What are plants?
C Main Idea
4 LS 2.a
Plants use the Sun’s
energy to make food
energy through a process
called photosynthesis.
C Vocabulary
photosynthesis , p. 28
solar energy , p. 28
environment , p. 32
biomass , p. 32
-Glossary
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C Reading Skill
Compare and Contrast
2WTTS`S\b
/ZWYS
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Plants are living things.
They do much more than just
add beauty to our world.
Plants give us the food we eat
and some of the clothes we
wear. They even give off a gas
that we breathe, called oxygen
(OK•suh•juhn). Without plants,
Earth would be an empty
place. With plants, our planet
is bursting with life.
Plants come in all sizes,
shapes, and colors. Some are
so small you can barely see
them. Others can be as tall
as skyscrapers. The giant
California redwoods are the
tallest living things on Earth.
Some are 112 meters (367 feet)
tall. That is taller than the
Statue of Liberty!
D How long does it take a tree to
grow this tall? Some redwood
trees are over 2,000 years old!
This pinecone is from
a redwood tree. B
26
EXPLAIN
Amazing Plants
PLANT NAME/FACT
PLANT
castor bean plant
the most
dangerous plant
bristlecone pine
the oldest tree
bamboo
the fastestgrowing plant
DESCRIPTION
Some plants are harmful
to people, such as
poison ivy. But the
deadliest plant of all is
the castor bean plant.
Animals that live near
this plant know to avoid
its poisonous leaves.
The world’s oldest
tree lives in California’s
White Mountains.
One bristlecone pine
has lived for almost
5,000 years!
In some places, tropical
bamboo plants grow
about 4 meters (13
feet) a week. That’s a
little more than two
centimeters an hour!
Bamboo is the world’s
fastest-growing plant.
Reading Charts
In all, there are about 400,000
different kinds of plants. Each one
is different. Yet most plants share
some basic parts. Roots anchor the
plant to the ground. They also take
in water and nutrients from the
soil. Stems hold the plant upright.
They move water and nutrients
throughout the plant. Leaves
connect to the stem and collect light
from the Sun.
Which plant is found in California?
Clue: Scan the chart for the word
“California.” Find the plant name
that matches that description.
Quick Check
Compare and Contrast What
structures do most plants share?
Critical Thinking How does a
plant’s leaves differ from its roots?
27
EXPLAIN
How do plants get energy?
Although plants differ in their shapes and sizes, all
plants are alike in one way. They make their own food in
a process called photosynthesis (foh•toh•SIN•thuh•suhs).
All organisms, or living things, need energy to grow,
stay healthy, and reproduce. Reproduce means to
make more of one’s own kind. Plants get the energy
they need from the food they make.
During photosynthesis, plants take in sunlight,
water, and a gas in the air called carbon dioxide.
Plants use these things to make sugar, which is a plant’s
source of food and energy.
Getting Sunlight
Plants have a material
called chlorophyll
(KLAWR•uh•fil) that helps
them take in sunlight.
Chlorophyll is the
material that gives plants
their green color. With
the help of chlorophyll,
plants take in energy
from the Sun and use it
to produce sugar. Energy
from the Sun is called
solar energy .
Reading Diagrams
Photosynthesis
Plants take
in sunlight.
Plants give
off oxygen.
Plants take in
carbon dioxide.
Which gas is made by the plant?
Clue: Follow the arrows pointing
out of the plant. Read all labels.
28
EXPLAIN
Plants take
in water and
nutrients from
the soil.
Getting Water and
Carbon Dioxide
Getting water is easy for some
plants. For example, moss leaves
soak up water straight from the
ground. In other plants, such as
oak trees, water has to travel a long
distance to get from the plant’s roots
to its leaves. Most large plants have
a system of tubes throughout the
plant. These tubes carry water and
nutrients from the bottom of the
plant to the top.
Carbon dioxide is part of the
air all around us. Plants take in
carbon dioxide through tiny holes
on the bottom of their leaves.
These tiny holes are called stomata
(STOH•muh•tuh).
stomata
Photosynthesis
Label two identical plants “Plant
A” and “Plant B.” Wrap each
leaf of Plant A with aluminum
foil. Keep the leaves of Plant B
uncovered. Put the plants on a
sunny windowsill. Make sure each
plant gets the same amount of
sunlight and water.
