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Latihan TOEFL Reading 12: The Cambrian Explosion

Baca passage berikut dengan teliti, lalu kerjakan 15 soalnya. Jawaban dan pembahasan bisa dibuka setelah kamu mencoba sendiri.

Roughly 541 million years ago, the fossil record shows a remarkably rapid diversification of animal life known as the Cambrian Explosion. Within a geological span of perhaps twenty million years, brief by evolutionary standards, most of the major animal body plans that exist today appeared for the first time, including early forms of arthropods, mollusks, and chordates.

Scientists have proposed several explanations for this sudden burst of diversity. Rising atmospheric oxygen levels may have permitted larger, more complex organisms to sustain higher metabolic rates. Others point to the evolution of hard body parts, such as shells and exoskeletons, which not only improved fossilization but also intensified predator-prey interactions, driving further evolutionary innovation in an escalating arms race.

Despite decades of study, the Cambrian Explosion remains only partially understood, and no single explanation has been universally accepted. Some researchers argue that the apparent suddenness is partly an illusion created by gaps in the fossil record, while others maintain that a genuine acceleration in evolutionary rates occurred, driven by a combination of environmental and ecological factors converging within a relatively narrow window of time.

Soal

1. What is the passage primarily about?

  1. Describing the Cambrian Explosion and the various explanations proposed for it
  2. Arguing that evolution does not occur gradually
  3. Explaining how fossils are formed generally
  4. Comparing modern and ancient predator behavior
Lihat jawaban dan pembahasan

Jawaban: A. Describing the Cambrian Explosion and the various explanations proposed for it

Passage menjelaskan fenomena Cambrian Explosion dan berbagai penjelasan ilmiah yang diajukan untuk itu.

2. The word 'diversification' in paragraph 1 is closest in meaning to

  1. A chemical reaction
  2. An increase in variety
  3. A type of fossilization
  4. A decrease in population size
Lihat jawaban dan pembahasan

Jawaban: B. An increase in variety

'Diversification of animal life' berarti bertambahnya keragaman bentuk kehidupan hewan.

3. According to paragraph 1, roughly how long did the Cambrian Explosion span?

  1. About two hundred years
  2. About twenty million years
  3. About twenty thousand years
  4. About two billion years
Lihat jawaban dan pembahasan

Jawaban: B. About twenty million years

Disebutkan eksplisit 'within a geological span of perhaps twenty million years'.

4. According to paragraph 1, which groups of animals had early forms appear during this period?

  1. Only single-celled organisms
  2. Only dinosaurs
  3. Only marine plants
  4. Arthropods, mollusks, and chordates
Lihat jawaban dan pembahasan

Jawaban: D. Arthropods, mollusks, and chordates

Disebutkan eksplisit ketiga kelompok hewan ini muncul untuk pertama kalinya.

5. It can be inferred that rising oxygen levels, according to paragraph 2, may have allowed organisms to

  1. Sustain higher metabolic rates as they grew larger and more complex
  2. Survive without any food source
  3. Become immune to predation entirely
  4. Live exclusively on land
Lihat jawaban dan pembahasan

Jawaban: A. Sustain higher metabolic rates as they grew larger and more complex

Disebutkan oksigen memungkinkan organisme 'permit larger, more complex organisms to sustain higher metabolic rates'.

6. Why does the author mention the evolution of hard body parts in paragraph 2?

  1. To argue that soft-bodied animals became extinct
  2. To explain one possible driver of both fossilization and evolutionary innovation
  3. To criticize current fossil dating methods
  4. To describe how shells are chemically formed
Lihat jawaban dan pembahasan

Jawaban: B. To explain one possible driver of both fossilization and evolutionary innovation

Bagian tubuh keras disebut memperbaiki fosilisasi sekaligus mempercepat inovasi evolusi lewat interaksi predator-mangsa.

