CBSE Class 12 Biology Biodiversity And Conservation Worksheet Set A

Question. When we conserve and protect the whole ecosystem, its biodiversity at all levels is called -
(a) In situ conservation
(b) Ex -situ conservation
(c) On site conservation
(d) Both (a) and (c)

Answer : D

Question. Which statement is incorrect -
(a) There is increase in biodiversity from pole to equator
(b) There is increase in biodiversity from low altitude to high altitude
(c) There is directly proportional relationship between area & biodiversity
(d) Tropics has less seasonal, relatively more constant and predictable environment.

Answer : B

Question. In equation log S = log C + Z log A, what is Z -
(a) Species richness
(b) Area
(c) Regression coefficient
(d) Y-intercept

Answer : C

Question. For frugivorous birds and mammals in tropical forest of different continents, the slope(Z) is found to be :-
(a) 0.1 - 0.2
(b) 0.6 - 1.2
(c) 1.15
(d) 11.5

Answer : C

Question. Select the wrong match for extinction of species as per the IUCN red list 2004 -
(a) Vertibrates - 338
(b) Invertebrates - 359
(c) Plants - 87
(d) Prokaryotes - 2001

Answer : D

Question. Alexander von Humboldt described for the first time :
(a) Ecological Biodiversity
(b) Laws of limiting factor
(c) Species-Area relationship
(d) Population Growth equation

Answer : C

Question. Sacred groves are specially useful in :
(a) preventing soil erosion
(b) year-round flow of water in rivers
(c) conserving rare and threatened species
(d) generating environmental awareness 

Answer : C

Question. Which of the following countries has the highest biodiversity?
(a) Brazil
(b) South Africa
(c) Russia
(d) India 

Answer : A

Question. The extinction of passenger pigeon was due to
(a) increased number of predatory birds.
(b) over-exploitation by humans.
(c) non-availability of the food.
(d) bird flu virus infection.

Answer : B

Question. Which one of the following shows maximum genetic diversity in India ?
(a) Rice
(b) Maize
(c) Mango
(d) Groundnut

Answer : A

Question. The historic convention on Biological Diversity held in Rio de Janeiro in 1992 is known as
(a) The CITES Convention
(b) The Earth Summit
(c) The G-16 Summit
(d) The MAB Programme

Answer : B

Question. World Summit on Sustainable Development (2002) was held in :
(a) Brazil
(b) Sweden
(c) Argentina
(d) South Africa 

Answer : D

Question. Which one of the following is not a major characteristic feature of biodiversity hotspots?
(a) Large number of species
(b) Abundance of endemic species
(c) Large number of exotic species
(d) Mostly located in polar regions 

Answer : D

Question. What is common to the following plants : Nepenthes, Psilotum, Rauwolfia and Aconitum?
(a) All are ornamental plants.
(b) All are phylogenic link species.
(c) All are prone to over-exploitation.
(d) All are exclusively present in the eastern Himalayas.

Answer : C

Question. According to ecologists warn that if the present trends continue. Nearly half of the species on earth might be wiped out within how many years -
(a) 100
(b) 1000
(c) 50
(d) 500

Answer : A

Question. In general, the loss of biodiversity in a region may not lead to -
(a) Decline in plant production
(b) Lowered resistance to environmental perturbations
(c) Constant pest and disease cycles
(d) Increased variability in certain ecosystem processes such as plant productivity

Answer : C

Question. Find out the right one -
(a) India has 7.1% species diversity
(b) India is one of the 22 mega diversity countries of world
(c) According to Robert May's global estimate only 22% of the total species have been recorded so for
(d) According to Robert May's estimation, more than 3,00,000 plant species yet to be discovered in India

Answer : C

Ques. Consider the following statements (A – D) each with one or two blanks.
(A) Bears go into (1) during winter to (2) cold weather.
(B) A conical age pyramid with a broad base represents (3) human population.
(C) A wasp pollinating a fig flower is an example of (4) .
(D) An area with high levels of species richness is known as (5) .
Which one of the following options, gives the correct fill ups for the respective blank numbers from (1) to (5) in the statements ?
(a) (3) – stable (4) – commensalism, (5)-marsh
(b) (1) – aestivation, (2) – escape, (3) – stable, (4) – mutualism
(c) (3) – expanding, (4) – commensalism, (5) – biodiversity park
(d) (1) – hibernation, (2) – escape, (3) – expanding (5) – hotspot 

Answer: D

Ques. Which one of the following is an example of ex-situ conservation?
(a) Wildlife sanctuary
(b) Seed bank
(c) Sacred groves
(d) National park 

Answer: B

Ques. Tiger is not a resident in which one of the following national parks?
(a) Sunderbans
(b) Gir
(c) Jim Corbett
(d) Ranthambhor 

Answer: B

Ques. Which one of the following is not observed in biodiversity hotspots?
(a) Lesser inter-specific competition
(b) Species richness
(c) Endemism
(d) Accelerated species loss 

Answer: A

Ques. World Summit on Sustainable Development (2002) was held in
(a) Argentina
(b) South Africa
(c) Brazil
(d) Sweden. 

Answer: B

Ques. Identify the odd combination of the habitat and the particular animal concerned.
(a) Sunderbans – Bengal Tiger
(b) Periyar – Elephant
(c) Rann of Kutch – Wild Ass
(d) Dachigam – Snow Leopard National Park 

Answer: D

Ques. Which of the following is considered a hotspot of biodiversity in India?
(a) Aravalli hills
(b) Western ghats
(c) Indo-gangetic plain
(d) Eastern ghats 

Answer: B

Ques. Which one of the following is not included under in situ conservation?
(a) National park
(b) Sanctuary
(c) Botanical garden
(d) Biosphere reserve

Answer: C

Ques. Which one of the following is the correctly matched pair of an endangered animal and a national park?
(a) Great Indian bustard : Keoladeo National Park
(b) Lion : Corbett National Park
(c) Rhinoceros : Kaziranga National Park
(d) Wild ass : Dudhwa National Park 

Answer: C

Ques. Biodiversity Act of India was passed by the Parliament in the year
(a) 1992
(b) 1996
(c) 2000
(d) 2002. 

Answer: D

Ques. In your opinion, which is the most effective way to conserve the plant diversity of an area?
(a) By tissue culture method
(b) By creating biosphere reserve
(c) By creating botanical garden
(d) By developing seed bank 

Answer: B

Ques. Viable material of endangered species can be preserved by
(a) gene bank
(b) gene library
(c) herbarium
(d) gene pool. 

Answer: A

Ques. MAB stands for
(a) mammals and biosphere
(b) mammals and biology programme
(c) man and biology programme
(d) man and biosphere programme. 

Answer: D

Ques. Identify the correct match between tiger reserve and its state.
(a) Manas - Assam
(b) Corbett - Madhya Pradesh
(c) Bandipur - Tamil Nadu
(d) Palamu - Odisha 

Answer: A

Ques. Which of the following is the matching pair of a sanctuary and its main protected wild animal?
(a) Kaziranga-Musk deer
(b) Gir-Lion
(c) Sunderban-Rhino
(d) All of these

Answer: B

Very Short Answer Type Questions

Question. What does ‘Red’ indicate in the IUCN Red list (2004)?
Answer : Red in the IUCN Red list (2004) refers to the taxa with the highest risk of extinction.

Question. What is common to the species shown in figures A and B?
Answer : Both the species are conserved in their natural habitats.

Question. What could have triggered mass extinctions of species in the past?
Answer : Nobody knows the real reason but the scientists believe that any one of the following could have triggered mass extinction of species in the past.
(i) Fall of sea levels. (ii) Change in temperature (freezing or warming).
(iii) Asteroid/meteorite hitting the planet.
(iv) Poisonous hydrogen sulphide emissions from the sea.
(v) Nova/super nova/gamma ray burst.
(vi) Plate tectonics.

Question. Why is genetic variation important in the plant Rauwolfia vomitoria?
Answer : Plant Rauwolfia vomitoria is a source of drug reserpine which acts as tranqulliser. Genetic variation shown by this medicinal plant might be in terms of the potency and concentration of active chemical (resperin) that plant produces.

Question. What is Red Data Book?
Answer : Red Data Book is a compilation of data or records of species threatened with risk of extinction (which are known to be endangered). The book is maintained by IUCN (headquartered at gland in Switzerland).

Question. Define gene pool.
Answer : Gene pool refers to the sum total of all genes of every individual in an inbreeding population.

