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May 23, 2012
Tony Pugh: More private colleges offering tuition discounts
Mary Beth Franklin: How to Choose the Right Annuity for You
Tina Susman: The wig wasn't enough: Man gets 13 years for posing as his dead mom
The Kosher Gourmet by Emma Christensen:A simple way to do fish right
May 22, 2012
Warren Richey: Can US group challenge overseas surveillance act? Supreme Court to decide
Thomas M. Anderson: Walking Away From a Mortgage
The Kosher Gourmet by Megan Gordon: Enjoy a celebration of the most rich and layered flavors: Black bean, sweet potato and quinoa chili
May 21, 2012
Mark Clayton: Cybersecurity: How US utilities passed up chance to protect their networks
Howard LaFranchi: NATO summit: Who will foot the bill for long-term Afghanistan security?
Chris Farrell : Earn Dividends in Emerging Markets with This WisdomTree ETF
Stephen Whiteside, Ph.D. : Mayo Clinic Medical Edge: Social anxiety disorder --- or just shy?
Guy Jackson : Victim's father regrets death of Lockerbie bomber
The Kosher Gourmet by Mario Batali: Famed chef's veal shoulder farsumagru: A festive meat course for late spring
May 18, 2012
Rabbi Berel Wein: Striving: The People of the Book's Book for (All of) the People
Steven Goldberg: 5 Great Stock Picks and the Exchange-Traded Fund that Owns Them
Mary Pickett, M.D.: Ask the Harvard Experts: Don't be forced into gluten-free lifestyle based merely on a doctor's false-positive test
The Kosher Gourmet by Carolyn Malcoun: DIY healthy lunchbox treats: HOMEMADE FRUIT BARS for kids and brown-bagging adults alike
May 17, 2012
Warren Richey: Teacher fired for being unwed and pregnant can sue religious school, court rules
Josh Mitnick: Netanyahu's 'centrist' coalition is already proving it's anything but
Steven Goldberg: Earn Dividends in Emerging Markets with This WisdomTree ETF
Amina Khan: Research links coffee to lower death rates
The Kosher Gourmet by Faith Duran : Cheesy Potato Breakfast Casserole with Cheddar and Sun-Dried Tomatoes
May 16, 2012
Carmen Terzic, M.D., Ph.D. : Mayo Clinic Medical Edge: A variety of exercises can help improve balance
Melissa Healy: National strategy on Alzheimer's disease aims to halt it by 2025
The Kosher Gourmet by Joyce White : GOODNESS GRACIOUS: GREENS! 4 winning recipes that are no longer just for down-home folks (Includes expert tips & techniques)
May 15, 2012
Kristen Chick: Obama administration resumes arms sales to Bahrain despite serious unresolved human rights issues. Activists feel abandoned
Pat Mertz Esswein: Homes are now affordable again and mortgage rates are low. What you need to know before you buy
Kathy Kristof: Our Practical Investor Fights Inflation with These 6 Investments
Sue Hubbard, M.D.: The Kid's Doctor: Lactose intolerant young child? Check again
The Kosher Gourmet by Kathy Hunt: Spread a Little Excitement with EXOTIC CONDIMENTS (4 RECIPES)
May 14, 2012
Lisa Gerstner: How to Protect Your Identity, Finances If You Lose Your Phone
Harvard Health Letters: Heart disease and dementia
The Kosher Gourmet by Megan Gordon: MANGO COCONUT OAT MORNING MUFFINS are a bright but hearty delight
May 11, 2012
Jessica L. Anderson: Get the Best Deal on a Used Car
Jett Stone: Forget face-lifts and fake knees. Scientists have seen the fountain of youth --- and it's broccoli
The Kosher Gourmet by Chef Mario Batali: The famed chef's vegetable dish that tastes true to the season: FAVAS AND SUGAR SNAP PEAS WITH POTATOES AND TARRAGON
May 10, 2012
Sergei L. Loiko: Putin sends warning to U.S., NATO in Victory Day speech at Red Square
Mary Rourke: How being a 'mentch' got Vidal Sasoon his start and fighting in Israel's War of Independence provided him with confidence and a strong sense of his own identity
Jeff Bertolucci: Get Home Phone Service for Less Than $10 a Month
The Kosher Gourmet by Betty Rosbottom: Gleaming with its golden, crimson, and snowy white hues, this silken smooth and creamy STRAWBERRY ORANGE TRIFLE looks impressive, but is easy to prepare
May 9, 2012
Sharon Palmer, R.D. How you can reduce your risk -- or delay -- chronic diseases associated with aging
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Jewish World Review
How sharks work
By
Marshall Brain
http://www.JewishWorldReview.com | (MCT)
The summer beach season is prime time for shark attacks in the United States. It seems like sharks are attacking all the time. But that is something of an illusion. Even though the number of attacks is very small (only 23 in Florida in 2006), each attack gets nationwide news coverage. Combined with movies like "Jaws" and sensational TV shows, it all feeds into a natural human fear of predators.
