Bacaan
Sleeping With One Eye Open
(1) For most mammals, sleep is an all-or-nothing state: the whole brain slows down together, and the body becomes still and largely unaware of its surroundings. A number of animals, however, have found a way around this risky arrangement. They can let one half of the brain sink into deep sleep while the other half stays awake. Scientists call this unihemispheric slow-wave sleep.
(2) Bottlenose dolphins are the best-known example. A dolphin has to swim up to the surface for every breath, so it cannot simply drift off for hours the way a person does in bed. By resting one half of the brain at a time, a dolphin can keep swimming, surfacing, and watching for danger while still getting the sleep it needs.
(3) Birds use the same trick. In a well-known experiment published in 1999, researchers filmed mallard ducks sleeping side by side in a row and recorded their brain activity. The ducks at the two ends of the row, which were the most exposed, spent much more time sleeping with one half of the brain than the ducks in the middle. They also tended to keep open the eye facing away from the group, the direction from which a predator would most likely come. Each open eye was linked to the half of the brain that was still awake.
(4) Some birds even sleep in the air. In 2016, scientists who recorded the brain activity of great frigatebirds during long flights over the ocean found that the birds slept mostly while circling upward in rising air, often with only one half of the brain at a time. In flight, however, they slept for less than an hour a day in total, compared with more than twelve hours a day once they were back on land.
(5) Humans cannot do anything as dramatic, but traces of the same idea may exist in us. A 2016 study of people sleeping in a laboratory for the first time found that, on the first night, the left half of the brain slept less deeply than the right and responded more strongly to unusual sounds. On the second night, the difference disappeared. The researchers suggested that this "night watch" may help explain why many people sleep poorly in a new place.
Soal 1 dari 3
Pilih satu jawabanWhich of the following best states the main idea of the passage?
Lihat kunci & pembahasan
Kunci: C
Kenapa benar
Gagasan utama teks: beberapa hewan dapat mengistirahatkan separuh otak sementara separuh lainnya tetap terjaga (lumba-lumba, bebek, burung frigata), dan manusia mungkin menunjukkan bentuk lemahnya (efek malam pertama). Pilihan ini mencakup paragraf (1) sampai (5), bukan hanya satu contoh.
Langkah
Baca kalimat kunci paragraf (1): sebagian hewan dapat membiarkan separuh otak tidur nyenyak sementara separuh lainnya terjaga.
Lihat peran paragraf (2)–(4): contoh lumba-lumba, bebek mallard, dan burung frigata. Paragraf (5): jejak gagasan yang sama pada manusia.
Pilih pernyataan yang merangkum semua bagian itu, bukan hanya satu contoh atau detail.
Tips: gagasan utama harus "memayungi" semua paragraf. Pilihan yang hanya cocok dengan satu paragraf biasanya terlalu sempit.
Kenapa opsi lain salah
- A.
Teks tidak menyebut lumba-lumba butuh tidur lebih sedikit. Lumba-lumba tetap tidur, hanya separuh otak bergantian. Pilihan ini juga terlalu sempit karena hanya membahas paragraf (2).
- B.
Teks mengaitkan mata yang terbuka dengan kewaspadaan terhadap pemangsa (paragraf 3), bukan dengan penghematan energi. Pilihan ini juga hanya menyentuh sebagian teks.
- D.
Paragraf (5) memakai kata suggested dan may help explain. Itu dugaan peneliti, bukan kepastian, sehingga know exactly melebihi isi teks.
- E.
Teks tidak membandingkan tidur berkelompok dengan tidur separuh otak. Bebek dalam percobaan justru melakukan keduanya sekaligus.
Konsep
Gagasan utama teks eksposisi adalah pernyataan umum yang didukung oleh semua paragraf penjelas; contoh dan detail bukan gagasan utama.
Jebakan umum
Memilih detail menarik dari satu paragraf (misalnya lumba-lumba) sebagai gagasan utama seluruh teks.
Tidak memperhatikan kata pelunak seperti may dan suggested sehingga menerima pilihan yang terlalu pasti.
Referensi
- Wikipedia, "Unihemispheric slow-wave sleep"
- Rattenborg, Lima & Amlaner (1999), "Half-awake to the risk of predation", Nature 397
- Rattenborg dkk. (2016), "Evidence that birds sleep in mid-flight", Nature Communications 7:12468
- Tamaki dkk. (2016), "Night watch in one brain hemisphere during sleep associated with the first-night effect in humans", Current Biology 26(9)