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College Biology 120

Which of these events occurred earliest in the history of Earth?

Formation of Oxygen

Which of these events occurred most recently in the history of Earth?

First Humans

Which of these events occurred during the Paleozoic?

Colonization of land by plants

Which of the following options lists major events in the history of life on Earth in the proper order, from earliest to most recent?

first prokaryotes; photosynthesis; first eukaryotes; colonization of land by plants and fungi.

If all of Earth's history were compressed into an hour, humans would first appear less than...

1 Second Ago

The technique called radiometric dating is based on...

the steady, clocklike decay of certain radioactive isotopes over time.

You find the frozen remains of a woolly mammoth in an Alaskan glacier. You analyze a bit of the tusk and find that its 14C:12C ratio is about one-fourth (25%) of the baseline level typically found in living organisms. Given that the half-life of 14C is 5,730 years, when did the mammoth die?

Almost 12,000 years ago

If an isotope has a half-life of 4 million years, and a fossil is 16 million years old, how much of the original isotope will be found in the fossil?

one-sixteenth of the original amount

According to this figure, if a species were found only in Laurasia 135 million years ago, on which modern continents would its descendants most likely be found today?

North America, Europe and Asia

Geologists have evidence that over the past 1.5 billion years,

Earth's land masses have joined into a single continent and split back apart again on three occasions.

Which of the following lines of evidence suggests that lungfishes evolved while Pangaea was intact?

Fossil lungfishes have been found on every continent except Antarctica.

Geological evidence indicates that two land masses became separated by a deep ocean channel 45 million years ago and have been moving apart ever since. You are studying a group of organisms that is widespread as a native part of the biota on both of the land masses. What can you conclude about the group's evolutionary history?

It depends on the dispersal abilities of the organism. If the organism cannot move across the open ocean, it is very likely that the group's ancestors were present on the original land mass before it broke up.

Over the past 500 million years, there have been ________ mass extinctions and each time, at least ________ of the species on Earth became extinct.

five . . . 50%

At the end of the ________, over 96% of marine species and many terrestrial species became extinct, possibly because intense volcanic activity warmed Earth's climate.


Scientists evaluating the Cretaceous mass extinction have concluded that...

the asteroid impact was probably the triggering event for the extinction.

Mass Extinctions...

remove well-adapted species and groups from the Earth, so that it may take millions of years for species diversity to recover.

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