C Main IdeaPlants 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 SkillCompare and Contrast

What are plants?

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

4 LS 2.a

26EXPLAIN

PLANT NAME/FACT PLANT DESCRIPTION

castor bean plant

the most dangerous plant

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.

bristlecone pine

the oldest tree

The world’s oldest tree lives in California’s White Mountains. One bristlecone pine has lived for almost 5,000 years!

bamboo

the fastest-growing plant

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.

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.

Quick Check

Compare and Contrast What

structures do most plants share?

Critical Thinking How does a

plant’s leaves differ from its roots?

Amazing Plants

Which plant is found in California?

Clue: Scan the chart for the word “California.” Find the plant name that matches that description.

Reading Charts

27EXPLAIN

Photosynthesis

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 .

Which gas is made by the plant?

Clue: Follow the arrows pointing out of the plant. Read all labels.

Reading Diagrams

Plants take

in sunlight.

Plants give

off oxygen.

Plants take in

carbon dioxide.

Plants take

in water and

nutrients from

the soil.

28EXPLAIN

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.

Quick Check

Compare and Contrast How are

plants alike? How do they differ?

Critical Thinking What might

happen to a plant that gets

sunlight but no water?

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?

Draw Conclusions Where on a plant does photosynthesis take place? How can you tell?

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).

Plant B

Plant A

stomata

29EXPLAIN

Animals depend on plants for food energy. B

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.

cattle grazing, Big Sur, California

30EXPLAIN

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?

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

A Plants give off oxygen into the air. When you

breathe in air, your body gets the oxygen it needs.

horseback riding, Mackerricher State Park, Mendocino, California

31EXPLAIN

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

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?

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.

32EXPLAIN

-Review Summaries and quizzes online @ www.macmillanmh.com

Plants are living things. Most plants have roots, stems, and leaves. (pp. 26–27)

Green plants carry out photosynthesis to make food energy from sunlight, water, and carbon dioxide. (pp. 28–31)

Plants make up most of the biomass in an environment. (p. 32)

Summarize the Main Idea Think, Talk, and Write

Main Idea How do plants use energy from the Sun?

Vocabulary What is photosynthesis?

Compare and Contrast How are the roles of a plant’s leaves and roots different? How are they alike?

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

Make aStudy Guide Make a layered look book. Use it to summarize what you learned.

Writing Link Health Link

Write an EssaySuppose we lived in a world without plants. Write an essay about what life might be like. Explain why life would be like this.

Plants as MedicineResearch 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.

33EVALUATE