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English · हिन्दी · తెలుగు · தமிழ் · മലയാളം · मराठी · ಕನ್ನಡ

What biodiversity is and where it is found

தமிழில் விளக்கம்

Biodiversity · Part 1 / 2 · Fact-checked on · how we check

Written with AI from the sources listed at the bottom of this page, then fact-checked by a separate AI.

The CBD definition and the three levels of biodiversity; species richness and evenness, alpha, beta and gamma diversity; the latitudinal gradient and the species–area relationship; India as a megadiverse country; biodiversity hotspots and India's four; the ten biogeographic zones; endemic species.

Each idea is explained first in Tamil (தமிழ்), ending with the English and Hindi exam terms, followed by the same point in exam English. UPSC Prelims is in English or Hindi, so understand it in Tamil and revise it in English.

சூழல் மண்டலங்கள் எப்படி இயங்குகின்றன என்று பார்த்தோம். இப்போது அவற்றில் எவ்வளவு உயிர் உள்ளது, எங்கே அதிகம், ஏன் ஆபத்தில் உள்ளது என்பது. பல்லுயிர்ப் பெருக்கம் என்றால் நம்மைச் சுற்றியுள்ள பலவகை உயிர்களின் செல்வம். இந்தப் பகுதியில்: அதன் பொருள், மூன்று நிலைகள், அளவிடுதல், எங்கே அதிகம், இந்தியா ஏன் வளமான நாடு, மையப்பகுதிகள், உயிர்ப் புவியியல் மண்டலங்கள். (→ English: biodiversity · हिन्दी: जैव विविधता)

In exam EnglishThe ecology chapter showed how ecosystems work. This chapter asks how much life they hold, where it is concentrated and why it is in danger. biodiversity is a word the Prelims returns to almost every year, through hotspots, endemic species, the IUCN Red List, protected areas and the treaties that protect nature. This first part builds the base: what biodiversity means and its three levels, how ecologists measure it, why it is spread so unevenly over the globe, why India counts among the richest countries, which parts of India are global hotspots, and how the country is divided into biogeographic zones. Part 2 turns to the value of biodiversity, the threats it faces, the Red List and the ways it is conserved.

பல்லுயிர்ப் பெருக்கத்துக்கு மூன்று நிலைகள். மரபியல் பன்முகத்தன்மை: ஒரே இனத்துக்குள் வகைகள், நம் ஊரில் பல வகை நெல், பல இன மாடுகள் இருப்பது போல. இனப் பன்முகத்தன்மை: ஒரு இடத்தில் எத்தனை வெவ்வேறு இனங்கள். சூழல் மண்டலப் பன்முகத்தன்மை: காடு, புல்வெளி, ஈரநிலம், அலையாத்திக் காடு, பவளப்பாறை. பெட்டிக்குள் சிறு பெட்டிகள் போல இவை ஒன்றுக்குள் ஒன்று. (→ English: genetic diversity; species diversity; ecosystem diversity · हिन्दी: आनुवंशिक विविधता; प्रजाति विविधता; पारिस्थितिकी तंत्र विविधता)

In exam EnglishBiodiversity is short for biological diversity, the variety of all life on Earth. The Convention on Biological Diversity (1992), in its Article 2, defines it as "the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems." Those last words give the three levels that every textbook and every exam uses. genetic diversity is the variety of genes within one species, which is why one crop can exist in hundreds of local varieties and one animal in many breeds. Species diversity is the variety of different species in an area. Ecosystem diversity is the variety of habitats and communities, such as forests, grasslands, wetlands, deserts, mangroves and coral reefs. The three levels are nested: many ecosystems, each with many species, each species carrying many forms of its genes.

