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Scott Foresman Science 5.2 Genre Comprehension Skill Text Features Science Content Nonfiction Draw Conclusions • Captions • Labels • Diagrams • Glossary Cells to Systems ISBN 0-328-13921-1 ì<(sk$m)=bdjcbh< +^-Ä-U-Ä-U

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  • Scott Foresman Science 5.2

    Genre Comprehension Skill Text Features Science Content

    Nonfi ction Draw Conclusions Captions

    Labels

    Diagrams

    Glossary

    Cells to Systems

    ISBN 0-328-13921-1

  • 1. What do sea urchins use their tube feet for?

    2. Jellyfi sh are a type of cnidarian. What does this name mean, and why is it a good name for jellyfi sh?

    3. Describe how the chambered nautilus grows.

    4. Many ocean animals have interesting ways of moving around. Write to explain a few of them. Use examples from this book.

    5. Draw Conclusions A giant blue clam and a squid are both mollusks, but only the clam has a shell. Why do you think this is?

    What did you learn?Extended Vocabularybivalvescartilagecephalopodscnidariansechinodermsfunnelmantlemolluskspropel

    Vocabulary

    cell membranecell wallchloroplastcytoplasmnucleusorgansorgan systemstissuesvacuole

    Picture CreditsEvery effort has been made to secure permission and provide appropriate credit for photographic material. The publisher deeply regrets any omission and pledges to correct errors called to its attention in subsequent editions.

    Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd).

    4 Bill Curtsinger/NGS Image Collection; 12 (BL) Andre Seale/Alamy Images.

    Scott Foresman/Dorling Kindersley would also like to thank: 11 (TR) Natural History Museum/DK Images.

    Unless otherwise acknowledged, all photographs are the copyright of Dorling Kindersley, a division of Pearson.

    ISBN: 0-328-13921-1

    Copyright Pearson Education, Inc. All Rights Reserved. Printed in the United States of America. This publication is protected by Copyright, and permission should be obtained from the publisher prior to anyprohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic,mechanical, photocopying, recording, or likewise. For information regarding permission(s), write toPermissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025.

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    by Laura Johnson

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  • What You Already Know

    Your whole body is made from tiny parts called cells. The cells work together to form tissues, and the tissues form organs. These organs work together in organ systems, and two or more systems may work together to let you do all the things you do.

    Your cells, as tiny as they are, have even smaller parts. These parts help the cell take in oxygen, process food, and get rid of wastes. A cell has all the same needs as you do. There are many different kinds of cells in your body, with different shapes to do different jobs. Some are long and thin to carry messages, while others are fl at to make up tough surfaces. Others are dish-shaped to carry oxygen through your body.

    Cells join together to form tissues. Muscle, bone, and nerve are three kinds of tissue. More than one kind of tissue can form an organ. Your heart, skin, and eyes are all organs.

    2

    human skeletal system

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    Groups of organs working to do the same job are called organ systems. Each of your bones is an organ, and they all work together to form the skeletal system. Your systems carry out the major work that needs to be done in your body, such as digesting food, taking in oxygen, and sending messages from your brain to the rest of your body.

    Your systems work together too. For example, you need both your skeletal system and your muscular system to move around. The bones support the muscles, and the muscles supply the motion.

    As you can see, the parts of your body are very complicated and interesting. Now well look to see whats inside sea creatures. These animals may be very different from you, but youll fi nd that they can be interesting too.

    scallops

    3

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  • Jellyfi sh are not made of jelly and they are not fi sh! They are 98 percent water. The rest of them is a jellylike material stiff enough to support their body structure. They belong to a group of animals called cnidarians, which means stinging creatures. All cnidarians have tentacles with stinging cells in their tips. These stinging cells contain springlike threads called nematocysts. When shrimp or other prey touch a tentacle, the nematocysts inject a poison into the victim and paralyze it.

    Some jellyfi sh just drift in the water. Others propel themselves by fi rst expanding, then quickly squeezing, their bag-shaped bodies. This action forces water out of an opening under their bodies. As they move, they keep their tentacles spread out to catch food.

    Jellyfi sh

    Have you ever seen a jellyfi sh, a sea urchin, or a squid? These animals are strange and amazing-looking on the outside. In this book youll learn that these animals, and a few others, are even more interesting on the inside!

    Introduction

    jellyfi sh

    4

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    The jellyfi sh releases its venom into the fi sh.

    Tentacles can be more than 10 feet in length.

