Objective
To identify the implied main idea and supporting details in a textbook passage.

Step 2: Read "Case Study Revisited." Then answer the questions that follow it. Your instructor will tell you whether to write your answers in your book or to submit your answers online for electronic grading.

Case Study Revisited: Did the Dinosaurs Die from Lack of Sunlight?

How did a giant meteorite hamper photosynthesis and exterminate dinosaurs? The force of impact pulverized the meteorite and smashed the Earth's crust, sending trillions of tons of debris rocketing into the atmosphere. This huge amount of debris was flung so high that it went into orbit around the planet. In addition, the heat of the blast caused huge, raging fires that may have burned 25% of all the vegetation on land. The resulting smoke and ashes, combined with the orbiting dust cloud, obliterated the sun. Earth was plunged into a night that lasted for months.

In the perpetual darkness of the post-impact world, the temperature dropped dramatically. This sudden winter must have placed tremendous stress on organisms accustomed to the tropical conditions that prevailed over large areas of the planet. Even more devastating, however, was the sudden decline in photosynthesis. With little sunlight reaching Earth's surface, the land plants that had survived the fires could not capture enough energy. In the sea, photosynthesis algae perished by the billions. As the photosynthesizers on land and in the sea declined, the organisms that depended on them for food also suffered. Large plant-eaters such as Triceratops, which needed to consume hundreds of pounds of vegetation daily, must have been especially vulnerable. Predators such as Tyrannosaurus, which fed on the disappearing plant-eaters, were soon without prey. Eventually, the severe stress of life on a plant with diminished photosynthesis spelled extinction for most of Earth's species.

       —Audesirk, Audesirk, & Byers, Life on Earth, 3/e, p 90.

		1. "How did a giant meteorite hamper photosynthesis and exterminate the dinosaurs?" Hamper means     a. keep from acting.   b. cause to act.   c. improve.   d. increase.
		2. "The force of the impact pulverized the meteorite and smashed the Earth's crust, sending trillions of tons of debris rocketing into the atmosphere." Pulverized means     a. overlooked.   b. crushed.   c. applauded.   d. avoided.
		3. "The resulting smoke and ashes, combined with the orbiting dust cloud, obliterated the sun." Obliterated means     a. blocked out completely   b. melted.   c. orbited beyond.   d. burned.
		4. "In the perpetual darkness of the post-impact world, the temperature dropped dramatically." Perpetual means     a. occurring off and on.   b. constant.   c. occasional.   d. not occurring.
		5. "In the sea, photosynthetic algae perished by the billions." Perished means     a. died.   b. survived.   c. fled.   d. increased.
		6. When the meteorite crashed into the earth, it    a. evaporated before hitting the surface.   b. landed in the ocean, causing a huge tidal wave.   c. became a lake in South America.   d. was crushed into dust and other debris.
		7. How much vegetation did the meteorite destroy?    a. 100 percent   b. 70 percent   c. 50 percent   d. 25 percent
		8. Scientists believe that the perpetual darkness was caused by all of the following except    a. dust.   b. ash.   c. solar eclipse.   d. smoke.
		9. Scientists know that photosynthesis is important to    a. animals   b. land plants   c. sea algae   d. all of the above.
		10. Scientists speculate that the dinosaurs died from a lack of    a. oxygen because of the intense smoke in the air.   b. sunlight, which was necessary for plant photosynthesis for food production.   c. organized survival tactics.   d. ability to get along with their enemies.