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Color use in nature
Nature is very colorful, full of different hues（色调）that delight the eye. What makes these colors and why do they exist?
Causes of Colors in Nature
Colors in nature are formed in two ways. Pigments, like the melanin in skin and many animal furs, produce most blacks, browns, reds and yellows. Most plants are green due to chlorophyll（叶绿素）. Other colors are caused by structure, like many greens, blues, and whites. Blue bird’s feathers actually contain black pigment, but their structure causes them to appear blue. The scattering of light by tiny dust particles in the air, viewed against the black background of space, makes the sky look blue too.
Color Use in Plants
Color has a great effect on the survival of plants and animals. Flowers have bright hues and patterns to attract insects. These insects move from one flower to another, making sure seeds are produced. Bees can see colors we cannot, i.e. ultraviolet, and follow these patterns of stripes or dots to the inside of the flower.  
Not only flowers but also fruits use color for the good of the plant. An unripe fruit mixes in with the leaves, but ripe berries contrast, becoming more appealing to the creatures who eat them. Birds are especially drawn to red fruit, and in turn help the plant by broadcasting its seeds.
Camouflage（伪装）in Nature
Many colors and patterns camouflage animals who want to avoid enemies. Some animals have damaging shapes to break up their outline, so an enemy will not recognize them. The eye, a very recognizable animal characteristic, is often disguised by a black stripe or patch. Light color below makes up for the shadow on the underside of many fish, amphibians and mammals.
Some animals even change colors to better camouflage themselves, seasonally like the snowshoe hare.
Warning Coloration and Mimicry（动态伪装）
Warning colors make an animal more visible rather than hidden. These usually indicate a negative aspect of the animal, like the bad taste of a monarch butterfly, smelly smell or painful bite of a bee. Usually black and a contrasting color (white, yellow, orange or red) form a striking pattern in these creatures, and frighten their enemies away. Nature is tricky, though, and sometimes harmless creatures pretend the patterns of harmful ones to scare off animals living on meat too.  
Social Coloration in Nature
Sometimes coloration is important socially. Male birds, typically more colorful, defend their territories and attract females. Eggs may use color and pattern to remain hidden. When they hatch, parents feed the nestlings when they see the bright pattern in their gaping mouths.
Taking a closer look at nature throws light on how color is used in marvelous ways!

Even if we have an extremely healthy diet and lifestyle, the human body is programmed to wear out at a maximum of about 120 years, and usually less. We all have a biological clock inside us which determines the moment when our organs cease to function properly. This is because our cells have stopped renewing themselves and our body can no longer repair itself. This is also the moment when we are more likely to begin to suffer from the diseases of old age such as arthritis and Alzheimer’s. However, rapid advances in DNA research are beginning to throw light on the secrets of the ageing process. By the end of this century we could literally have the power of life over death.

Although it has long been accepted that humans have a fixed lifespan, it is also a fact that certain other organisms, such as reptiles and amphibians, appear to live indefinitely. The only reason we do not see 500-year-old alligators is because in the wild their lives are always in danger, from man, from pollution and from other animals. When they are kept in zoos they do not seem to age at all after they are fully grown. The same is true of some species of fish, which grow indefinitely and show no signs of ageing. The existence of animals with no fixed lifespan seems to indicate that an age gene really does exist. It is this gene which scientists are searching for, which may delay or repair damage to the body caused by ageing.

Another new area of research involves the oxidation（氧化） theory, which says that ageing is caused by the same process that makes iron rust. In controlled experiments, the lifespans of certain animals were shown to be lengthened with anti-oxidants; for example, the lifespan of mice can be increased by 30%. Antioxidants are already being used in face creams and other cosmetics, and they are likely to play an important part in keeping people physically young.

Perhaps the most immediate advance we are likely to see in the battle to halt（停止）the ageing process will be organ replacement. By the year 2020 it is likely that we will be replacing injured bones or even organs like livers and kidneys with ones “grown” in laboratories. By 2050 perhaps every organ in the body, except the brain, will have become commercially available. Recent experiments also show that it may one day be possible to “grow” new organs inside our body to replace worn-out ones, something which lizards and alligators already do.