Question. What does the term ‘Frugivorous’ mean?
Answer : Frugivorous term is used for those animals which eat only fruits or eat fruit as their staple diet.

Question. What is the expanded form of IUCN?
Answer : IUCN stands for ‘International Union for Conservation of Nature and Natural Resources’. Its headquarters are situated at gland in Switzerland.

Short Answer Type Questions

Question. Discuss one example, based on your day-to-day observations, showing how loss of one species may lead to the extinction of another.
Answer : Co-extinction is the extinction of two mutually related or interelated species for instance a host fish extinction leads to the extinction of all those parasites exclusively found on it. Another example is plant pollinator mutualism, where extinction of one leads to the extinction of other. Insect, aphids are polyphagous (feed on more than one plant species) or monophagous (feed on a particular species of plant). Monophagous insects may become extinct, if the plant species upon which they feed becomes extinct.

Question. 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 more that is why the curve is much steeper. This is because the larger area has more, food availability and other resources, so obviously more species may thrive.

Question. Is it true that there is more solar energy available in the tropics? Explain briefly.
Answer : Yes, There is more solar energy available in the tropics because
(i) The sun’s rays are more concentrated.
(ii) The sun’s rays have less atmosphere to pass through, so less energy is lost in absorption and reflection by the atmosphere.
(iii) Tropical rainforest areas absorbs radiations due to presence of dense vegetation. Availability of more solar energy in tropics contribute higher productivity which in turn might contribute greater maximum biodiversity.

Question. What is co-extinction? Explain with a suitable example?
Answer : 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. This is called co-extinction. Some other examples of co-extinction are; plant-pollinator mutualism where extinction of one leads to the extinction of other. Monophagous insect that feeds on particular plant species becomes extinct due to extinction of that plant species.

Question. Why are the conventional methods not suitable for the assessment of biodiversity of bacteria?
Answer : Many bacteria cannot be cultured under normal conditions in vitro, which creates a problem in studying their morphological and biochemical characteristics. Morphology and biochemistry along with some other characteristics are used for the assessment of biodiversity of bacteria. Thus, conventional methods are not suitable for the assessment of biodiversity of bacteria.

Question. 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) Number 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. What could be the possible explanation for greater vulnerability of amphibians to extinction as compared to other animal groups?
Answer : Amphibians are more vulnerable to extinction
(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 require only one habitat type.
(ii) Habitat Fragmentation This means 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 These changes can further modify aquatic habitats, preventing amphibians from spawning.

Question. How is the presently occurring species extinction different from the earlier mass extinctions ?
Answer : In earlier time extinction of species occurred due to natural causes or calamities like flood, volcanic eruption, prolonged drought and landslides, etc. While at present human activities are the major cause of species extinction.

Long Answer Type Questions

Question. Can you think of a scientific explanation, besides analogy used by Paul Ehrlich, for the direct relationship between diversity and stability of an ecosystem?
Answer : Scientific explanation for the direct relationship between diversity and stability of an ecosystem could be as follows Imagine a forest area, where diverse species of plants are growing. Plants harbour a variety of insects on which a lot of bird species would depend for their food. If a specific plant species dies, the related insect population will be affected that would lead to food unavailability for the birds. In addition, if the plant species was a nitrogen fixer, the death of these plants would mean no replenishment 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.

Question. The relation between species richness and area for a wide variety of taxa turns out to be a rectangular hyperbola. Give a brief explanation.
Answer : According to AV Humboldt, a German scientist within, a region, species richness increased with increasing explored area (only upto a limit). Accordingly the relation between species richness and area for a wide variety of taxa (birds, bat, angiosperms, aquatic fishes) turns out to be a rectangular hyperbola. The relationship depicts a straight line on a logaithimic scale described by the following equation log S = log C + Z log A Where, ‘S’ stands for species richness, ‘A’ is area and ‘Z’ and ‘C’ are slope of line (regression coefficient) and y intercept respectively. (Image 275)

