Cryptic (隐蔽的，隐藏的) species—animals that appear identical but are genetically quite distant—may be much more widespread than previously thought. The findings could have major implications in areas ranging from biodiversity (生物多样性) estimates and wildlife management, to our understanding of infectious diseases and evolution.
Reports of cryptic species have increased dramatically over the past two decades with the advent of relatively inexpensive DNA (脱氧核糖核酸) sequencing technology. Markus Pfenninger and Klaus Schwenk, of the Goethe-Universitat in Frankfurt, Germany, analyzed all known data on cryptic animal species and discovered that they are found in equal proportions throughout all major branches of the animal kingdom and occur in equal numbers in all biogeographical (生物地理学的) regions.
Scientists had previously speculated that cryptic species were
A. The WCU are interbreeding those elephants.
B. They are interbreeding species.
C. They are two genetically distant species.
D. They depend on each other for survival.
Cryptic (隐蔽的，隐藏的) species—animals that appear identical but are genetically quite distant—may be much more widespread than previously thought. The findings could have major implications in areas ranging from biodiversity (生物多样性) estimates and wildlife management, to our understanding of infectious diseases and evolution.
Reports of cryptic species have increased dramatically over the past two decades with the advent of relatively inexpensive DNA (脱氧核糖核酸) sequencing technology. Markus Pfenninger and Klaus Schwenk, of the Goethe-Universitat in Frankfurt, Germany, analyzed all known data on cryptic animal species and discovered that they are found in equal proportions throughout all major branches of the animal kingdom and occur in equal numbers in all biogeographical (生物地理学的) regions.
Scientists had previously speculated that cryptic species were
A. The results of the research can help the development of many other research areas.
B. The results of the research can help the development of biodiversity estimates.
C. The results of the research can help our understanding of infectious disease evolution.
D. The results of the research can help our understanding of "survival of the fittest".
The term "Ice Age" may give a wrong impression. (46) The epoch that spanned the 1.5 to 2.0 million years prior to the current geologic epoch was not one long continuous process, but a period of fluctuating climate with ice advances interrupted by times of climate not very different from the climate experienced now. Ice sheets that derived from an ice cap centered on northern Scandinavia reached southward to Central Europe. And beyond the margins of the ice sheets, climatic oscillations affected most of the rest of the world; for example, in the deserts, periods of wetter conditions (pluvials) contrasted with drier, interpluvial periods. (47) Although the time involved is so short, about 0.04 percent of the total age of the Earth, the amount of attention devoted has been incredibly large, probably because of its immediacy, and because the epoch largely coincides with the appearance on Earth of humans and their immediate ancestors.
There is no reliab
"Motherhood may make women smarter and may help prevent dementia(痴呆) in old age by bathing the brain in protective hormones," US researchers reported on Thursday.
Tests on rats show that those who raise two or more litters of pups do considerably better in tests of memory and skills than rats who have no babies, and their brains show changes that suggest they may be protected against diseases such as Alzheimer’s dementia (早老痴呆症). University of Richmond psychology professor Craig Kinsley believes his findings will translate into humans.
"Our research shows that the hormones of pregnancy (怀孕) are protecting the brain, including estrogen (雌激素), which we know has many neuroprotective (保护神经的) effects," Kinsley said.
"It’s rat data but humans are mammals just like these animals are mammals," he added in a telephone interview. "They go through pregnancy and hormonal changes."
Kinsley said he hoped public
A. Some researchers have told them.
B. Many women say so.
C. They know it by experimenting on rats.
D. They know it through their own experience.
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