2 . In times of intense stress, people sometimes let it out with a scream and a new study suggests that plants might do the same. Researchers at Tel Aviv University in Israel has found that plants let out ultrasonic (超声的) screams when damaged or stressed by drought.

The noises, falling within a range of 20 to 100 kilohertz, are too high-frequency for humans to hear, but other plants and some animals perceive them. Insects might be listening for sounds from stressed plants to assess their condition before laying eggs on their leaves. A moth (蛾) may decide against laying eggs on a plant that sounds water-stressed.

Researchers attached recording devices directly to plants to listen for secret sounds inside their stems (茎). In drought, air bubbles formed, burst and caused vibrations (振动) within the tissue that normally carries water up the plants’ stems. The process was picked up by the attached recording devices, but researchers wanted to know if any plant sounds could travel through the air.

So the team placed microphones 10 centimetres from stressed-out tomato and tobacco plants. They subjected one set of crops to drought and another to physical damage. A third group was untouched.

The microphones did pick up distinct sounds. On average, drought-stressed tomato plants let out about 35 ultrasonic screams per hour, while those with cut stems made about 25. Drought-stressed tobacco plants let out about 11 screams per hour, and cut crops made about 15 sounds in the same time. The average number of sounds from untouched plants fell below one per hour.

The researchers also attempted to identify each plant group just based on its screams. Using a type of artificial intelligence calculations, the team picked out distinct features in each set of sounds and successfully sorted their plants into three kinds: “dry, cut or untouched.”

If it is not too costly to set up the recording in a field situation, farmers might be able to hear these stress signals too. In future, enabling farmers to listen for water-stressed plants could “open a new direction”, which will be increasingly important as climate change exposes more areas to drought.

4 . If you think of a game of fetch, you might picture a dog running back and forth, eagerly recovering a ball. But a new study shows that they’re not the only pets that like the game: Cats play fetch, too, just on their own unique terms.

The researchers discovered almost 1,000 owners of 1,154 cats to find out if and why. According to their findings, nearly 95% of the cat owners reported that their cats fetched items naturally. One respondent said his cat returned the toy completely for no reason.

Fetching was mainly first noticed when cats were under I year old. What’s more, “cats who fetch largely determine when they engage in fetching activities and actively influence the play behavior of their owners,” according to the study. “So, it can say a bit about cats being in control of their interactions and being in control of their environments, even being in control of us. You might even go so far to say,” says Jemma Forman, the co-author of the study.

But the motivation for cats to fetch objects seems to be different from that for dogs. Cats are more likely to play on their own with objects similar to prey (猎物). For dogs, play is more social, involving either another dog or human.

In general, play has major advantages for both the pet and the owner, as it not only helps to prevent attack towards, the owner, but also models the act of preying on real animals, an important kind of play behavior. “So even if your cat doesn’t play fetch, obviously it’s a really good idea to try and engage them in any sort of play. Play does have a lot of benefits,” says Forman. “It’s about owner acceptance to your fur baby,” she says.

5 . It is believed that it’s dangerous to have plants in the bedroom. Plants take in carbon dioxide (CO₂) and produce oxygen (氧气) in the day.     1    . The build-up of CO₂ is a real problem for indoor air quality, which has been shown to influence health, so it is easy to see where the concern comes from. But to consider whether sharing our bedroom with our plants can harm health, we should consider three things.

Firstly, how much CO₂ do plants produce at night compared with what they take in during the day?     2     For the answer depends on everything from species to light levels and even room temperature.

Thankfully, in 2015, researchers at Turkey’s Kastamonu University found that large houseplants take in between six and eight times as much CO2 in the day as they produce at night.

    3     A single human breath contains around 40, 000 ppm of CO2, more than 10 times the effect a plant could have in 8 hours, so you might want to throw your partner out before your plants.

Finally, we don’t live in the sealed (密封的) boxes in which these studies are carried out.     4     The air is even exchanged when we move around. According to one recent review, we need houseplants to keep indoor air fresh, and to fight some pollution.     5    

Let’s enjoy houseplants whenever we like, because if sleeping near plants were bad for our health, camping in a forest would be deadly.

6 . Mobile Bay in Alabama is home to a strange and unique occurrence. During the summer months, hundreds of fish and crustaceans (甲壳纲动物) from the deep waters of the bay move to the shallow waters. The free seafood is so plentiful and easy to catch with nets or bare hands that locals gather to fill their buckets with it. This natural phenomenon has existed for centuries.

Sarah Van Winkle, a student at the Alabama School of Math & Science, is no stranger to the scene. Growing up there, the rich plants and animals never stop to amaze her.

As the world’s oceans face numerous issues such as pollution, overfishing, and habitat destruction, she intended to figure out whether Mobile Bay was experiencing similar environmental threats in her most recent science project. Sarah studied the environment of Mobile Bay and she even extended the range of the research to the Mobile Tensaw-Delta, and the canals of a living district in Fairhope, Alabama. She analyzed key nutrient and metal levels in the ocean ecosystem.

