Biodiversity and Conservation
Welcome to HSLC Guru! In this lesson, we explore Chapter 15 — Biodiversity and Conservation from the ASSEB Class 12 Biology syllabus. This chapter introduces the variety of life on Earth, the patterns of its distribution, the threats it faces, and the strategies adopted to conserve it. We will study the levels of biodiversity, latitudinal gradients, the species-area relationship, the importance of biodiversity, biodiversity hotspots, in-situ and ex-situ conservation, the IUCN Red List, the Convention on Biological Diversity (CBD), and CITES. The notes are written in clear English and aligned with the ASSEB Class 12 Biology textbook so students can prepare confidently for school examinations and the Higher Secondary final examination.
Chapter Summary
Concept and Levels of Biodiversity: The term biodiversity was popularised by the sociobiologist Edward O. Wilson in 1992 to describe the combined diversity of all forms of life on Earth at all levels of biological organisation. Biodiversity exists at three primary levels.
Genetic diversity refers to the variation of genes within a single species; for example, Rauwolfia vomitoria growing in different Himalayan ranges shows variation in the potency and concentration of the active chemical reserpine. India has more than 50,000 genetically different strains of rice and 1,000 varieties of mango. Species diversity refers to the variety of species in a region; for example, the amphibians of the Western Ghats are far more diverse than those of the Eastern Ghats. Ecological (ecosystem) diversity refers to the variety of ecosystems — deserts, rainforests, mangroves, coral reefs, wetlands, estuaries and alpine meadows. India, with its varied terrain, shows great ecosystem diversity.
Patterns of Biodiversity: The most well-known pattern is the latitudinal gradient: species diversity decreases as we move from the equator towards the poles. Tropical regions (latitudes 23.5 deg N to 23.5 deg S) harbour more species than temperate or polar regions because tropics have remained relatively undisturbed for millions of years, providing a long evolutionary time; tropical environments are less seasonal, more constant and predictable; and there is more solar energy available which contributes to higher productivity. Colombia near the equator has nearly 1,400 species of birds, while New York at 41 deg N has 105 and Greenland at 71 deg N has only 56.
The Amazonian rainforest of South America has the greatest biodiversity on Earth, with more than 40,000 species of plants, 3,000 fishes, 1,300 birds, 427 mammals, 427 amphibians, 378 reptiles and over 1,25,000 invertebrates. Another important pattern is the species-area relationship, given by the German naturalist Alexander von Humboldt: within a region, species richness increases with explored area, but only up to a limit. The relation is described by the equation log S = log C + Z log A, where S is species richness, A is area, Z is the slope of the line (regression coefficient) and C is the Y-intercept. The value of Z lies between 0.1 and 0.2 for small areas and rises to 0.6 – 1.2 for very large areas like entire continents.
Importance of Biodiversity: The importance of biodiversity may be grouped into three categories. Narrowly utilitarian arguments emphasise economic benefits — food (cereals, pulses, fruits), fibres, firewood, construction material, industrial products (tannins, lubricants, dyes, resins, perfumes) and medicinal products (drugs from plants and microbes). Today more than 25 per cent of the drugs in the global market come from plants, and 25,000 species of plants contribute to traditional medicines. Broadly utilitarian arguments highlight ecosystem services such as production of oxygen by Amazonian forests (about 20 per cent of total atmospheric oxygen), pollination by bees, bumblebees, birds and bats, climate regulation, flood and erosion control, water purification, nutrient cycling and pest control. The aesthetic pleasures — walking in dense woods, watching spring flowers in bloom, sunrise from a hill — also count. The ethical argument urges that every species has an intrinsic value and we owe a moral duty to pass on the planet’s biological wealth in good order to future generations.
Loss of Biodiversity: Biodiversity loss is occurring at an alarming rate. The IUCN Red List (2004) records that since 1500 AD, 784 species (including 338 vertebrates, 359 invertebrates and 87 plants) have become extinct. The four major causes (called The Evil Quartet) are: habitat loss and fragmentation (the most important cause; tropical rainforest cover reduced from 14 per cent to 6 per cent of land area; the Amazon rainforest, the lungs of the planet, is being cleared for soya bean cultivation), over-exploitation (Steller’s sea cow and passenger pigeon were driven to extinction; many marine fishes are over-harvested), alien species invasions (Nile perch introduced into Lake Victoria led to the extinction of more than 200 cichlid fish species; carrot grass Parthenium, water hyacinth Eichhornia crassipes and Lantana are notorious invasives in India; the African catfish Clarias gariepinus is endangering native catfishes), and co-extinctions (when a host species becomes extinct its obligate parasites or pollinators also disappear).
Biodiversity Hotspots: The British environmentalist Norman Myers proposed the concept of biodiversity hotspots — regions with very high levels of species richness, high degree of endemism (species confined to that region) and a serious level of habitat threat. Initially 25 hotspots were identified; the number has now risen to 34 globally. India has four biodiversity hotspots: the Western Ghats and Sri Lanka, Indo-Burma, the Himalayas and Sundaland. Although these hotspots cover less than 2 per cent of the Earth’s land area, strict protection could reduce ongoing mass extinctions by almost 30 per cent.
Conservation: Conservation is broadly of two types. In-situ conservation protects species in their natural habitats: biosphere reserves (14 in India), national parks (more than 90), wildlife sanctuaries (about 448) and culturally protected sacred groves (Khasi and Jaintia hills in Meghalaya, Aravalli hills of Rajasthan, the Western Ghats of Karnataka and Maharashtra, and Sarguja, Chanda and Bastar in Madhya Pradesh — these protect many rare and threatened plants). Ex-situ conservation protects threatened species outside their natural habitats: zoological parks, botanical gardens, wildlife safari parks, seed banks, gene banks, pollen banks, in-vitro fertilisation, tissue culture and cryopreservation of gametes at -196 deg C in liquid nitrogen.
Global Conservation Efforts: The IUCN Red List classifies species into categories such as Extinct, Extinct in the Wild, Critically Endangered, Endangered, Vulnerable, Near Threatened, Least Concern and Data Deficient. Two important international agreements are the Convention on Biological Diversity (CBD) signed at the Earth Summit in Rio de Janeiro in 1992, which calls for conservation of biodiversity, sustainable use of its components and equitable sharing of benefits; and the World Summit on Sustainable Development held in Johannesburg in 2002, which pledged to reduce the rate of biodiversity loss. CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) regulates international trade and protects endangered species from over-exploitation.
Question and Answer
1-Mark Questions
Q1. Who popularised the term biodiversity?
Answer: The American sociobiologist Edward O. Wilson popularised the term biodiversity in 1992.
Q2. Name the three levels of biodiversity.
Answer: Genetic diversity, species diversity and ecological (ecosystem) diversity.
Q3. Who proposed the concept of biodiversity hotspots?
Answer: The British ecologist Norman Myers proposed the concept of biodiversity hotspots.
Q4. How many biodiversity hotspots are there in the world today and how many are in India?
Answer: There are 34 hotspots globally, of which 4 are in India.
Q5. Name the four biodiversity hotspots of India.
Answer: Western Ghats and Sri Lanka, Indo-Burma, Himalayas and Sundaland.
Q6. Write the species-area relation equation given by Alexander von Humboldt.
Answer: log S = log C + Z log A, where S is species richness, A is area, Z is the slope (regression coefficient) and C is the Y-intercept.
Q7. Where and when was the Convention on Biological Diversity (CBD) held?
Answer: The CBD was held at the Earth Summit in Rio de Janeiro, Brazil, in June 1992.
Q8. Give two examples of invasive alien species in India.
Answer: Water hyacinth (Eichhornia crassipes) and Lantana; also Parthenium (carrot grass).
Q9. What is the full form of CITES?
Answer: Convention on International Trade in Endangered Species of Wild Fauna and Flora.
Q10. Define endemism.
Answer: Endemism is the phenomenon in which species are restricted to a particular geographical region and are not found anywhere else.
2- to 3-Mark Questions
Q1. Distinguish between genetic, species and ecosystem diversity with one example each.
Answer: Genetic diversity is the variation of genes within a species; for example, Rauwolfia vomitoria shows different concentrations of reserpine across the Himalayas. Species diversity is the variety of species in a region; for example, amphibian diversity is far higher in the Western Ghats than in the Eastern Ghats. Ecosystem diversity is the variety of ecosystems; for example, India has deserts, rainforests, mangroves, coral reefs and alpine meadows.