Question. Though the conflict between humans and wildlife started with the evolution of man, the intensity of conflict has increased due to the activities of modern man. Justify your answer with suitable examples.
Answer : The humans first evolved around 2.5 million years ago and agriculture began about 11 thousand years ago. It is since then that humans have started to exploit the forest land for agriculture. Development in medical technology has increased the lifespan of humans, decreased the mortality 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 monumental amount of waste is 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. What is an ecosystem service? List any four important ecosystem services provided by the natural ecosystems. Are you in favour or against levying a charge on the service provided by the ecosystem?
Answer : Ecosystem Services The products of ecosystem processes are termed as ecosystem services. Forests are the major sources of ecological services. Some of the ecosystem services they provide are (i) Purification of air and water. (ii) Mitigating droughts and floods. (iii) Cycling nutrients. (iv) Generating fertile soils (v) Providing wildlife habitat. (vi) Maintenance of biodiversity. (vii) Pollination of crops. (vii) Providing storage site for carbon. (ix) Providing aesthetic, cultural and spiritual values. Robert Constanza and his colleagues tried to put price tags on nature's life support services, which was about US $ 33 trillion a year. No, i am not in favour of levying a charge on ecological services but it is very important, to understand how much nature is providing us for free and if we overuse or misuse its resources, we'll have to pay a heavy price for it.

Diversity at all levels of biological organisation Questions and Answers

Ques.A study of latitudinal gradient of biodiversity of birds is as follows:
India- 8 o North—1200 Species
Greenland-71 o North-55 Species
By analyzing the above data what does it indicate about the distribution of birds.
Answer : Species diversity decreases from equator towards the poles.

Ques.What favours the genetic variation shown by the medicinal plant Rauwolfia vomitoria growing in different Himalayan ranges ?
Answer : Genetic variation shown due to the potency and concentration of active chemical (reserpine) produced by the plant.

Ques.Why is Ecological diversity seen more in India as compared to Scandinavian country Norway.
Answer : As India is rich in various ecosystem level with deserts ,rain forest,mangroves,coral reef,wetlands,estuaries and alpine meadows so greater ecosystem diversity.

Ques. Match the following:
1.IUCN(2004) total number of plant animal species discovered so far ----7 million
2.Robert May estimate of global species diversity-----.5 million
3.70 % of all recorded are-----.1 %
4. Among animals the most rich species are----plants (algae, fungi, bryophytes, gymnosperm and angiosperms).
5.India has only 2.4 % of land area, its share of global species diversity is---- insects

Answer : Match the following:
1. IUCN (2004) total number of plant animal species described so far---- 1.5million
2. Robert May estimate of global species diversity----- 7 million
3. 70 % of all recorded are- ----plants(algae,fungi,bryophytes,gymnospers and angiosperms)
4. Among animals the most rich species are—---- insects
5. India has only 2.4 % of land area, its share of global species diversity is---- 8.1 %

Ques.Why are biologist not able to give the estimate of Prokaryotes in nature ?
Answer : Because the the conventional taxonomic methods are not suitable for identifying microbial species

Pattern of Biodiversity Questions and Answers

Ques. Answer in one word or one sentence
a) Why species diversity is more in India than in Greenland?
b) The scientist has found that the slope of line of regression is found to be more than 0.2. In which condition this will be possible?
Answer : Biodiversity decreases from equator to pole; When large areas like whole continent are taken for analysis.

Ques. Fill in the blank
a) The shape of graph in species area richness relationship in bats is -------------------.
b) Niche specialization thereby leading to greater species diversity in tropic is due to------------.
c) Frequent glaciations in temperate region leads to less-------------.
d) Species richness is related with-------------- up to a certain limit.
Answer : Rectangular hyperbola; More constant and predictable environment; Species diversification; area

Ques. Match the followings
1. Environment in temperate region. a) Steeper slope of line
2. More solar energy. b) More constant and more predictable.
3. Tropical latitudes c) Leads to more species diversity.
4. Constant environment d) More species diversification.
5. High regression coefficient e) More biodiversity.
Answer : 1-b; 2-c; 3-e; 4-d; 5- a

Ques. Choose the correct answer
a)The slope of line in species area relationship graph is 1.15
a) Angiosperm plants
b) mammals
c) birds
d) fresh water fishes
Answer : B

b) Scientists have estimated that about two million insects species are yet to be discovered in
a) Greenland
b) Equador
c) Amazonian Rain forest
d) India
Answer : C

c) As we move from 41oN to 71oN, the species diversity
a) Increases
b) Decreases
c) Remain the same
d) Doubled
Answer : B

d) Frequent glaciations leads to
a) Increase species diversification
b) High productivity
c) Decrease species diversification
d) Niche specialization
Answer : C

Ques. The following graph depicts the species-area relationship. Answer the following questions

1) Give the equation of “A” and equation of ‘B”.
2) What does steeper slope in curve “B” represents?
3) Who studied the species – area relationship in South African jungles?
4) What does Z stands for? In which range does the normal value of Z lies?

