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从托福阅读材料看鲨鱼的方向感从哪来-智课教育旗下
智课教育
三只脚本文是智课教育小编为考生带来的关于鲨鱼靠气味追踪猎物的托福阅读材料。大家在积累相关词汇的同时，也要注意学习相关的背景知识。
智课教育小编为考生带来了关于鲨鱼靠气味追踪猎物的托福阅读材料。传统理论中，鲨鱼是靠猎物留下的气味浓度的不同来指引自己的方向，但最新一项研究表明，它是靠最先感知到气味的鼻子来辨别方向的。感觉疑惑了吗?hdtune
To follow the scent trail left by their prey across the ocean sharks swim in the direction of the nostril tha
t sniffed the odor first scientists have found. Their rearch challenges the classic notion that sharks orient themlves bad on the differences between odor concentration received at each nostril.
Shark prey--whether living injured or dead--leaves behind swirling odor plumes that break apart with distance. The latest work published online June 10 in Current Biology suggests that when a shark moves into a patch of odor the smell hits one nostril before the other--and that tells the shark to turn either left or right. By moving from side to side from one patch to another the animal maintains contact with the odor plume as it tracks its prey says Jayne Gardiner at the University of South Florida in Tampa co-author of the study.
Ocean odors mix chaotically so for sharks to steer using odor concentration they would need to compare the average concentration at the two nostrils over a period of veral minutes to determine the prey’s direction. They would then have to reposition themlves and start again--a slow process. But by using timing cues says Gardiner sharks receive directionality in under a cond.
Squid marinade腌牛排的方法
不将就李荣浩
五字开头成语The study centered around lab studies of eight smooth dogfish (Mustelus canis) a small gray-brown shark. To recreate prey odor Gardiner marinated squid--what she calls "junk food for dogfish"--in 50 liters of awater. She fitted the sharks with headgear consisting of two tubes delivering this squid marinade to one nostril and then the other. She found that for delays between 0.1 and 0.5 conds the sharks turned toward the side receiving the first stimulus. If there was no time lag or if the lag was a cond or longer the sharks were equally likely to turn in either direction.
In addition to timing delays Gardiner delivered varying concentrations of squid sauce to the sharks’ nostrils. This was Gardiner’s update of a 25-year-old experiment involving similar headgear on bonnethead sharks (Sphyrna tiburo). Gardiner delivered diluted squid esnce to one nostril 0.5 conds before delivering the full-strength squid broth to the other nostril. The animals turned towards the side receiving the first albeit weaker stimulus. "It was timing every time" Gardiner says.
蝉简笔画"The previous dogma has always been that sharks orient towards odor by detecting greater concentration on one side of the head over the other" says shark nsory biologist Stephen Kajiura from Florida Atlantic University in Boca Raton. "In this study timing ems to trump concentration. It’s an exciting alternative way of looking at how we understand shark processing."
Speedy hammerheads
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The results of this study may also have implications for the evolution of other shark species. For example according to anecdotal evidence hammerhead sharks em to swim faster towards their prey than many other sharks--suggesting that they might have a better n of smell. The swimming speed of sharks as they track prey may be limited by the spacing of their
