Sharks may be able to smell blood from miles away, but they probably don’t know how red it is. It is likely that they only see the world in black and white according to a study that is the first to investigate sharks’ visual system.
A team at the University of Western Australia studied the visual systems of many different species of sharks and what they have found is diversity in eye design that mirrors the ecological and behavioral diversity of the shark species. The team looked at the retinal cells of 17 species of sharks caught off Queensland and Western Australia and found out that the cells are responsible for sharks’ color blindness.
According to the study, these animals are color-blind due to the light receptors they have got in their eyes. There are two main types of light-sensitive cells to allow animals to see: rod cells help measure brightness because they are highly sensitive to light and allow night vision but cannot tell colors apart, while various types of cone cells help distinguish colors. They peeked at the structure of sharks’ rod and cone cells in the retina. Human eyes come with red, green and blue cone variations, while sharks appear to have just one kind of cone cells.
The study suggests that contrast against the background, rather than color itself, might be more important for object detection by sharks. Costumes that camouflage swimmers’ bodies in sea water are less likely to draw a shark’s attention than ones with bright, solid colors that emphasize their outline. “It’s the high contrast against the water rather than the color itself which is probably attractive to sharks,” said Professor Nathan Hart who led the study.
1. What is paragraph 2 mainly about?| A．The importance of the research. |
| B．The features of sharks’ retinal cells. |
| C．The process and the result of the study. |
| D．The functions of sharks’ visual systems. |
| A．Their fragile rod cells. | B．Their lack of various cone cells. |
| C．Their dark living environment. | D．Their weak sensitivity to light. |
| A．hide | B．fit | C．beautify | D．protect |
| A．To clear up a wrong belief. | B．To raise funds for a program. |
| C．To show a unique phenomenon. | D．To present a scientific discovery. |
相似题推荐
【推荐1】In general, just about every mammal (哺乳动物) relies on a community of gut bacteria (肠道细菌) for health and survival. Many animals have even developed to the point that closely related host species typically share more similar gut bacteria. But a new study has identified a converse phenomenon on one group of mammals — bats. The gut bacteria of closely related bats can be totally distinct from each other.
To learn about the relationships between bats and their gut bacteria, post-doctoral researcher Holly Lutz and her co-workers took samples of bacteria from the skin, tongues, and guts of 497 bats from 31 different species in Kenya and Uganda. They discovered bats have fewer bacterial species living in their guts than in their mouths and on their skin. What’s more, gut bacteria living in different bats are individually distinctive, following no apparent pattern. This struck the scientists as strange, since for most other mammals that have been studied, closely related hosts share more similar gut bacteria.
“There’s essentially no relationship between bats’ gut bacteria and their evolutionary (进化的) history,” says Lutz. While host identity is still an important factor in predicting the species of gut bacteria, this may simply be tied to where those bats live and what they eat. The fact that bats’ gut bacteria are more closely tied to where bats live than where those bats fall on the bat family tree indicates that developing a special relationship with just-right gut bacteria may not have been as important for bats as it has been for other mammals.
Lutz suspects that bats’ unique relationships with gut bacteria are related to the feature that sets them apart from other mammals: their ability to fly. “Bats have extremely shortened guts,” she explains. “Food takes just fifteen to thirty minutes to pass through a bat’s digestive system, a third as long as it would take for a similarly sized animal. That’s likely because a long, winding digestive canal would weigh the bats down.”
1. Which is closest in meaning to the underlined word “converse” in paragraph 1?| A．Typical. | B．Potential. | C．Inspiring. | D．Opposite. |
| A．Gut bacteria vary with related bats. | B．Mammals share similar gut bacteria. |
| C．There are 497 varieties of bats in Kenya. | D．Bats have the most bacteria in their mouths. |
| A．To quicken their food digestion. | B．To make them lighter for flight. |
| C．To help improve their ability to fly. | D．To fit in with their digestive system. |
| A．Bats contain a diverse range of bacteria. |
| B．Bats don’t seem to need gut bacteria to evolve. |
| C．Bacteria play a big role in bats’ health and survival. |
| D．Bats don’t rely on gut bacteria the way other mammals do. |
【推荐2】When I was six, Dad brought home a dog one day, who was called “Brownie”．My brothers and I all loved Brownie and did different things with her. One of us would walk her, another would feed her, and then there were baths, playing catch and many other games. Brownie, in return, loved each and every one of us. One thing that most touched my heart was that she would go to whoever was sick and just be with them. We always felt better when she was around.
One day, as I was getting her food, she chewed up (咬破) one of Dad's shoes, which had to be thrown away in the end. I knew Dad would be mad and I had to let her know what she did was wrong. When I looked at her and said, “Bad girl,” she looked down at the ground and then went and hid. I saw a tear in her eyes.