Answer : S= CAZ ; log S= log C + Z log A ; Higher regression coefficient; regression coefficient, 0.1 to 0.2

Domestic sewage and industrial effluents Questions and Answers

Ques. Write scientific name of water hyacinth? why it is known as “terror of Bengal”?
Answer : Eichhornia crassipes. It results in eutrophication

Ques. Introduction of which nutrient in water bodies result eutrophication?
Answer : Nitrogen and phosphorus

Ques. Give reasons why there is a continuous increase in the DDT content in different trophic levels of the chain?
Answer : This happens because a toxic substance accumulated by an organism cannot be metabolized or excreted,and is thus passed on to the next higher trophical level.

Ques. What percentage of global warming is contributed by each of the following?
i)Carbon di oxide
ii)chlorofluorocarbons
iii)nitrous oxide and
iv) methane
Answer : i)60%, ii) 14%, iii)6%, iv) 20%

Ques. Ornithologists observed a decline in the bird population I the area near a lake after the setting of an industrial unit in the same area. explain the cause responsible for the decline observed?
Answer : High concentration of DDT interferes with calcium metabolism in birds and cause thinning of egg shells and their premature breaking,this eventually leads to a decline in bird population.

Important Notes for Class 12 Biology Chapter 13 Organisms And Populations

There are millions of plants and animals present on earth. Every distinct geographical location has its own set of flora and fauna. Immense diversity exists at all levels of biological organisation from micromolecules within cell to biomes. This staggering variety of life forms is referred to as biodiversity.

Biodiversity
It refers to the variety and variability of living organisms on the earth. It can also be defined as the variety of life forms, gene pools and habitats found in an area. The term ‘biodiversity’ was popularised by sociobiologist Edward Wilson to describe the combined diversity at all the levels of biological organisation.
The biodiversity can be described by the following three interrelated components or hierarchical levels of biological organisation.

Genetic Diversity
It is the measure of variety in genetic information contained in the organisms. It enables a population to adapt to its environment. A single species shows high diversity at the genetic level. There are more than 20,000 species of ants, 3,00,000 species of beetles, 28,000 species of fishes and nearly 20,000 species of orchids. Greater the genetic diversity among organisms of a species, more sustenance it has against the environment disturbances.
Genetic diversity within the species creates different subspecies, variety, breed, forms, etc.
For example,
(i) India has more than 50,000 genetically different strains of rice and 1,000 varieties of mango.
(ii) The genetic variation shown by the medicinal plant Rauwolfia vomitoria, growing in different Himalayan ranges can be in terms of concentration and potency of the active chemical reserpine that the plant produces.

Species Diversity
It is the diversity at the species level or the measure of the variety of species and their relative abundance within a region, e.g. Western Ghats have more amphibian species diversity than Eastern Ghats.

Two important measures of species diversity are
(i) Species richness It refers to the number of species per unit area. Species diversity increases, if the species richness is higher.
(ii) Species evenness It refers to the relative abundance of species in an area. The number of individuals and variety determine the level of diversity of an ecosystem.

Ecological Diversity
It refers to the diversity at ecosystem level. Due to the presence of more variety of ecosystems and habitats, i.e. rainforest, desert, wetlands, mangroves, coral reefs and alpine meadows. India has a greater ecological diversity than Scandinavian countries (e.g. Norway).

