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揽瓜阁俱乐部 Day9 2020.05.19
【自然科学-生物】 How Whales Became the Biggest Animals on the Planet （707字 精读 必做篇）
Whales are big. Really big. Enormously big. Tremendously big.
Fin whales can be 140,000 pounds. Bowhead whales tip the scales at 200,000 pounds. And the big mama of them all, the blue whale, can reach a whopping 380,000 pounds — making it the largest animal to have ever lived.
But for as long as whales have awed us with their great size, people have wondered how they became so colossal.
In a study published Tuesday in the journal Proceedings of the Royal Society B, a team of researchers investigated gigantism in baleen whales, the filter-feeding leviathans that include blue whales, bowhead whales and fin whales. The marine mammals became jumbo-size relatively recently, they found, only within the past 4.5 million years. The cause? A climatic change that allowed the behemoths to binge-eat.
Whales have an interesting evolutionary history. They began as land-dwelling, hoofed mammals some 50 million years ago. Over several millions of years they developed fins and became marine creatures. Between about 20 million and 30 million years ago, some of these ancient whales developed the ability to filter-feed, which meant they could swallow swarms of tiny prey in a single gargantuan gulp. But even with this feeding ability, whales remained only moderately large for millions of years.
“But then all of a sudden — ‘boom’ — we see them get very big, like blue whales,” said Nick Pyenson, the curator of fossil marine mammals at the Smithsonian Institution’s National Museum of Natural History and an author of the paper. “It’s like going from whales the size of minivans to longer than two school buses.”
Dr. Pyenson and his colleagues measured more than 140 museum specimens of fossilized whales, and then plugged that data into a statistical model. It showed that several distinct lineages of baleen whales became giants around the same time, independently of one another. Starting around 4.5 million years ago, giant blue whales were popping up in oceans across the world alongside giant bowhead whales and giant fin whales.
The researchers suspected that an environmental change happened during that time that essentially caused the baleen whales to bulk up. After some investigation, they found that this time period coincided with the early beginnings of when ice sheets increasingly covered the Northern Hemisphere.
Runoff from the glaciers would have washed nutrients like iron into coastal waters and intense seasonal upwelling cycles would have caused cold water from deep below to rise, bringing organic material toward the surface. Together these ecological effects brought large amounts of nutrients into the water at specific times and places, which had a cascading effect on the ocean’s food web.
Throngs of zooplankton and krill would gather to feast on the nutrients. They would form dense patches that could stretch many miles long and wide and be more than 65 feet thick. The oceans became the whales’ giant all-you-can-eat buffets.
“Even though they had the anatomical machinery to filter-feed for a long, long time,” said Jeremy Goldbogen, a comparative physiologist from Stanford University and author of the paper, “it wasn’t until the ocean provided these patchy resources that it made bulk filter-feeding so efficient.”
The baleen whales could now gulp down much larger amounts of prey, which allowed them to get bigger. But that was only part of the equation.
“Plentiful food everywhere isn’t going to get you giant whales,” said Graham Slater, an evolutionary biologist at the University of Chicago and the study’s lead author. “They have to be separated by big distances.”
Because the ecological cycles that fuel the explosions of krill and zooplankton occur seasonally, Dr. Slater said the whales must migrate thousands of miles from food patch to food patch. Bigger whale ancestors that had bigger fuel tanks had a better chance of surviving the long seasonal migrations to feed, while smaller baleen whales became extinct.
If the food patches were not far apart, Dr. Slater said, the whales would have grown to a certain body size that was comfortable for that environment, but they would not be the giants we see today.
“A blue whale is able to move so much further using so much less energy than a small-bodied whale,” Dr. Slater said. “It became really advantageous if you’re going to move long distances if you’re big.”
Source: The New York Times
【自然科学-生物】 Snapping Shrimp Make More Noise in Warmer Oceans （336字 2分23秒 精听 必做篇）
先做精听再核对原文哦~
Rice Krispies? Rain hitting a tin roof? Bacon frying? How about noisy creatures known as snapping shrimp.
Warm temperate and tropical coastal waters around the world are teeming with these noisy little creatures. They snap their claws so fast that they produce a bubble. When the bubble bursts, it makes a loud popping sound.
