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Tardigrades: Microscopic Superheroes — Reading Comprehension

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Grades

Standards

MS-LS2-1
RI.6.3
RI.7.3
RI.8.8

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Aligned to MS-LS1-1, this passage examines how tardigrade cell structures (TDP proteins, DNA-repair enzymes) allow survival in space, deep sea, and volcanoes. Students analyze cryptobiosis mechanisms, radiation resistance, and temperature tolerance (-272°C to 150°C) through the lens of cellular structure/function relationships.

CONTENT PREVIEW

"First Recorded Image of Tardigrade" by Johann August Ephraim Goeze / Wikimedia Commons.

Tardigrades possess extraordinary cellular adaptations that allow them to defy death in environments lethal to other lifeforms. When faced with extreme dehydration, their cells don’t simply dry out—they undergo cryptobiosis, a state of suspended animation where metabolic activity drops to 0.01% of normal levels.

In this "tun" state, tardigrades replace the water in their cells with special Tardigrade-Specific Disordered Proteins (TDPs). These remarkable molecules form a glass-like matrix that preserves cellular structures intact for decades, preventing the fatal damage that normally occurs when cells lose water.

But their survival toolkit doesn’t stop there. Tardigrade cells produce:

● DNA armor: Unique repair enzymes that instantly fix radiation-shattered DNA strands, allowing survival in space’s intense cosmic rays

● Thermal protectants: Sugar-based molecules that act as cellular antifreeze (-272°c) and heat shields (150°c)

● Pressure-resistant membranes: Reinforced cell walls that withstand 6,000 times atmospheric pressure

These microscopic superheroes have conquered Earth’s most hostile environments:

● Mountain Peaks: Thriving at 6,000m altitudes in the Himalayas where oxygen is scarce and UV radiation intense

● Ocean Depths: Flourishing near hydrothermal vents where pressures reach 1,000+ atmospheres and temperatures swing violently

● Space Vacuum: Surviving unprotected on satellite exteriors during ESA’s 2007 FOTON-M3 mission, enduring complete vacuum, freezing temperatures, and lethal solar radiation

Fun Fact: When NASA exposed tardigrades to space vacuum, 68% survived the ordeal—and some even produced healthy offspring afterward!

What cellular state do tardigrades enter when dehydrated?

PhotosynthesisCryptobiosisMitosisOsmosis

Which protein protects tardigrade cells without water?

HemoglobinTardigrade-specific Disordered Proteins (TDPs)CollagenKeratin

What makes tardigrade cells unique compared to human cells?

They photosynthesizeThey lack DNAThey survive complete dehydrationThey’re the largest known cells

Where have tardigrades NOT been found living?

Deep-sea ventsActive volcanoesHimalayan glaciersOuter space

The term "cryptobiosis" means:

Rapid reproductionTemporary metabolic shutdownGlowing in the darkSwimming in circles

In this passage, "TDPs" refers to: