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Overview
Gliding through the water at breakneck speeds--a fin, just skimming the surface of the water. The biggest jaws you've ever seen. These are the iconic images that flash through all our minds when we think of sharks, but there's so much more to know about these majestic predators of the sea.
If you're already a fan of the Discovery's phenomenon Shark Week, then you will love this book! From the unique look of the prehistoric Whorl shark, to the hunting techniques of the Great White, all the thrills and chills of Shark Week are now here for year-round reading. Filled with photos, first-hand accounts of shark attacks, and unbelievable facts (Did you know that there are sharks that live in volcanoes?), this book is for every shark fanatic who wants to get even more up close and personal.
Now you really can live every week like it's shark week.
Product Details
| ISBN-13: | 9781250097798 |
|---|---|
| Publisher: | Feiwel & Friends |
| Publication date: | 05/17/2016 |
| Sold by: | Macmillan |
| Format: | eBook |
| Pages: | 160 |
| File size: | 44 MB |
| Note: | This product may take a few minutes to download. |
| Age Range: | 9 - 12 Years |
About the Author
Discovery (Discovery, Inc.) is a communications company that operates factual television networks including Discovery Channel, Animal Planet, Investigation Discovery, Science Channel, and The Learning Channel.
Martha Brockenbrough draws on her diverse experience in journalism, research, nonfiction, and literary teen fiction to bring Alexander Hamilton to life in Alexander Hamilton, Revolutionary. A powerful storyteller and narrative voice, Brockenbrough is also the author of the critically acclaimed YA novels The Game of Love and Death and Devine Intervention. She enjoys reading Hamilton's original correspondence, playing board games, and spending time with her family. She lives in Seattle, Washington.
Read an Excerpt
Shark Week
Everything You Need to Know
By Martha Brockenbrough
Feiwel and Friends
Copyright © 2016 Discovery ChannelAll rights reserved.
ISBN: 978-1-250-09779-8
CHAPTER 1
SHARK LIFE — THE INS AND OUTS OF A SHARK'S WORLD
HOW LONG SHARKS HAVE LIVED
By any measure, sharks are magnificent animals. They're older than dinosaurs. They can grow larger than elephants. They're powerful hunters — the biggest, strongest, and fastest fish in the sea. The more you know about these creatures, the more you will admire them.
A few facts to start with:
THEY'RE AN ANCIENT CREATURE. The earliest-known shark fossils are more than 400 million years old. The oldest-known dinosaur fossil is 240 million years old. The shark is a survivor, evolved to inhabit every ocean of the world. Sharks have outlasted dinosaurs and giant mammals and, with care from humanity, might continue to thrive.
THEY'RE DIVERSE. The tiniest are a few inches long. The biggest can grow up to 45 feet.
THEY CAN LIVE LONG LIVES. Some can live a century — sharks alive today might have been around, for example, when the Titanic sank.
THEY HAVE SENSES THAT HUMANS DON'T. Think about how much information you glean from your senses. Touch. Taste. Hearing. Smell. Sight. Sharks can do all of that (and in many cases better than we can). Plus, they can sense vibrations in the water and the electricity generated by living things.
SHARK EVOLUTION
Sharks have had the same basic body shape and structure for hundreds of millions of years: a head, a body, a tail, gills, and fins. This doesn't mean sharks haven't changed over time; they have, and some species have evolved in spectacular ways. And the idea that sharks are "living fossils" is being modified the more we know about them. Some sharks are similar to extinct ones. But many modern sharks have more advanced gills than extinct sharks, according to a team of researchers led by the American Museum of Natural History.
We're only learning this now because there aren't a lot of fossilized gill arches, and because older technology didn't let us study these as closely as newer devices. In short, sharks are complicated, highly evolved, and worthy of close study to understand not only them, but also how things like jaws and human hearing evolved.
Some people mistakenly believe evolution is an unproven theory. This is not the case. Evolution describes the way living things change over time and pass changes on to their offspring. There are theories about how this happens, and one of the most fundamental is natural selection: traits that help species survive long enough to reproduce are the ones that are passed on.
Whatever the mechanism for evolution, the key central idea is that all life on earth shares a common ancestor. We are all connected, even if we are not all the same.
Each vertebrate — a classification that includes mammals, birds, fish, reptiles, amphibians, and fish — is descended from tiny, simple creatures that developed in the oceans during the Cambrian period, about 500 million years ago.
