E
A recent study of ancient and modern elephants has come up with the unexpected conclusion that the African elephant is divided into two distinct (不同的) species.
The discovery was made by researchers at York and Harvard Universities when they were examining the genetic relationship between the ancient woolly mammoth and mastodon to modern elephants—the Asian elephant, African forest elephant,and African savanna elephant.
Once they obtained DNA sequences (序列) from two fossils (化石), mammoths and mastodons, the team compared them with DNA from modern elephants.They found to their amazement that modern forest and savanna elephants are as distinct from each other as Asian elephants and mammoths.
The scientists used detailed genetic analysis to prove that the African savanna elephant and the African forest elephant have been distinct species for several million years.The divergence of the two species took place around the time of the divergence of Asian elephants and woolly mammoths.This result amazed all the scientists.
There has long been debate in the scientific community that the two might be separate species, but this is the most convincing scientific evidence so far that they are indeed different species.
Previously, many naturalists believed that African savanna elephants and African forest elephants were two populations of the same species, despite the elephants' significant size differences.The savanna elephant has an average shoulder height of 3.5 metres while the forest elephant has an average shoulder height of 2.5 metres.The savanna elephant weighs between six and seven tons, roughly double the weight of the forest elephant.But the fact that they look so different does not necessarily mean they are different species.However the proof lay in the analysis of the DNA.
【2017届广东省广州市天河区重点学校高考英语一轮复习检测:8(含答案)】相关文章:
★ 2014届高考英语一轮复习课时作业(九)必修2Module 3《Music》(外研版)
★ 山西省永济市涑北中学高三英语总复习:美文欣赏(2)(What Will Matter in Life)
★ 【优化方案】2017届高考英语二轮复习全国卷Ⅱ题型重组训练:第9组(含解析)
★ 湖南省岳阳市2014高考英语一轮单项选择训练题(6)及答案
★ 2017高考四川省广安市英语阅读理解一轮系列训练:20(含解析)
★ 2017届高考英语二轮复习大题冲关秘籍完形填空之记叙文:体验真题(含解析)
★ 2014届高考英语一轮复习课时作业(四)必修1Module 4《A Social Survey—My Neighbourhood》(外研版)
★ 2014届高考英语一轮复习课时作业(十五)必修3Module 3《The Violence of Nature》(外研版)
★ 2017届高考英语二轮复习大题冲关秘籍完形填空之夹叙夹议文:考纲分析(含解析)
最新
2017-04-24
2017-04-24
2017-04-24
2017-04-24
2017-04-21
2017-04-21