Image showing a variety of creatures
Natural Visions/Alamy Stock Photo (chlorohydra); Dennis Kunkel Microscopy/Science Source (hydra); Barroa Artwork/Shutterstock.com (middle tardigrade); Adisha Pramod/Alamy Stock Photo (jellyfish); iStockPhoto/Getty Images (all other images)
Short Read,

What Do These Creatures Have in Common?

They have a superpower: immortality.

By Allison Friedman
From the April 2023 Issue
Complexity Factors
  • Purpose
    This article explores how several creatures avoid old age—and how that could help humans.
  • Structure
    The text is informational.
  • Language Conventionality and Clarity
    Vocabulary: some challenging vocabulary (e.g., genetic, microscopic, specialized) Conventionality: The language is mostly conventional.
Lexile: 940L
Featured Skill: Constructed Response,
Common Core Standards
  • Anchor Standards
    R.1, R.2, R.3, R.4, R.5, W.2, SL.1, L.4, L.5, L.6
  • Grade 6
    RI.6.1, RI.6.2, RI.6.3, RI.6.4, RI.6.5, W.6.2, L.6.4, L.6.5, L.6.6
  • Grade 7
    RI.7.1, RI.7.2, RI.7.3, RI.7.4, W.7.2, L.7.4, L.7.5, L.7.6
  • Grade 8
    RI.8.1, RI.8.2, RI.8.3, RI.8.4, RI.8.5, W.8.2, L.8.4, L.8.5, L.8.6
TEKS Standards
  • Grades 6, 7, 8
    1d, 2a, 2b, 3a, 4a, 5a, 5b, 5c, 5d, 5e, 5f, 5g, 5h, 5i, 6a, 6b, 6c, 6d, 6e, 6f, 6g, 6h, 6i, 8d, 8f, 9a, 9b, 9c, 9d, 9e, 9f, 11b, 11c

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Barroa Artwork/Shutterstock.com

The mythological hydra has a special power: Cut off one of its heads, and two will grow in its place.

A tiny tube-shaped creature floats through the water. A cluster of skinny tentacles wave around the creature’s head, ready to shove prey into its waiting mouth. 

But before it gets the chance . . .

Snap! 

A passing fish chomps off the creature’s head. 

Game over, right?

Not so fast. Over the next few days, a brand-new head and tentacles sprout from the creature’s body. Then it continues hunting for food as if nothing had happened.

This strange and amazing creature is called a hydra. Named after the sea monster from Greek mythology, hydras live in freshwater and are generally about an inch long. Their extraordinary ability to regrow body parts allows them to survive all sorts of injuries and diseases. It also allows them—perhaps most astoundingly—to avoid old age.

Today scientists are studying the hydra and other animals with similar powers with one big question in mind: Can they teach us how to live forever?

Death-Defying Powers

Natural Visions/Alamy Stock Photo 

The hydra

All living things, including humans, are made up of microscopic building blocks called cells. The human body contains trillions of cells, and they have all sorts of functions. Cells give our bodies their structure, for example, and convert nutrients from food into energy. 

Most cells have specialized jobs. There are blood cells that carry oxygen throughout our bodies, nerve cells that transmit information between our brains and our limbs, and skin cells that form our protective outer layer.

As we (and most other creatures) age, our cells function less and less well. The result? Skin droops. Muscles weaken. Memories falter. 

But the hydra doesn’t experience this aging process. Its body consists mostly of special cells called stem cells, which constantly renew themselves. If the hydra loses a body part—like, say, its head—the stem cells can grow into whatever the hydra needs. This has led some researchers to speculate that, under the right conditions, the hydra could live forever—or at least a very, very long time. 

The hydra isn’t the only organism on Earth with death-defying powers. The so-called immortal jellyfish can reboot its cells to a younger state, essentially transforming from an adult back into a baby. Some turtles show almost no signs of aging because their cells repair themselves. A microscopic animal called the tardigrade is thought to be nearly indestructible because it can survive for decades in a sleeplike state, protecting its cells with a coating that resembles glass.

Unlocking Secrets 

iStockPhoto/Getty Images

The tardigrade

Scientists are working hard to unlock the secrets of these fascinating creatures. In the cases of the hydra and the immortal jellyfish, researchers have identified genetic features that may be behind the creatures’ ability to regenerate.   

Could these discoveries—and others like them—help humans become immortal too? 

The answer, for now, is probably not. After all, the human body is extremely complex. But these discoveries might help us treat age-related diseases, lengthening our life spans. Doctors may one day be able to grow new heart cells for people who have suffered heart attacks, for example, or new brain cells for patients who have suffered strokes.

So while “forever” might remain out of reach, we humans may one day live long enough to meet our great-great-great grandchildren. Unless a giant fish bites off our heads, in which case we are definitely goners.

Short Write: What might be gained by studying nearly indestructible creatures?

Directions: In your own document, answer the question above in a well-organized paragraph. Be sure to use at least two pieces of text evidence to support your answer.

This article was originally published in the April 2023 issue.

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Activities (5)
Core Skills Workout
  • The Core Skills Workout is a series of skill-based activities that will help your students "bulk up" in the comprehension skills they need most to become strong, analytical readers. The Core Skills Workout comes with every issue and will support your reading program no matter what your scope and sequence.
Reference
Skill-Building Activities
Skills Activities
Quizzes (1)
Answer Key (1)
Audio ()
Activities (5)
Core Skills Workout
  • The Core Skills Workout is a series of skill-based activities that will help your students "bulk up" in the comprehension skills they need most to become strong, analytical readers. The Core Skills Workout comes with every issue and will support your reading program no matter what your scope and sequence.
Reference
Skill-Building Activities
Skills Activities
Quizzes (1)
Answer Key (1)
Step-by-Step Lesson Plan

Close Reading, Critical Thinking, Skill Building

Download the Lesson Plan

1. PREPARING TO READ

Project the Words and Definitions handout and preview the vocabulary.

2. READING AND DISCUSSING 

Read the article as a class. Alternatively, you can play the audio version while students follow along in their printed issues.

3. DOING THE ACTIVITY 

Have students work in small groups to complete the activity at the end of the article. They will write a claim, find a piece of text evidence, and explain why that evidence supports their claim.

4. WRITING 

  • To go deeper, use the Short Write Kit. First, project the How to Answer a Constructed-Response Question handout and review it as a class. Then have students work on their own or in groups to complete the self-guided writing activity Constructing a Response.
  • Have students use their completed activities to craft their own constructed responses.
Text-to-Speech