But putting aside the fear factor for a moment, have you ever wondered about the sharks themselves? It turns out that sharks are absolutely fascinating creatures. They have existed on our planet for hundreds of millions of years because the basic shark design is extremely well adapted to life in the ocean.
One key to the shark's success is its diversity. There are over 400 species of shark today. Half of these species are small, at less than a meter in length full grown. But sharks can also get huge. A whale shark can grow as long as 45 feet and it feeds on plankton like many whale species. This wide range of sizes lets sharks fit into many different ecological niches.
Unlike mammals, birds and most fish, a shark does not have a skeleton. Instead it has a cartilage chassis like a ray does. The biggest piece of cartilage that is visible on a human is our ear lobes. By looking at your lobes, you can see that cartilage is strong, light and flexible compared to bone. The most important advantage that cartilage gives a shark is a weight reduction. Unlike most fish, a shark does not need an air bladder to compensate for the weight of calcium-rich bones.
Muscles and fins give the shark its speed and maneuverability in the water. A shark's front fins act like the wings of an airplane and let it "fly" through the water. The tail acts like a high-power propeller. The fastest sharks can swim at more than 20 mph.
But the big thing that gives the shark its edge in the ocean is its sensory package. The package includes the shark's eyes, ears, skin, nose and mouth, as well as electric sensing.
A shark's nose is probably its most important sense. If you were to put a single drop of blood in an Olympic size swimming pool containing more than 600,000 gallons of water, a great white shark could smell that. And most sharks have directional smell, so they can tell the direction that the smell is coming from. If something bleeds, a shark can smell it miles away. Many sharks can also hear sounds of distress from miles away.
Sharks handle their electric sensing using cells located in the head. Whenever something moves using its muscles, a shark can detect the electrical impulses flowing to those muscles. This is a short-range sense, but makes it very easy for a shark to electrically "see" anything that has muscles, even if it is hiding or the water is murky.
Sharks even have vibration sensors in their skin that work a little bit like our ears do. Tubes along the sides of a shark contain small sensitive hairs. When something moves near the shark, the tubes pick the pressure changes and the hairs inside the tubes send signals to the brain. Even if the shark cannot "see" something nearby with its eyes or electrosense, it can "feel" it moving when the shark swims by. 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 sharks don't hunt human prey on a regular basis. In many cases, if a shark bites a human, the shark will let go and flee. On the other hand, people love to hunt sharks. Millions and millions of sharks die every year, to the point where certain species of sharks may start disappearing. Without protection, extinction is a definite possibility.
Every weekday JewishWorldReview.com publishes what many in the media and Washington consider "must-reading". Sign up for the daily JWR update. It's free. Just click here.
Comment by clicking here.
Previously:
How mosquitoes work
How diesel engines work
How water towers work
How the Dawn mission works
How Kassam rockets work
How the North American Eagle works
Why aren't we flying to work?
How tofu and soy milk work
How Colony Collapse Disorder works
How airbags work
How the U.S. income tax works
How gum works
How caffeine works
How Daylight Saving Time works
How a cruise missile works
How snow making works
© 2007, How Stuff Works Inc. Distributed by McClatchy-Tribune Information Services.
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