7. The word 'intensified' in paragraph 2 is closest in meaning to

  1. Weakened
  2. Eliminated
  3. Measured precisely
  4. Made stronger
Lihat jawaban dan pembahasan

Jawaban: D. Made stronger

'Intensified predator-prey interactions' berarti interaksi itu menjadi lebih kuat/intens.

8. According to paragraph 3, what do some researchers argue about the apparent suddenness of the explosion?

  1. It happened over billions of years
  2. It may partly be an illusion caused by gaps in the fossil record
  3. It only affected plant life
  4. It is completely fabricated by scientists
Lihat jawaban dan pembahasan

Jawaban: B. It may partly be an illusion caused by gaps in the fossil record

Disebutkan eksplisit sebagian peneliti berpendapat kesan mendadak itu 'partly an illusion created by gaps in the fossil record'.

9. It can be inferred that the fossil record is

  1. A perfectly complete record of all past life
  2. An imperfect and incomplete source of evidence about evolutionary history
  3. Irrelevant to understanding evolution
  4. Only useful for dating rocks
Lihat jawaban dan pembahasan

Jawaban: B. An imperfect and incomplete source of evidence about evolutionary history

Disebutkan adanya 'gaps in the fossil record' yang bisa menciptakan kesan salah tentang kecepatan evolusi.

10. What is the function of paragraph 3 in relation to paragraph 2?

  1. It repeats the same information as paragraph 2
  2. It completely refutes the explanations in paragraph 2
  3. It introduces an unrelated new topic
  4. It shows that the explanations in paragraph 2 remain debated rather than settled
Lihat jawaban dan pembahasan

Jawaban: D. It shows that the explanations in paragraph 2 remain debated rather than settled

Paragraf 3 menegaskan bahwa penjelasan-penjelasan di paragraf 2 masih diperdebatkan, belum ada konsensus tunggal.

11. The word 'converging' in paragraph 3 is closest in meaning to

  1. Accelerating alone
  2. Disappearing
  3. Coming together
  4. Moving apart
Lihat jawaban dan pembahasan

Jawaban: C. Coming together

'Factors converging' berarti berbagai faktor yang bertemu/bergabung dalam satu periode waktu.

12. According to paragraph 2, what effect did hard body parts have on predator-prey interactions?

  1. They only affected plants
  2. They had no effect on evolution
  3. They eliminated all predation
  4. They intensified these interactions, driving further evolutionary innovation
Lihat jawaban dan pembahasan

Jawaban: D. They intensified these interactions, driving further evolutionary innovation

Disebutkan eksplisit efek ini 'intensified predator-prey interactions, driving further evolutionary innovation'.

13. According to paragraph 3, has a single explanation for the Cambrian Explosion been universally accepted?

  1. Yes, hard body parts alone explain it
  2. The passage does not discuss this
  3. No, no single explanation has been universally accepted
  4. Yes, oxygen levels alone explain it
Lihat jawaban dan pembahasan

Jawaban: C. No, no single explanation has been universally accepted

Disebutkan eksplisit 'no single explanation has been universally accepted'.

14. It can be inferred that the 'arms race' mentioned in paragraph 2 refers to

  1. An escalating cycle of adaptations between predators and prey
  2. A race to discover fossils first
  3. A competition between different research teams
  4. An actual military conflict
Lihat jawaban dan pembahasan

Jawaban: A. An escalating cycle of adaptations between predators and prey

Istilah 'arms race' di sini metaforis, merujuk pada siklus adaptasi yang saling meningkat antara predator dan mangsa.

15. What is paragraph 2 mainly about?

  1. Methods of fossil excavation
  2. The extinction of dinosaurs
  3. The exact dates of the Cambrian period
  4. Possible explanations for the rapid diversification of life during this period
Lihat jawaban dan pembahasan

Jawaban: D. Possible explanations for the rapid diversification of life during this period

Paragraf 2 mendaftar beberapa hipotesis ilmiah tentang penyebab ledakan keragaman ini.

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