Over tens of millions of years, these animals became more fishlike, developing a backbone, fins, and mouths that could be used to scoop food.
Around 400 million years ago, these fish ancestors split into two groups: bony fish and cartilaginous fish.
Sharks, which don't have bones, come from the cartilaginous line. There are some sharks alive today that are amazingly similar to sharks that lived 150 million years ago. Rays and chimaeras are also cartilaginous fish, and there are about 1,100 species of those we know of. You can think of those as close relatives to the shark. Cartilaginous fish are less common than bony fish, which come in about 25,000 varieties. That said, we discover new animals all the time, and it's certain that very rare species become extinct without ever being discovered — so these numbers are best guesses.
BASIC FACTS
HOW MANY KINDS OF SHARKS ARE THERE?
Possibly more than 500 species.
HOW LONG DO SHARKS LIVE?
Different species have different life spans. Also, sharks in captivity don't live as long as sharks in the wild (possibly because they don't get to swim around as much).
The more we learn about shark behavior, including migration patterns, the more we will know about their life spans. Scientists today are using GPS to track sharks and learn this — and more — information.
Here are a few life-span ranges:
GREAT WHITE SHARK: These creatures live 70 years or more, a lot like humans. This is much longer than we previously thought, according to a 2014 study conducted at Woods Hole Oceanographic Institution in Massachusetts.
It's tricky to determine how old a shark is (you can't exactly ask).
One method is to look at a shark's skeleton and count the "rings" of cartilage. This isn't a perfect system, though. As with tree rings, the shark rings vary in width and can be difficult to distinguish.
The Woods Hole study used this technique and the remnants of nuclear bomb testing conducted in the 1950s and 1960s to measure the life span of great whites. These nuclear weapons tests produced something called carbon-14, a radioactive variant of carbon. Marine animals alive during those tests absorbed the unusual isotope, so it stands out like a flag where it's present. The biggest male shark they examined was 73 years old, based on the rings they counted before and after those nuclear test years. The oldest female was 40, which could mean female sharks don't live as long, but not necessarily. Discovery has footage of what is believed to be a pregnant 50-year-old great white, so it seems just as likely they simply didn't find an older female.
WHALE SHARK: The biggest surviving species of shark might also have a supersize life span. One way to guess a shark's life span is to study when it is able to reproduce. This happens at the 20 percent marker of their life span. Male whale sharks can breed when they're about 30 years old. This would be 20 percent of a 150-year life span.
TIGER SHARK: They can live up to 50 years in the wild. Their reproduction rates are slow, which is typical of animals with long life spans. It's worrisome with the tiger shark, though, which is a target for its fins, skin, flesh, and liver. Because they are such a popular catch, they are listed as a near-threatened species everywhere they live.
HOW FAST ARE SHARKS?
Sharks are phenomenal swimmers. There are three components of swimming: lift; balance and steering; and forward motion, which comes from pushing water backward.
Sharks get lift from their very oily and fatty livers (unlike fish, which have a little balloon of air inside of them).
They get their balance and steering from their fins.
Their forward motion comes from their powerful tails, which swing from side to side.
A shark's shape is related to its speed. The fastest sharks are the most aerodynamic in shape — like torpedoes. They have tail fins that are more symmetrical. Slower sharks are longer and thinner, and their tail lobes tend to be asymmetrical.
Researchers studied the side-to-side motion of the tail fins of spiny dogfish and chain dogfish. By putting small particles in water and using lasers to reflect light off the particles, the scientists discovered that shark tails generate twice as many jets of water as other fish tails. In other words, their tails are pushing more water backward — it's like having a more powerful engine.
So how do these dogfish do it? They stiffen their tails mid-swing. The behavior gives sharks almost continuous forward thrust.
SHORTFIN MAKO SHARK: This is the fastest shark. Speed estimates vary, though some estimates clock it at 60 miles per hour over short distances. Unlike many sharks, which have a bigger top lobe on their tail fin, the mako's is nearly symmetrical. The shortfin mako has to be fast. It eats tuna, swordfish, other sharks, and squid — all speedy movers.
GREENLAND SHARK: This is the slowest-known shark — at least for its size. It's also the slowest-known fish, inch for inch. They swim at 1.7 miles per hour, the pace of a leisurely walk. They achieve this speed by swinging their tails a mere nine times per minute, according to a study from the National Institute of Polar Research.
