Class 12 Biology Chapter 15 Biodiversity and Conservation The answer to each chapter is provided in the list so that you can easily browse through different chapters Assam Board HS 2nd Year Biology Chapter 15 Biodiversity and Conservation Question Answer.
Class 12 Biology Chapter 15 Biodiversity and Conservation
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(F). Long Answer Questions (Five Marks Each) :
Q.1. Why does the tropics represents great biological diversity? Explain.
Ans : The diversity of flora and fauna is not uniform throughout the world but it shows a rather uneven distributions. In general, Species Diversity decreases as we move away from the equator towards the poles. With very few exceptions, tropics which lies in the latitudinal range of 23.5°N to 23.5°S harbour more species than temperate or polar areas. Columbia located near the equator has nearly 1,4000 species of birds while New York at 410N has 105 species and Greenland 71°N only 56 species.
India, with much of its land area in the area in the tropical region like equator has more than 1,200 species of birds. A forest in a tropical region like equator has upto 10 times as many species of vascular plants. A largely tropical Amazonian rain forest in South America has the greatest biodiversity on earth. It is now to more than 40,000 species of plants. 3,000 of fishes, 1,300 of birds, 427 of mammals, 427 of amphibians, 378 of replites and more than 1,25,000 invertebrates and many are yet to be discovered.
The greater Biodiversity in tropics is due to :
(i) Speciation is generally a function of time, unlike temperate regions subjected to frequent glaciations in the past, tropical latitudes have remained relatively undisturbed millions of years and thus, had a long evolutionary time for species diversification.
(ii) Tropical environments, unlike temperate one, are less seasonal, relatively more constant and predictable which promote niche specialisation and lead to greater species diversity. and
(iii) There is more solar energy available in the tropics, which contributes to higher productivity this in turn might contribute to greater diversity.
(iv) It has more rainfall, more flurtuations of temperature, flecfuation of distribution of minerals etc.
Q.2. Explain the Species-Area relationships with the help of graph.
Ans : There is a relationship between species and area which indicates the biodiversity. It was forwarded by German naturalist and Geographer Alexander Von Humbolt. He observed that within a region species richness increase with increasing explored area but only up to a limit. In fact, the relationship between species richness and area for a wide variety of taxa out to be a rectangular hyperbola. On logarithmic scale, the relationship is a straight line described by the equation –
log S = log C+Z log A
where, S = Species richness
Z = Slope of the line (regression co-efficient)
A = Area
C = Y- intercept
Ecologists have discovered that the value ofz lines in the range of 0.1- 0.2 regardless of the taxonomic group or the region. But, if species area relationship is analysed among very large areas like the entire continents, the slope of the lines will be much steeper-z values in the range of 0.6 – 1.2.
Q.3. Write note on the causes of biodiversity losses.
Ans : The biodiversity wealth of the planet has be declining due to human civilization and human activity. These are due to destruction of forests for fulfilling different types of human needs by themselves. For example – the colonisation of tropical pacific Islands by humans is said to have led to the extinction of more than 2,000 species of native birds.
The IUCN Red List (2004) documents the extinctions of 784 species among which 338 are vertebrates, 359 invertebrates and 87 plants in the last 500 Some recent extinctions include – dodo (Mauritius), quagga (Africa), thylacine (Australia) etc. The last twenty years alone have witnessed the disappearences of 27 species. Careful analysis of records shows that extinctions across taxa are not random, presently 12 percent of all bird species, 23 percent of all mammal species. 32 percent of all amphibian species,and 31 percent of all gymnosperm species in the.world face the threat of extinction.
From a study of the history of life on Earth before humans appeared on scene, the causes of species extinctions were natural. But the current species extinction rates are estimated to be 100 to 1,000 times faster than in the pre-human times and according to scientists if the present trends continue, nearly half of all the species on earth might be wiped out within the next 100 years.
In general, loss of biodiversity in a region may lead to :
(a) decline in plant production.
(b) lowered resistance to environmental perturbations such as draught.
(c) increased variability in certain ecosystem processes such as productivity, water use and pest and disease cycles. and
(d) Affected the animals life by loss of habitat etc.
| Sl. No. | CONTENTS |
| Chapter 1 | Reproduction in Organisms |
| Chapter 2 | Sexual Reproduction in Flowering Plants |
| Chapter 3 | Human Reproduction |
| Chapter 4 | Reproductive Health |
| Chapter 5 | Principles of Inheritance and Variation |
| Chapter 6 | Molecular Basis of Inheritance |
| Chapter 7 | Evolution |
| Chapter 8 | Human Health and Disease |
| Chapter 9 | Strategies for Enhancement in Food Production |
| Chapter 10 | Microbes in Human Welfare |
| Chapter 11 | Biotechnology: Principles And Processes |
| Chapter 12 | Biotechnology and its Applications |
| Chapter 13 | Organisms and Populations |
| Chapter 14 | Ecosystem |
| Chapter 15 | Biodiversity and Conservation |
| Chapter 16 | Bioresources of Assam |
| Chapter 17 | Environmental Issues |
Q.4. Explain why biodiversity should be conserved?