Through the project, Sarah found that turbidity, an important indicator of water quality, increased sharply. This result showed, clearly that the area is filled with tiny pieces of matter, making the water there quite opaque.

For the project. Sarah was chosen as one of this year’s 24 Society for Science & the Public Community Innovation Award winners. “To me, this honor symbolizes that the ten months of late night readings, weekend field trips, and after-school sessions in the laboratory have truly come to fruition and impacted lives,” Sarah noted.

“Our local ocean ecosystem is in danger of chemical pollution from a variety of sources,” Sarah explained in an interview. “The bay plays a vital role in our community and every local should value what the bay offers. It’s our responsibility to work together to preserve it.”

8 . The “mark test” (or “mirror test”) is a way to test animal intelligence — whether an animal can recognize itself, especially animals with large brains. A mark is put on an animal, usually in a spot that can only be seen with a mirror. Then the animal is allowed to look in a mirror. If the animal seems to pay attention to the mark, scientists believe the animal has recognized itself.

But some scientists believe the mark test doesn’t work well for all animals. Roosters (公鸡) are a good example. Scientists at the University of Bonn recently ran the mark test on roosters. They put a pinkish triangle on the chest of the roosters. But when the roosters looked in a mirror, they didn’t seem to notice the mark.

The scientists needed a different way to test whether the roosters could recognize themselves. When there’s danger — like a hawk (鹰) flying above — roosters make loud calls to warn nearby chickens. But roosters only make the cries if other chickens can hear them. If they’re alone, they remain quiet so the hawk won’t see them. The scientists realized that they could use the shadow of a hawk to test if roosters could recognize themselves in a mirror.

First, the scientists let the roosters spend time getting used to being in a closed-in space and having a mirror around. Then, they ran several tests by making a hawk shadow appear above the bird and watching how the rooster reacted.

When there was no mirror, the roosters reacted as usual. They called out when they were near another rooster, but remained quiet when they were alone. But when a rooster was in a space where it could see itself in the mirror, it wasn’t fooled into thinking there was another rooster. It remained silent despite the hawk shadow.

It proves the roosters knew they were seeing themselves in the mirror, and not other roosters. That suggests that the mark test may not be a good test of whether an animal can recognize itself.

The scientists hope their results will encourage other scientists to look for better ways of testing self-recognition in animals.

9 . Five months ago, a new species of box jellyfish was discovered in Hong Kong. It is a relative of the deadly Australian box jellyfish, one of the most venomous (有毒的) animals on Earth. One sting (刺伤) from it can kill a person in minutes.

A university team in Hong Kong, led by Qiu Jianwen from the Hong Kong Baptist University, discovered it at the Mai Po Nature Reserve, a local wetland area. It was the first discovery of a new box jellyfish species in Chinese waters.

But it’s not the first time biology professor Qiu has discovered a new creature. He’s made more than 30 discoveries in about 20 years spent exploring new marine (海洋的) animals.

Qiu doesn’t go looking for new species on purpose. In 2014, he did research on the health of coral in Hong Kong waters. To learn more, Qiu and his team needed to find all of the coral species involved. And in doing so, they discovered four new coral species.

Finding new species reminds Qiu of how biologically diverse Hong Kong’s waters are. Hong Kong takes up just 0.03 percent of China’s total marine area, yet it is home to more than 25 percent of all marine species recorded in China, a report by the University of Hong Kong showed.

However, Hong Kong’s marine animals face threats, due to factors including habitat loss, climate change and overuse of natural resources.

Although action is being taken, it focuses more on bigger creatures, like dolphins and birds. “Many marine species are small and they are often overlooked. If these species were to become extinct, few people would notice or care. But for me, each one has its rightful place,” said Qiu.

He hopes everyone can recognize the importance of the ocean. “When more people show concern for the ocean, we are, in fact, acting for our own benefit,” he said.

Jiangxi Province has taken many measures to protect finless porpoises (江豚),     1     have faced dramatic changes in their living environment as Poyang Lake, China’s largest freshwater lake, suffered a severe drought.

The species,    2     (list) as critically endangered by the International Union for Conservation of Nature, now lives only along the middle and lower reaches of the Yangtze River. The number of finless porpoises    3     (drop) significantly in the past few years, with only 457     4     (live) in Poyang Lake.

As the water level dropped to less than 12 meters, the lake officially entered this year’s dry season on August 6,     5     (early) than at any time since records began in 1951. Severe drought has reduced the lake by 75 percent. This change will     6     (undoubted) increase the risk of the finless porpoises hitting boats and also result     7     a food shortage for the porpoises.

Wang Liang, who works for the provincial Department of Agriculture and Rural Affairs of Jiangxi, said the province has released     8     total of 200 million fish, shrimps (虾) and crabs into the waters     9     (enrich) the food supply and more than 2,000     10     (volunteer) have been trained to rescue the species.