How Life Survives the Deep Sea's Extremes

Science · Animals of the World · ages 12-13

Name ______________________ Date ____________

A tardigrade has been dried out in cryptobiosis for years. What can wake it up?
- A loud noise nearby
- Sunlight warming its skin
- Water returning to its home
A tardigrade's mossy puddle dries up completely in a hot summer. What will the tardigrade most likely do?
- Crawl away at night to find a new puddle
- Pull in its legs and dry out into a still ball, waiting for water to return
- Grow a thick shell and sleep like a bear
What does an enzyme do inside a cell?
- It stores oxygen for later
- It makes light so the animal can see
- It speeds up chemical reactions
What do Antarctic icefish have in their blood that stops it from freezing?
- Warm body fat
- Antifreeze glycoproteins
- Extra red blood cells
Many surface fish have a gas-filled swim bladder that helps them float. Why would that bladder be a problem 4,000 meters down?
- The cold water would freeze the gas solid
- Salt water would leak in and fill the bladder
- Deep pressure squeezes gas hard, so the bladder would be crushed
Enzymes speed up chemical reactions in cells. Why do deep-sea animals need specially built enzymes?
- Their enzymes must boil water to keep them warm
- Ordinary enzymes would stop working under high pressure, so theirs are built to keep working there
- Their enzymes need to glow in the dark to find food
Surface pressure is 1 atmosphere. At 4,000 meters deep it is about 400 atmospheres. How many times greater is the deep-sea pressure?
Answer: ______________
A wood frog has 45 grams of water in its body. In winter, up to two-thirds of its body water can freeze. How many grams of water is that?
Answer: ______________
Scientists find microbes thriving in a spring that is very hot, very salty, and harsh. Based on the lesson, is this surprising?
- No. Extremophiles like thermophiles and halophiles already thrive in extreme heat and salt
- Yes. Life can only survive where conditions are mild
- Yes. Microbes cannot live in water
The icefish stops ice crystals from growing in its blood. The wood frog lets ice form but protects its cells with glucose. What do both survival tricks have in common?
- Both keep ice from destroying the animal's cells
- Both keep the animal's whole body completely ice-free
- Both only work when the water is above freezing

Answer key

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How Life Survives the Deep Sea's Extremes W1-mt_ot9rcUwBtK-s1

Water returning to its home · A tardigrade can stay in cryptobiosis for years, then revive within hours once water returns.
Pull in its legs and dry out into a still ball, waiting for water to return · When conditions turn deadly, a tardigrade enters cryptobiosis: legs tucked in, almost all its water gone, metabolism nearly stopped. It waits like that until water returns.
It speeds up chemical reactions · Enzymes are molecules that speed up the chemical reactions a cell needs to stay alive.
Antifreeze glycoproteins · These proteins stick to forming ice crystals and stop them from growing bigger.
Deep pressure squeezes gas hard, so the bladder would be crushed · Gas compresses under pressure. A gas-filled bladder at about 400 atmospheres would be squeezed flat.
Ordinary enzymes would stop working under high pressure, so theirs are built to keep working there · High pressure can stop ordinary enzymes, so deep-sea animals have enzymes built to work under that pressure.
400 · 400 atmospheres divided by 1 atmosphere is 400 times greater.
30 · Two-thirds of 45 grams is 30 grams, since one-third of 45 is 15.
No. Extremophiles like thermophiles and halophiles already thrive in extreme heat and salt · Thermophiles thrive in scalding vents and halophiles in super-salty water, so hot, salty conditions suit some life just fine.
Both keep ice from destroying the animal's cells · Each trick protects cells in its own way: the icefish blocks crystal growth, and the frog shields its cells with glucose while ice forms around them.