Q2. Explain the latitudinal gradient in biodiversity. Give the three hypotheses proposed for this pattern.
Answer: Species diversity decreases as we move from the equator towards the poles. Tropics support more species than temperate or polar regions. Three hypotheses: (i) tropics have remained undisturbed for millions of years, allowing long evolutionary time; (ii) tropical environments are less seasonal, more constant and predictable; (iii) tropics receive more solar energy, leading to higher productivity and species diversity.
Q3. What is meant by the species-area relationship? Mention the value of slope Z for small and large areas.
Answer: Species richness increases with the area explored, up to a limit. The relation log S = log C + Z log A, drawn on a log-log scale, gives a straight line. The slope Z lies between 0.1 – 0.2 for small areas (within a continent) but rises to 0.6 – 1.2 for very large areas like entire continents.
Q4. List the four causes of biodiversity loss known as ‘The Evil Quartet’.
Answer: (i) Habitat loss and fragmentation, (ii) over-exploitation of natural resources, (iii) alien species invasions, and (iv) co-extinctions.
Q5. What are sacred groves? Give two examples from India.
Answer: Sacred groves are tracts of forest set aside in which all trees and wildlife are venerated and given total protection by tribal and religious communities. Examples include the Khasi and Jaintia hills of Meghalaya, the Aravalli hills of Rajasthan, Sarguja, Chanda and Bastar areas of Madhya Pradesh, and the Western Ghats of Karnataka and Maharashtra.
Q6. Distinguish between in-situ and ex-situ conservation with two examples each.
Answer: In-situ conservation protects species in their natural habitat — examples: national parks (Kaziranga), wildlife sanctuaries, biosphere reserves and sacred groves. Ex-situ conservation protects species outside their natural habitat — examples: zoos, botanical gardens, seed banks, cryopreservation and tissue culture.
Q7. Explain co-extinction with an example.
Answer: Co-extinction is the loss of one species following the extinction of another to which it is closely linked. For example, when a host fish becomes extinct, all its obligate parasites also die out. Similarly, the disappearance of a unique pollinator can drive its plant partner to extinction. The loss of one species in a coevolved pair (such as a fig and its specific fig wasp) leads to a chain of disappearances.
Q8. What are the criteria used by Norman Myers to identify a biodiversity hotspot?
Answer: A region qualifies as a biodiversity hotspot when it has (i) a very high level of species richness, (ii) a high degree of endemism (at least 1500 endemic vascular plants), and (iii) a serious habitat threat (loss of at least 70 per cent of its primary vegetation). India has four hotspots — Western Ghats and Sri Lanka, Indo-Burma, Himalayas, and Sundaland.
5- to 7-Mark Questions
Q1. Discuss the three patterns of biodiversity in detail.
Answer: Three major patterns are observed in the global distribution of biodiversity.
(i) Latitudinal gradient: Species richness decreases steadily from the equator to the poles. The tropical Amazon rainforest holds about 40,000 plant species, while Greenland has only 56 bird species. The reasons include long undisturbed evolutionary time, low seasonality and high solar energy at low latitudes.
(ii) Species-area relationship: Alexander von Humboldt observed that within a region, species richness increases with area, but only up to a limit. The relation log S = log C + Z log A produces a rectangular hyperbola on an arithmetic scale and a straight line on a log scale. Z values are 0.1 – 0.2 for small areas and 0.6 – 1.2 for entire continents (frugivorous birds and mammals of tropical forests).
(iii) Productivity-diversity: Tropical regions also show higher net primary productivity, which supports more species. Together these patterns explain the global distribution of life and form the scientific basis of conservation priorities.
Q2. Explain the importance of biodiversity to human society under the headings narrowly utilitarian, broadly utilitarian and ethical.
Answer: Narrowly utilitarian: Direct economic benefits — food (cereals, pulses, fruits), firewood, fibres, construction material, industrial products (tannins, lubricants, dyes, resins, perfumes) and medicinal products. More than 25 per cent of modern drugs come from plants; 25,000 plant species contribute to traditional medicine. Bioprospecting (exploring molecular, genetic and species-level diversity for products of economic importance) is a fast-growing field.
