4th Grade Assessment – Unit 2: RI.4.1, RI.4.2, RI.4.4, RI.4.8
Justice February 1, 2015
Directions : Read this story. Then answer questions 1 through 6.
When Animals Snoozzzzzze
by Elizabeth Schleichert
1 Cat nap, anyone? Big cats are big sleepers. They may doze 12 to 20 hours a day, and in all kinds of places. Leopards sprawl out on branches. Lions and tigers doze every which way on the ground. But cats aren’t the only animals to kick back and catch some zzz’s! The animal world is filled with sleepyheads.
SNOOZING BASICS
2 But wait! What exactly is sleep? Here’s how many scientists define it: Sleep is a period of rest when an animal is less aware of its surroundings. The animal’s breathing and heartbeat slow down. And its brain waves show a pattern that is different from when the animal is awake.
3 Why do animals sleep? Many experts say sleep brings animals back to peak performance. It restores their bodies and gives them new energy to go about their normal activities. It’s kind of like recharging a cell phone.
CHILL-OUT ARTISTS
4 Bet you’re wondering if all animals sleep. Mammals and birds do, for sure. (They may also dream.) But what about other animals—reptiles, fish, amphibians, and insects, for instance? It’s not so easy to tell what’s going on with them, and experts disagree about whether they sleep.
5 Still some of these animals often look as if they’re sleeping. It’s just that their brain waves don’t show the usual sleep patterns. Who knows? Maybe they’re just having a slightly different kind of sleep.
WHATEVER WORKS!
6 Sleeping animals doze in different ways. Take elephants. Like you, they lie down at night. But they don’t always snooze straight through. They may rise and feed a bit, then settle back down again—averaging about five hours of sleep a night. During the day, the elephants in a herd nod off now and then. When the calves lie down to nap, the adults often gather around them in a protective circle.
7 Animals that are active at night often sleep during the day. Fruit bats in Africa, for example, roost (rest or sleep) in the daylight. They crowd together in trees. Here, thousands of them hang upside down by their rear feet, which automatically tighten and get a grip so the bats don’t fall.
NORTHERN NAPS
8 Polar bears nap when there’s nothing better to do, especially after big meals. In summer, they may flop down on ice or snow—not just to sleep, but also to cool off. With its super-warm coat, a bear can easily overheat. So it has to chill out!
9 Other animals living in snowy places have the opposite problem: how to stay warm while sleeping! Foxes curl up and use their tails as scarves to help keep the cold off.
FISHY TRICKS
10 Fish brain waves may never show sleep patterns, but many fish seem to do some serious resting. The parrotfish, for example, squeezes itself into a rocky crevice at night and puts up its very own “tent.” The tent is actually a bubble made of clear mucus. The mucus oozes from the fish’s mouth, forming a protective sac. The mucus may keep tiny pests away, as well as help hide the fish’s scent from eels and other predators. The bubble may also act as an alarm. If a predator touches it, the parrotfish “wakes up,” bursts out, and swims off.
SPLISH, SPLASH, YAWN
11 Water is where you’ll often find hippopotamuses sleeping, too. They loll their days away on river banks or in shallow lakes, using each other as puffy pillows. A hippo can doze nearly totally submerged but still be on the alert. That’s because its eyes, ears, and nostrils are on top of its head. But don’t be fooled by a sleeping hippo’s lazy, lumpy looks. If alarmed, it can awaken and charge a would-be attacker in an instant.
SLEEP ON THE FLY?
12 An albatross spends most of its life gliding on wind currents at sea. How does it find time to sleep? Experts aren’t sure. The bird may alight on the water’s surface and sleep there. Or, while flying, it may close down half of its brain—keeping the other half awake—for several seconds at a time.
PAUSE THAT REFRESHES
13 Many grazing animals live out in the open. They have to be on guard, ready to run from danger. So they often snatch short naps. Horses, for instance, sleep for only a few minutes at a time, often while standing. A horse’s legs can “lock” in place, so the animal can sleep without the risk of falling down!
14 So now you know what’s up when animals settle down!