of Biodiversity

(iii) The IUCN Red List (2004) documents the extinction of 784 species (including 338 vertebrates, 359 invertebrates and 87 plants) in the last 500 years.

(ii) Some examples of recent extinctions include the dodo (Mauritius), quagga (Africa), thylacine (Australia), Steller’s Sea Cow (Russia) and three sub-species (Bali, Javan, Caspian) of tiger.

(iii) The last twenty years alone have witnessed the disappearance of 27 species.

(iv) Ecologists warn that if the present trends continue, nearly half of all the species on Earth might be wiped out within

the next 100 years.

(v) The loss of biodiversity in a region may lead to

(a) Decline in plant production. 

(b) Lowered resistance of plants to environmental conditions like drought, etc.

(c) Negative impact on ecosystem processes such as plant productivity, water use pest and disease cycles. 

(D) Lowered plant productivity means loss of economically important materials for human usage and low food availability.

7. The Causes of Biodiversity Loss are 

(i) Habitat loss and fragmentation Population explosion, air pollution, urbanisation and industrialisation have Tudestroyed forest land, which meant the loss of habit for several species, e.g.,

Once covering more than 14% of the Earth’s of beta land surface, the Amazonian rain forests now cover less than 6% as they are being cut and cleared for cultivation or conversion to grasslands for raising beef cattle. This has caused a loss of habitat for lots of species and has put tremendous pressure on the ecosystem.

(ii) Over-exploitation Uncontrolled overuse leads to A over-exploitation of natural resources and animals which harms the species. e.g., Many species extinctions in the last 500 years (Steller’s sea cow, passenger pigeon), many marine fish

populations were due to over-exploitation by humans. 

(iii) Alien species invasions When alien species are introduced unintentionally or deliberately in a habitat, some of them can cause the decline or extinction of indigenous species, e.g., Extensive environmental damage caused and the threat posed to our native species by invasive weed species like carrot grass (Parthenium), Lantana and water hyacinth (Eichhornia). 

(iv) Co-extinctions When a species becomes extinct, the plant and animal species associated with it, in an obligatory way, also become extinct, e.g., When a host fish species becomes extinct, its parasites also vanish. 8. Biodiversity Conservation There are several reasons that can be grouped into three categories narrowly utilitarian, broadly utilitarian and ethical.

(i) The narrowly utilitarian arguments for conserving biodiversity are that humans derive numerous direct economic benefits from

(a) food product (cereals, pulses and fruits).

(b) firewood.

(c) fibre (cotton, jute from plants and silk, wool from animals).

(d) construction material (timber for making furniture, houses, and sports goods).

(e) industrial products (tannins, lubricants, dyes, resins, perfumes).

(f) products of medicinal importance (about 25000 plants used in traditional medicine). (ii) The broadly utilitarian view is that biodiversity plays a major role in many ecosystem services that nature provides.

(a) Pure oxygen The Amazon forest is estimated to produce, through photosynthesis, 20% of the total oxygen in the Earth’s atmosphere.

(b) Pollination without which plants cannot give us fruits or seeds, is another service, ecosystems provide through pollinators-butterflies, bees, bumblebees, birds and bats.

(c) Flood and soil erosion control occur due to plants which help water retention, percolation and prevent soil erosion.

(d) Nutrient replenishment is due to plant biomass that falls on the ground being the biggest source of recycled nutrients after decomposition. 

(e) Waste recycling by microbes and other insects, etc.

(f) Aesthetic pleasure that we derive from nature.

(iii) The ethical argument for conserving biodiversity relates to our moral obligation to conserve the planet that we share with millions of plant, animal and microbe species.

(a) We need to realise that every species has an intrinsic bot to value, even if it may not be of current or any economic value to us. 

(b) We have a moral duty to care for their well-being and pass on our biological legacy in good order to future ninth generations.

9. Conservation of biodiversity means protection, judicious and minimal use and rebuilding the damaged units. There are two basic approaches to the conservation of biodiversity. These are in situ conservation and ex-situ conservation.

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credit- his owner

(i) In situ conservation involves the protection of species in their natural habitat. 

(a) Hot spots are regions of high levels of species richness and a high degree of endemism. Endemic species are confined only to a limited region. There are 34 hotspots in the world. Three of these Hotspots in India are the Western Ghats and Sri Lanka Indo-Myanmar Eastern Himalaya-cover-our country’s exceptionally high biodiversity regions.