One reason these big sharks are so poky is they live in very cold water. Their pokiness doesn't prevent them from eating the much-faster seals, though. Seals sleep underwater, probably to stay safe from polar bears. This makes them an easy catch.
MOST SURPRISING TRAVELING HABITS: For the longest time, we thought tiger sharks were a coastal species. But a recent study from Nova Southeastern University's Guy Harvey Research Institute in Florida shows otherwise.
These animals are long-distance travelers, moving every year between the coral reefs of the Caribbean to the open waters of the mid–North Atlantic Ocean. What's more, they spend winters in the same spot each year, which makes habitat preservation crucial.
Some shark migration patterns are even more complex. Shark species that reproduce every two years have been tagged and found to follow two-year migration patterns. These return to pupping grounds every other year to have babies.
The biggest-known shark migration in US waters happens on Florida's Atlantic coast. Five-foot-long blacktip sharks cruise by the coast in the winter, sometimes in groups of thousands. They're heading for bays and estuaries where they will mate and have pups. These are the source of some unprovoked shark bites in Florida (none were fatal, and experts believe they happened when sharks confused swimmers with food).
WHERE DO SHARKS LIVE?
There are two ways of looking at a shark's habitat: which bodies of water they inhabit, and where in the water they reside — near the surface, in the depths of the ocean, or at the bottom of shallower waters.
Sharks are in every ocean around the world (though not in all parts of all oceans). They aren't in Antarctica, but warmer waters brought about by climate change might make it possible for them to survive there. Some sharks can even survive in freshwater rivers.
One of the most famous sharks, the great white, is also found in the most places. They can live in shallow coastal waters and the deep ocean, and in tropical and even subpolar waters.
COLD, SHALLOW COASTAL WATERS: This is the preferred environment for sevengill sharks. These sharks are slow moving and prefer continental shelves, bays, and fjords that are 160 feet deep or less. They keep to the bottom.
WARM COASTAL REGIONS, TROPICAL AND TEMPERATE SEAS: Tiger sharks love these environments and swim thousands of miles from continent to continent. You won't find them in the Mediterranean, though.
Hammerheads also like warm and tropical waters around the globe. They're sometimes near the shore and sometimes in the open sea, and they can skim the surface or dive 1,000 feet deep. Some have even been found living near an underwater volcano.
THE OPEN SEA: Oceanic whitetips sometimes travel closer to land, but generally are found in warm waters in the ocean.
WHO LIKES IT COLD? The big, slow-moving Green-land shark can take the frigid waters of the North Atlantic. You'll also find them near Iceland.
HOW BIG CAN THEY GET?
There are hundreds of species of sharks, each of which comes in a range of sizes. Female sharks are often bigger than males.
THE BIGGEST: The biggest sharks can be almost as long as school buses (which are 45 feet).
These are whale sharks, slow-moving, gentle giants that eat plankton and tiny fish by swimming along with their mouths open and vacuuming their meals from the upper layer of the tropical seas they inhabit.
They range in size on average from 18 to 30 feet, though they can get larger. They also weigh around 20 tons, or more than 40,000 pounds.
THE SMALLEST: While there are many sharks you could hold in your palm, a rare creature called a pale catshark might just be the tiniest one. A single, young female catshark that measured a little over eight inches long was found near Indonesia. These are so rare scientists do not yet know how big (or small) the average one is.
Another tiny and spectacular shark is the green lanternshark, which is believed to live in the northwest Atlantic Ocean, in the northern Gulf of Mexico and Caribbean, and maybe also Brazil. These small sharks are just over 10 inches long. Little is known about this species, which has tiny, light-producing organs on its sides.
HOW DO SHARKS SWIM?
Sharks are flexible because they don't have bony skeletons. They get their structure from light and bendy cartilage. They move when their powerful side muscles contract, one side at a time. They're powered by their caudal, or tail, fins.
If you were to watch one from above, you'd see them curve in a bit of an S shape. But too much bending would be inefficient, so they stiffen their bodies and make less of that S shape once they get going.
Surprisingly, some sharks walk, sometimes as much as they swim. These sharks tend to have muscular front fins that they use to walk around the seafloor, and sometimes — in the case of bamboo sharks — they'll even scoot from one tide pool to another, crawling out of the water as they do.
