Class 9 BiologyChapter 12NCERT 12.1 and 12.2
India as a biodiversity hotspot
Snow peaks, deserts, rainforests and coral seas, all in one country.
Think it over
- A Nilgiri tahr lives on a few hilltops in South India and nowhere else on the planet. What would it take to lose it for ever?
- Two forests hold the same number of tree kinds, but one also has a river, a grassland and caves. Which would you call richer in life, and why?
- Why would a farmer plant five varieties of rice when one gives the biggest harvest?
In one minute
- Biodiversity is the whole variety of living organisms, from microbes to trees and whales.
- India packs mountains, desert, rainforest, plateau and two long coasts, each with its own soil and climate, so it holds a huge range of species.
- Endemic species occur naturally in one region only: the Nilgiri tahr, the lion-tailed macaque, Nepenthes khasiana and Neelakurinji are found only in India.
- A biodiversity hotspot has many endemic species and has already lost much of its habitat. India shares four: Western Ghats, Himalayas, Indo-Burma and Sundaland.
- Today's diversity built up over vast time, as small differences that helped survival and reproduction piled up across generations.
Why India is so rich in life
Count every kind of living thing on the planet, from a soil microbe to a banyan tree, and add up the habitats they fill: the total is biodiversity. None of it is spare. Take one breath and thank the ocean: much of that oxygen came from algae you could never see. A flower that sets fruit was probably visited by a bee, a bird or a bat, the soil it grows in was made by fungi and bacteria working through dead leaves, and almost every meal on the Earth starts as sunlight caught by a plant.
India is a good place to see it. Start on a coast, either the Arabian Sea side or the Bay of Bengal side, climb onto the old plateaus of the south, cross to the dry west, the rainforests of the North East or the snow line of the Himalayas: the soil, the temperature and the rainfall keep changing, and so does the cast of species living there.
A few of them have one home on the whole planet. A species that occurs in the wild in a single region and nowhere else is endemic to it. The Nilgiri tahr, the lion-tailed macaque, India's own pitcher plant Nepenthes khasiana and the Neelakurinji shrub are found naturally only in India.
Landscapes and hotspots
The Himalayas
The mountain arc across the north
- Red panda Lives in the cool forests of the eastern Himalayas. (not endemic, also found outside India) You may also meet
Indo-Burma
Includes North East India
- Nepenthes khasiana India's own pitcher plant, found in the hills of Meghalaya and nowhere else.
- Sangai, the dancing deer Endemic to Manipur, living on the floating grasslands of Loktak lake.
The Western Ghats
The hills along the west coast
- Nilgiri tahr A wild mountain goat of the high grassy slopes.
- Lion-tailed macaque A monkey with a silver mane, living in the rainforest canopy.
- Neelakurinji A shrub that turns whole hillsides blue when it flowers.
- Purple frog Spends most of the year underground in the Sahyadri hills.
Sundaland
Includes the Nicobar Islands
- Nicobar pigeon A shimmering green pigeon of the island forests. (not endemic, also found outside India) You may also meet
Put two facts together: a region with many endemic species that has already lost a large part of its natural habitat. That region is a biodiversity hotspot. Hotspots matter most for conservation, because what is lost there is lost everywhere. Four global hotspots reach into India: the Western Ghats, the Himalayas, Indo-Burma (which takes in North East India) and Sundaland (which takes in the Nicobar Islands).
Protecting a hotspot protects more than its rare animals. Its food webs stay whole, and the ecosystem keeps working.
- Biodiversity
- The full variety of living organisms on the Earth.
- Endemic species
- A species found naturally only in one particular region of the world.
- Biodiversity hotspot
- A region with a large number of endemic species that has suffered heavy habitat loss.
Quick check
The lion-tailed macaque lives naturally only in the Western Ghats. Such a species is called:
Show the answer
B. Endemic A species found naturally only in one region of the world is endemic to it.
How has biodiversity evolved?
The living world has not always looked the way it does now. No two individuals of a species are exactly alike. When conditions change, some of those small differences help their owners survive and have young, and so they turn up more often in the next generation.
Repeat that over many, many generations and the differences add up, until new forms of life appear. Step through a simple picture of the idea below.
Individuals of one kind differ a little: here, in shell colour. On pale sand, all of them get by.
- 1No two alike
Individuals of one kind differ a little: here, in shell colour. On pale sand, all of them get by.
- 2Conditions change
The ground turns dark. Now the small difference matters: pale beetles stand out and are spotted more often.
- 3Some do better
Individuals whose differences suit the new conditions survive more often and leave more young.
- 4Differences pile up
Over many generations the helpful differences build up. Given vast spans of time, such changes give rise to new forms of life.
So the diversity around us is the result of change over an enormous span of time, shaped by how organisms and their surroundings act on each other. To study such a vast variety in an orderly way, scientists need a framework. That framework is classification, and it is what the rest of this chapter builds.
Quick check
Which statement best describes how today's biodiversity came about?
Show the answer
B. Small differences that helped survival built up over many generations Differences that improved survival and reproduction were passed on and accumulated over a vast span of time, giving rise to new forms.