Magnitude of Biodiversity

- According to the IUCN 2004, more than 1.5 million species have been recorded in the world, but we have no idea of how many species are yet to be discovered and described. A sound estimate of global species diversity of about 7 million was given by Robert May.
- More than 70% of all the species recorded are animals, while plants comprise not more than 22%. Out of total animals recorded, 70% are insects (i.e. out of every 10 animals on this planet, 7 are insects).
- The number of fungi species is more than all the vertebrate species of fishes, amphibians, reptiles and mammals combined in the world and it is interesting to know that the diversity of microbial species alone might run into millions.
- Indian biodiversity India is one of the 12 megadiverse countries of the world. Though India has only 2.4% of the world’s land but it shares an impressive 8.1% of the world’s species diversity.
- There are about 45,000 species of plants and twice as many of animals have been recorded in India.
- India probably has more than 1,00,000 species of plants and 3,00,000 species of animals yet to be discovered and described. If we apply RobertMay’s global estimate then only 22% of species of the world have been recorded.

Patterns of Biodiversity

Biodiversity is not uniform throughout the world. It varies with the changes in latitude and altitude. For many groups of animals and plants, there are specific patterns in diversity based on the favourable environmental conditions as plants and animals are more diverse in areas, which are best suited for their survival.
Therefore, following patterns of biodiversity are seen

1. Latitudinal Gradients
- Species diversity decreases as we move away from the equator towards the poles. It means biodiversity is more at lower latitude (equator) than the higher latitude (poles). Tropics (latitudinal range of 23.5°N to 23.5°S) harbour more species than temperate or polar areas, e.g. Colombia located near the equator, has 1,400 species of birds, New York located at 41°N has 105 species of birds, while Greenland at 71°N has only 56 species of birds.
- India, with most of its area in tropical latitude has more than 1,200 species of birds. A forest of equal area in tropical region (like equator) has ten times more species of vascular plants than in temperate region (like Mid-West of USA).
- Amazonian rainforest in South America has the greatest biodiversity on the earth with more than 40,000 species of plants, 3,000 of fishes, 1,300 of birds, 427 of mammals and amphibians, 378 of reptiles and more than 1,25,000 of invertebrates. About 2 million species of insects are still waiting to be discovered and named in these rainforests as estimated by scientists.

Reasons for Greater Biodiversity in Tropics
Some hypothesis proposed by scientists to explain the rich biodiversity in tropical regions are
- The temperate regions were subjected to frequent glaciations in the past, whereas tropical latitudes have remained relatively undisturbed for millions of years.
- Tropical environments are less seasonal, relatively more constant and predictable than temperate region. This promotes niche specialisation and leads to a greater species diversity.
- Availability of more solar energy in the tropics, contributes to higher productivity, this in turn might contribute indirectly to greater species diversity.

2. Species-Area Relationships
- German naturalist and geographer Alexander von Humboldt observed that within a region, species richness increased with the increasing available area, but only upto a limit.

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

- Where, S = Species richness, A = Area, Z = Slope of the line (regression coefficient) and C = y-intercept.
- Ecologists have discovered that the value of Z lies in the range of 0.1 to 0.2, when analysis is done in small areas regardless of the taxonomic group or area. But the species-area relationships among very large areas (continents), will give a much steeper slope and Z values in the range of 0.6 to 1.2, e.g. for frugivorous birds and mammals in the tropical forests, the slope is found to be 1.15. Thus, it can be said that the larger the area, the steeper is the slope.

Importance of Species Diversity to the Ecosystem

- Communities with more species diversity, generally, tend to be more stable than those with less species. This is because such communities are more resistant or resilient to occasional disturbances (natural or man-made) and invasions by alien species.
- These communities do not show much variation in productivity from year to year.
- David Tilman discovered that increased diversity contributed to higher productivity and also proved that species richness is the key to the well-being of any ecosystem.It is also essential for the survival of man on this planet earth.
- Ecosystem health Ecologist Paul Ehrlich gave an analogy, Rivet Popper hypothesis, to understand the effect of loss of species biodiversity.
– This hypothesis explain that ecosystem is an airplane and the species are the rivets joining all the parts together.
– If every passenger travelling in the airplane starts taking rivets home (causing a species to become extinct), initially it may not affect flight safety, but as more and more rivets are removed, over a period of time the plane becomes weak and poses threat to flight safety. However, if rivets on wings (keystone) species are removed, it would pose a more serious threat to flight safety.