மரபியல் பன்முகத்தன்மை மாற்றத்தைத் தாங்கும் திறனைத் தருகிறது. ஒரே வகைப் பயிர் போட்டால் ஒரு நோய் வந்தாலும் முழுதும் போய்விடும்; 1840களில் அயர்லாந்தில் சில வகை உருளைக்கிழங்கையே நம்பியதால் நோயால் பயிர் முழுதும் அழிந்து பஞ்சத்துக்கு வழிவகுத்தது. அதனால்தான் நம் பழைய நாட்டு விதைகள் மதிப்புள்ளவை. ஈரநிலங்கள் வெள்ள நீரைத் தேக்குகின்றன, அலையாத்திக் காடுகள் கரையைக் காக்கின்றன. (→ English: genetic diversity · हिन्दी: आनुवंशिक विविधता)

In exam EnglishEach level matters for its own reason. Genetic variety is the raw material for adapting to change: a population whose members differ can survive a new disease or a hotter climate because some individuals happen to cope. Its loss can be costly. In Ireland in the 1840s, most of the poor depended on potatoes of very few varieties, and when a blight arrived almost the whole crop failed together, contributing to a famine. For the same reason plant breeders value the wild relatives of crops and old farmers' varieties, which carry genes for resistance and hardiness. India is one of the regions where crops such as rice, many pulses, mango and citrus have long been grown and varied, so its traditional varieties are a genetic treasury. Ecosystem diversity matters because each kind of ecosystem supplies its own services: wetlands store floodwater, mangroves shield coasts, forests protect catchments.

பன்முகத்தன்மையைக் கணக்கிடுதல்: ஒரு இடத்தில் எத்தனை இனங்கள் என்பது இன வளம். ஒரே மர இனம் காடு முழுதும் இருந்தால் பன்முகத்தன்மை குறைவு, அதனால் சமநிலையும் பார்க்கப்படுகிறது. ஆல்ஃபா: ஒரு தோப்பின் உள்ளே. பீட்டா: ஒரு தோப்பிலிருந்து அடுத்த தோப்புக்குப் போனால் எவ்வளவு மாறுகிறது, மலை ஏறும்போது மரங்கள் மாறுவது போல. காமா: முழுப் பகுதியும் சேர்த்து. (→ English: species richness; alpha, beta and gamma diversity · हिन्दी: प्रजाति समृद्धि; अल्फ़ा, बीटा और गामा विविधता)

In exam EnglishCounting diversity is harder than it sounds. The simplest measure is species richness, the number of species in a place. But two forests with twenty species each are not equally diverse if in one forest a single species makes up almost every tree; so ecologists also look at evenness, how equally individuals are shared among species. The American ecologist Robert Whittaker separated diversity by scale. Alpha diversity is the diversity within one habitat or community, such as one patch of forest. Beta diversity is the change in species from one habitat to another, for example as one climbs a mountain or moves from a dry to a wet slope; high beta diversity means neighbouring communities share few species. Gamma diversity is the total diversity of a whole landscape or region, combining the first two. A region like the Western Ghats scores high on all three: rich individual forests, sharp changes over short distances, and a very large overall total.

பூமியில் உயிர் சமமாக இல்லை. நிலநடுக்கோட்டு அருகே வெப்ப மண்டலத்தில் இனங்கள் அதிகம், துருவங்களை நோக்கிப் போகப் போகக் குறைகின்றன. காரணங்கள்: அங்கே நீண்ட காலமாகக் காலநிலை நிலையாக உள்ளது, ஆண்டு முழுதும் பெரிய மாற்றம் இல்லை, வெயில் அதிகம். இரண்டாவது: பரப்பு பெரிதானால் இனங்கள் அதிகம், ஆனால் இருமடங்கு பரப்புக்கு இருமடங்கு இனங்கள் வராது. அதனால் காட்டைத் துண்டாக்கினால் இனங்கள் இழக்கப்படும். (→ English: latitudinal gradient; species–area relationship · हिन्दी: अक्षांशीय प्रवणता; प्रजाति-क्षेत्र संबंध)

