BIOLOGY 3 Marks Question

→ 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 situ conservation has advanced beyond keeping threatened species in enclosures.
→ Now gametes of threatened species can be preserved in viable and fertile condition for long periods using cryopreservation techniques
→ Eggs can be fertilized in vitro.
→ Plants can be propagated using tissue culture methods.
→ Seeds of different genetic strains of commercially important plants can be kept for long periods in seed banks.

→ When alien species are introduced unintentionally or deliberately for whatever purpose, some of them turn invasive, and cause decline or extinction of indigenous species.
→ The Nile perch introduced into Lake Victoria in east Africa eventually led to the extinction of an ecologically unique assemblage of more than 200 species of cichlid fish in the lake.
→ The environmental damage caused and threat posed to our native species by invasive weed species like carrot grass (Parthenium), Lantana and water hyacinth (Eicchornia).
→ The recent illegal introduction of the African catfish Clarias gariepinus for aquaculture purposes is posing a threat to the indigenous catfishes in our rivers.

→ The most important of them are:
(i) Genetic diversity :
→ A single species might show high diversity at the genetic level over its distributional range.
→ The genetic variation shown by the medicinal plant Rauwolfia vomitoria growing in different Himalayan ranges might be in terms of the potency and concentration of the active chemical (reserpine) that the plant produces.
→ India has more than 50,000 genetically different strains of rice, and 1,000 varieties of mango.
(ii) Species diversity :
→ The diversity at the species level, for example, the Western Ghats have a greater amphibian species diversity than the Eastern Ghats.
(iii) Ecological diversity :
→ At the ecosystem level, India, for instance, with its deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows has a greater ecosystem diversity than a Scandinavian country like Norway.

→ For many decades, ecologists believed that communities with more species, generally, tend to be more stable than those with less species.
→ A stable community should not show too much variation in productivity from year to year; it must be either resistant or resilient to occasional disturbances (natural or man-made), and it must also be resistant to invasions by alien species.
→ We don't know how these attributes are linked to species richness in a community, but David Tilman's long-term ecosystem experiments using outdoor plots provide some tentative answers.
→ Tilman found that plots with more species showed less year-to-year variation in total biomass.
→ He also showed that in his experiments, increased diversity contributed to higher productivity.
→ Rich biodiversity is not only essential for ecosystem health but imperative for the very survival of the human race on this planet.
→ Biodiversity contributes to many important ecological services.

→ The broadly utilitarian argument says that biodiversity plays a major role in many ecosystem services that nature provides.
→ The fast dwindling Amazon forest is estimated to produce, through photosynthesis, 20 per cent of the total oxygen in the earth's atmosphere.
→ Some idea by finding out how much your neighborhood hospital spends on a cylinder of oxygen.
→ Pollination (without which plants cannot give us fruits or seeds) is another service, ecosystems provide through pollinators layer - bees , bumblebees , birds and bats. 
→ There are other intangible benefits that we derive from nature-the aesthetic pleasures of walking through thick woods, watching spring flowers in full bloom or waking up to a bulbul's song in the morning.
→ We have a moral duty to care for their well- being and pass on our biological legacy in good order to future generations.

→ Colombia located near the equator has nearly 1,400 species of birds while New York at 41° N has 105 species and Greenland at 71° N only 56 species.
→ India, with much of its land area in the tropical latitudes, has more than 1,200 species of birds.
→ A forest in a tropical region like Equador has up to 10 times as many species of vascular plants as a forest of equal area in a temperate region like the Midwest of the USA.
→ The largely tropical Amazonian rain forest in South America has the greatest biodiversity on earth- it is home to more than 40,000 species of plants, 3,000 of fishes, 1,300 of birds, 427 of mammals, 427 of amphibians, 378 of reptiles and of more than 1,25,000 invertebrates.
→ Scientists estimate that in these rain forests there might be at least two million insect species waiting to be discovered and named.