Loss of Biodiversity

- Biological wealth of earth is declining rapidly and human activities are the major reasons for it, e.g. the colonisation of tropical Pacific Islands by humans has led to the extinction of more than 2,000 native bird species.
- The International Union for Conservation of Nature and natural resources (IUCN) was founded in 1948. Its headquarter is at Switzerland. It works in the field of nature conservation and sustainable use of natural resources.
- IUCN red list of threatened species is an inventory of global conservation status of biological species, which is compiled in Red Data Book. It was initiated in 1963.
- IUCN Red List (2004) enlists the extinction of 784 species (including 338 vertebrates, 359 invertebrates and 87 plants) in the last 500 years. The red list of 2012 contains 132 plant and animal species of India. Some examples of recent extinction are

(i) Dodo (Mauritius), Quagga (Africa), Thylacine (Australia),Steller’s sea cow (Russia) and three subspecies of tiger (Bali, Javan and Caspian).

(ii) About 27 species have disappeared in the last 20 years in the world, with more than 15,500 species are endangered. Presently 12% of all bird species, 23% of all mammal species, 32% of all amphibian species and 31% of all gymnosperms are facing extinction threat with amphibians which are more vulnerable to extinction.

(iii) Endangered species are those species which are facing a high risk of extinction in the near future due to decrease in its habitat, excessive predation or poaching. Some of the endangered species are Asiatic lion, Bengal tiger, Lion-tailed Macaque, Nilgiri Langur, Gangas river dolphin, etc.

Extinction in Biodiversity

- Study of fossil record reveals that large scale loss of species had also occurred earlier, even before humans appeared on the scene. There have been five episodes of mass extinctions during the long period of >3 billion years due to natural calamities, e.g. extinction of dinosaurs.
- Currently, the earth is heading towards the sixth extinction, which is different from the previous episodes in the rates. The current species extinction rates are estimated to be 100-1,000 times faster than in the prehuman times and human activities are responsible for the faster rates. If the present rate of species extinction goes on, 50% of the species might be wiped out within next 100 years.

In general, loss of biodiversity may lead to
(i) Decline in plant production.
(ii) Lower resistance and resilience to environment perturbations such as drought.
(iii) Increased variability in ecosystem processes such as plant productivity, water use, pest and disease cycles, etc.

Causes of Biodiversity Loss
Habitat loss and fragmentation, overexploitation, alien-species invasion, coextinction are the four (Evil Quartet) major causes of loss of biodiversity.

1. Habitat loss and fragmentation occurs due to population explosion that has destroyed forest land, which leads to the loss of habitat of several species, e.g. once covering more than 14 % of the earth’s land surface, the Amazonian rainforests (‘lungs of the planet’) now cover less than 6 % as they are being cut and cleared for cultivation of soybeans or conversion into grasslands for raising beef cattle. This has caused loss of habitat for lots of species and has put tremendous pressure on the ecosystem.

2. Overexploitation Uncontrolled or overuse of resources by humans leads to overexploitation of natural resources.
Many species extinctions in the last 500 years such as of Steller’s sea cow, passenger pigeon, etc., due to the overexploitation by humans.
Currently, many marine fish populations are being over harvested, endangering the continued existence of some commercially important species.

3. Alien-species invasions When alien-species are introduced unintentionally or deliberately in a habitat, some of them turn invasive and can cause decline or extinction of indigenous species, e.g. the Nile perch introduced into lake Victoria (East Africa) cause extinction of cichlid fishes, invasive weed species like carrot grass (Parthenium), Lantana and water hyacinth (Eichhornia) also can cause environment damage and threaten the existence of native species. African catfish called, Clarias gariepinus is posing a threat to the indigenous catfish in our rivers.

4. Coextinctions 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.

Biodiversity Conservation

Conservation of biodiversity is protection, upliftment and scientific management of biodiversity so as to maintain it at the optimum level and derive sustainable benefits for the present as well as future generations.

Reasons for Conserving Biodiversity

There are many reasons for conservation of biodiversity, but all reasons are equally important. They can be grouped into three categories which are as follows

1. Narrowly Utilitarian Argument
These are based on obvious reasons. Humans derive countless direct economic benefits from the nature like food (cereals, pulses and fruits), firewood, fibre, construction material, industrial products (tannins, lubricants, dyes, resins and perfumes) and products of medicinal importance. More than 25% of the drugs currently sold in the market worldwide are derived from plants and 25,000 plant species are used in traditional medicines.
Moreover, biodiversity rich countries expect to reap more benefits from the increasing resources put into bioprospecting,i.e. exploration of molecular, genetic and species-level diversity for obtaining products of economic importance.