In exam EnglishLife is not spread evenly over the planet. The clearest pattern is the latitudinal gradient: for most groups of plants and animals, the number of species is highest in the tropics and falls steadily towards the poles. A few hectares of Amazon or South-East Asian rainforest can hold more tree species than the whole of a temperate country. Several reasons are offered. The tropics have had a long and relatively stable history, so species have had more time to evolve; their climate varies less through the year, which favours specialists; and they receive more solar energy, which supports higher productivity and so more life. A second pattern links diversity to area. The naturalist Alexander von Humboldt noticed that larger areas hold more species, but not in proportion: richness rises quickly at first and then more slowly. Plotted on logarithmic scales the relationship becomes a straight line, which is why breaking a habitat into small pieces is expected to lose species.

உலகின் 17 மிகுபல்லுயிர் நாடு பட்டியலில் இந்தியா ஒன்று. நம்மிடம் உலக நிலப்பரப்பில் சுமார் 2.4 சதவீதமே உள்ளது, ஆனால் பதிவான இனங்களில் 7 முதல் 8 சதவீதம். ஏனென்றால் நம் நாட்டில் தீவுகள், இமயமலை, ஈரமான வடகிழக்கு, பாலைவனம் எல்லாம் உள்ளன; மூன்று வெவ்வேறு உயிர்ப் பகுதிகளின் உயிர்கள் இங்கே சந்திக்கின்றன. மூன்று மாநில எல்லை ஊரில் மூன்று மொழிகளும் கேட்பது போல. (→ English: megadiverse country · हिन्दी: महाविविधता वाला देश)

In exam EnglishIndia is one of the world's 17 megadiverse country group, a list drawn up by Conservation International in 1998 of the countries that together hold most of the planet's species. Measured against its size, India is crowded with life: by the figures of the Ministry of Environment, Forest and Climate Change, its share of the planet's recorded species, some 7 to 8 per cent, is about three times its share of land, roughly 2.4 per cent. The reasons lie in its geography. India stretches from tropical islands to the high Himalaya and from the wet north-east to the Thar desert, so it contains almost every major type of ecosystem. It also sits where three great biological realms meet, the Indo-Malayan, the Palaearctic to the north and the Afro-tropical to the west, so its plants and animals have mixed origins. Long isolation of the Peninsula and of islands such as the Andaman and Nicobar group has added species found nowhere else. India is also a member of the Like-Minded Megadiverse Countries group formed in 2002 to coordinate positions in international talks on biodiversity.

பாதுகாப்புக்குப் பணம் குறைவு என்பதால் எங்கே காத்தால் அதிக இனங்கள் தப்பும் என்று கண்டறிந்தனர், அவையே பல்லுயிர் மையப்பகுதி. இரண்டு நிபந்தனைகள்: வேறெங்கும் இல்லாத 1,500 தாவர இனங்கள் அங்கே இருக்க வேண்டும், மூல இயற்கைத் தாவரத்தில் 70 சதவீதம் ஏற்கனவே அழிந்திருக்க வேண்டும். அதாவது மிக மதிப்பானது, மிக ஆபத்தில் உள்ளது. வீட்டில் தீப்பிடித்தால் முதலில் அரிய, ஆபத்தில் உள்ள பொருளைக் காப்பது போல. உலகில் 36 உள்ளன. (→ English: biodiversity hotspot · हिन्दी: जैव विविधता हॉटस्पॉट)

In exam EnglishSince money and effort for conservation are limited, scientists have tried to identify the places where protection would save the most species. The British ecologist Norman Myers proposed the idea of biodiversity hotspots in 1988, and Conservation International later adopted it with two fixed tests. A region qualifies only if it holds at least 1,500 species of vascular plants found nowhere else in the world, and only if it has already lost at least 70 per cent of its original natural vegetation. The first test measures how irreplaceable the region is; the second measures how threatened it is. Both must be met, so a region that is very rich but still largely intact, such as much of the Amazon, is not a hotspot. There are now 36 hotspots. Together they cover only about 2.5 per cent of the Earth's land surface, yet more than half of the world's plant species are endemic to them, which is why they are seen as the best value for conservation effort.

