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How Water Climbs a Tall Tree

8th grade nonfiction passage about how trees move water: 295 words, six questions, an answer key and vocabulary.

8th grade nonfiction how trees move water 295 words

How Water Climbs a Tall Tree

A tall tree lifts water from its roots to leaves many stories above the ground, and it does so without a heart or a pump. The tree gets help from the sun and from some remarkable properties of water.

Inside the trunk, narrow tubes called xylem run from the roots to the leaves, and water moves up through them in a long, unbroken column that is driven mainly by evaporation. Leaves have tiny openings called stomata, and when sunlight warms a leaf, water escapes through them as vapor, a process called transpiration.

As each water molecule leaves, it pulls on the one behind it, because water molecules stick to one another, a stickiness called cohesion. Water also clings to the walls of the narrow tubes, which helps keep the column from breaking, and the pull travels all the way down the tube and draws more water in through the roots.

Think of drinking through a straw: pulling at the top moves the liquid at the bottom. A tree's leaves do the pulling, and the sun supplies the energy. Only a small part of the water that travels up the trunk is used to build the tree. Much of it is released into the air, which is why trees in hot, dry weather can struggle if the soil also runs dry.

Scientists who study trees have measured this pull directly, and they find that the water inside the xylem is often under tension, like a stretched rope. This explains why a tree does not need a strong push from below to lift its water. The roots are not pumping. They simply supply water to the column as it is drawn upward, which is a very different system from the one that moves blood through an animal.

Questions

  1. What are the narrow tubes inside a tree trunk called? in the text

  2. What are stomata? in the text

  3. What is the main driver that moves water up the tree? in the text

  4. What is cohesion? in the text

  5. How is a tree like a person drinking through a straw? think about it

  6. Why might a tree struggle in hot, dry weather? think about it

Words to know

xylem
the tubes in a plant that carry water upward
evaporation
the change of a liquid into a vapor or gas
stomata
tiny openings in leaves that let water vapor and air pass
transpiration
the loss of water vapor from a plant's leaves
cohesion
the way molecules of the same kind stick together
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One passage, three levels

The same topic and facts written three ways, so a mixed class can read and talk about one text. Each group’s sheet shows only a shape; the key says which is which.

● Easier · 259 words · Flesch-Kincaid grade 3

A tall tree lifts water from its roots to leaves high above the ground. It has no heart and no pump. It gets help from the sun and from how water behaves.

Inside the trunk, thin tubes called xylem run from the roots to the leaves. Water moves up them in a long chain. The main push is evaporation. Leaves have tiny holes called stomata. When the sun warms a leaf, water escapes through the holes as vapor. This is called transpiration.

When one water molecule leaves, it pulls on the next one. Water molecules stick to one another. This sticking is called cohesion. Water also clings to the walls of the tubes. This helps keep the chain from breaking. The pull goes all the way down and draws more water in through the roots.

It is like drinking through a straw. You pull at the top, and the liquid at the bottom moves. The leaves do the pulling, and the sun gives the energy. Only a small part of the water is used to build the tree. Most is let out into the air. So trees can struggle in hot, dry weather when the soil dries out too.

Scientists have measured this pull. They find that the water in the xylem is often under tension, like a stretched rope. So a tree does not need a strong push from below. The roots are not pumping. They just supply water to the chain as it is drawn up. This is very different from how blood moves through an animal.

▲ This passage · 295 words · Flesch-Kincaid grade 8.5

A tall tree lifts water from its roots to leaves many stories above the ground, and it does so without a heart or a pump. The tree gets help from the sun and from some remarkable properties of water.

Inside the trunk, narrow tubes called xylem run from the roots to the leaves, and water moves up through them in a long, unbroken column that is driven mainly by evaporation. Leaves have tiny openings called stomata, and when sunlight warms a leaf, water escapes through them as vapor, a process called transpiration.

As each water molecule leaves, it pulls on the one behind it, because water molecules stick to one another, a stickiness called cohesion. Water also clings to the walls of the narrow tubes, which helps keep the column from breaking, and the pull travels all the way down the tube and draws more water in through the roots.

