20090729 -- How Sharks Work (2)

How Sharks Work

Sharks handle their electric sensing using cells located in the head. Whenever something moves using its muscles, a shark can detect the electric impulses flowing to those muscles. A shark can electrically "see" anything that has muscles even if it is hiding or the water is murky. Sharks even have vibration sensors in their skin. When something moves near the shark, tubes pick up the pressure changes and hairs inside the tubes send signals to the brain. This extra sense allows a shark to turn quickly and attack again.

When you put all these different senses together, it makes the shark a nearly ideal hunter. A shark can detect prey from miles away and then use eyes, electrosensing and movement sensing to home in. Strangely, sharks do not seem to use these senses to home in on people. The very low number of shark attacks tells us that shark don't hunt human prey on a regular basis. On the other hand, people love to hunt sharks.
Millions and millions of sharks die every year. Without protection, extinction is a definite possibility.

impulse n. (電)脈衝
=> small short/quick burst electricity
eg: When you touch something, your skin sends an impulse to your brain.

murky adj. 暗的/含糊的
eg: After the storm, the water was so murky we couldn't see the bottom of the lake.
eg: The water in the river became murky and dirty after the typhoon.
eg: The criminal was chained in a murky dungeon(地牢).

murky adj. 黑暗的/複雜的
=> not clear
eg: She wants to forget about her murky past and move on.

prey n. 獵物
eg: The eagle swooped down and caught it prey.

prey n. 人
eg: The thief is looking for his next prey.

prey v. 獵食
prey on
eg: Wolves prey on rabbits.

home in (v phr.)
home in on someone or something 針對/對準某個對象
eg: The fighter plane(戰鬥機) homed in on a tank on the ground.
eg: Our discussion should home in on the solution to the problem.

vibration n. 擺動

extinct adj. 絕種的
extinction n. 滅絕
eg: This kind of lion is in danger of extinction
eg: The dinosaur is extinct.

definite adj. 限定的

//== Chat room ==//

pick up 察覺/感應到
tubes pick up the pressure changes
=> here pick up means sense/detect
eg: A radar may pick up enemy planes.

pick up 很容易學會/有學習的天份
=> to learn naturally
eg: pick up a bad habit

pick up 購買
=> buy
eg: pick up some milk
eg: Can you pick up some milk for me?

pick up someone 去接某人
drop off 讓...下車
picked up by the police => be arrest 被警察逮捕
pick up speed => accelerate 加速
pickup n. 載貨用的小貨車