Broadly utilitarian: Ecosystem services — Amazonian forests produce 20 per cent of total atmospheric oxygen; bees, bumblebees, birds and bats provide pollination; ecosystems regulate climate, control floods, purify water, recycle nutrients and control pests. Aesthetic pleasures (walking in woods, watching flowers, sunrise from a hill) also enrich human life.
Ethical: Every species has intrinsic value and we have a moral duty to leave the planet’s biological wealth intact for future generations. The combination of these three arguments forms the rationale for global conservation policy.
Q3. Describe the four major causes of loss of biodiversity (The Evil Quartet) with examples.
Answer: (i) Habitat loss and fragmentation: The most important driver. Tropical rainforests, once covering more than 14 per cent of land surface, now cover only 6 per cent. The Amazon rainforest is being cleared for soya bean cultivation. Fragmentation reduces population sizes of mammals and birds and disrupts migration.
(ii) Over-exploitation: Steller’s sea cow (Russia) and the passenger pigeon (North America) were hunted to extinction; many marine fish populations are over-harvested. The greed for commercial gain often pushes harvest beyond sustainable levels.
(iii) Alien species invasions: Introduction of Nile perch into Lake Victoria led to the extinction of more than 200 species of native cichlid fishes; carrot grass (Parthenium), Lantana and water hyacinth (Eichhornia crassipes) damage native flora; the African catfish (Clarias gariepinus) is endangering Indian native catfishes.
(iv) Co-extinctions: When a host or partner species becomes extinct, the dependent species also disappear, e.g. obligate parasites of an extinct host, or plant-pollinator pairs whose partners are gone.
Q4. Explain in-situ and ex-situ conservation strategies and mention the international efforts to conserve biodiversity.
Answer: In-situ conservation conserves species in their natural habitat. India has 14 biosphere reserves, more than 90 national parks, around 448 wildlife sanctuaries, and many sacred groves (Khasi and Jaintia hills, Aravalli hills, Sarguja, Western Ghats). The hotspot strategy concentrates protection on the 34 globally identified hotspots, of which India has four.
Ex-situ conservation protects species outside their habitat using zoological parks, botanical gardens, wildlife safaris, seed banks, gene banks, pollen banks, in-vitro fertilisation, tissue culture and cryopreservation of gametes at -196 deg C in liquid nitrogen.
International efforts: The Convention on Biological Diversity (CBD) signed at the Rio Earth Summit in 1992 calls for conservation, sustainable use and equitable benefit sharing. The World Summit at Johannesburg in 2002 pledged to reduce biodiversity loss. CITES regulates international trade in endangered species. The IUCN maintains the Red List of threatened species.
Q5. What are biodiversity hotspots? Why is their conservation important?
Answer: A biodiversity hotspot, as defined by Norman Myers, is a region with exceptional species richness, a very high degree of endemism, and a serious level of habitat threat. Originally 25 hotspots were identified; the number now stands at 34. Although hotspots cover less than 2 per cent of the Earth’s land area, they contain a disproportionately large fraction of biodiversity.
India has four hotspots — Western Ghats and Sri Lanka, Indo-Burma, Himalayas and Sundaland. Conservation of hotspots is important because strict protection of these regions could reduce the ongoing mass extinction by almost 30 per cent. They also hold key endemic species, ecosystem services and cultural value, making them priority areas for global conservation funding and policy.
Multiple Choice Questions (MCQ)
Q1. The term biodiversity was popularised by:
(a) Robert May (b) Edward Wilson (c) Norman Myers (d) Alexander von Humboldt
Answer: (b) Edward Wilson.
Q2. Number of biodiversity hotspots in the world today is:
(a) 25 (b) 34 (c) 17 (d) 50
Answer: (b) 34.
Q3. Which of the following is NOT a biodiversity hotspot of India?
(a) Western Ghats (b) Indo-Burma (c) Sundaland (d) Eastern Ghats
Answer: (d) Eastern Ghats.
Q4. The species-area relationship was given by:
(a) Wilson (b) Humboldt (c) Myers (d) Tansley
Answer: (b) Humboldt.
Q5. The introduction of which fish caused the extinction of cichlid fishes in Lake Victoria?
