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Fast, playful, and clever—dolphins are amazing animals! How do they get the energy to do all their tricks? Do they sleep? Let’s learn all about how dolphins sleep.
◆ Do dolphins sleep?
Yes, dolphins sleep with half of their brain active at all times.
In order to stay close to the surface so they can breathe, dolphins must stay partially (部分地) awake while they sleep. This is called unihemispheric sleep and it lets a dolphin sleep with “one eye open”. Dolphins alternate which side of their brain is asleep and awake every 2 hours. This way, each side gets rest. It also helps dolphins stay watchful for danger.
◆ How do dolphins breathe when sleeping?
Dolphins need to surface (浮出水面) for air even when they’re sleeping.
Dolphins may live in the water, but they’re mammals (哺乳动物), not fish. This means they need to breathe. With one side of its brain being awake at all times, a dolphin is able to surface for air while sleeping. Usually, a dolphin needs to surface for air every 15 to 17 minutes; however, they surface less often when asleep because only one side of their brain is awake.
◆ Where do dolphins sleep?
Dolphins sleep in groups while hovering (盘旋) in the water.
These beautiful animals are social creatures, so we seldom see them alone. Sleeping in a group provides protection. If one dolphin finds danger when sleeping, they will wake up the rest of their family and quickly swim away or plan an attack.
( ) 32. Why does the writer use three positive adjectives in the beginning?
A. To draw pictures of dolphin shows. B. To build an image and attract readers.
C. To express the happiness of dolphins. D. To show the weakness of dolphins.
(
A. Exchange. B. Decide. C. Choose. D. Organize.
(
A. They always sleep without breathing.
B. They always sleep with two eyes open.
C. They can breathe freely underwater.
D. They can stay awake on one side of their brain.
(
A. By telling stories. B. By listing numbers.
C. By giving examples. D. By asking questions.
Fast, playful, and clever—dolphins are amazing animals! How do they get the energy to do all their tricks? Do they sleep? Let’s learn all about how dolphins sleep.
◆ Do dolphins sleep?
Yes, dolphins sleep with half of their brain active at all times.
In order to stay close to the surface so they can breathe, dolphins must stay partially (部分地) awake while they sleep. This is called unihemispheric sleep and it lets a dolphin sleep with “one eye open”. Dolphins alternate which side of their brain is asleep and awake every 2 hours. This way, each side gets rest. It also helps dolphins stay watchful for danger.
◆ How do dolphins breathe when sleeping?
Dolphins need to surface (浮出水面) for air even when they’re sleeping.
Dolphins may live in the water, but they’re mammals (哺乳动物), not fish. This means they need to breathe. With one side of its brain being awake at all times, a dolphin is able to surface for air while sleeping. Usually, a dolphin needs to surface for air every 15 to 17 minutes; however, they surface less often when asleep because only one side of their brain is awake.
◆ Where do dolphins sleep?
Dolphins sleep in groups while hovering (盘旋) in the water.
These beautiful animals are social creatures, so we seldom see them alone. Sleeping in a group provides protection. If one dolphin finds danger when sleeping, they will wake up the rest of their family and quickly swim away or plan an attack.
( ) 32. Why does the writer use three positive adjectives in the beginning?
A. To draw pictures of dolphin shows. B. To build an image and attract readers.
C. To express the happiness of dolphins. D. To show the weakness of dolphins.
(
A
) 33. What does the underlined word “alternate” mean in the passage?A. Exchange. B. Decide. C. Choose. D. Organize.
(
D
) 34. What can we learn about dolphins?A. They always sleep without breathing.
B. They always sleep with two eyes open.
C. They can breathe freely underwater.
D. They can stay awake on one side of their brain.
(
D
) 35. How does the writer develop the passage?A. By telling stories. B. By listing numbers.
C. By giving examples. D. By asking questions.
答案
32. B 33. A 34. D 35. D
