1 . Biologists who study evolution (进化) have always been interested in animals that developed on islands. In some situations, animals on islands changed over time and came to look very different from the same species that lived on the mainland.
The experts point to animals such as the dwarf elephant that once lived on the Mediterranean island of Cyprus. The animal is now extinct. When it lived, however, it was only the size of a small horse. Elephants that live today in Africa and Asia are much larger than that. In the West Indies, researchers found a giant rodent (啮齿动物) that looked like a rat. However, it was about the same size as an American black bear. Rats are, of course, many times smaller than bears.
Evolutionary experts came to call this phenomenon “island effect”. They used this term to describe the fact that animals who normally have small bodies “upsize” on an island, while the opposite is true for animals who usually have large bodies.
The “island effect” produces strange-sized animals because large animals require more food than small animals. On an island, there is a limited amount of food. As a result, larger animals become smaller over generations in order to survive with lower food intake. For small animals, there is not as much risk from predators on an island, so they often grow larger.
Recently, researchers released their findings about 1,231 existing animals and 350 extinct ones that represent 23 million years of life. They found that animals on islands were more at risk of extinction compared to their relatives on the mainland. The arrival of human settlers increased the extinction risk for these strange animals.
Roberto Rozzi, a paleoecologist at Martin Luther University Halle-Wittenberg in Germany said that the extinction line has become even sharper in recent decades.
The researchers call the islands “biodiversity hotspots”. Even though they only make up 7 percent of the Earth’s land mass, they account for 20 percent of the land species.
1. Why are the animals introduced in paragraph 2?| A．To compare the two species. | B．To lead in the “island effect”. |
| C．To show two kinds of rare animals. | D．To stress the change of surroundings. |
| A．Animals of normal small bodies “upsize” on an island. |
| B．Animals of normal small bodies “downsize” on an island. |
| C．Animals of normal large size have small bodies on an island. |
| D．Animals of normal large size have larger bodies on an island. |
| A．Some things never change. | B．The gain outweighs the loss. |
| C．Humans live in harmony with nature. | D．The fittest animals survive in natural selection. |
| A．The History of Unique Island Animals | B．The Benefits of Saving Island Animals |
| C．Unique Island Animals at Greater Changes | D．Biological Diversity Threatened by Humans |
2 . Hundreds of native North American plants, often dismissed as weeds, deserve a lot more respect, according to a new study. These plants, distant cousins of foods like sunflowers and lettuce (莴苣), actually represent a botanical treasure now facing increased threats from climate change and habitat loss. The crops that the human race now depends on, including grains like wheat and tree fruit like peaches, originally were selected or bred (培育) from plants that grew wild hundreds or thousands of years ago. In the U.S., there are wild ancestors of blueberries, sweet potatoes, onions, potatoes, and many other food crops. “Some of them are quite common,” says Colin Khoury, a research scientist at the International Center for Tropical Agriculture. “Wild lettuce plants grow along sidewalks, or in backyards, but go unrecognized.”
Other crop relatives are rare and threatened. One of Khoury’s favorites is the paradoxical sun flower.” It grows just in wetlands of the deserts of New Mexico and Texas. Little salty areas where there’s a little bit of water beneath the soil,” he says. So plant growers crossbred it with commercial sunflowers and created new varieties that can grow in places where the soil contains more salt. Other wild relatives may be hiding similarly remarkable gifts, Khoury says, such as genes that could help their domesticated relatives survive diseases, or deal with pests.
Khoury and some of his colleagues just finished a survey of about 600 wild crop relatives that grow in North America, and they found that most of these plants are threatened by things like fires, farming and development. The scientists argue that they deserve more protection. For one thing, “gene banks” should collect and preserve them. In addition, these plants need more protection in their natural habitat.
According to Khoury, that doesn’t necessarily mean setting aside land for them. In many cases, the plants already are growing on public land that’s managed by the U.S. Forest Service (USFS) or the Bureau of Land Management (BLM). “It’s more about just being aware that these plants actually exist,” he says.
1. What did the new study mainly focus on?| A．Endangered plant species. |
| B．Wild relatives of food crops. |
| C．The impacts of climate change. |
| D．The threats from plant habitat loss. |
| A．It needs much water to grow well. |
| B．It grows along sidewalks or in backyards. |
| C．It seems capable of surviving various diseases. |
| D．It helps commercial sunflowers adapt to salty soil. |
| A．Relieved. | B．Concerned. | C．Annoyed. | D．Critical. |
| A．Join hands with the USFS. |
| B．Set aside land for wild plants. |
| C．Collect genes of threatened crop species. |
| D．Learn about plants on its managed land. |
3 . When Joseph Cook first landed on the Greenland ice sheet in 2010, he was expecting to see a primitive white environment. What he found was "colorful mix"-from blacks and grays to greens, purples and browns, with blue streams cutting through the ice. the rainbow colors Cook encountered are created by a collection of tiny life forms that reproduce on the surface of the ice sheet. Biodiversity is usually considered a good thing, but in this case the abundance of tiny life is speeding up ice melt, and likely causing global sea levels to rise faster than scientists have predicted
Cook says the tiny life forms he studies are contributing to the problem. One of these organisms is an algae(海藻) that grows in the thin layer of water on the surface of the ice. it produces purple-brown- pigment(色素) which acts “like a natural sunscreen, "says Cook, protecting the algae from the full force of the Arctic sunlight. The pigment also causes the ice to heat up and melt.
“If you go out on a hot day wearing a black T-shirt, you get warmer than if you go out on a hot day wearing a white T-shirt. The same thing happens on the ice," says Cook. "These algae, like the black T-shirt for the glacier, are causing it to warm up in the sun and melt faster.”
Cook’s research on a part of the Greenland ice sheet covering 3, 900 square miles revealed that algae is responsible for up to 13% of the ice melt. In some localized areas, the algae boosted melting by up to 26%.
Glacier algae are not a new phenomenon-there are records of them in the diaries of polar explorers from the 1870s, says Cook. What's becoming clear is that ice sheets are surprisingly dynamic and complex environments. "There are so many questions to answer, "says Cook. "It's kind of like a theme park for a scientist because there's just so much to do.
1. What is quickening the ice melt?| A．The algae. | B．Human activities. |
| C．Global warming. | D．Blue melt streams. |
| A．To clarify a rule. | B．To explain the phenomenon. |
| C．To add humour. | D．To make a conclusion. |
| A．Scientists will avoid exploring polar regions. |
| B．Cook feels proud of the current results. |
| C．A theme park will be built on ice sheets. |
| D．There's a long way for research into ice sheets. |
| A．A news review. | B．A travel brochure. |
| C．A geography textbook. | D．A science magazine |
