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Chapter 11: Geologic Time
Terms in this set (100)
a time line of Earth's past is called a geologic ______.
the longest units of geologic time are __________.
the geologic time scale contains ______ eons.
eons are subdivided into smaller units of time called _____.
eras are subdivided into _________.
periods are subdivided into __________.
when the geologic time scale was developed, the boundaries of time units were based on the ________ in different rock layers.
_________ rock layers contained only fossils of small, relatively simple life-forms.
__________ rock layers contained fossils of simple life-forms, as well as fossils of more complex organisms.
a __________________ is the extinction of many species on Earth winthin a short period of time.
one reason for extinctions is quick changes to the _____________, when some organisms cannot adapt.
some scientists hypothesize that the mass extinction of dinosaurs was caused by a __________________.
evidence of the collision is provided by rocks containing the element ___________, which is in meteors.
gas and dust
other extinctions could have been caused by environmental changes based on the ____ and _____ from volcanoes.
________________ is the change in species over time as organisms adapt to their environments.
the slow movement of Earth's _________ plates can affect evolution.
when plates move, sea level can drop, forming __________, which connect continents that had been separated by water.
land bridges allow organisms to _____ into new areas with new environments.
__________________ is the separation of a population of organisms from the rest of its species because of a physical barrier.
early geologists hypothesized that __________ organisms first evolved in the Cambrian period.
time before cambrian was called ____________ time.
precambrian life led to a sudden appearance of new types of multicellular organisms in what is known as the cambrian ____________.
these new organisms were more easily preserved as fossills because they had ______ body parts.
the oldest era of the phanerozoic eon is the _________________.
the middle era of the phanerozoic eon is the ________________.
the _________________ is the youngest era of the phanerozoic eon.
organisms from the early paleozoic were _________________ that lived in the oceans.
these animals have no ________________.
during the early paleozoic , the shapes of the __________ were different from today.
during this time, Earth's climate was _______.
rising oceans flooded the continents, forming shallow _______________.
during the early Paleozoic, the landmass that would become North America was near the ______________.
although the early Paleozoic ended with mass extinction, many _________________ survived.
animals with backbones, or _________________, evolved.
some of the earliest vertebrates were _________.
in addition to fishes, insects evolved, and Earth's first ____________ appeared.
major collisions between ___________ occurred at this time.
some of these collisions formed the __________________________.
the middle Paleozoic also ended in a ___________________ event.
many ____________ invertebrates and some land animals disappeared.
fishlike organisms evolved into organisms that had _______ and could breathe air.
these ______________ had thick skins and strong limbs.
amphibians must return to water to _______.
____________ evolved toward the end of the Paleozoic era.
reptiles were the first animals that did not require _______ for reproduction.
reptiles can spend all their time on _____.
during the late Paleozoic period, tropical forests grew in ___________ along shallow inland seas.
when the plants died, they sank into swamps called ______swamps.
a coal swamp is an ________-poor environment where, over time, plant material changes into coal.
Earth's continents moved close together and formed a giant ______________.
a supercontinent is an ancient landmass that separated into present-day _____________.
this Paleozoic supercontinent has been named _______________.
the largest known mass extinction of Earth occurred at the end of the __________ era.
during this mass extinction, ____ percent of marine life-forms and 70 percent of all life on land became extinct.
some scientists hypothesize that this mass extinction was caused by a sudden ___________ change.
other scientists propose that a large ___________ or large volcanic eruptions resulted in sunlight being blocked for a long period of time.
the Mesozoic era is divided into Triassic period, the ________ period, and the cretaceous period.
the dminant geologic event of the Mesozoic era was the breakup of ____________.
Pangea broke into two continents during the late ___________ period.
one of the continents was _____________________, which included the future continents of South America, Africa, Antarctica, and Australia.
the other continent was ___________, which included the future continents of North America, Europe, and Asia.
the climate during the Mesozoic era was ________ than the climate of the Paleozoic era.
throughout the Mesozoic era, North America drifted steadily __________.
North America hit a plate to the west, the ____________________ formed.
_____________ share a common ancestor with present-day reptiles such as the crocodile.
dinosaurs and crocodiles differ in their _____ structure.
dinosaurs were dominant Mesozoic land vertebrates that walked with their legs positioned directly __________ their hips.
scientists hypothesize that some dinosaurs were more closely related to present-day ______ than to present-day reptiles. some had wings, feathers, claws and teeth.
___________ were the dominant reptiles on land.
other types of reptiles lived in the sea and flew in the _____.
__________ were Mesozoic marine reptiles that had small heads, long necks, and flippers.
_________ were Mesozoic flying reptiles that had large, batlike wings.
___________ evolved during the Mesozoic era, but they remained small.
the mass extinction that ended the Mesozoic era was called the ____________________ event.
scientists hypothesize that a large ____________ hit Earth, creating large amounts of dust that blocked sunlight.
large volcanic _________________ could have added to the sunlight-blocking dust.
without sunlight, ________ died.
without plants, __________ died.
people know more about the ___________ era than an other because its fossils and rocks are well preserved.
the Cenozoic era is divided into the _______ period.
at the beginning of the Cenozoic era, some _______________ collided, forming mountain ranges.
collisions formed the ____________ in Asia and the Alps in Europe.
the Cascades and the _________ rose on the coast of North America.
the early Cenozoic era was __________, but the climate began to cool.
by the ____________ eopch, ice covered the poles and high mountains.
during the first eopch of the Quaternary period, the ________________________, glaciers advanced and retreated many times.
during the _____________, glaciers covered as much as 30 percent of Earth's land surface.
the deep grooves made by rocks carried in glaciers are called ______________.
because glaciers contained so much water, ____________ dropped and inland seas drained.
flowering _______ evolved and began to dominate the land.
some Cenozoic mammals were so large that they are called ____________________.
fossils of these animals have been discovered, preserved in tar pits and in _________.
different mammals evolved on different continents they became geographically ___________.
most mammals in Australia are __________________, which carry their young in pouches.
scientists hypothesize that the ancestors of Australian marsupials migrated from ________________ when landmasses were connected to Australia.
the oldest human fossils have been discovered in _________.
modern humans did not evolve until the ________________________.
early humans migrated to North America from _______ across a land bridge.
many scientists hypothesize that present-day Earth is undergoing a __________________ climate change.
humans are contributing to this climate change by using ____________.
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