Vocabulary cell chloroplast cytoplasm genus invertebrates nucleus species vertebrates Picture Credits Every effort has been made to secure permission and provide appropriate credit for p
Trang 1Scott Foresman Science 4.1
Nonfi ction Compare and
Contrast
• Labels
• Captions
• Diagrams
• Glossary
Classifying Plants and Animals
ISBN 0-328-13860-6
ì<(sk$m)=bdigaj< +^-Ä-U-Ä-U
Scott Foresman Science 4.1
Nonfi ction Compare and
Contrast
• Labels
• Captions
• Diagrams
• Glossary
Classifying Plants and Animals
ISBN 0-328-13860-6
ì<(sk$m)=bdigaj< +^-Ä-U-Ä-U
Trang 21 Describe how organisms are built from cells.
2 What are the fi ve groups of vertebrates?
3 What are adaptations? Give an example
of one
nonvascular Describe on your own paper how they differ Include details from the book to support your answer
5 Compare and Contrast Think about
crocodiles and alligators How are they similar? How are they different?
What did you learn?
Vocabulary
cell
chloroplast
cytoplasm
genus
invertebrates
nucleus
species
vertebrates
Picture Credits
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Opener: (B) Bryan F Peterson/Corbis, (C) Frans Lanting /Minden Pictures; 4 (BR) Science Photo Library/
Photo Researchers, Inc.; 8 (CR) Mary Ann McDonald/Corbis (CB, CRB) ”Jerry Young/DK Images;
9 (CL, CR, C, C1) Mary Ann McDonald/Corbis, (CLB, CBL, CBR, CRB) ”Jerry Young/DK Images, (CA, CAR, CRA) ”Barry Watts/
DK Images; 13 (CR) Bryan F Peterson/Corbis, (BR) Frans Lanting /Minden Pictures; 18 (BR) Fred Bavendam /Minden Pictures;
19 (T) Ken Lucas/Ardea, (BC) Fred Bavendam/Minden Pictures; 22 Kennan Ward/Corbis.
Unless otherwise acknowledged, all photographs are the copyright © of Dorling Kindersley, a division of Pearson
ISBN: 0-328-13860-6
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,
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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
by Laura Johnson
Trang 3The Building Blocks
of Living Things
Think about the building blocks you played with
when you were younger You started with just one block
If you put a few blocks together, you could build a
house If you put many blocks together, you could build
something complicated, like a castle with towers All
living things—plants and animals—are made of cells
A cell is the smallest unit of a living thing You can
think of cells as building blocks Some living things
are made of just one block, or cell Most plants and
animals are made by putting thousands, millions,
or even billions of cells together
Cells can have many jobs Some cells help a living thing to be healthy Other cells help
it to adapt to its environment
Microscopes make objects appear larger than they really are By looking
at cells under a microscope, scientists can see inside them and learn how they work
blood cell
3
The Parts of a Cell
Cells have different parts, and each part has a
specifi c job to do The nucleus is like the “brain” of
the cell The instructions for the cell’s job are stored
in the nucleus
The cell membrane is a thin covering all around the cell It has two jobs It separates the cell from things around it It also acts as a guard that decides what can come into and go out of the cell
Cytoplasm holds everything a cell needs to carry
out its life processes It is a material similar to jelly that
fi lls the cell The nucleus fl oats in the cytoplasm
Plant cells have the same parts as animal cells—
plus some extras The cell wall is outside of the cell membrane The walls of all the cells help hold up a
plant Chloroplasts are the parts of a cell that trap
energy from sunlight so a plant can make its own food
cell wall
plant cell animal cell
membrane
cytoplasm
chloroplasts
nucleus nucleus
Trang 4From Cells to Organisms
Cells have different shapes, depending on the kinds
of jobs they do For example, nerve cells are very thin
They act like wires that send messages through the
body Nerve cells can be as long as your arm or
as short as the period at the end of this sentence
Cells that look alike and have the same shape do
the same job These cells combine to build tissue
For example, nerve tissue is made of nerve cells
Tissues of the same type combine to form organs
For example, the brain is an organ that is made of
nerve tissue
5
Organs that work together form an organ system Two organs—the brain and the spinal cord—build the central nervous system in your body
An organism is the complete living thing that is made when all the parts are combined
An organism is made of many cells Unlike an organism, a virus is a very tiny particle with similarities
to both living and nonliving things It uses plant and animal cells to make more viruses
brain
central nervous system
Trang 5Sorting Living Things
Into Groups
There are more than a million organisms Who
keeps track of them all? Biologists! In order to identify,
compare, and study all these organisms, biologists use a
classifi cation system Using this system, they place every
kind of organism into a group All the organisms in a
group have common characteristics
Biologists would ask questions like these to help them
decide if a shark and a dolphin belong in the same group
Do sharks and dolphins have one cell or many cells?
