1 . Many animals depend upon sound to find food, detect predators and communicate with one another. These species understandably suffer when loud motorways cut through their habitats. Some deal with this problem by singing more loudly, some change the timing of their calls to occur when fewer people are driving, others just move to quieter places.
It has always been assumed that noise is a problem unique to animals. But a new study by Ali Akbar Ghotbi-Ravandi, a botanist at Shahid Beheshti University in Tehran, has revealed that plants suffer too.
That plants can be affected indirectly by noise pollution has never been in doubt. Since most flowering species depend upon pollinators and most fruit-bearing species need animals to disperse their seeds, it is obvious that if these animal partners are harmed by noise then their botanical plants will do badly, too. What has remained unknown is whether or not plants themselves suffer directly from noise pollution.
Sounds are pressure waves transmitted through gases, liquids and solids. Scientists have previously predicted that plants may be able to sense these waves as they are struck by them. A number of experiments have confirmed this in recent years — plants attacked with ultrasound in the lab have shown a range of hurtful responses, including the expression of stress-related genes, underdeveloped growth and reduced germination (发芽) of seeds.
Working with a team of colleagues, Dr. Ghotbi-Ravandi grew two species in his lab that are commonly found in urban environments. The plants were grown from seeds and allowed to mature for two months in the same space before they were divided into two groups. One group was exposed to 73 decibels (分贝) of traffic noise recorded from a busy motorway in Tehran for 16 hours a day. The other group was left to grow in silence. After 15 days, samples were taken from the youngest fully expanded leaves on every plant in the experiment and studied.
None of the plants exposed to the traffic noise did well. Analysis of their leaves revealed that all of them were suffering. Harmful chemicals in them are indicators of stress in plants and both were found at much higher levels in the plants exposed to the traffic noise. Most notably, levels of the harmful chemicals in the plants exposed to noise were two to three times what they were in those grown in silence. The findings make it clear that the noise of traffic bothers the plants.
1. What’s the function of the first two paragraphs?| A．To lead in the topic of the passage. |
| B．To prove that only animals suffer from noise. |
| C．To introduce how animals avoid the urban traffic noise. |
| D．To compare the different effects of noise on animals and plants. |
| A．Classify. | B．Spread. | C．Damage. | D．Collect |
| A．Urban traffic noise mainly poses a threat to animals. |
| B．Plants themselves suffer indirectly from noise pollution. |
| C．Plants exposed to the traffic noise bear higher levels of stress. |
| D．Plants that don't need animals for growth will not be influenced by noise. |
2 . The Greenwood fire took its name from the nearby lake where lightning struck on Aug.15, causing a wildfire that burned for weeks. Fueled by drought and wind, its persistence dominated headlines for much of late summer and early fall in Minnesota. When the last flames were finally put out, the northern Minnesota fire had consumed nearly 27,000 acres, countless firefighting resources, and at its worst, the lives that some had built around nearby McDougal Lake. Vast areas of forest were left burned-out, with the black and bare remains of what were once massive pines.
But, despite the destruction left behind, Mother Nature is set to a comeback. When organic matter is burned from the forest floor, seeds dropped by plants and trees begin to take hold, with the sprouting species emerging first. The trees above have died, which sends a chemical signal to the root system that is actually more expansive than just under that tree, and that chemical response encourages those root systems to re-grow. Ten years ago, a fire ripped through 93,000 acres of Minnesota forest in and around the BWCA. Today, that burnt area's rebirth is well underway.
"Here in the Pagami Creek wildfire scar, we have Jack Pine, Red Pine, Black Spruce, Aspen and paper birch-those are our main species, those are the ones that are growing quickly. It's 10 years on, and these trees are 10 to 15 feet tall in many areas," said Kyle Stover from the U.S. Forest Service.
A wildfire kills most things in its path, but despite the flames and intense temperatures, rarely is everything reduced to ashes -and that plays a key role in a forest's regeneration. Just one year after the fire, the survivors dominate the forest, and grasses replace the burnt ground. Wildflowers are abundant bushes and small trees have started to grow, and Jack Pine returned. So, it's an amazing ecological system of creating new forest life when it appears that all is lost, one that has evolved throughout the ages, where fire has always played a vital role.
1. What can we learn about the Greenwood fire?| A．It was a natural occurrence | B．It was caused by drought. |
| C．it gained half-year fame. | D．It took many people's lives. |
| A．Seeding growth is held up. | B．Burnt organic matter hardly functions. |
| C．Root systems spread further and wider | D．Chemicals in the soil are in greater demand. |
| A．They are flammable | B．They are fire-resistant |
| C．They are fire-adapted. | D．They are overgrown. |
| A．A fire. | B．A life | C．A time. | D．A system |