2. Broadly Utilitarian Argument
According to this argument, biodiversity plays a major role in ecosystem services that nature provides.
Some of these are
(i) Production of oxygen, e.g. Amazon forests produce 20% of the total oxygen in the earth’s atmosphere via photosynthesis.
(ii) Pollination of flowers without which fruits and seeds are not produced, is provided by pollinator layer, i.e. bees, bumble bees, birds and bats.
(iii) Control of floods and soil erosion.
(iv) Intangible benefits of nature like aesthetic pleasures of watching spring flower in full bloom, walking through thick forest, listening to bulbul’s song, etc.

3. Ethical Argument
Every species has an intrinsic value, even if it is not of any economic value to us. It is our moral duty to care for their well-being and pass on our biological legacy in good order to future generations. Moreover, many plants like tulsi and peepal have religious importance as well.

Approaches to Conserve Biodiversity

- Biodiversity can be conserved by protecting its whole ecosystem. There are two basic approaches for conservation of biodiversity.

I. In Situ (On-site) Conservation

It is the conservation and protection of the whole ecosystem and its biodiversity at all levels in order to protect the threatened species. However, it is not economically feasible to conserve all the biological wealth at all the existing ecosystems. Methods used in in situ conservation are

1. Biodiversity Hotspots

These are regions with very high levels of species richness, high degree of endemism (species confined to a region and not found anywhere else) and accelerated habitat loss. Initially, 25 biodiversity hotspots were identified. Now, there are 34 hotspots all over the world.
These hotspots are in India, i.e. Western Ghats and Sri Lanka, Indo-Burma and Eastern Himalaya. If all the biodiversity hotspots are put together, they cover less than 2% of the earth’s land area, but harbour extremely high diversity. Ongoing mass extinctions could be reduced by 30% through strict protection of these hotspots.

2. Protected Areas

These are especially dedicated areas for protection and maintenance of ecologically unique and biodiversity rich regions. Protected areas are classified as

(i) National parks These are government maintained areas (90 in India), reserved for the betterment of wildlife and where activities such as cultivation, grazing, forestry and habitat 

manipulation are not allowed. The first National park was established in India in 1936, i.e. Hailey’s National Park.
(ii) Wildlife sanctuaries They are tracts of land with or without lake where wild animals/fauna can take refuge without being hunted. There number is 448 in India. Other activities like collection of forest products, harvesting of timber, private ownership of land, tilling of land, etc., are allowed here.

(iii) Biosphere reserves These are large tracts of protected land with multiple use preserving the genetic diversity of ecosystem by protecting wildlife, traditional lifestyles of tribals and varied plants and animal genetic resources. They have been setup under MAB (Man and Biosphere) programme of UNESCO. There are 14 biosphere reserves in India. A biosphere reserve consists of three zones as shown below

MAB Programme
Man and Biosphere Programme is an international biological programme of UNESCO started in 1971 but introduced in India in 1986. MAB has studied human environment, impact of human interference and pollution on biotic and abiotic environments and conservation strategies for the present as well as future.

(iv) Sacred groves These are small groups of forests with special religious importance in a particular culture and are also of mythological importance.
- These are undisturbed forests without any human interventions and include a number of rare, endangered and endemic species.
- Sacred groves are found in Khasi and Jaintia Hills in Meghalaya, Aravalli Hills of Rajasthan, Western Ghat regions of Karnataka and Maharashtra and the Sarguja, Chanda and Bastar areas of Madhya Pradesh.
- These are protected by native people as a part of cultural traditions. In Meghalaya, the sacred groves are the last refuges for a large number of rare and threatened plants.

(v) Ramsar sites These are the wetlands designated as internationally important under the convention on wetlands held at Ramsar, Iran in 1971 for the conservation and wise use of wetlands. Thus, known as Ramsar convention The wise use of wetlands is defined as ‘the maintenance of their ecological character achieved through the implementation of ecosystem approaches, within the context of sustainable development’.
It means wise use of wetlands and their resources, for the benefit of humankind. There are 26 Ramsar sites in India. Some of these are Ashtamudi wetland (Kerala), Sambhar lake (Rajasthan), Chilka lake (Odisha), Renuka wetland (Himachal Pradesh), etc.