"It's this sort of persistent background noise, these snapping shrimp kind of crackling."
Aran Mooney, a marine biologist at Woods Hole Oceanographic Institution.
The shrimp produce the loud sound to stun prey. So how would this shrimp be affected by oceans getting warmer in coming years? To find out, Mooney and his colleague Ashlee Lillis analyzed audio recordings of the critters in their natural environment.
They also performed lab experiments with snapping shrimp collected from the wild, in water of varying temperatures. And they found that when water heats up, the shrimp start snapping more—and the water's soundscape gets louder. They shared their findings in February at the Ocean Sciences Meeting 2020 in San Diego.
The researchers aren't sure what's causing this change in shrimp behavior—but they have an idea.
"We don't precisely know the mechanism of why they're snapping more often. What we think is that these guys are basically just ectothermic animals. So that means they're directly responding to environmental conditions around them. So basically, as you increase the water temperature, it increases their metabolic rate—they get more metabolically active, so they are able or trying to snap more."
If these shrimp do make the ocean noisier as the climate warms, it could be a problem for both marine creatures and humans. Many ocean animals use sound to communicate. And both the Navy and fishermen rely on marine acoustics to do their work.
"You know, we never really thought about how that ocean its own background noise or its own fog is naturally increasing, and what we think is temperature driven or climate change driven. So as you raise those levels, it gets harder to ‘see' through that acoustic fog."
Source: Scientific American
【自然科学-生物】 Readying for Second Wave of Locusts in Africa （349字 2分43秒 精听 选做篇）
先做精听再核对原文哦~
East Africa, particularly the Horn of Africa region, is facing the worst locust outbreak in decades. City-sized swarms of these insects are eating their way through vegetation and pastures, leaving little or nothing for local people and their cattle.
Desert locusts are the world’s oldest and most destructive migratory pest.Human history has recorded locust invasions going back thousands of years, and it just takes a confluence of just the right conditions, particularly warm weather and heavy rains, to promote rapid breeding. That is what happened last year. By late summer, huge swarms of these insects began moving from Yemen across the Red Sea and the Gulf of Aden, devouring enough green plants every day to feed 35,000 people.
Now the rainy season is once again approaching in East Africa, and with it, another wave of these pests is expected in Kenya, Ethiopia, Somalia and other countries in the region. According to the United Nations Food and Agriculture Organization, “if left unchecked, the number of locusts in East Africa could explode 400-fold by June. That would devastate harvests in a region with more than 19 million hungry people.”
The best way to stop desert locusts is by aerial and ground spraying, as well as through constant tracking of the swarms.Timing is critical. We must reduce locust numbers now, before the spring planting season gets underway, even as we face the added challenge of the global coronavirus pandemic.
That is why the United States Government, through the U.S. Agency for International Development, is providing an additional $10 million in humanitarian assistance to Ethiopia, Kenya and Somalia, the hardest-hit countries. The funds will support regional operations to control desert locusts. This new funding brings the U.S. humanitarian response to the infestation to $19 million.
Throughout the region, USAID has disaster experts who are evaluating humanitarian needs and coordinating response efforts with local governments and aid organizations. They will work closely with these groups to determine whether additional assistance is necessary.
The United States calls upon other donors to contribute funds to address the immediate needs of communities throughout the Horn of Africa.
Source: VOA
【笔记格式要求】
精读笔记格式要求： 1.总结文章中心大意 2.总结分论点或每段段落大意 3.摘抄印象深刻或者觉得优美的句子 4.总结文章中的生词 5.记录阅读时间、总结时间、总时间
精听笔记格式要求： 1.逐句听写整篇文章 2.对照原文修改听写稿，标记出错原因 3.总结文章中心大意 4.总结精听过程中的生词 5.记录听写时间、总结时间、总时间
这里也给大家两点学习小建议哦~ 精读：如遇到读不懂的复杂句，建议找出句子主干，分析句子成分，也可以尝试翻译句子来帮助理解~ 精听：建议每句不要反复纠结听，如果听 5 遍都没听出来，那就跳过，等完成后再回听总结原因，时间宝贵，不要过于执着哦~
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发表于 2020-5-18 22:23:10
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