(b) Protected areas are ecologically unique and biodiversity-rich regions that are legally protected as biosphere reserves, national parks and sanctuaries. India has 14 biosphere reserves, 90 national parks and 448 wildlife sanctuaries.

There were areas in forests that were set aside and all the trees and wildlife within were venerated and given total protection. Such sacred groves are found in Khasi and Jaintia Hills in Meghalaya.

Aravalli Hills of Rajasthan. Western Ghat regions of Karnataka, Maharashtra.

The Sarguja, Chanda and Bastar areas of Madhya Pradesh. Meghalaya.

(ii) Ex situ conservation is the approach in which threatened animals and plants are taken out from their natural habitat and placed in special settings, where they can be protected and given special care. 

(a) Zoological parks, botanical gardens and wildlife safari parks are used for ex-situ conservation.

(b) many animals have become extinct in wildlife but continue to be maintained in zoological parks. 10. Scientific technology has enabled ex-situ conservation in the following ways:

(i) Cryopreservation of gametes of threatened species and keeping them preserved in viable and fertile conditions for long periods at very low temperatures.

(ii) In vitro fertilisation to propagate endangered species. Offsprings can be produced by using preserved sperm to fertilise the eggs in vitro and then implanted in female animals.

(iii) Tissue culture can be used to propagate plant species. 

(iv) Seed banks seeds of different genetic strains of commercially important plants can be kept for long periods, under specific conditions. Conventions on Biodiversity

(i) The historic convention on biological diversity (the Earth Summit) held in Rio de Janeiro in 1992, called upon all nations to take appropriate measures for the conservation of biodiversity and sustainable utilisation of its benefits.

(ii) The World Summit on Sustainable Development held in 2002 in Johannesburg, South Africa, 190 countries pledged their commitment to achieving by 2010, a significant reduction in the current rate of biodiversity loss at global, regional and local levels.

biodiversity and conservation class 12 Notes – Exercises

Question 1. Name the three important components of biodiversity.

Answer Three important components of biodiversity are genetic, species and ecological diversity.

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

Answer Ecologists make a statistical comparison of the species richness of systematically studied groups of insects of the temperate and tropical regions and extrapolate this ratio to other groups of animals and plants. It is to calculate the gross estimate of the total number of species existing on this planet.

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

Answer The three hypotheses for explaining why tropics show the greatest levels of species richness are 

(i) Speciation is generally a function of time and environmental stability. The temperate regions were subjected to frequent glaciations in the past, whereas tropical latitudes have remained relatively undisturbed for millions of years and thus, had a long evolutionary time for species diversification. 

(ii) Tropical environments provide continued favourable seasons that are relatively more constant and predictable. Such a constant environment promotes niche specialisation and leads to greater species diversity.

(iii) Availability of more solar energy in the tropics contributes to higher productivity; this in turn might contribute indirectly to greater diversity. 

Question 4. What is the significance of the slope of regression in a species-area relationship

Answer When the analysis of a species-area relationship is done, amongst small areas, the values of slopes of regression are similar, irrespective of the taxonomic group or the region.

Nevertheless, when such an analysis is done amongst large areas, like continents, the slope of regression would be much steeper.

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

Answer The major causes of species losses in a geographical region

(i) Habitat loss and fragmentation are:

(ii) Over-exploitation of natural resources.

(ii) Alien species invasions can cause the decline or extinction of indigenous species.

(iv) Co-extinctions When a species becomes extinct, the plant and animal species associated with it, in an obligatory way, also become extinct. 

Question 6. How is biodiversity important for ecosystem functioning?

Answer Biodiversity plays a major role in many ecosystem services that nature provides. 

(i) Pure oxygen The Amazon forest is estimated to produce, through photosynthesis, 20% of the total oxygen in the Earth’s atmosphere. 

(ii) Pollination without which plants cannot give us fruits or seeds, is another service, ecosystems provide through pollinators – butterflies, bees, bumblebees, birds and bats. 

(iii) Flood and soil erosion control plants help water retention, percolation and prevent soil erosion.