    Inside each tentacle are thousands of nematocysts.

    how the box jellyfi sh paralyzes its prey

    5

    Barbed tubes pierce the fi shs scales.

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  • ScallopScallops belong to a group of animals

    called mollusks. Mollusks have soft bodies without skeletons to support them. A layer of fl esh, called a mantle, covers their bodies. The mantle makes a very thin chemical layer. This chemical hardens and slowly builds up to form a shell that protects the animals organs.

    Scallops are bivalves. This means they have two shells that are connected by a hinge. The hinge is actually a strong muscle. Scallops swim by fl apping their shells.

    great scallop

    Most bivalves dont swimthey remain attached to objects. The scallops ability to swim makes it quite unusual.

    Tiny eyes in the mantle detect light and dark.

    66

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    Gills absorb oxygen from the water.

    The mantle controls the fl ow of water into the shell.

    The heart pumps blood to the tissues and gills.

    When the shell opens, water fl ows in the front. When the shell snaps shut, water shoots out the back and the scallop swims forward.

    As they swim, scallops feed on microscopic food, such as algae and plankton, that fl oat in the water.

    Around the edge of the mantle is a row of blue eyes. Although they cant see very well, these eyes can sense movement and tell when enemies, such as sea stars, are near.

    Common scallops are about two to three inches wide. However, the giant scallop, or great scallop, can grow to be eight inches wide.

    Giant Blue Clam

    The largest bivalve, the giant blue clam, can weigh more than fi ve hundred pounds! The blue pigment, or coloring, in the clams mantle protects it from too much sunlight.

    7

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  • 8

    All sea urchins have a fi ve-fold symmetry. This means that their bodies have fi ve sections that are all the same, like the sections of an orange.

    Sea urchins belong to a group of animals called echinoderms. Echinoderms are spiny-skinned invertebrates that move slowly across the ocean fl oor. Sea urchins have a round body that is divided into fi ve equal segments. Close-fi tting, bony plates under their skin form a shell.

    Most sea urchins have long, movable spikes on their shells. They can push themselves along fl at surfaces with these spines. Between the spines are rows of tube feet with suction cups. They are used to climb, to grab on to surfaces, and to catch food. Some sea urchins use tube feet to gather shells and seaweed and cover themselves to hide from predators. Sharp spines are the sea urchins best defense.

    Sea Urchin

    Sea urchins can be black, brown, green, purple, red, or white.

    8

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    Teeth can move in different directions.

    Muscles move the teeth.

    Ball-and-socket joints allow the spines to move in all directions.

    sea urchin

    Sea urchins eat plants that grow on rocks and on the ocean fl oor. A powerful jaw on the underside of their bodies can scrape up food. Their mouths have fi ve teeth that can move in different directions.

    Sea urchins have no brain. They have a very simple circulatory system of water-fi lled channels that fl ow through their body.

    9

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  • The chambered nautilus has irregular brown and white stripes. It can grow to a width of 10 inches.

    Chambered NautilusAnother mollusk, the chambered nautilus, begins life

    in a shell with seven small sections, or chambers. Like the scallop, it has a mantle that helps it form a shell. As the soft body of the animal grows, it adds new, larger chambers to its shell. Each chamber is sealed off as the nautilus moves into a new chamber. A full-grown nautilus may have up to thirty-eight chambers. A cone-shaped head, surrounded by sixty to ninety short tentacles, can stick out of the open chamber.

    The closed chambers are fi lled with nitrogen and other gases. A narrow tube called a siphuncle winds through all the chambers. Depending on the mixture of fl uids and gases in the chambers, the nautilus either rises in the water or sinks.

    When the nautilus retreats into its shell, a fl eshy shield covers the entrance.

    Water is expelled through the funnel to provide thrust.

    10

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    To swim, the nautilus forces water through a movable funnel below its head. This funnel is called a siphon. As it forces water through the siphon, it swims backward. During the day the chambered nautilus lives at great depths. At night it rises to feed among the coral reefs in shallow water.

    chambered nautilus

    The nautilus lives only in the outer chamber.

    As the nautilus grows it constructs new chambers.

    11

    Fossils like this provide valuable information about the nautilus. During prehistoric times, there were 10,000 kinds of nautilus. Only a few species still live today.

    Nautilus Fossil

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  • Squid belong to a group of mollusks called cephalopods. Cephalopods have large heads and long arm structures that look like many feet. Their name comes from Greek words that mean head and foot. A squids head is in the middle of its body. Behind the head is a bullet-shaped sac covered by a special layer called a mantle. The space inside the sac, called the mantle cavity, holds the squids organs, including its ink sac. A squid can squirt ink from this organ to hide itself from predators. Unlike a nautilus, a squids mantle doesnt make a hard shell.

