- There are five distinct mass extinctions where the number of taxonomic families drops sharply. - occur at the end of the Ordovician, Devonian, Permian, Triassic, and Cretaceous time periods.

- Much of the fossil record reflects a slow evolutionary change. - Evolutionary biologists are still debating the cause of these events

- characterized by a massive glaciation event. The glaciers resulted in a drop in ocean temperature and level (50 meters). Eighty-five percent of the species (all of which were marine) became extinct. - 500-440 million years ago

Devonian flora and fauna

- consisted of marine and early land organisms such as cephalopods, jawed fish, amphibians, scorpions, spiders, and land plants. Scientists think that a continental collision caused a drop in ocean temperature. Eighty percent of marine species were wiped out. - 400-345 million years ago

- Giant insects and a variety of reptile species characterized the Permian time period. The supercontinent Pangea formed and most of the land mass was subject to cold temperatures. Glaciers and volcanoes were prevalent. Ninety percent of land and marine species were wiped out. - 290-245 million years ago - age of insects - reptiles

- During the Triassic, giant reptiles and gymnosperms flourished. Seventy-five percent of the species went extinct, possibly because of a meteor impact. - 240-210 million years ago

Cretaceous extinction

- Before the Cretaceous extinction, mammals comprised a relatively small fraction of the taxonomic families. Dinosaurs comprised a large portion of taxonomic families. Seventy five percent of vertebrates larger than 25 kilograms were wiped out. The extinction probably resulted from a meteor impact. A layer of iridium, an element that is rare on earth but common in meteorites, is found between Cretaceous and Tertiary sediments - 65 million years ago

Why is an iridium-rich layer of rock significant in evidence bearing on the Cretaceous–Tertiary extinction?

- Iridium is rare on earth but common in extraterrestrial rocks.

The fossil record tells us that mass extinctions occurred because

- there are periods during which there is a sharp decline in the number and types of fossils found.

During what period did the dinosaurs suddenly disappear from the record?

- Cretaceous, 65 million years ago

Which of the statements regarding the Permian time period is incorrect?

- The earth was populated by small mammals

The prevailing theories about mass extinction are that the causes may have been

- glacier formation, meteorites crashing into the earth, and movement of continents

Which of the following is true about the mass extinction that occurred during the Ordovician period?

- Eighty-five percent of the species (all of which were marine) were wiped out.

1.5.5 Mass Extinctions: An Asteroid Can Ruin Your Day Flashcards by Irina Soloshenko

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1.5.5 Mass Extinctions: An Asteroid Can Ruin Your Day Flashcards

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