Scientists warn that human activity may threaten the survival of some species考生如果怕自己錯過考試報名時間和考試時間的話，可以 免費預約短信提醒，屆時會以短信的方式提醒大家報名和考試時間。

Background: 科學家們研究出一項新的方式來估計在地球上生物的總數，據統計一共有8百70萬種不同類型的生物。這同過去使用的評估方式得到的結果差距很大?？茖W家們的發現將在網絡科研期刊《生物科學公共圖書館》上發表。

It's generally accepted that very many species have yet to be discovered, but until now nobody has devised a reliable way to find out just how many. Suggestions for total numbers have ranged from 3 million to a hundred million, but most of these have been no more than intelligent guesses.

Scientists from the Census of Marine Life devised a counting method by identifying numerical patterns linking data on known species. They reckon that there should be about 8.7 million types of living organisms, three-quarters of them animals and the rest plants.

However, since the introduction of the current classification system by Carl Linnaeus in 1758, only a million and a quarter have been catalogued.

The scientists warn that human activity is hastening extinctions, and they note a touch wistfully, that many of the hitherto unknown species may vanish before we even know of their existence.

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