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VOA科学技术2022--耳化石揭秘恒温动物起源

时间:2022-08-25 02:41:17

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(单词翻译)

Mammals can produce their own body heat and control their body temperatures. This process is known as endothermy or warm-bloodedness.

Scientists believe that it may be the reason why mammals likely rule almost every ecosystem1. Warm-blooded mammals are more active than cold-blooded animals. They can live in different environments, from the frozen arctic to the boiling desert. And they reproduce faster.

The soft tissues that would give information about warm- or cold-bloodedness are rarely preserved in fossils. So, paleontologists, or experts in the study of fossils, do not know exactly when mammals developed and changed into warm-blooded creatures.

A group of scientists tried to answer that question in a study recently published in Nature.

Ricardo Araújo is a paleontologist at the University of Lisbon. Araújo and a group of researchers proposed that the shape and size of the inner ear structures called canals could be used to study body temperature.

The movement of fluid through the ear canals helps the body to preserve balance and movement. This fluid in cold-blooded animals is cooler and thicker, meaning wider canals are needed. Warm-blooded animals have less ear fluid and smaller canals.

The research team suggested that as body temperature increased and the animals became more active, the shape and size of ear canals changed to preserve balance and movement.

The researchers compared ear canals in 341 animals. They said the ear canals showed that warm-bloodedness, or endothermy, appeared around 233 million years ago, millions of years later than some previous estimates.

Araújo said, "Endothermy is a defining feature of mammals, including us humans. Having a ... high body temperature regulates all our actions and behaviors."

But the first creatures that showed warm-bloodedness are not officially considered to be mammals. These ancient animals known as mammaliamorph synapsids had traits linked with mammals. The first true mammals, the researchers said, appeared roughly 30 million years later.

Importance of being warm-blooded

Ken2 Angielczyk of the Field Museum in Chicago is a co-leader of the study. He said, "Given how central endothermy is to so many aspects of the body plan, physiology3 and lifestyle of modern mammals, when it evolved in our ancient ancestors has been a really important unsolved question..."

Endothermy evolved at a time when important elements of the mammal body plan were falling into place, including changes to the backbone4, breathing system, and hearing system.

Having warm-bloodedness also helped mammals at an important evolutionary5 moment when dinosaurs7 and flying reptiles8 first appeared on Earth. And mammals took over after the dinosaur6 mass extinction9 event 66 million years ago. Among today's animals, mammals and birds are warm-blooded.

"It is maybe too far-fetched, but interesting, to think that the onset10 of endothermy in our ancestors may have ultimately led to the construction of the Giza pyramids or the development of the smartphone," Araújo said.

"If our ancestors would have not become independent of environmental temperatures, these human achievements would probably not be possible."

Words in This Story

ecosystem – n. everything that exists in a particular environment

preserve – v. to keep (something) in its original state or in good condition

fossil – n. something (such as a leaf, skeleton, or footprint) that is from a plant or animal which lived in ancient times and that you can see in some rocks

feature – n. an interesting or important part, quality, ability, etc.

regulate – v. to set or adjust the amount, degree, or rate of (something)

trait – n. a quality that makes one person or thing different from another

aspect – n. a part of something

evolve – v. to change or develop slowly often into a better, more complex, or more advanced state : to develop by a process of evolution

far-fetched – adj. not likely to happen or be true


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1 ecosystem Wq4xz     
n.生态系统
参考例句:
  • This destroyed the ecosystem of the island.这样破坏了岛上的生态系统。
  • We all have an interest in maintaining the integrity of the ecosystem.维持生态系统的完整是我们共同的利益。
2 ken k3WxV     
n.视野,知识领域
参考例句:
  • Such things are beyond my ken.我可不懂这些事。
  • Abstract words are beyond the ken of children.抽象的言辞超出小孩所理解的范围.
3 physiology uAfyL     
n.生理学,生理机能
参考例句:
  • He bought a book about physiology.他买了一本生理学方面的书。
  • He was awarded the Nobel Prize for achievements in physiology.他因生理学方面的建树而被授予诺贝尔奖。
4 backbone ty0z9B     
n.脊骨,脊柱,骨干;刚毅,骨气
参考例句:
  • The Chinese people have backbone.中国人民有骨气。
  • The backbone is an articulate structure.脊椎骨是一种关节相连的结构。
5 evolutionary Ctqz7m     
adj.进化的;演化的,演变的;[生]进化论的
参考例句:
  • Life has its own evolutionary process.生命有其自身的进化过程。
  • These are fascinating questions to be resolved by the evolutionary studies of plants.这些十分吸引人的问题将在研究植物进化过程中得以解决。
6 dinosaur xuSxp     
n.恐龙
参考例句:
  • Are you trying to tell me that David was attacked by a dinosaur?你是想要告诉我大卫被一支恐龙所攻击?
  • He stared at the faithful miniature of the dinosaur.他凝视著精确的恐龙缩小模型。
7 dinosaurs 87f9c39b9e3f358174d58a584c2727b4     
n.恐龙( dinosaur的名词复数 );守旧落伍的人,过时落后的东西
参考例句:
  • The brontosaurus was one of the largest of all dinosaurs. 雷龙是所有恐龙中最大的一种。 来自《简明英汉词典》
  • Dinosaurs have been extinct for millions of years. 恐龙绝种已有几百万年了。 来自《简明英汉词典》
8 reptiles 45053265723f59bd84cf4af2b15def8e     
n.爬行动物,爬虫( reptile的名词复数 )
参考例句:
  • Snakes and crocodiles are both reptiles. 蛇和鳄鱼都是爬行动物。 来自《简明英汉词典》
  • Birds, reptiles and insects come from eggs. 鸟类、爬虫及昆虫是卵生的。 来自《现代汉英综合大词典》
9 extinction sPwzP     
n.熄灭,消亡,消灭,灭绝,绝种
参考例句:
  • The plant is now in danger of extinction.这种植物现在有绝种的危险。
  • The island's way of life is doomed to extinction.这个岛上的生活方式注定要消失。
10 onset bICxF     
n.进攻,袭击,开始,突然开始
参考例句:
  • The drug must be taken from the onset of the infection.这种药必须在感染的最初期就开始服用。
  • Our troops withstood the onset of the enemy.我们的部队抵挡住了敌人的进攻。

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