Plant B
Plant A
Predict What do you think will
happen to each plant?
Observe Uncover Plant A
after four days. Record your
observations about each plant in
a chart.
Infer Why do Plant A and Plant
B differ after four days?
Quick Check
Compare and Contrast How are
Draw Conclusions Where on a
plant does photosynthesis take
place? How can you tell?
plants alike? How do they differ?
Critical Thinking What might
happen to a plant that gets
sunlight but no water?
29
EXPLAIN
Why are plants
important?
Plants need photosynthesis to
survive and grow. Did you know
that you need photosynthesis too? In
fact, most animals depend on plants
making their own food. Why?
Animals cannot make their own
food the way plants can. Instead
they must eat other organisms to
get the energy they need. Plants
provide the energy that travels from
one organism to another. Plants
capture energy from the Sun to
make their own food. They use most
of their food energy as they grow
and reproduce. They also store some
energy in their roots, stems, leaves,
and other structures. When an
animal, such as a grasshopper, eats
a plant, stored energy passes from
the plant to the animal. The animal
uses most of this energy to grow
and reproduce. It also stores some
energy. When an animal, such as a
bird, eats the grasshopper, stored
energy passes to the bird. In this
way, most animals depend on plants
for energy.
Animals depend on plants for food energy. B
cattle grazing, Big Sur, California
30
EXPLAIN
horseback riding, Mackerricher State Park, Mendocino, California
A Plants give off oxygen into the air. When you
breathe in air, your body gets the oxygen it needs.
In addition to providing animals
with energy, plants also provide
animals with the oxygen they
need. Most animals cannot survive
without oxygen for more than a
few minutes. They need oxygen to
carry out life processes. Most of
the oxygen we breathe comes from
plants and plant like living things
that make their own food.
Plantlike living things in the ocean,
such as this kelp, produce much of
the oxygen you breathe. B
Quick Check
Compare and Contrast
How does the way plants get
energy differ from the way
animals get energy?
Critical Thinking Would animals
be able to live without plants?
Why or why not?
31
EXPLAIN
A Compare the number of plants to the number of animals you see in this picture.
Plants make up most of the biomass in this rain-forest environment.
Where do plants grow?
Plants can be found all over
Earth. They live in a variety of
environments from oceans to deserts.
An environment is everything that
surrounds a living thing. Plants live
in any environment where they can
get water, carbon dioxide, sunlight,
and nutrients.
Plants make up most of the
biomass in an environment. Biomass
is a measure of the amount of living
things in an environment. There are
more plants in most environments
32
EXPLAIN
than any other living thing. Plants
are the main source of matter and
energy in an environment. The
animals in an environment use
plants as a source of food and energy.
Quick Check
Compare and Contrast
How does the number of plants in
an environment compare to the
number of animals?
Critical Thinking How would an
environment’s biomass change
if plants could not carry out
photosynthesis?
Summarize the Main Idea
Plants are living things.
Most plants have roots,
stems, and leaves.
Think, Talk, and Write
Main Idea How do plants use energy
from the Sun?
(pp. 26–27)
Vocabulary What is photosynthesis?
Green plants carry
out photosynthesis to
make food energy from
sunlight, water, and
carbon dioxide.
Compare and Contrast How are the
roles of a plant’s leaves and roots
different? How are they alike?
2WTTS`S\b
/ZWYS
2WTTS`S\b
(pp. 28–31)
Plants make up most
of the biomass in an
environment.
(p. 32)
Make a
Study Guide
Make a layered
look book. Use it
to summarize what
you learned.
Critical Thinking Suppose you were
starting a space colony on a planet
with no oxygen. Why would it be a
good idea to bring green plants
with you?
Test Practice A plant uses all of the
following to carry out photosynthesis
EXCEPT
A
sunlight
B oxygen gas
C carbon dioxide gas
D water
Writing Link
Write an Essay
Suppose we lived in a world without
plants. Write an essay about what
life might be like. Explain why life
would be like this.
Health Link
Plants as Medicine
Research plants that are used as
herbs and medicines. Make a chart to
list what the herb or medicine is used
for. List the plant that it comes from.
-Review Summaries and quizzes online @ www.macmillanmh.com
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EVALUATE