They have many cells That is a common characteristic,
so they belong in the same group
Where do sharks and dolphins live? They live in the
ocean That is another common characteristic, so they
still belong in the same group
How do sharks and dolphins get oxygen? Sharks get
oxygen from the water Dolphins get oxygen from the
air That is a different characteristic, so they belong in
different groups
7
Kingdoms—The Largest Group
Kingdoms are the largest groups in the classifi cation system Many scientists divide organisms into six kingdoms The kingdom that
an organism belongs to depends mostly on how many cells it has, what cell parts it has, where it lives, and how it gets its food
their own food
and other cell places on land some make
and other cell parts
organs, systems
The Six Kingdoms of Living Things
Trang 6Dividing the Kingdoms
Sorting living things into six kingdoms is only the
beginning! Next, scientists divide the members of each
kingdom into smaller and smaller groups They use
organisms’ features to decide which organisms are in
each group After kingdoms, the groups are divisions,
classes, orders, and families The last two groups are
genus and species Scientists use these last groups to
name animals A genus is a group of animals that are
similar in many ways For example, a dog and a wolf are
members of the same genus Their genus is Canis The
genus group is divided one more time into groups of
species A species is a group of animals whose members
can reproduce The species name often describes where
the animal lives or what color it is
The fi rst part of an animal’s scientifi c
name is the genus The second part is the
species So, although you might name
your pet dog Max, his
scientifi c name would
be Canis familiaris.
FAMILY GENUS
SPECIES
9
KINGDOM DIVISION
CLASS ORDER
How Living Things Are Classifi ed
At the right of the chart is the kingdom, the largest group to which your family dog belongs
The groups get smaller and smaller, and more and more specifi c, until the fi nal two
groups, which form the animal’s scientifi c name.
Trang 7How Scientists
Classify Plants
To sort plants into groups, scientists look at two main
characteristics One is the way that a plant transports
water and nutrients The other is how a plant reproduces
Moving Water and Food
Some plants, called vascular plants, have parts that
look like tubes Water and nutrients from the soil
move up and down these tubes to the roots, stems, and
leaves Vascular plants are all around you You may have
stepped on some this morning, if you walked on grass
If you had celery with your lunch, you ate one! The
tissue that makes up the tubes supports a plant’s stems
and leaves Because of this, vascular plants can grow to
be very tall
moss
11
Reproduction
The second way that scientists classify plants is by how they reproduce, or make new plants
One group reproduces by making seeds A seed is a structure with
a protective covering Inside the seed is a young plant In plants with
fl owers, the seeds are in the fl owers
Conifers are plants that make seeds but do not have fl owers In conifers, the seeds are in the cones
Some plants have no seeds at all They use spores to reproduce A spore is a single cell surrounded by a cell wall It can grow into a new plant if it falls on a place where
it can get the water and food it needs Ferns and mosses have spores
Plants without these tubes are called nonvascular plants These plants pass water and nutrients through cell walls, from one cell to the next This process is very slow, so nonvascular plants usually grow close to the ground That way, water and nutrients do not have to travel so far Some nonvascular plants are mosses, lichen, and algae
seed
Trang 8How Scientists
Classify Animals
The animal kingdom is divided into two main
groups One group is vertebrates, or animals with
a backbone The other group is invertebrates, or
animals without a backbone
Vertebrates
Scientists have divided vertebrates into fi ve smaller
groups This chart shows the characteristics that are
true for most of the vertebrates in each group
13
Reptiles
Let’s take a closer look at one group of vertebrates—
reptiles Reptiles include lizards, snakes, turtles, crocodiles, and alligators These animals live in the water and on land As you can see from the chart, reptiles breathe air with their lungs Many people are very surprised when they touch a reptile for the fi rst time
They expect them to be wet and slimy, but they have dry skin covered with scales
People often confuse crocodiles and alligators because the bodies of these reptiles are similar in many ways An easy way to tell them apart is to look at their mouths You can see a crocodile’s teeth when its mouth
is shut, but you cannot see an alligator’s teeth in that position
alligator
crocodile
Trang 9The Life Cycle of a Reptile
Sea turtles spend most of their time underwater,
where they swim, sleep, and eat Like all reptiles,
they have to come to the surface to breathe air
with their lungs If they are swimming, they
need to come up for air about every fi ve or ten
minutes However, if they are asleep, they can stay
underwater for hours Male sea turtles rarely come
on land, but female sea turtles come on land about
six times each nesting year to lay their eggs
A female sea turtle lays her eggs on land.