Suddenly immortality（不死，不朽） seems within reach. We can begin to imagine a future where we are born, we grow to maturity, but we never grow old and die. But do we really want to live forever?

1. When all humans reach a certain age,         .

A．they suffer the effects of their diet and lifestyle

B．the organs stop to perform appropriately

C．their cells continue to renew themselves

D．they develop arthritis and Alzheimer’s

2. The purpose of showing the case of alligators is to prove         .

A．alligators are in danger in the wild because of the threat from man, pollution and other animals

B．it is widely accepted that humans have a fixed lifespan

C．there exists an age gene which may control ageing

D．the age gene damages the body

3.The underlined phrase “live indefinitely” in Paragraph 2 probably mean         .

A．live for a period of time without a fixed end

B．live without a clear aim

C．live in an uncertain way

D．live without being fully grown

4.It can be inferred from Paragraph 4 that         .

A．by 2050 we might have most of our worn-out organs replaced with new ones commercially

B．never can the ageing process be avoided

C．livers and kidneys are sure to be grown in laboratories by the year 2020

D．lizards and alligators grow new organs inside their body to replace worn-out ones

5. What is the main topic of this passage?

A．DNA researches show how our cells renew themselves.

B．Anti-oxidants are likely to play an important part in keeping people young.

C．How our biological clock works?

D．Eternal（永恒的） youth: new developments in anti-ageing research.

6.By saying “But do we really want to live forever”, the author may probably mean         .

A．a future where we are born, we grow to maturity, but we never grow old and die is on its way

B．he is uncertain whether we can live forever

C．it remains to be seen whether immortality is a blessing or a curse

D．immortality is no longer a dream

Scientists discovered 163 new species in Southeast Asia’s Greater Mekong region last year，but all are at risk of extinction due to climate change，the WWF said in a report released Friday.

The newly discovered creatures include a bird?eating frog with fangs (毒牙)，a bird that would rather walk than fly and a gecko (壁虎) whose alien appearance inspired the report’s title of “Close Encounters”，the conservation group said.

The report was released ahead of major UN talks on climate change in Bangkok next week，which are being held before a make?or?break summit in Copenhagen this December.

“Some species will be able to adapt to climate change，and many will not，potentially resulting in massive extinction，” Stuart Chapman，director of the WWF Greater Mekong program，said in the report.“Rare and endangered species like those newly discovered are especially vulnerable (易受伤害的) because climate change will further shrink their already restricted habitats，” he said.

“The new discoveries in 2010 include 100 plants,28 fish,18 reptiles,14 amphibians,2 mammals and a bird，”the WWF report said.The area spans Cambodia，Laos，Myanmar，Thailand，Vietnam and China’s Yunnan Province.

“Among the new species is the bird?eating fanged frog，which remains hidden in a protected area of Thailand despite the fact that scientists are studying there for 40 years，” the report said.

The tiger?striped pit viper was discovered accidentally on an island off the coast of Vietnam when a scientist was looking? for a lizard and his son pointed out that his hand was on a rock right next to? the snake’s fangs.“We caught the snake and the gecko and they both proved to be new species，” researcher Lee Grismer of La Sierra University in California was quoted as saying in the report.The leopard gecko，found on another Vietnamese island，has the coloring of a leopard and bizarre orange，cat?like eyes and thin legs.

The Greater Mekong region has proved a rich area? for scientists.The WWF said in December 2010 that it had found 1,068 new species there between 1997 and 2009.

1. What is special about the newly discovered bird?

A．It usually walks.

B．It likes walking and flying.

C．It can eat other birds.

D．It can eat frogs.

2. Stuart Chapman believes that________.

A．most of the newly discovered species can adapt to climate change

B．climate change can cause massive extinction of the newly discovered species

C．the newly discovered species are not so vulnerable to climate change

D．many species have already died out because of climate change

3. When Lee Grismer discovered the tiger?striped pit viper，he probably felt________.

A．frightened? B．disappointed

C．excited? D．puzzled

4.What does the passage mainly tell us?