(a) African catfish (b) Nile perch (c) Tilapia (d) Carp
Answer: (b) Nile perch.
Q6. The Convention on Biological Diversity (CBD) was signed at:
(a) Johannesburg 2002 (b) Stockholm 1972 (c) Rio de Janeiro 1992 (d) Kyoto 1997
Answer: (c) Rio de Janeiro 1992.
Q7. Sacred groves are an example of:
(a) Ex-situ conservation (b) In-situ conservation (c) Cryopreservation (d) Bioprospecting
Answer: (b) In-situ conservation.
Q8. The slope value Z in the species-area relation for very large areas is:
(a) 0.1 – 0.2 (b) 0.3 – 0.5 (c) 0.6 – 1.2 (d) 2.0 – 3.0
Answer: (c) 0.6 – 1.2.
Q9. Which of the following is an example of ex-situ conservation?
(a) Biosphere reserve (b) National park (c) Seed bank (d) Sacred grove
Answer: (c) Seed bank.
Q10. The most important cause of biodiversity loss is:
(a) Co-extinction (b) Habitat loss and fragmentation (c) Alien invasions (d) Over-exploitation
Answer: (b) Habitat loss and fragmentation.
Fill in the Blanks
Q1. The term biodiversity was popularised by ____________.
Answer: Edward O. Wilson.
Q2. India has ____________ biodiversity hotspots.
Answer: four (4).
Q3. The species-area relationship is given by the equation log S = log C + ____________.
Answer: Z log A.
Q4. The Amazon rainforest produces about ____________ per cent of total atmospheric oxygen.
Answer: 20.
Q5. Storage of seeds, pollen and gametes at very low temperature is called ____________.
Answer: cryopreservation.
True or False
Q1. Tropical regions have lower species diversity than polar regions.
Answer: False.
Q2. The Western Ghats and Sri Lanka form a single biodiversity hotspot.
Answer: True.
Q3. Norman Myers proposed the concept of biodiversity hotspots.
Answer: True.
Q4. Eichhornia crassipes is an indigenous Indian aquatic plant.
Answer: False (it is an invasive alien species).
Q5. The Convention on Biological Diversity was held in 1992 at Rio de Janeiro.
Answer: True.
Glossary
| Term | Meaning |
|---|---|
| Biodiversity | The variety and variability of life at all levels of biological organisation; term popularised by E. O. Wilson (1992). |
| Genetic diversity | Variation of genes within a single species across its range. |
| Species diversity | The variety of species found in a particular region. |
| Ecosystem diversity | The variety of habitats, biotic communities and ecological processes in a region. |
| Endemism | Restriction of a species to a particular geographical region. |
| Latitudinal gradient | Pattern of decreasing species diversity from equator to poles. |
| Species-area relation | Humboldt’s law: species richness rises with area; log S = log C + Z log A. |
| Slope Z | Regression coefficient in species-area relation; 0.1 – 0.2 for small areas, 0.6 – 1.2 for continents. |
| Bioprospecting | Exploration of biodiversity for commercially valuable genetic and biochemical resources. |
| Evil Quartet | The four major causes of biodiversity loss: habitat loss, over-exploitation, alien invasions and co-extinctions. |
| Biodiversity hotspot | Region with high species richness, high endemism and high threat (Myers); 34 globally, 4 in India. |
| In-situ conservation | Protection of species in their natural habitat (parks, sanctuaries, biosphere reserves, sacred groves). |
| Ex-situ conservation | Protection of species outside their natural habitat (zoos, botanical gardens, seed and gene banks, cryopreservation). |
| Cryopreservation | Storage of gametes, seeds and tissues at very low temperature (-196 deg C in liquid nitrogen). |
| Sacred grove | Forest tract preserved by tribal/religious tradition; e.g. Khasi hills, Aravallis. |
| IUCN Red List | Global list of species classified by threat status (Extinct to Least Concern). |
| CBD | Convention on Biological Diversity, signed at Rio Earth Summit, 1992. |
| CITES | Convention on International Trade in Endangered Species of Wild Fauna and Flora. |
| Co-extinction | Extinction of a species caused by extinction of another species on which it depends. |
| Lantana / Eichhornia / Nile perch | Notable invasive alien species causing biodiversity loss. |