Brownie turned out to be more than just our family pet. She went everywhere with us. People would stop and ask if they could pet her. Of course she'd let anyone pet her. She was just the most lovable dog. There were many times when we'd be out walking and a small child would come over and pull on her hair. She never barked or tried to get away. Funny thing is she would smile. This frightened people because they thought she was showing her teeth. Far from the truth, she loved everyone.
Now many years have passed since Brownie died of old age. I still miss the days when she was with us.
1. What would Brownie do when someone was ill in the family?| A．Look at them sadly. | B．Keep them company. |
| C．Play games with them. | D．Touch them gently. |
| A．She was too hungry. | B．She chewed up one of the shoes. |
| C．The author criticized her. | D．The author didn’t prepare food for her. |
| A．Shouted. | B．Smiled. | C．Cried. | D．Jumped. |
| A．Shy. | B．Polite. | C．Brave. | D．Caring. |
【推荐3】Brownie and Spotty were neighbor dogs who met every day to play together. Like pairs of dogs you can find in any neighborhood, these two loved each other and played together so often that they had worn a path through the grass of the field between their houses.
One evening, Brownie’s family noticed that Brownie hadn’t returned home. They went looking for him with no success. Brownie didn’t show up the next day, and, although they made their efforts to find him, by the next week he was still missing, Curiously, Spotty showed up at Brownie’s house alone, barking and jumping. Busy with their own lives, they paid no attention to the nervous little neighbor dog.
Finally, one morning Spotty refused to take “no” for an answer. Ted, Brownie’s owner, was continuously disturbed by the angry, determined little dog. Spotty followed Ted about, barking all the time, then darting toward a nearby empty lot and back, as if to say, “Follow me! It’s urgent!”
Eventually, Ted followed Spotty across the empty lot as Spotty stopped to race back and barked encouragingly. The little dog led the man to a deserted spot a half mile from the house. There Ted found his beloved Brownie alive, one of his legs crushed in a steel trap (圈套). Frightened, Ted now wished he had taken Spotty’s earlier appeals seriously.
Then Ted noticed something. Spotty had done something else besides leading Brownie’s human owner to his trapped friend. In a circle around the injured dog, Ted found some food remains of every meal. Brownie had been fed that week! Spotty had been visiting Brownie regularly, in the hope of keeping his friend alive. Spotty had actually stayed with Brownie to protect him from hunger and other dangers, and keep his spirits up.
Brownie’s leg was carefully treated and he soon got well again. For many years thereafter the two families watched the faithful friends chasing each other down that well-worn path between their houses.
1. At the very beginning, Ted paid little attention to Spotty because __________.| A．he was not free at the moment | B．he was sure Brownie would be OK |
| C．he didn’t like Spotty at all | D．his missing dog made him sad |
| A．rushing | B．shouting | C．walking | D．looking |
| A．managed to free his dog at once | B．was very thankful to Spotty |
| C．regretted not following Spotty earlier | D．was angry with the trap-maker |
| A．humans and animals depend on each other for comfort |
| B．it’s not right to hunt for animals in any neighborhood |
| C．Ted has to take better care of his beloved dog later on |
| D．Brownie would have died without Spotty’s timely help |
【推荐1】Some colors people see late at night could cause signs of clinical（临床的）depression (沮丧). That was the finding of a study that builds on earlier study findings. They show that individuals (个人) who live or work in low levels of light overnight (整夜) can develop clinical depression. Doctors use the word “clinical depression” to describe severe form of depression. Signs may include loss of interest or pleasure in most activities, low energy levels and thoughts of death or suicide.
In the new study, American investigators designed an experiment that exposed hamsters（仓鼠）to different colors. The researchers chose hamsters because they are nocturnal（夜行的）, which means they sleep during the day and are active at night.
The animals were separated into four groups. One group of hamsters was kept in the dark during their night-time period. Another group was placed in front of a blue light, a third group slept in front of a white light, while a fourth was put in front of a red light.
After four weeks, the researchers noted how much sugary water the hamsters drank. They found that the most depressed animals drank the least amount of water.
Randy Nelson heads the Department of Neuroscience at Ohio State University. He says animals that slept in blue and white light appeared to be the most depressed. “What we saw is that these animals didn’t show any sleep uneasiness (不安) at all but they did mess up biological clock genes and they did show depressive sign while if they were in the dim（微弱）red light, they did not.”
Randy Nelson notes that photosensitive（感光）cells in the eyes have little to do with eyesight. He says these cells send signals to the area of the brain that controls what has been called the natural sleep-wake cycle.
He says there’s a lot of blue in white light. This explains why the blue light and white light hamsters appear to be more depressed than the hamsters seeing red light or darkness.
