Odpowiedzi na pytania badawcze: Wymarcie dinozaurów

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1. If species go extinct all the time, how do scientists know when a mass extinction occurred? How do they know which organisms went extinct?

Answer: Scientists know about mass extinctions by studying fossils. Fossils that are abundant in earlier rock layers are not present in later rock layers. When a fossil disappears like this, scientists determine it went extinct. When this happens to a wide range of many organisms at one time, scientists can infer that a mass extinction occurred.

2. Scientists think a giant asteroid impact and huge volcanic eruptions may have contributed to the mass extinction 65 million years ago. List at least three ways that these events could have changed the environment.

Answer: Scientists think the asteroid impact and volcanic eruptions could have led to other changes in the environment, such as:

3. Extinction theories suggest that blocked sunlight would have decreased photosynthesis in plants. Which kinds of dinosaurs—plant-eaters or meat-eaters—would have been affected by a change in photosynthesis? Explain your answer.

Answer: A decrease in photosynthesis would have affected all dinosaurs. A decline in plants would mean less food for plant-eating dinosaurs. But meat-eating dinosaurs prey on plant-eaters for food, so they would have less food to eat too. Without enough food, all dinosaur populations would eventually disappear.

4. Scientists say that dinosaurs are not extinct. In fact, you see them every day. What do they mean?

Answer: Dinosaurs are not extinct because birds are a living group of dinosaurs. They descended from the common ancestor of all dinosaurs. So every time you see a bird, you see a dinosaur!