HOW DO THEY BREATHE?
Most sharks have five gills. The ones with six — called sixgills — are believed to be more primitive, because they resemble fossils of the oldest sharks. These tend to be big, about the size of great whites. They're also hard to find because they stay deep in the ocean, away from light.
Some sharks have spiracles, which are special gills that provide oxygen to the eyes and brain. These are right behind the shark's eye.
Unlike bony fish, shark gills don't have gill coverings.
All sharks need water moving over their gills to breathe and stay alive. But not all sharks do this the same way.
Certain ones swim fast with their mouths open. This kind of breathing is called ram ventilation.
Other kinds of sharks, especially the slower swimmers, have muscles in their mouths that suck in water and wash it over their gills. This means they can stay still and continue to breathe. This is called buccal pumping, named after the buccal muscles in the mouth.
Some sharks can switch breathing types. Others, including the great white, mako, and whale shark, can't and must keep moving to keep oxygen flowing in and carbon dioxide flowing out.
HOW DO THEY STAY AFLOAT?
Bony fish have an airbag inside that keeps them from sinking. Think of it as nature's equivalent to those inflatable floaties some small children use when swimming.
Sharks don't have airbags. They've evolved other ways of achieving buoyancy. Part of this comes from their lightweight, cartilaginous skeletons.
Part of it, though, comes from their livers. These store lightweight oils, and in deepwater sharks, about a quarter of the animal's weight comes from this oil. (They also help sharks store energy.)
Sand tigers have a do-it-yourself air bag. They gulp air at the surface and hold it in their stomachs. This helps them hover in the water without moving.
WHAT DO THEY EAT?
Sharks mostly eat smaller fish, but some sharks eat seals, sea lions, and other marine mammals.
The biggest sharks — whale sharks — eat tiny food, including plankton, which is a name given to a wide variety of small sea life that drift in ocean currents (they can't swim against it). Plankton can be plants, animals, and even bacteria.
No sharks are strict vegetarians. No sharks are evolved to eat people, either, though it has on very rare occasions happened.
ARE SHARKS WARM- OR COLD-BLOODED?
Most fish are cold-blooded. Some sharks, though, are able to keep their body temperature higher than the water they swim in. Their powerful muscles generate heat while they're swimming. For most sharks, this heat dissipates when their blood flows through their gills, which are always bringing in cold water from the sea. Sharks that can hang on to this warmth, like white sharks and porbeagles, have a hunting advantage. The heat-keepers don't do this with blubber, like whales and other aquatic mammals. Instead, they've evolved two sets of blood vessels that work together to hold in heat. Called capillaries, the blood vessels carrying oxygen-rich blood that's been chilled by the sea run in the opposite direction of other blood vessels carrying blood that's been warmed by the shark's activity. It's like holding a cold hand in a warm hand — the heat exchange warms the cold hand right up.
HOW SHARKS ARE BORN
Animal reproduction is a fascinating subject. It's also one that we don't study enough (probably because people think it's embarrassing and gross).
One scientific journal that studies how animals reproduce tracked 12,000 studies over a ten-year period. They discovered that 90 percent of the studies looked at the same species: mice, rats, and cows.
We're missing out. Reproduction is a wonder. For example, sea horse dads are the ones who get pregnant and go through labor (and can have up to 1,500 babies at a time).
Reproduction can also happen in many different ways. Sometimes it requires two parents. This is almost but not always the case with more complex animals.
(Continues...)
Excerpted from Shark Week by Martha Brockenbrough. Copyright © 2016 Discovery Channel. Excerpted by permission of Feiwel and Friends.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.
Table of Contents
Contents
Title Page,Copyright Notice,
INTRODUCTION,
CHAPTER ONE: SHARK LIFE — THE INS AND OUTS OF A SHARK'S WORLD,
CHAPTER TWO: THE PERFECT PREDATOR — SHARKS AND THEIR ARMOR,
CHAPTER THREE: STRANGE & WONDERFUL SHARKS,
CHAPTER FOUR: SHARK FIGHT! SHARKS VERSUS OTHER PREDATORS,
CHAPTER FIVE: EVEN SHARKS HAVE ENEMIES,
CHAPTER SIX: AMAZING SURVIVOR STORIES,
RESOURCES & PHOTO CREDITS,
INDEX,
About the Author,
Copyright,