5 2 inside sea creatures (life science)

Genre

Nonfiction

Comprehension Skill

Draw Conclusions

Text Features

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Captions
Labels
Diagrams
Glossary

Science Content

Cells to Systems

Scott Foresman Science 5.2

ISBN 0-328-13921-1

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Vocabulary

Extended Vocabulary

cell membrane
cell wall
chloroplast
cytoplasm
nucleus
organs
organ systems
tissues
vacuole

bivalves
cartilage
cephalopods
cnidarians
echinoderms
funnel
mantle
mollusks
propel

Picture Credits
Every 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 any
prohibited 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 to
Permissions 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

What did you learn?
1. What do sea urchins use their tube feet for?
2. Jellyfish are a type of cnidarian. What does
this name mean, and why is it a good name
for jellyfish?
3. Describe how the chambered nautilus grows.

by Laura Johnson
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 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 flat
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.

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 we’ll look to see
what’s inside sea creatures. These animals may be very
different from you, but you’ll find that they can be
interesting too.

scallops
human skeletal
system

2

3


Introduction

how the box jellyfish
paralyzes its prey

Have you ever seen a jellyfish, a sea urchin, or a

squid? These animals are strange and amazing-looking
on the outside. In this book you’ll learn that these
animals, and a few others, are even more
interesting on the inside!

Jellyfish
Jellyfish are not made of
jelly and they are not fish!
They are 98 percent water.
The rest of them is a jellylike
material stiff enough to support
their body structure. They belong to
jellyfish
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 jellyfish just drift in the water. Others propel
themselves by first 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.

4

Tentacles can
be more than

10 feet in
length.

Inside each
tentacle are
thousands of
nematocysts.

Barbed tubes pierce
the fish’s scales.

The jellyfish releases
its venom into the fish.

5


Scallop

great scallop

Scallops 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 animal’s 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
flapping their shells.

The heart
pumps blood
to the tissues
and gills.

When the shell opens, water flows 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 float in the water.
Around the edge of the mantle
is a row of blue eyes. Although they
can’t 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

Most bivalves don’t swim—
they remain attached to
objects. The scallop’s ability to
swim makes it quite unusual.

Tiny eyes in the
mantle detect
light and dark.

The mantle controls
the flow of water
into the shell.
Gills absorb oxygen
from the water.

6

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

7


Sea Urchin
Sea urchins belong to a group

of animals called echinoderms.
Echinoderms are spiny-skinned
invertebrates that move slowly
across the ocean floor. Sea urchins
have a round body that is divided
into five equal segments. Close-fitting,
bony plates under their skin form a shell. All sea urchins have
a five-fold symmetry.
Most sea urchins have long, movable
This means that their
bodies have five
spikes on their shells. They can push
sections that are all
themselves along flat surfaces with these
the same, like the
spines. Between the spines are rows of
sections of an orange.
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 urchin’s best defense.

Sea urchins eat plants that grow on rocks and on the
ocean floor. A powerful jaw on the underside of their
bodies can scrape up food. Their mouths have five teeth
that can move in different directions.
Sea urchins have no brain. They have a very simple
circulatory system of water-filled channels that flow

through their body.
sea urchin

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

Teeth can move in
different directions.

8

Muscles move
the teeth.

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

9


Chambered Nautilus
Another 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 filled with
When the nautilus
nitrogen and other gases. A narrow tube
retreats into its shell,
a fleshy shield covers
called a siphuncle winds through all the
the entrance.
chambers. Depending on the mixture of
fluids and gases in the
chambers, the nautilus
either rises in the
water or sinks.

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

10

Water is expelled
through the funnel
to provide thrust.

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

Nautilus Fossil

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.

As the nautilus
grows it constructs
new chambers.

The nautilus
lives only in the
outer chamber.

11

Squid
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 squid’s 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 squid’s organs,
including its ink sac. A squid can squirt
ink from this organ to hide itself from
predators. Unlike a nautilus, a squid’s
mantle doesn’t make a hard shell.

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

eye

squid

ink sac

The position of the flexible
funnel controls the direction
of the squid’s travel.

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.
13


Spinner Shark
Sharks are cartilaginous fish. Their skeletons
are not made of bones, but of a rubberlike material
called cartilage. Sharks have a large liver filled with
oil. Because oil is lighter than water, the oil keeps
the shark from sinking. Sharks’ fins also
keep them floating. Two pectoral,

or side, fins 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
constantly—even when they
are sleeping!

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

spinner shark

Leopard sharks use their

Sharks have several rows
of teeth. When a tooth in the
liver
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 fish and spins very quickly, snapping its
mouth open and closed to catch food.

14

pectoral fin

The largest known
coloring as camouflage
shark is about forty feet
among rocks and coral.
long. The smallest is
about five inches. Scientists are not sure how
many different kinds of sharks there are—
perhaps as many as 350.
Sharks and the other creatures of the sea
you’ve 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!

15


Extended Vocabulary

Vocabulary

Glossary

bivalves
cell membrane
cartilage
cell wall
cephalopods
chloroplast

bivalves
invertebrates that have two connected
cnidarians
cytoplasm
shells that can close like a mouth
echinoderms
nucleus
funnel
organs
cartilage
tough, rubberlike material found in animals
mantle
organ systems
mollusks
tissues
cephalopods invertebrates with soft bodies, large heads,
propel
vacuole
and tentacles
cnidarians

funnel

a body part that some invertebrates use to
get around

mantle

a layer of flesh that covers some invertebrates

mollusks

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

Picture Credits
Every 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.

to move one’s self

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 any
prohibited 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 to
Permissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025.

16

1. What do sea urchins use their tube feet for?
2. Jellyfish are a type of cnidarian. What does
this name mean, and why is it a good name
for jellyfish?
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?

simple invertebrates with tentacles around
their mouths

echinoderms invertebrates that are round and have shells
and tube feet

propel

What did you learn?

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