history of life

An asteroid that impacted Earth about 66 million years ago is believed to be responsible for ____.

• the creation of life on Earth

• a global catastrophe that may have wiped out the dinosaurs

• the splitting of one land mass into continents

• the evolution of Earth’s oceans

The process of fossilization typically begins when an organism or traces of it ____.

• settle on the seafloor

• are pressurized under the weight of sediment

• are saturated with groundwater

• become covered with sediments, mud, or ash

​____ are examples of trace fossils.

• Shells

• Footprints

• Leaves

• Skeletons

The geologic time scale is often subdivided on the basis of ____.

• periods of mass extinction

• the appearance of new species

• levels of background extinction

• climate change

Which statement about the geologic time scale is false?

• Mammals originated early in the Mesozoic era.

• Radiations of marine invertebrates took place in the Mesozoic era.

• Mass extinction of the dinosaurs occurred about 65 million years ago.

• Eukaryotes originated during the Proterozoic eon.

The Cretaceous is the most recent period of the ____ era.

• Archaean

• Cenozoic

• Mesozoic

• Proterozoic

Most fossils ____.​

• ​

  form without water

• are impervious to erosion

• contain remnants of soft body parts

• are found in sedimentary layers of rock

​____________________ are evidence of life in the distant past.