题型：阅读理解 题类：模拟题 难易度：普通
上海宝山区2019届高三英语二模考试试卷
The koala is an unusual creature. Native to Australia and a bit bigger than a rabbit, it spends most of its time in eucalyptus trees（桉树）, feeding on leaves that are poisonous to nearly every other animal on the planet.
The koala sleeps about 22 hours a day and spends the remainder of its time eating and resting. It might spend 10 minutes a day moving, experts say, usually from one tree to another. It has a soft pad at the end of its spine and extra thick fur on its rear end to make the effort, of sitting more comfortable.
Threats and protective measures
The unique lifestyle of the koala has helped it prosper, but today the cute and iconic creature is facing threats from habitat loss, disease and a changing climate. Koala populations are expected to decline by 50 percent in the next 20 years according to the Australian Museum.
To help protect these animals, which bring in an estimated $1.1 billion to Australia each year through koala-related tourism, an international team of researchers has published the first complete genome（基因组）of the koala. Their hope is that the keys to the marsupial's（有袋动物）long-term survival might be planted in its genetic code.
"The ultimate goal is that we won't have to…rescue them from the edge of extinction," said Rebecca Johnson of the Australian Museum Research Institute in Sydney, who led the work.
"Now we have a really good understanding of the koala genome, and we are in a fantastic position to use that knowledge to help us manage them."
Early findings
An elementary analysis of the koala's genome, published in Nature Genetics, has already yielded some interesting findings.
For example, the authors found that, compared to other mammals, the koala's DNA includes an expansion in the number of genes that encode for enzymes involved in anti-poison. That allows them to have a diet that depends almost entirely on eucalyplus leaves which are unusually high in poison. However, it also means that koalas metabolize（代谢）medicines like anti-chlamydia antibiotics faster than other animals.
The koala genome also revealed why koalas are such famously picky eaters. They are known to consume leaves from just 20 of Australia's 60 known eucalyplus species. And even when they are in one of their preferred trees, koalas take leaf selection very seriously.
Information waiting to be discovered
Johnson said that the information encoded in the koala's DNA is already being included in management strategies by conservation groups. However, she said the findings described in the new paper represent the early stages of what can be gleamed from the marsupial's genome.
"The data is public, and I would love for anyone to start mining it and see what other amazing things they can find," she said." Once you have a genome of this quality, the sky's the limit with what you can do with it."
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