இந்தியாவில் நான்கு மையப்பகுதிகள்: இமயமலை; வடகிழக்கு மாநிலங்கள் உள்ள இந்தோ-பர்மா; இலங்கையுடன் சேர்ந்த மேற்குத் தொடர்ச்சி மலை; நிகோபார் தீவுகள் உள்ள சுந்தாலாந்து. கிழக்குத் தொடர்ச்சி மலை, தார் பாலைவனம், சுந்தரவனம் முக்கியமானவைதான், ஆனால் பல்லுயிர் மையப்பகுதி பட்டியலில் இல்லை, இங்கேதான் பலர் தவறுகிறார்கள். (→ English: biodiversity hotspot · हिन्दी: जैव विविधता हॉटस्पॉट)

In exam EnglishFour of the 36 hotspots reach into India, and the exam often asks which. The Himalaya hotspot covers the mountain arc from the north-west to the east, with steep changes in climate over short distances. The Indo-Burma hotspot takes in much of India's north-east and runs through Myanmar and South-East Asia; it is rich in orchids, bamboos, primates and freshwater fish. The Western Ghats and Sri Lanka hotspot is a single unit shared with the island across the Palk Strait; the Ghats run parallel to the west coast and stand out for their many endemic amphibians, reptiles and flowering plants. The Sundaland hotspot centres on Malaysia and western Indonesia, and India's share is the Nicobar Islands. A common error is to name the Eastern Ghats, the Thar or the Sundarbans as hotspots: they are important ecosystems but none of them is on the list.
India's four biodiversity hotspots
HotspotIndia's partShared with
HimalayaThe Himalayan arc, north-west to eastNepal, Bhutan and neighbours
Indo-BurmaMuch of the north-eastMyanmar and South-East Asia
Western Ghats and Sri LankaWestern Ghats along the west coastSri Lanka
SundalandNicobar IslandsMalaysia and western Indonesia

இந்தியாவைப் பத்து உயிர்ப் புவியியல் மண்டலம் களாகப் பிரித்தார்கள்: டிரான்ஸ்-இமயம், இமயம், பாலைவனம், அரை வறண்ட பகுதி, மேற்குத் தொடர்ச்சி மலை, தக்காண தீபகற்பம், கங்கைச் சமவெளி, வடகிழக்கு, கடற்கரைகள், தீவுகள். எல்லாவற்றிலும் பெரியது தக்காணம். ஏனென்றால் ஒவ்வொரு மண்டலத்திலும் கொஞ்சம் காக்கப்பட வேண்டும்; ஊராட்சியில் ஒவ்வொரு தெருவுக்கும் ஒரு பிரதிநிதி இருப்பது போல. (→ English: biogeographic zone · हिन्दी: जैव-भौगोलिक क्षेत्र)

In exam EnglishTo plan protected areas sensibly, India also needed a map of its own natural regions. The Wildlife Institute of India, in a classification prepared by W. A. Rodgers and H. S. Panwar, divided the country into ten biogeographic zones, each with a distinct mix of climate, landform, plants and animals, and subdivided them further into provinces. The ten are the Trans-Himalaya, the Himalaya, the Indian Desert, the Semi-Arid zone, the Western Ghats, the Deccan Peninsula, the Gangetic Plain, the North-East, the Coasts and the Islands. The Deccan Peninsula is by far the largest. The point of the scheme is representation: a good network of protected areas should include samples of every zone, not just the scenic mountains or famous tiger forests, so that grasslands, deserts and coasts are protected too. The zones also help explain the hotspots, since the Himalaya, the Western Ghats, the North-East and the Islands are the zones richest in species found only there.
India's ten biogeographic zones (Wildlife Institute of India)
ZoneWhere
Trans-HimalayaCold desert of Ladakh and Lahaul–Spiti
HimalayaThe main mountain ranges
Indian DesertThar and Kachchh
Semi-AridPunjab plains to Gujarat and the drier Deccan edge
Western GhatsHills along the west coast
Deccan PeninsulaThe central and southern plateau; the largest zone
Gangetic PlainPlains of the Ganga and its tributaries
North-EastBrahmaputra valley and north-eastern hills
CoastsThe west and east coastal belts
IslandsAndaman and Nicobar, Lakshadweep

