Пробне НМТ (варіант 1)

Read the texts below. Match choices () to (1-5). There are three choices you do not need to use.

ANCIENT DNA REWRITES THE HISTORY OF THE WOOLLY MAMMOTH.

Fifteen thousand years ago, woolly mammoths and North American horses roamed the cold grasslands. They're extinct now, but we know quite a bit about them because of the fossils they left behind in places like Old Crow, the Klondike, and parts of Alaska.

However, we don't know when they disappeared or why. The conditions that preserve bits of dead animals as fossils are rare, and the chances of finding the fossil remains of the last woolly mammoth or the last North American horse are so small that they make winning the lottery look like a sure thing.

But animals leave more than bones behind. Animals shed bits of their genetic material as they move through a landscape. It comes from their urine, dropped hairs, and even sloughed-off skin cells. Modern instruments and lab techniques can detect that genetic material.

If the circumstances are right, the genetic material - the DNA - can be preserved for thousands of years. University of Alberta researcher Duane Froese and an international team are analysing sediment cores from several places in the Yukon and Alaska in search of the last of the big ice age mammals, the megafauna.

The first of the evidence is in, and it's startling. Sediment cores from a site near Stevens Village, on the Yukon River in Alaska, show that woolly mammoths and North American horses survived in that area until at least 10,500 years ago, and maybe even later.

Froese says the Blitzkrieg hypothesis argues that when humans arrived in the Americas, they hunted the large mammals to extinction very quickly. However, the DNA evidence shows that humans coexisted with the ice-age animals for thousand of years.

"Interestingly, even though the DNA is fragmented and quite short, we could establish that there were two different mammoths that contributed DNA to the sample, and that they both belonged to a particular herd that were related to the last surviving populations recovered in Siberia on Wrangell Island."

The DNA itself can't be dated, but its age can be determined by dating the sediment layer in which it occurs. In the parts of Alaska and the Yukon where the glaciers didn't reach, tens of thousands of years od sediment layers have accumulated beneath the current ground surface. Froese and his colleagues have been sampling and dating those sediment layers for many years, but the idea of searching them for DNA first came up in 2003.

The researchers have spent two summers sampling and dating the Klondike sediments. The abundant plant material trapped in the sediments makes it possible to date them accurately. It also provides information about the environment of the past.

To state the reasons of North American horses extinction is difficult because _________.

ANCIENT DNA REWRITES THE HISTORY OF THE WOOLLY MAMMOTH.

Fifteen thousand years ago, woolly mammoths and North American horses roamed the cold grasslands. They're extinct now, but we know quite a bit about them because of the fossils they left behind in places like Old Crow, the Klondike, and parts of Alaska.

However, we don't know when they disappeared or why. The conditions that preserve bits of dead animals as fossils are rare, and the chances of finding the fossil remains of the last woolly mammoth or the last North American horse are so small that they make winning the lottery look like a sure thing.

But animals leave more than bones behind. Animals shed bits of their genetic material as they move through a landscape. It comes from their urine, dropped hairs, and even sloughed-off skin cells. Modern instruments and lab techniques can detect that genetic material.

If the circumstances are right, the genetic material - the DNA - can be preserved for thousands of years. University of Alberta researcher Duane Froese and an international team are analysing sediment cores from several places in the Yukon and Alaska in search of the last of the big ice age mammals, the megafauna.

The first of the evidence is in, and it's startling. Sediment cores from a site near Stevens Village, on the Yukon River in Alaska, show that woolly mammoths and North American horses survived in that area until at least 10,500 years ago, and maybe even later.

Froese says the Blitzkrieg hypothesis argues that when humans arrived in the Americas, they hunted the large mammals to extinction very quickly. However, the DNA evidence shows that humans coexisted with the ice-age animals for thousand of years.

"Interestingly, even though the DNA is fragmented and quite short, we could establish that there were two different mammoths that contributed DNA to the sample, and that they both belonged to a particular herd that were related to the last surviving populations recovered in Siberia on Wrangell Island."

The DNA itself can't be dated, but its age can be determined by dating the sediment layer in which it occurs. In the parts of Alaska and the Yukon where the glaciers didn't reach, tens of thousands of years od sediment layers have accumulated beneath the current ground surface. Froese and his colleagues have been sampling and dating those sediment layers for many years, but the idea of searching them for DNA first came up in 2003.

The researchers have spent two summers sampling and dating the Klondike sediments. The abundant plant material trapped in the sediments makes it possible to date them accurately. It also provides information about the environment of the past.

Scientists can use _______ as the genetic material for experiments.