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Jonathan Tobin: Defending the Right to a Jewish State

Heather Hale: Compliment your kids without giving them big heads

Megan Shauri: 10 ways you are ruining your own happiness

Carolyn Bigda: 8 Best Dividend Stocks for 2015

Kiplinger's Personal Finance editors: 7 Things You Didn't Know About Paying Off Student Loans

Samantha Olson: The Crucial Mistake 55% Of Parents Are Making At Their Baby's Bedtime

Densie Well, Ph.D., R.D. Open your eyes to yellow vegetables

The Kosher Gourmet by Megan Gordon With its colorful cache of purples and oranges and reds, COLLARD GREEN SLAW is a marvelous mood booster --- not to mention just downright delish
April 18, 2014

Rabbi Yonason Goldson: Clarifying one of the greatest philosophical conundrums in theology

Caroline B. Glick: The disappearance of US will

Megan Wallgren: 10 things I've learned from my teenagers

Lizette Borreli: Green Tea Boosts Brain Power, May Help Treat Dementia

John Ericson: Trying hard to be 'positive' but never succeeding? Blame Your Brain

The Kosher Gourmet by Julie Rothman Almondy, flourless torta del re (Italian king's cake), has royal roots, is simple to make, . . . but devour it because it's simply delicious

April 14, 2014

Rabbi Dr Naftali Brawer: Passover frees us from the tyranny of time

Greg Crosby: Passing Over Religion

Eric Schulzke: First degree: How America really recovered from a murder epidemic

Georgia Lee: When love is not enough: Teaching your kids about the realities of adult relationships

Cameron Huddleston: Freebies for Your Lawn and Garden

Gordon Pape: How you can tell if your financial adviser is setting you up for potential ruin

Dana Dovey: Up to 500,000 people die each year from hepatitis C-related liver disease. New Treatment Has Over 90% Success Rate

Justin Caba: Eating Watermelon Can Help Control High Blood Pressure

The Kosher Gourmet by Joshua E. London and Lou Marmon Don't dare pass over these Pesach picks for Manischewitz!

April 11, 2014

Rabbi Hillel Goldberg: Silence is much more than golden

Caroline B. Glick: Forgetting freedom at Passover

Susan Swann: How to value a child for who he is, not just what he does

Cameron Huddleston: 7 Financial Tasks You Should Tackle Right Now

Sandra Block and Lisa Gerstner: How to Profit From Your Passion

Susan Scutti: A Simple Blood Test Might Soon Diagnose Cancer

Chris Weller: Have A Slow Metabolism? Let Science Speed It Up For You

The Kosher Gourmet by Diane Rossen Worthington Whitefish Terrine: A French take on gefilte fish

April 9, 2014

Jonathan Tobin: Why Did Kerry Lie About Israeli Blame?

Samuel G. Freedman: A resolution 70 years later for a father's unsettling legacy of ashes from Dachau

Jessica Ivins: A resolution 70 years later for a father's unsettling legacy of ashes from Dachau

Kim Giles: Asking for help is not weakness

Kathy Kristof and Barbara Hoch Marcus: 7 Great Growth Israeli Stocks

Matthew Mientka: How Beans, Peas, And Chickpeas Cleanse Bad Cholesterol and Lowers Risk of Heart Disease

Sabrina Bachai: 5 At-Home Treatments For Headaches

The Kosher Gourmet by Daniel Neman Have yourself a matzo ball: The secrets bubby never told you and recipes she could have never imagined

April 8, 2014

Lori Nawyn: At Your Wit's End and Back: Finding Peace

Susan B. Garland and Rachel L. Sheedy: Strategies Married Couples Can Use to Boost Benefits

David Muhlbaum: Smart Tax Deductions Non-Itemizers Can Claim

Jill Weisenberger, M.S., R.D.N., C.D.E : Before You Lose Your Mental Edge

Dana Dovey: Coffee Drinkers Rejoice! Your Cup Of Joe Can Prevent Death From Liver Disease

Chris Weller: Electric 'Thinking Cap' Puts Your Brain Power Into High Gear

The Kosher Gourmet by Marlene Parrish A gift of hazelnuts keeps giving --- for a variety of nutty recipes: Entree, side, soup, dessert

April 4, 2014

Rabbi David Gutterman: The Word for Nothing Means Everything

Charles Krauthammer: Kerry's folly, Chapter 3

Amy Peterson: A life of love: How to build lasting relationships with your children

John Ericson: Older Women: Save Your Heart, Prevent Stroke Don't Drink Diet

John Ericson: Why 50 million Americans will still have spring allergies after taking meds

Cameron Huddleston: Best and Worst Buys of April 2014

Stacy Rapacon: Great Mutual Funds for Young Investors

Sarah Boesveld: Teacher keeps promise to mail thousands of former students letters written by their past selves

The Kosher Gourmet by Sharon Thompson Anyone can make a salad, you say. But can they make a great salad? (SECRETS, TESTED TECHNIQUES + 4 RECIPES, INCLUDING DRESSINGS)

April 2, 2014

Paul Greenberg: Death and joy in the spring

Dan Barry: Should South Carolina Jews be forced to maintain this chimney built by Germans serving the Nazis?

Mayra Bitsko: Save me! An alien took over my child's personality

Frank Clayton: Get happy: 20 scientifically proven happiness activities

Susan Scutti: It's Genetic! Obesity and the 'Carb Breakdown' Gene

Lecia Bushak: Why Hand Sanitizer May Actually Harm Your Health

Stacy Rapacon: Great Funds You Can Own for $500 or Less

Cameron Huddleston: 7 Ways to Save on Home Decor

The Kosher Gourmet by Steve Petusevsky Exploring ingredients as edible-stuffed containers (TWO RECIPES + TIPS & TECHINQUES)

Jewish World Review

How sharks work

By Marshall Brain

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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.

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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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