A．The Greater Mekong region is a rich area for scientists.

B．Many rare species remain to be discovered in the Mekong region.

C．Scientists have discovered many new species in the Mekong region.

D．Climate change threatens Mekong new species.

A breathtaking trick potentially left over from our ancestors might be found in us — the ability to sense oxygen through our skin.
Amphibians, animals such as frogs that can live both on land and in water, have long been known to be capable of breathing through their skin. In fact, the first known lungless frog that breathes only through its skin was discovered recently in the rivers of Borneo.
Now the same oxygen sensors found in frog skins and in the lungs of mammals (哺乳动物) have unexpectedly been discovered in the skin of mice.
“No one had ever looked,” explained Randall Johnson, a biologist researcher.
Mice and frogs are quite distant relatives, so the fact they have these molecules (分子) in common in their skin suggests they might well be found in the skin of other mammals, such as humans.
“We have no reason to think that they are not in the skin of people too,” Johnson said.
These molecules not only detect oxygen, but help increase levels of vital red blood cells, which carry oxygen around the body. Normal mice breathing in air that is 10 percent oxygen—a dangerously low level similar to conditions at the top of Mount Everest, and about half that of air at sea level. However, mice that had the oxygen sensor HIF-1a genetically removed from their skin failed to produce this hormone (荷尔蒙) even after hours of such low oxygen.
These findings, if they hold true in humans, suggest one could raise the level of oxygen circulating inside the body. This could help treat lung diseases and disorders such as anemia (贫血症) without injecting drugs, which make up a multibillion-dollar market, Johnson said.
Athletes also often try to get more oxygen delivered to their muscles in order to improve their performance. They often do this by training at high altitudes or in low-oxygen tents. The new study suggests they might want to expose their skin as well as breathing in low-oxygen air to improve their performance. “It’s hard to say what exactly might be done, however—there’s a lot we don’t know yet,” Johnson explained.
The scientists detailed their findings in the April 18 issue of the journal Cell.
【小题1】Which of the following statements is TRUE according to the passage?

Some of the planet’s most precious animals and plants are disappearing, according to the World Conservation Union (IUCN). The group, based in Switzerland, works with governments and experts to protect threatened species. On September 12, the IUCN released its Red List, a list of species at greatest risk of extinction.
The list includes 41,415 animals and plants. The IUCN says that habitat destruction, hunting and other causes threaten one in four mammals, one in eight birds and one in three amphibians(两栖动物).
Who is to blame?
Scientists believe that 99 percent of threatened species are at risk because of human activity. “We are losing animals and plants at a high rate,” says Julia Marton-LefEevre, director general of the IUCN. “We need to change our behavior.” Warmer oceans and over-fishing are changing sea life. This year for the first time corals(珊瑚) made their appearance on the list. The gharial, a crocodile living in India and Nepal, has lost almost 60 percent of its population in the last 10 years. It is a victim（受害者）of habitat destruction.
Still, the news is not all bad. Thanks to efforts made to protect it, the Mauritius echo parakeet, a bird once endangered, has seen an increase in its population. “This shows that protection methods can work,” says Marton-LefEevre. “That’s the message we want to send to young people.”
In China the new reserve（保护区）itself is part of green efforts that have seen more than 2,400 nature reserves of various kinds being set up, covering more than 15 percent of the nation's land area, official figures showed.
"The country's natural resources(资源) have benefited from conservation," said Lei Guangchun, director of the nature reserve department of Beijing Forestry University. "It is a big increase nowadays compared with other countries." Lei said.
The total areas of China’s natural reserves have covered 1.38 million km2, which accounts for 15.4% of China’s area, higher than both the world average（平均水平） of 11% and the rate in most developed countries.
Li Zhong, an official in charge of the nature reserves office with the State Forestry Administration, thought it was important to increase investment（投资） in such reserves at all levels.
【小题1】What do we know about the IUCN?