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Listen to a lecture in a biology class, take detailed notes while listening.
catastrophic – disastrous
emerge – to come out
mass extinction – a large scale death of many species
particle – an extremely small piece of something
wipe out – to kill entirely
Fill in the following diagram.
Theory:
1.
Support:
2.
Now answer the questions using your notes.
Meteors and Mass Extinctions
Summarize the text using your notes and diagram.
- 1: A meteor caused mass extinction 250 million years ago.
- 2: Remains of a huge 250-million-year-old meteor have been found in Antarctica.
Listen again:
M1: We all know that dinosaurs once roamed the Earth, Then, just like that, they disappeared. What most people don't know is that a similar mass extinction occurred before the dinosaurs ever existed, wiping out most life on Earth.
W: Then how come there, is so much life on Earth today?
M2: I think I know the answer. Because new life forms emerged when old ones died out.
M1: Exactly. And of course, new species, like the ancestors to dinosaurs, evolved from those that survived. The important thing here is that the fossil record shows that a mass extinction occurred about 250 million years ago. In fact, 70% of the species on land and 95% of the species living in the oceans died off rapidly. What could have caused this?
W: Maybe climate changed?
M1: In a way. An important new theory states that around 250 million years ago a huge meteor hit the Earth. It caused an extreme climate change that would've wiped out most of Earth's species.
M2: How do they know it was a meteor?
M1: Good question. Recently, researchers found metal particles in Antarctica, They' learned that these must have come from outer space. Their composition is identical to other ancient meteorites. These space particles were about 250 million years old. That means they fell to Earth around the same time as the mass extinction. They are likely the remains of a giant meteor that hit Earth.
W: But does this mean the meteor caused the extinction?
M1: It is not direct evidence, but since the meteor hit at around the same time as the mass extinction, it is likely that the two are related. A similar catastrophic event is probably what killed off the dinosaurs millions of years later.