    Squid

    The tentacles have suckers on their ends.

    Many squid can change color to hide from enemies or attract mates. Some can even light up.

    12

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    At the other end of the head are eight sucker-lined arms and two extra-long feeding arms. When hunting, a squid sneaks up on its prey and quickly grabs it with its two long tentacles. The arms can taste food. If the squid likes the taste, it pulls the victim into its mouth. There, a hard beak crushes or tears the food apart.

    To swim, a squid sucks water in through holes between its head and mantle. Then it squirts jets of water out of a tube called a funnel. Squid prefer to swim backwards. But by pointing this funnel in different directions, squid can also swim forward or sideways to catch prey.

    eye

    The position of the fl exible funnel controls the direction of the squids travel.

    ink sac

    squid

    13

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  • Sharks are cartilaginous fi sh. Their skeletons are not made of bones, but of a rubberlike material called cartilage. Sharks have a large liver fi lled with oil. Because oil is lighter than water, the oil keeps the shark from sinking. Sharks fi ns also keep them fl oating. Two pectoral, or side, fi ns act like airplane wings. A powerful tail acts like an engine. Together, they provide lift that keeps the shark from sinking. The only problem is that this only works when sharks are swimming. So, they have to swim constantlyeven when they are sleeping!

    Spinner Shark

    Sharks have several rows of teeth. When a tooth in the front falls out, one from the row behind it takes its place.

    The spinner shark is a fast-moving shark that often leaps right out of the water. It charges into schools, or groups, of fi sh and spins very quickly, snapping its mouth open and closed to catch food.

    liver

    14

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    The largest known shark is about forty feet long. The smallest is about fi ve inches. Scientists are not sure how many different kinds of sharks there areperhaps as many as 350.

    Sharks and the other creatures of the sea youve read about may look as strange to us as animals we might see in movies or comic books. But their odd outsides are just the beginning. These creatures are amazing on the inside too!

    spinner shark

    Leopard sharks use their coloring as camoufl age among rocks and coral.

    Most sharks have streamlined bodies that help them move quickly through the water.

    15

    pectoral fi n

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  • 16

    Glossarybivalves invertebrates that have two connected

    shells that can close like a mouth

    cartilage tough, rubberlike material found in animals

    cephalopods invertebrates with soft bodies, large heads, and tentacles

    cnidarians simple invertebrates with tentacles around their mouths

    echinoderms invertebrates that are round and have shells and tube feet

    funnel a body part that some invertebrates use to get around

    mantle a layer of fl esh that covers some invertebrates

    mollusks an invertebrate with a soft body with only one section, often covered with a shell

    propel to move ones self

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    1. What do sea urchins use their tube feet for?

    2. Jellyfi sh are a type of cnidarian. What does this name mean, and why is it a good name for jellyfi sh?

    3. Describe how the chambered nautilus grows.

    4. Many ocean animals have interesting ways of moving around. Write to explain a few of them. Use examples from this book.

    5. Draw Conclusions A giant blue clam and a squid are both mollusks, but only the clam has a shell. Why do you think this is?

    What did you learn?Extended Vocabularybivalvescartilagecephalopodscnidariansechinodermsfunnelmantlemolluskspropel

    Vocabulary

    cell membranecell wallchloroplastcytoplasmnucleusorgansorgan systemstissuesvacuole

    Picture CreditsEvery effort has been made to secure permission and provide appropriate credit for photographic material. The publisher deeply regrets any omission and pledges to correct errors called to its attention in subsequent editions.

    Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd).

    4 Bill Curtsinger/NGS Image Collection; 12 (BL) Andre Seale/Alamy Images.

    Scott Foresman/Dorling Kindersley would also like to thank: 11 (TR) Natural History Museum/DK Images.

    Unless otherwise acknowledged, all photographs are the copyright of Dorling Kindersley, a division of Pearson.

    ISBN: 0-328-13921-1

    Copyright Pearson Education, Inc. All Rights Reserved. Printed in the United States of America. This publication is protected by Copyright, and permission should be obtained from the publisher prior to anyprohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic,mechanical, photocopying, recording, or likewise. For information regarding permission(s), write toPermissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025.

    3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06 05

    13921_01-04_CVR_FSD.indd Cover213921_01-04_CVR_FSD.indd Cover2 5/10/05 1:35:34 PM5/10/05 1:35:34 PM

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