Think of drinking through a straw: pulling at the top moves the liquid at the bottom. A tree's leaves do the pulling, and the sun supplies the energy. Only a small part of the water that travels up the trunk is used to build the tree. Much of it is released into the air, which is why trees in hot, dry weather can struggle if the soil also runs dry.

Scientists who study trees have measured this pull directly, and they find that the water inside the xylem is often under tension, like a stretched rope. This explains why a tree does not need a strong push from below to lift its water. The roots are not pumping. They simply supply water to the column as it is drawn upward, which is a very different system from the one that moves blood through an animal.

■ Harder · 325 words · Flesch-Kincaid grade 9.3

A tall tree lifts water from its roots all the way to leaves many stories above the ground, and remarkably, it accomplishes this without a heart or a pump of any kind. The tree relies instead on the energy of the sun and on some extraordinary properties of water.

Inside the trunk, narrow tubes called xylem extend from the roots to the leaves, and water travels upward through them in a long, unbroken column, and the principal driving force behind this upward journey is evaporation. Leaves are dotted with tiny openings called stomata, and when sunlight warms a leaf, water escapes through those openings as vapor, a process that is known as transpiration.

As each water molecule departs, it tugs on the molecule behind it, because water molecules are attracted to one another. This attraction is called cohesion. Water also clings to the walls of the narrow tubes, which helps prevent the column from breaking. The pull travels all the way down the tube and draws additional water in through the roots.

Consider what happens when you drink through a straw: pulling at the top moves the liquid at the bottom. A tree's leaves do the pulling, and the sun supplies the energy. Only a small portion of the water that travels up the trunk is actually used to build the tree. Much of it is released into the air, which is why trees can struggle in hot, dry weather if the soil also runs dry.

Scientists who study trees have measured this pull directly, and they find that the water inside the xylem is often under tension, like a stretched rope. This explains why a tree does not require a strong push from below in order to lift its water. The roots are not pumping at all. They simply supply water to the column as it is drawn upward, which is a very different system from the one that moves blood through an animal.

Download as one PDF

How to use it

  1. Press Read it big (or B) to put the text on the projector, or Full screen (F) to fill the whole screen.
  2. Ask the questions one at a time and use Show answer when the class has decided. A shows or hides every answer.
  3. Print student copy for the class, or Print with answers for yourself.

Ideas for class

  • Before reading, put xylem, evaporation, stomata, transpiration and cohesion on the board with their meanings from the Words to know section and have students predict what the text will be about.
  • Read it aloud once while students follow along, then have them reread it alone or with a partner. At a calm 100 words a minute it takes about 3 minutes to read aloud.
  • Use the Read it big button (or B) to put the text on the projector, and Show answer on one question at a time so the class commits to an answer first.
  • Question 5 asks the reader to infer. Ask students to point to the words in the passage that led them to their answer.
  • Ask students to write one question the passage did not answer, then look for the answer in a book or on a classroom screen.
  • Print the student copy for independent work and keep the answer-key copy for yourself.

Related

Questions

What reading level is "How Water Climbs a Tall Tree"?

It was written for 8th grade. It has 295 words and works out to a Flesch-Kincaid grade level of about 8.5. That is a formula's estimate from sentence length and syllables, and it is not a Lexile or a guided reading level, so check it against your students.

What do the questions ask?

There are six. 4 ask for something the text says directly and 2 ask the reader to work something out from clues. Each has an answer in the key, and the answers are written as a teacher would accept them, not as the only possible wording.

How long does it take to read?

About 3 minutes read aloud at 100 words a minute. For a one-minute fluency check, paste it into the fluency timer and use the word count.

Can I print it?

Yes. Print student copy gives the passage, the questions with lines to write on, and the word meanings. Print with answers gives the same page with the answers filled in. Both are made in your browser.

Is this passage from a published book?

No. It was written for Peabody Teach, so there is no book to buy and no login to read it.

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