Ans : There are a number of reasons to conserve the biodiversity.
The reasons can be grouped into :
(a) Narrowly utilitarian.
(b) Broadly utilitarian.
(c) Ethical Method.
(a) Narrowly utilitarian : Human derive countless direct economic benefits from nature like – food (eg. – cereals, pulses, fruits), firewood, fibre, construction material, industrial products (tannins, lubricants, dyes, resins, perfumes) and products of medicinal importance. More than 25 percent of the drugs currently sold in the market world wide are derived from plants and 25,000 species of plants contribute to the traditional medicines used by native peoples around the world. Yet more medicinally useful plants in tropical rain forests waiting to be explored. With increasing resources put into exploring molecular, genetic and species-level diversity for products of economic importance and nations endowed with rich biodiversity can expect to reap enormous benefits.
(b) Broadly utilitarian : This argument says that biodiversity plays a major role in many ecosystem services that nature provides. The fast dwindling forest is estimated to produce, through photo synthesis, 20 percent of the total oxygen in the Earth’s atmosphere. Pollination is another service that ecosystem provide through pollinators. These are other
intangible benefits that we derive from nature the aesthetic pleasures of walking through thick woods, watching spring flowers etc.
(c) Ethical : Ethical argument for conserving biodiversity relates to what we are to millions of plant, animal and microbe species with whom we share this planet. Philosophically and spiritually, we need to realise that every species has an intrinsic value, even if it may not be of current or any economic value to us. We have moral duty to care for their well being and pass on our biological legacy in good order to future generations.
Q.5. What are the different ways by which biodiversity can be conserved?
Ans : Faced with the conflict between development and conservation, many nations find it unrealistic and economically not feasible to conserve all their biological wealth. With the increasing population many forests has been destroyed.
So there is a need to conserve biodiversity by two different ways :
(i), In Situ Conservation. and
(ii) Ex-Situ Conservations.
(i) In-Situ Conservation : In this type of conservation system some regions with very high levels of species richness and high degree of endemism are identified for maximum protection. Although all the “biodiversity hotspots’ put together cover less than 2 percent of the Earth’s land area, the number of species they collectively harbour is extremely high and strict protection of these hotspots could reduce the ongoing mass extinction by almost 30 percent. For this various biodiversity rich regions are legally protected as biosphere reserves, national parks and sanctuaries etc.
(ii) Ex-Situ Conservation : In this approach, threatened animals and plants are taken out from their natural habitat and placed in special setting where they can be protected and given special care. Zoological parks, botanical gardens and wildlife safari parks serve this purpose. There are many animals that have become extinct in the wild but continue to be maintained in zoological parks. In recent years ex-site conservation has advanced beyond keeping threatened species in enclosers. Now gametes also can be preserved in viable and fertile condition for long periods using cryopreservation fechnique. Plants can be propagated using tissue culture technique.
Q.6. Write briefly on the pattern of biodiversity.
Ans : There are two patterns of biodiversity.
They are :
(i) Latitudinal Gradient.
(ii) Species-Area relationship.
(i) Latitudinal Gradient : The biological wealth of our planet has been declining rapidly and the accusing finger is clearly pointing to human activities. These are due to destruction of forests for fulfilling different types of human needs by themselves. For example – the colonisation of tropical pacific Islands by humans is said to have led to the extinction of more than 2,000 species of native birds. The IUCN Red List (2004) documents the extinctions of 784 species among which 338 are vertebrates, 359 invertebrates and 87 plants in the last 500 years. Some recent extinctions include – dodo (Mauritius), quagga (Africa), thylacine (Australia) etc. The last twenty years alone have witnessed the disappearence of 27 species. Careful analysis of records shows that extinctions across taxa are not random, presently 12 percent of all bird species, 23 percent of all mammal species, 32 percent of all amphibian species and 31 percent of all gymnosperm species in the world face the threat of extinction.
