Biodiversity and Conservation: common doubts, answered
The questions students ask most often about Biodiversity and Conservation, each with a short answer. For the full chapter, read the Biodiversity and Conservation notes.
What biodiversity is
Read this section in the notes →What are the three levels of biodiversity?
They are genetic, species and ecological diversity. Genetic diversity is variation within a species, as in the many rice and mango varieties of India. Species diversity is the variety of species in a region, and ecological diversity is the variety of ecosystems. The Western Ghats has more amphibian species than the Eastern Ghats, an example of species diversity.
What is the example of genetic diversity in Rauwolfia vomitoria?
Rauwolfia vomitoria, the medicinal plant that gives the drug reserpine, shows variation in the potency and concentration of the chemical in plants growing in different Himalayan regions. This is genetic diversity within one species. India also has more than 50,000 genetically different strains of rice and about 1,000 varieties of mango.
How many species on Earth
Read this section in the notes →How many species have been described and estimated to exist?
More than 1.5 million species have been recorded and described. Robert May's global estimate is about 7 million, while some extreme estimates reach 20 to 50 million. Among those recorded, animals are more than 70 per cent, of which insects are the majority, and plants are no more than 22 per cent.
Do plants or animals make up most known species?
Animals do. More than 70 per cent of the recorded species are animals and plants make up no more than 22 per cent. Among animals, insects form the largest group, since more than 70 per cent of the animal species are insects. The number of fungus species is greater than that of fishes, amphibians, reptiles and mammals together.
Biodiversity of India
Read this section in the notes →What makes India a mega diversity country?
India has only 2.4 per cent of the world's land area but about 8.1 per cent of the world's species, making it one of the 12 mega diversity countries. It has about 45,000 plant species and roughly twice as many animal species. A common slip is to say India has 8.1 per cent of the world's land.
Latitudinal gradients
Read this section in the notes →Why does species diversity decrease from the equator towards the poles?
Three reasons are usually given. The tropics have stayed largely undisturbed by glaciations for millions of years, giving species a long time to form and diversify. Their climate is less seasonal, more constant and predictable, which favours niche specialisation. And they receive more solar energy, which raises productivity and can indirectly support more species. Temperate and polar regions lack these advantages.
How does the number of bird species vary with latitude?
Colombia, near the equator, has nearly 1,400 bird species, whereas New York at 41° N has 105 and Greenland at 71° N only 56. India has more than 1,200. The numbers fall steadily as you go from the tropics toward the poles, which illustrates the latitudinal gradient.
Species-area relationship
Read this section in the notes →What is the species-area relationship?
Alexander von Humboldt found that species richness increases with the area explored, but only up to a limit. The plot is a rectangular hyperbola, and on logarithmic scales it is a straight line given by log S = log C + Z log A. Here S is species richness, A is area, and Z is the slope of the line.
What are the typical values of Z in the species-area relationship?
Z is between 0.1 and 0.2 irrespective of the taxonomic group or region. The slope is much steeper, from 0.6 to 1.2, when analysing very large areas such as whole continents. For frugivorous birds and mammals in tropical forests it is 1.15. So the small-region value is not the steep one.
Diversity and ecosystem stability
Read this section in the notes →What did David Tilman's experiments show?
Tilman studied many experimental plots and found that those holding more species varied less in total biomass from one year to the next. The more diverse plots were also more productive. His work supports the view that a species-rich community is steadier and yields more, which is one argument for protecting biodiversity.
What is the rivet popper hypothesis?
Proposed by Paul Ehrlich, it compares an ecosystem to an aeroplane and its species to the rivets joining the parts. Losing a few rivets may not be dangerous, but losing a key rivet, such as one on the wings, could cause a crash. Similarly, some key species have a greater role in the ecosystem than others.
Loss of biodiversity
Read this section in the notes →What is the Sixth Extinction?
The Sixth Extinction is the current episode of species loss, which differs from the five earlier mass extinctions because it is caused by human activity and is much faster. The rate is estimated to be 100 to 1,000 times faster than the pre-human rates. If it continues, a large part of the world's species could be lost.
The evil quartet
Read this section in the notes →What is the evil quartet?
The evil quartet is the name for the four major causes of biodiversity loss: habitat loss and fragmentation, over-exploitation, alien species invasions and co-extinctions. Habitat loss is the most important of these, as seen in the clearing of tropical rain forests. Over-exploitation by humans drove animals such as Steller's sea cow and the passenger pigeon to extinction within the last 500 years.
What is the Nile perch example of alien species invasion?
The Nile perch was introduced into Lake Victoria in East Africa and eventually led to the extinction of more than 200 species of cichlid fish in the lake. It shows how an alien species can drive native species to extinction. In India, invasive weeds such as carrot grass (Parthenium), Lantana and water hyacinth harm the environment, and the African catfish Clarias gariepinus, brought in illegally for aquaculture, endangers the country's own catfish species.
What is co-extinction?
Co-extinction is when the extinction of one species causes the extinction of another species that depends on it. If a host fish species becomes extinct, its unique parasites also die out. Another example is the coevolved plant-pollinator mutualism, where the loss of one partner leads to the loss of the other.
Why conserve biodiversity
Read this section in the notes →Why should biodiversity be conserved?
NCERT groups the reasons as narrowly utilitarian, broadly utilitarian and ethical. Narrowly utilitarian reasons are direct benefits like food, firewood and medicines. Broadly utilitarian reasons are indirect, for example oxygen from photosynthesis and pollination. Ethical reasons say that every species has an intrinsic value and we have a moral duty to care for it.
In situ conservation
Read this section in the notes →What is a biodiversity hotspot and how many are there in India?
A hotspot is a region with very high species richness, many endemic species and high habitat loss. There are 34 hotspots in the world, and three of them cover India: the Western Ghats and Sri Lanka, Indo-Burma, and the Himalaya. The Eastern Ghats is not a hotspot.
What is the difference between in situ and ex situ conservation?
In situ conservation protects species in their natural habitat, through protected areas such as national parks, sanctuaries, biosphere reserves and sacred groves. Ex situ conservation protects them outside their habitat, in zoos, botanical gardens, seed banks, and by cryopreservation. A sacred grove is in situ, since the forest stays where it is.
How many national parks, sanctuaries and biosphere reserves does India have?
India has 14 biosphere reserves, 90 national parks and 448 wildlife sanctuaries, according to the NCERT text. Biosphere reserves, national parks and sanctuaries are all protected areas used for in situ conservation. The numbers are asked often as data questions, so the correct pairing matters.
Ex situ conservation
Read this section in the notes →What are the methods of ex situ conservation?
Methods include zoological parks, botanical gardens and wildlife safari parks, where threatened animals and plants are maintained. Gametes can be preserved by cryopreservation at low temperature, eggs can be fertilised in vitro, and plants can be propagated by tissue culture. Seeds of different genetic strains can be kept in seed banks.
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