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Cells, the Building Blocks of Life

7th grade nonfiction passage about life science: 273 words, seven questions, an answer key and vocabulary.

7th grade nonfiction life science 273 words

Cells, the Building Blocks of Life

Look at a leaf, a fingertip, or a drop of pond water through a microscope, and you will see tiny units packed together. These are cells, the smallest units of life. Every living thing is made of one or more cells. A bacterium is a single cell, while a person is made of trillions.

Scientists summarize what they know in the cell theory. All living things are made of cells. The cell is the basic unit of structure and function in living things. And all cells come from other cells that already exist, when one cell divides in two.

Plant and animal cells share the same basic parts. The cell membrane is a thin boundary that controls what enters and leaves. Inside is the cytoplasm, a jelly-like fluid that holds the other parts. The nucleus holds the cell's DNA, the instructions for how the cell works. Small structures called mitochondria release energy from food so that the cell can do its work.

Plant cells have a few extra parts. A stiff cell wall outside the membrane gives a plant cell its shape and strength. Plant cells also contain chloroplasts, where photosynthesis takes place. Chloroplasts hold chlorophyll, the green substance that captures energy from sunlight.

Different cells have different jobs. Nerve cells carry messages. Red blood cells carry oxygen. Muscle cells contract to move the body. Cells with the same job group together into tissues, tissues form organs such as the heart, and organs work together in organ systems.

Whether a living thing has one cell or trillions, its cells are always busy: taking in materials, releasing energy, and getting rid of waste.

Questions

  1. What are the three parts of the cell theory? in the text

  2. What does the cell membrane do? in the text

  3. What does the nucleus hold? in the text

  4. What is the job of the mitochondria? in the text

  5. What are two parts that plant cells have and animal cells do not? in the text

  6. How are tissues, organs, and organ systems related to cells? in the text

  7. Why does the author say a cell is "always busy"? think about it

Words to know

cell theory
the idea that all living things are made of cells, and that all cells come from other cells
membrane
a thin boundary that controls what goes in and out
nucleus
the part of a cell that holds its DNA
mitochondria
small parts of a cell that release energy from food
chloroplasts
parts of plant cells where photosynthesis takes place
tissues
groups of cells that do the same job

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 cell theory, membrane, nucleus, mitochondria, chloroplasts and tissues 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 7 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 "Cells, the Building Blocks of Life"?

It was written for 7th grade. It has 273 words and works out to a Flesch-Kincaid grade level of about 6.1. 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 seven. 6 ask for something the text says directly and 1 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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