From a study of the history of life on earth before humans appeared on scene, the causes of species extinctions were natural. But the current species extinction rates are estimated to be 100 to 1,000 times faster than in the pre-human times and according to scientists if the present trends continue nearly half of all the species on earth might be wiped out within the next 100 years.
In general, loss of Biodiversity in a region may lead to :
(a) decline in plant production.
(b) lowered resistance to environmental perturbations such as draught. and
(c) increased variability in certain ecosystem processes such as productivity, water use and pest and disease cycles.
(ii) Species-area relationship : Species area relationship is a pattern of Biodiversity, the great German naturalist and Geographer Alexander yon Humboldt observed that within a region species richness increase with increasing explored area but only up to a limit. In fact, the relation between species richness and area for a wide variety of taxa out to be a rectangular hyperbola. On logarithmic scale, the relationship is a straight line described by the equation –
log S = log C+ Z log A
Where, S = Species richness
Z = Slope of the line (regression co-efficient)
A = Area
C = Y-intercept
Ecologists have discovered that the value of z lines in the range of 0.1-0.2 regardless of the taxonomic group or the region. But, if species area relationship is analysed among very large areas like the entire continents, the slope of the lines will be much steeper- z values in the range of 0.6- 1.2.
Q.7. Write a note on Kaziranga National Park mentioning its important fauna.
Ans : Kaziranga National Park which is situated on the Southern bank of river Brahmaputra covers an area of 430 sq.km and is located in the districts of Golaghat and Nagaon. This is the house of more than two third of the worlds one horned rhino population.
To protect and rear the one horned rhinoceros, it is declared as a reserved forest in 1908. In the year 1916 it was declared as a Game Sanctuary. It was again declared as wildlife sanctuary in 1950 and ultimately on Ist January, 1974 Kaziranga was accorded the status of a National Park.
The forests of Kaziranga are of four types, which are :
(a) Semi evergreen forest.
(b) Alluvial grassland.
(c) Low alluvial Savanahs. and
(d) Mixed deciduous forest.
Though the park is famous for rhinos it has also rich in variety of other mammalian, ovarian, reptilian and oiscion fauna.
Among mammals the important ones found in Kaziranga National Parks are-Hooleck gibbon, Tiger,,Bear, Indian elephant, Sambar, swamp deer etc.
Total 304 varieties of birds recorded in Kaziranga which include -Pelican, Hornbill, Petridges, Bengal florican, Egrets etc.
The reptilian fauna include various species of tortoises and varamus etc.
The census of the large mammals has been carried out by the Forest Development of Assam every six years since 1966 in Kaziranga National Park.
The population of different species of large mammals recorded in 1993 is given below :
| Mammalia | Number | |
| (a) | Rhinoceros | 1,164 |
| (b) | Elephant | 511 |
| (c) | Swamp Deer | 34 |
| (d) | Tiger | 8 |
| (e) | Beer | 2 |
| (f) | Buffalo | 62 |
Q.8. Write about Nameri National Park stating its important fauna.
Ans : Nameri National Park is in the district Sonitpur. The area is of 137 Sq. km. In 1985, It was declared as wild life sanctuay but in 1995 it was upgraded to national park. The important fauna of Nameri National Park are :
(a) Elephant.
(b) Slow loris.
(c) Porcupine.
(d) Banking deer.
(e) Royal bengal tiger.
(f) Different snakes – like Cobra, Kruit python etc.
(g) Different birds.
(h) Other-insects, snails, fisher, auphibia.
Q.9. Describe the life cycle and rearing of eri silk moth.
Ans : Like other insects, life cycle of Eri worm is completed in following stages-
(i) Egg.
(ii) Larva.
(iii) Pupa. and
(iv) Adult.
(i) Egg : After copulation, a femalemoth lays about 300-500 eggs in cluster. Egg laying may continue for 3-4 days. Matching of place after about 10 days.
(ii) Larva : Newly hatched creature are know as larva. First moulting of larva occurs after 3 days of hatching. A larva matures in 17-45 days. A finally formed larva just before becoming a cocoon stops feeding. This stage is called ‘Pucca cocoon.’
(iii) Pupa : The creature inside a cocoon transforms into a brown coloured chrysalid. It is a non-feeding stage. During this period, the creature undergoes series of changes called metamorphosis.
(iv) Moth : After pupal metamophosis is over, the creature emerge out by opening the cocoon within a period of 2 weeks. This stage is called moth. The body consists of 3 segments head, thorax and abdomen. The head possess a pair of antenna a pair of compound eyes and month part. The thorax possess three pairs of walking legs. The meso and meta thorax possess one pair of wing each. After emergence the adult moth starts copulation again.
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