1. Which of the following statements about the K-T boundary are true? (Note: More than one answer is correct.)

1. The K-T boundary is marked by a thin layer of clay found only in Gubbio, Italy.
2. The K-T boundary separates rock layers of the Cretaceous period from those of the Tertiary period.
3. The K-T boundary dates to about 65 million years ago, when the dinosaurs disappeared.
4. The K-T boundary in Zumaia, Spain, shows an abrupt change in the marine ecosystem.

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2. How do foraminifera found in rock layers above the K-T boundary compare to those in rock layers below?

1. Foraminifera above the boundary are smaller and less diverse than those below.
2. Foraminifera above the boundary are smaller and more diverse than those below.
3. Foraminifera above the boundary are larger and less diverse than those below.
4. Foraminifera above the boundary are larger and more diverse than those below.

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3. Iridium is a component of cosmic dust that rains down on Earth at a constant rate. Why did Dr. Luis Alvarez suggest measuring iridium levels across the K-T boundary?

1. He hypothesized that the layer was caused by an asteroid impact.
2. He hypothesized that the layer was caused by a supernova explosion.
3. He wanted to determine how quickly the layer had been deposited.

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4. The scientific community was slow to accept the asteroid impact hypothesis. Why?

1. Most global extinctions were thought to occur as a result of supernovas.
2. At the time, most geologists thought that Earth's systems changed gradually and not rapidly from major catastrophic events.
3. Foraminifera appear on both sides of the K-T boundary.
4. Dinosaur fossil evidence contradicted the asteroid hypothesis.

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5. Which evidence is consistent with the asteroid impact hypothesis? (Note: More than one answer is correct.)

1. Iridium
2. Plutonium-244
3. Shocked quartz in the K-T boundary layer
4. Tektites, a type of melted rock

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6. What was the critical piece of evidence that supported the hypothesis that an asteroid struck Earth about 65 million years ago?

1. The Chicxulub crater in Mexico
2. Tsunami deposits in the Brazos River Basin in Texas
3. Gravitational anomalies on the Yucatán peninsula, from surveys done for oil exploration
4. Spherules and shocked quartz in Haiti

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7. Which of the following effects of the asteroid impact would have caused large numbers of different species of animals and plants to die throughout the entire planet?

1. Tsunamis, landslides, earthquakes, and heat caused by the impact
2. The explosion caused by the impact
3. Debris from the impact orbiting Earth shielding sunlight and halting photosynthesis

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8. Which characteristic was NOT advantageous for organisms in the million years after the catastrophic asteroid impact?

1. Self-contained spores
2. Large body size
3. Dwelling underground
4. Dwelling in swamps or rivers

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