1. Researchers use hamsters in the experiment because __________.| A．they are similar to humans in dealing with colors |
| B．they are easy to observe and study |
| C．they are sensitive to colors like human beings |
| D．they are active at night and sleep during the day |
| A．They drink less sugary water. | B．They don’t sleep well. |
| C．Their eyesight becomes worse. | D．Their energy level becomes low. |
| A．Not being exposed to dim red light when using computers. |
| B．Equipping their computer screens to put it more in the reddish light. |
| C．Living or working in low levels of light overnight. |
| D．Going to see doctors of clinical depression regularly for help. |
【推荐2】
Located in the northeast of Italy, Venice is well-known for its cultural treasures, romantic atmosphere and unusual living-on-water experience. The city spreads out over 118 islands, which are linked by more than 400 bridges, in the Venetian Lagoon.
Venice’s historical center consists of six regions. San Polo in the middle and San Marco in the south, the busiest main regions, are linked by the Rialto Bridge. The famous stone arch bridge crosses Venice’s main waterway — the Grand Canal. When night falls, many tourists enjoy dinner at the outside tables by the Grand Canal while watching colorfully lit boats going by.
Near the end of the S-shaped Grand Canal lies St. Mark’s Basilica, a must-see. Inside, beautiful mosaics tell stories of Bible figures. Nearby are the Doges Palace and the Bridge of Sighs. These were made famous by Lord Byron, “I stood in Venice on the Bridge of Sighs, a palace and prison on each hand.” Legend has it that if a couple passes under the bridge, their love will last forever.
In the square outside the Basilica, lovers of literature can sit at Caffe Florian, regarded as the oldest coffee house in Europe. Charles Dickens, Henry James as well as Lord Byron enjoyed the wonderful drink here.
Art lovers should buy a museum pass and visit some of the city’s unusual museums. They can view works by Venetian masters like Giovanni, Titian and Tintoretto.
On five small islands in the Venetian Lagoon, Murano has been home to glass-makers since 1291. Tourists can visit factories, studios and the Glass Museum. Glass artists produce everything from simple souvenir pieces to beautiful works of modern art. Only glassworks made using traditional methods on Murano can be called Murano Glass. The nearby island of Burano is famous for lace making and colorful houses. Looking at the colorful houses and kaleidoscopic streets makes people feel as if they were walking in the fairy tale.
The City of Water promises beauty of all kinds, and it definitely lives up to its promise.
1. Why does the author mention Lord Byron’s words?| A．To introduce the famous British poet. |
| B．To explain why the two places are famous. |
| C．To show why St. Mark’s Basilica is a must-see. |
| D．To compare the Doges Palace and the Bridge of Sighs. |
| A．Caffe Florian. | B．The city’s museum. |
| C．St. Mark’s Basilica. | D．The Bridge of Sighs. |
| A．Bridges. | B．Lace making. | C．Glassworks. | D．Colorful houses. |
| A．Venice’s modern art. | B．Venice’s local customs. |
| C．Venice’s natural scenery. | D．Venice’s attractions with its beauty. |
【推荐3】If you’re not at least a bit terrified by the climate and ecological breakdown unfolding before our eyes, you haven’t grasped the scale of the crisis. Eco-anxiety, defined as “a chronic(长期的)fear of environmental doom”, is on the rise. But redirecting this anxiety into anger and collective action might just pull humanity back from the brink.
We don’t yet know how deeply eco-anxiety affects people, but we can learn not to repeat the mistakes of long-gone societies lost to environmental collapse. Jared Diamond’s Collapse: How Societies Choose to Fail or Succeed uncovers the common driver that led to the fall of ancient civilizations such as the Central American Mayan, the remote Pacific Easter Island, and the Mycenae: People accidentally destroyed the environmental resources on which their societies depended.
Today, we are living in a new climate and ecological age. The new normal is one that humans have never before experienced on earth, and that has occurred within a single generation. We can’t claim ignorance. Numerous scientific reports show: unprecedented(空前的)wildfires in the Arctic, heatwaves annually breaking records, the Amazon shrinking and drying, and species extinction rates accelerating. Nature’s dangerous decline is unprecedented.
So, it’s not surprising that eco-anxiety is on the rise. Anxiety is often a private emotional state: We feel alone, stuck inside our own heads, and our emotions stop us from doing the things we want. But anger, directed appropriately, can fuel powerful collective action for change.
We are on a pathway to destroy the global conditions for human survival. Unlike previous civilizations, we have the science and technology to understand our danger and chart a new pathway. This is a moment for all of us to channel our eco-anxiety, fear and anger into energy for change.
1. Which of the following best describes “eco-anxiety”?| A．Uncertainty about the future. | B．Anxiety about modern civilization. |
| C．Fear of changes in the living standard. | D．Worries about the destruction of nature. |
| A．To warn people to learn a lesson from the past. |
| B．To prove the importance of ancient civilizations. |
| C．To present the collapse of ancient civilizations. |
| D．To add some background information on eco-anxiety. |
| A．People lack the knowledge about nature. | B．Nature is in its most dangerous state ever. |
| C．Climate issues can’t be solved effectively. | D．People have limited access to natural resources. |
| A．Frustrated. | B．Doubtful. | C．Hopeful. | D．Concerned. |