ஒரே பகுதியில் மட்டும், வேறெங்கும் இல்லாத இனங்கள் அகணிய இனங்கள். தீவுகளும் தனித்த மலைகளும் இவற்றின் இருப்பிடம். மேற்குத் தொடர்ச்சி மலையில் நீலகிரி வரையாடு, சிங்கவால் குரங்கு, ஊதா தவளை; மணிப்பூரில் சங்காய் மான்; கிர் காட்டில் ஆசியச் சிங்கம். ஊரில் ஒரே வீட்டில் மட்டும் உள்ள பழைய சமையல் முறை போல: அந்த வீடு போனால் அந்த முறை உலகிலேயே போய்விடும். (→ English: endemic species · हिन्दी: स्थानिक प्रजाति)

In exam EnglishAn endemic species is one that occurs naturally in a single area and nowhere else; endemism is the share of a region's species that are endemic. Isolation breeds endemics, which is why islands, isolated mountain ranges and old, stable landscapes have many. India's main centres of endemism are the Western Ghats, the north-east, the Himalaya and the Andaman and Nicobar Islands. Examples that the exam likes include the Nilgiri tahr and the lion-tailed macaque of the Western Ghats, the purple frog that spends most of its life underground in the same hills, the Sangai or brow-antlered deer of Manipur's Keibul Lamjao, and the Narcondam hornbill confined to a single small island in the Andaman Sea. The Asiatic lion now survives in the wild only in the Gir landscape of Gujarat. Endemic species carry a special risk: if their small home is damaged there is no other population to fall back on, so a local loss becomes a global extinction.

முழுப் பகுதியும் ஒரு சங்கிலி: பல்லுயிர்ப் பெருக்கம் மூன்று நிலைகளில் உள்ளது, அதைக் கணக்கிடுகிறார்கள், வெப்பப் பகுதிகளிலும் பெரிய தனித்த பகுதிகளிலும் அதிகம். அதனால் இந்தியா வளமானது. மையப்பகுதிகள் மதிப்பானவை, ஆபத்தில் உள்ளவை; மண்டலங்கள் எல்லா வகை இயற்கையையும் காக்க உதவுகின்றன; அகணிய இனங்கள் சிறு இடம் போனால் இனமே போகும் என்று நினைவூட்டுகின்றன. அடுத்த பகுதி: ஏன் அழிகிறது, எப்படிக் காக்கிறோம். (→ English: biodiversity · हिन्दी: जैव विविधता)

In exam EnglishThe ideas in this part fit together as a chain. Biodiversity exists at three nested levels, genes, species and ecosystems, and each level gives life a different kind of insurance. It is measured by richness and evenness and compared within habitats, between them and across regions. It is concentrated in the tropics and in large, varied, isolated areas, which is why India, with its range of climates and its meeting of biological realms, ranks among the megadiverse countries. Hotspots single out regions that are both irreplaceable and badly damaged, and India shares four of them; the ten biogeographic zones make sure that conservation covers every kind of Indian landscape, and endemic species show why losing a small area can mean losing a species for ever. With this map of where life is, Part 2 asks why it is being lost and what is being done to save it.

Exam traps

Recap

Practice questions

Q1. The existence of many traditional varieties of rice in India is an example of

  1. species diversity
  2. genetic diversity
  3. ecosystem diversity
  4. gamma diversity
Show answer

Answer: B. genetic diversity

All rice varieties belong to one species, so their variety is genetic diversity. Species diversity needs different species, ecosystem diversity needs different habitats, and gamma diversity is the total diversity of a region, not variation within a crop.