(iv) Nutrient replenishment plant biomass that falls on the ground is the biggest source of recycled nutrients after decomposition. en

(v) Waste recycling by microbes and other insects, etc., without which the Earth would simply become a huge pile of garbage and polluting material. 

(vi) Aesthetic pleasure that we derive from nature, by walking through thick woods, watching spring flowers in full bloom or waking up to a bulbul’s song in the morning.

biodiversity and conservation neet questions

Question 1. What characteristics make a community stable?

Answer The characteristics that make a community stable are 

(i) Less variation in productivity from year to year.

(ii) Resistance or resilience to occasional disturbances (natural man-made). 

(iii) Resistance to invasions by alien species. or

Question 2. What could have triggered mass extinctions of species in the past?

Answer Nobody knows the real reason but scientists believe that any one of the following could have triggered mass extinctions of species in the past

(i) Fall of sea levels.

(ii) Change of temperatures (freezing or warming).

(iii) Asteroid/meteorite hitting the planet. (iv) Poisonous hydrogen sulphide emissions from the seas. Nova/supernova/gamma-ray burst.

(vi) Plate tectonics.

Question 3. What accounts for the greater ecological diversity of India?

Answer The greater ecological diversity of India is because of the geographical diversity in terms of varying topography, e.g., deserts, rain forests, mangroves, coral reefs, wetlands, estuaries and alpine meadows. This results in the building of a different variety of ecosystems.

Question 4. What does ‘Red’ indicate in the IUCN Red list (2004)? 

Answer ‘Red’ indicates the taxa at the highest risk of extinction.

Question 5. Explain as to how the protection of biodiversity hot spots alone can reduce up to 30% of the current rate of species extinction.

Answer The biodiversity hotspots are regions with very high levels of species richness. These regions can be protected as biological reserves, national parks and sanctuaries.

Question 6. How does species diversity differ from ecological diversity? 

Answer Species diversity refers to the number and distribution of species in an area. It is expressed in terms of the ‘number of species per unit area’ and also as the number of individuals of different species in an area. Ecological diversity refers to the diversity at the ecosystem level. This can include a variety of habitats, trophic levels, food webs, ecological processes and biotic interactions, etc.

Question 7. Define gene pool.

Answer Gene pool refers to the total of genes of every y individual in an interbreeding population.

Question 8. What does the term ‘Frugivorous’ mean?

Answer The term ‘Frugivorous’ refers to fruit-eating birds.

Question 9. Define the terms (i) Bioprospecting and (ii) Endemism.

Answer

(i) Bioprospecting is a term that describes the process of discovery and commercialisation of new products based on biological resources. 

(ii) Endemism refers to a phenomenon of the presence of some species in particular regions only and nowhere else. 

biodiversity and conservation class 12 ncert solutions

Question 1. Of the four major causes for the loss of biodiversity (Alien species invasion, habitat loss and fragmentation, over-exploitation and co-extinctions which according to you is the major cause for the loss of biodiversity? Give reasons in support. 

Answer The major causes of the loss of biodiversity are

(i) Habitat loss and fragmentation caused by clearing and overexploitation of forest areas for agriculture, urbanisation and industrialisation. 

(ii) Increasing human population has overburdened the forest resources and has destroyed forest land, which meant the loss of habitat for several species. 

(ii) In addition, large habitats are broken up into small fragments because of which mammals and birds requiring large territories and with migratory habits are badly affected, leading to population decline.

Question 2. A species-area curve is drawn by plotting the number of species against the area. How is it that when a very large area is considered the slope is steeper than that for smaller areas?

Answer In very large areas, the number of species is much which is why the curve is much steeper. This is because the area is more, the food availability and other resources are much greater, so obviously more species can thrive.

Question 3. Is it possible that the productivity and diversity of a natural community remain constant over some time of, say one hundred years?

Answer Yes, the productivity and diversity of a natural community may remain constant over the period provided.

(i) The natural habitat is maintained. 

(ii) reasonably abundant resources are available.

(iii) environmental conditions for survival and conducive. 

All these factors encourage healthy interaction between species and the environment leading to continuous productivity and proliferation.

Question 4. What criteria should one use in categorising a species as threatened?

Answer The criteria that should be used in categorising a species as threatened are

(i) numbers of the members of the species are declining at an alarming rate.

(ii) their habitat is being modified or destroyed.

