IELTS Academic
Listening Part 4: How animals sleep (lecture)
Part 4 · Note completion. Read the questions first, then play the recording. The transcript appears after you submit.
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Almost every animal that has been studied carefully shows some form of sleep, but the way animals sleep varies enormously.
Dolphins are a striking example. They rest one half of the brain at a time, while the other half stays awake. This allows them to keep swimming, come up to breathe and watch for predators.
Some birds appear to do something similar, particularly on long flights over the sea, when there is nowhere to land.
Large grazing animals often sleep very little. Giraffes, for instance, take short naps, frequently standing up, which allows them to react quickly if a predator appears.
Why is sleep so universal, given the risks of being unaware of danger? One idea that has received a lot of attention is that sleep helps the brain clear away waste products that build up while we are awake.
Sleep also seems to be important for memory, though that’s a topic for next week.
How animals sleep
Dolphins rest one (1) ___ of the brain at a time.
This lets them keep (2) ___ and watch for danger.
Some birds do the same when flying long (3) ___.
Giraffes sleep for short periods, often (4) ___ up.
Sleep may help the brain remove (5) ___ products.
1.Write ONE WORD AND/OR A NUMBER.
2.Write ONE WORD AND/OR A NUMBER.
3.Write ONE WORD AND/OR A NUMBER.
4.Write ONE WORD AND/OR A NUMBER.
5.Write ONE WORD AND/OR A NUMBER.
6.What will the next lecture be about?
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