Baby turtles hatch from the
eggs between forty-fi ve and
seventy days later, and they
make their way to water.
15
Scientists are not sure how old female sea turtles are when they nest for the fi rst time But they do know that they swim back to the same area where they were hatched
as babies—even if that place is miles and miles away
The turtles grow to
be adults who will reproduce.
Trang 10Animals Without
A Backbone
Animals without a backbone are called
invertebrates You might be surprised to learn that
most animals in the world are invertebrates
Arthropods are the largest group of invertebrates
This group includes ticks, spiders, bees, shrimp,
scorpions, and centipedes At fi rst, these animals seem
very different because some swim, some fl y, and some
crawl However, they have two common characteristics
that cause scientists to group them together The
fi rst characteristic is that all arthropods have legs
and a body that are divided into sections The
second is that all arthropods are covered with
a lightweight, hard skin that protects them
This hard skin is called an exoskeleton
centipede bee
17
The second largest group of invertebrates are mollusks This group includes scallops, oysters, squid, and snails Mollusks have soft bodies Some have a hard shell and some don’t Most mollusks live in water, but some live on land in damp places Most mollusks are only a few inches long,
but a few kinds are huge!
Giant clams, for example, can grow to more than four feet long and weigh more than
fi ve hundred pounds!
scallop
squid
Trang 11The Life Cycle
Of a Mollusk
When octopuses are ready to mate, the
male fertilizes the female’s eggs The female
attaches the fertilized eggs to a rock or places
them in a hole Over the course of several days,
a female may lay more than 100,000 eggs! If
the female has laid her eggs in a hole, she will
often seal up the hole to protect the eggs
and ensure that they are not harmed
Females guard the eggs constantly
Depending on temperature, the eggs
hatch anytime between four weeks
and seven months later A short
time after the baby octopuses
emerge from their eggs, the
female octopus dies
When the baby octopuses
emerge from their eggs, they
fl oat to the top of the water
They stay there until they
grow larger and can return
to the bottom of their
water habitat
eggs
19
baby octopus
adult octopus
Trang 12Animal Adaptations
Adaptations are physical features or behaviors
passed on from parents Adaptations help animals get
food, protect themselves, move, and reproduce Animals
with the best adaptations have a better chance at getting
the resources they need, so they have a better chance
of reproducing
Adaptations That
Help and Protect
Many animals have physical adaptations that help
them move Did you know that birds have hollow bones
to make them lighter? Did you know that fi sh have bags
of air in them that help them fl oat? Or that fl amingoes
have long necks so they can submerge their heads in
water and fi nd food in the muddy bottom? What about
snails? They have a fl at foot that oozes a sticky liquid
They move by sliding along paths of their own slime
Shapes and colors can provide protection by making
animals nearly invisible When the long, thin razor
fi sh holds itself straight up and down in the water,
it looks like a piece of fl oating grass
Features such as claws, tusks, and horns protect some animals
21
Chemicals are another kind of adaptation Some chemicals give animals a nasty smell or taste so other animals won’t eat them Others poison their victims
An octopus can use its sharp teeth to drill a hole in a clamshell It then injects poison through the hole After the clam is poisoned, its shell can be opened easily
sharp teeth