(iii) predator or poacher activities are increasing.

Question 5. What could be the possible explanation for the greater vulnerability of amphibians to extinction as compared to other animal groups?

Answer This is because of

(i) Habitat modification or destruction Amphibians generally need aquatic and terrestrial habitats to survive; threats to either habitat can affect populations. Hence, amphibians may be more vulnerable to habitat modification than organisms that only require one habitat type

(ii) Habitat fragmentation which means the isolation of a few areas by habitat modification. Small populations that survive within such fragments are often susceptible to inbreeding, genetic drift or extinction due to small fluctuations in the environment.

(iii) Large-scale climate changes can further modify aquatic habitats, preventing amphibians from spawning. 

Question 6. Humans benefit from the diversity of life. Give two examples.

Answer

(i) Humans derive numerous direct economic benefits from a diversity of organisms. 

  • (a) Food product (cereals, pulses and fruits).
  • (b) Firewood.
  • (c) Fibre (cotton, jute from plants and silk, wool from animals). 
  • (d) Construction material (timber for making furniture, houses and sports goods).
  • (e) Industrial products (tannins, lubricants, dyes, resins and shed perfumes): 
  • (f) Products of medicinal importance (about 25000 plants used in traditional medicine). you

(ii) There are huge intangible benefits that humans derive from the diversity of life. 

  • (a) Pure oxygen.
  • (b) Natural pollinators.
  • (c) Flood and soil erosion control. 
  • (d) Nutrient replenishment.
  • (e) Waste recycling by microbes and other insects, etc.
  • (f) Aesthetic pleasure and mental peace.

Question 7. List any two major causes other than anthropogenic causes of the loss of biodiversity. 

Answer The two major causes other than anthropogenic causes of the loss of biodiversity are

(i) Alien species invasions When alien species are introduced unintentionally or deliberately in a habitat, some of them can cause the decline or extinction of indigenous species.

(ii) Co-extinctions When a species becomes extinct, the plant and animal species associated with it, in an obligatory way, also become Textinct.

Question 8. What is an endangered species? Give an example of an endangered plant and animal species.

Answer An endangered species is a population of organisms that is facing a high risk of becoming extinct because of

(i) Its numbers are very low. 

(ii) It is threatened by changing environment.

(iii) It is facing predator threat. et disenchant

Endangered plant species– Venus fly trap Endangered animal species- Siberian tiger

Question 9. Suggest a place where one can go to study coral reefs, mangrove vegetation and estuaries.

Answer Coral reefs-Andaman and Nicobar Islands. Mangrove vegetation-West Bengal. Estuaries-Coastal areas of Karnataka.

biodiversity and conservation notes

Question 1. Can you think of a scientific explanation, besides the analogy used by Paul Ehrlich, for the direct relationship between? diversity and stability of an ecosystem?

Answer Scientific explanation could be as follows:

Imagine a forest area, where diverse species of plants are growing. Plants harbour a variety of insects for which a lot of bird species would depend for their food. If a specific plant species die, the harbouring insect population will be affected which would lead to food unavailability for the birds. 

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

Question 2. Though the conflict between humans and wildlife started with the evolution of man, the intensity of the conflict has increased due to the activities of modern man. Justify your answer with suitable examples.

Answer The first humans evolved around 2.5 million years ago. Agriculture began 11 thousand years ago leading to a huge increase in population size. It is since then that humans have started to exploit forest land for agriculture. A few centuries ago, development in medical technology increased the lifespan of humans and decreased the mortality rate of mother and child, further aggravating the problem of the human howe population. 

Along with this, the industrial revolution caused enormous consumption of Earth’s resources and gave back nothing but a monumental amount of waste destroying the natural habitat of other species, be it aquatic or terrestrial, endangering and later causing extinction thereof. This is how human activities have led to the increase in conflict between humans and wildlife.

Question 3. Species diversity decreases as we move away from the equator towards the poles. What could be the possible reasons? 

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

(i) Temperature decreases and conditions become harsh. 

(ii) Solar radiation, amount and intensity both decrease.

(iii) Vegetation decreases.

(iv) Fewer resources available to support species.nd Speciation is generally a function of time and environmental stability, so if conditions are too harsh, it is difficult for the species to survive and adapt. This results in a decrease in biodiversity towards the poles.

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