Q2. The change in species composition as one moves from one habitat to another along an environmental gradient is called

  1. alpha diversity
  2. beta diversity
  3. gamma diversity
  4. species evenness
Show answer

Answer: B. beta diversity

Beta diversity measures turnover between habitats. Alpha is diversity within one habitat, gamma is the total for a region, and evenness describes how equally individuals are spread among species.

Q3. Consider the following statements:
1. A region must have lost at least 70 per cent of its original natural vegetation to qualify as a biodiversity hotspot.
2. Any region with very high species richness qualifies as a hotspot even if its habitat is largely intact.
Which of the statements given above is/are correct?

  1. 1 only
  2. 2 only
  3. Both 1 and 2
  4. Neither 1 nor 2
Show answer

Answer: A. 1 only

Statement 1 is one of the two required tests. Statement 2 is wrong because the threat test must also be met; a rich but intact region is not a hotspot. So '2 only', 'both' and 'neither' are wrong.

Q4. Which one of the following is NOT a biodiversity hotspot that includes any part of India?

  1. Indo-Burma
  2. Sundaland
  3. Eastern Ghats
  4. Himalaya
Show answer

Answer: C. Eastern Ghats

The Eastern Ghats are not a hotspot. Indo-Burma includes much of the north-east, Sundaland includes the Nicobar Islands, and the Himalaya hotspot covers the Indian Himalaya, so those three options all include India.

Q5. Consider the following statements:
1. India is one of the 17 megadiverse countries.
2. India has about 2.4 per cent of the world's land area.
3. India accounts for about a quarter of the world's recorded species.
Which of the statements given above is/are correct?

  1. 1 and 2 only
  2. 2 and 3 only
  3. 1 and 3 only
  4. 1, 2 and 3
Show answer

Answer: A. 1 and 2 only

Statements 1 and 2 are correct. Statement 3 is wrong: India's share is about 7 to 8 per cent, not a quarter. So every option containing statement 3 is wrong.

Q6. Which is the largest of India's ten biogeographic zones?

  1. Western Ghats
  2. Gangetic Plain
  3. Deccan Peninsula
  4. Himalaya
Show answer

Answer: C. Deccan Peninsula

The Deccan Peninsula covers the vast central and southern plateau and is the largest zone. The Western Ghats are a narrow hill belt, and the Gangetic Plain and the Himalaya, though large, are smaller than the Deccan.

Q7. Match the endemic species with their regions:
A. Sangai (brow-antlered deer) 1. Western Ghats
B. Lion-tailed macaque 2. Andaman Sea island
C. Narcondam hornbill 3. Gujarat
D. Asiatic lion 4. Manipur
Select the correct answer using the code given below:

  1. A-4, B-1, C-2, D-3
  2. A-1, B-4, C-2, D-3
  3. A-4, B-1, C-3, D-2
  4. A-2, B-1, C-4, D-3
Show answer

Answer: A. A-4, B-1, C-2, D-3

The Sangai lives in Manipur's Keibul Lamjao, the lion-tailed macaque in the Western Ghats, the Narcondam hornbill on Narcondam island and the wild Asiatic lion in Gir, Gujarat. The second code swaps the deer and the macaque, the third swaps the hornbill and the lion, and the fourth swaps the deer and the hornbill.

Q8. Which one of the following best explains why species richness is generally highest in the tropics?

  1. Tropical regions have the largest human populations
  2. A long, relatively stable history, less seasonal climate and more solar energy
  3. Tropical soils are always the most fertile in the world
  4. The tropics were repeatedly covered by ice sheets
Show answer

Answer: B. A long, relatively stable history, less seasonal climate and more solar energy

The usual explanations are a long stable history, a less seasonal climate and more solar energy. Human numbers do not create species richness, many tropical rainforest soils are in fact poor, and ice sheets covered high latitudes, not the tropics, which is one reason the tropics had longer undisturbed time.

All partsNext: Part 2 →

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