Download Chapter 8

Chapter 8 Study Guide
Name: ____________________________
Date: ________________Per. __________
Lesson 1: GEOLOGIC TIME AND MASS EXTINCTION – Fossils provide evidence of how life and environmental conditions
have changed over time. Geologists used fossils to create the geologic time scale.
Essential (4.g)
A. Development of the Geologic Timescale
1. The changes to _______ and the _________ that have occurred throughout time are recorded on a timeline called the
___________________ ________________________, the time scale’s units are _____________________.
2. To organize geologic time unto units, paleontologists study the ___________ and ages of fossils in rock layers and decide
where to mark the _________.
3. Units on the timescale are described by the presence or absence of certain types of fossils called __________ fossils.
4. There are several major divisions of the geologic timescale. The longest are called _______. These have been broken into
smaller units called eras which have in turn been divided into _________ and ___________.
5. Paleontologists have defined three eras within the ___________________ eon.
a. The Paleozoic era, which means “ancient ______”, dominated by invertebrate ____________ animals.
b. During the Mesozoic era, which means “__________ life”, dinosaurs and mammals lived on _________.
c. The __________ era, which means “_________ life” (continues today) when modern mammals and ___________evolved.
B. What are Mass Extinctions
1. Several units on the geologic timescale begin and end with mass ______________. A mass ________________ is the
dying off of many different __________ of organisms over a short period of geologic time.
C. Possible Causes of Mass Extinctions
1. Once paleontologists recognized that mass extinctions occurred throughout ____________time, they began to search for
__________________ events that might cause them.
2. A catastrophic event is ________________________________________________________________________________
_____________________________________________________________________________________________________.
3. Scientists still do not fully understand the specific catastrophic events that have ________ each of the mass extinctions.
4. They have identified several types of _________ however, that have the ability to cause mass extinctions. These include
climate, volcanic _____________, and asteroid _____________.
a. There is ___________that some mass extinctions were caused by relatively _________ changes in climate.
-Global Warming – an increase in the atmospheric temperature-could result in ______________________________
______________________________________________________________________________________________.
-Global Cooling – a decrease in atmospheric temperature-could result in ___________________________________
______________________________________________________________________________________________.
b. When you think of a _____________ eruption, you might think of an explosion, however the dust, ash, _______, and
_________ emitted from volcanic eruptions can affect climate and organisms.
-a volcanic eruption is one of the ____________ hypothesis proposed to explain the mass extinction event at the end of
the ______________________ period.
c. The location of a possible asteroid _______________ is the ______________ Penninsula in Mexico. Some geologists
propose that this impact sent enough ______ and other material into the atmosphere to block sunlight which resulted in
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________.
5. Species that survive mass extinction inherit an _________________ with few competitors, in time their descendents
populate the Earth.
Lesson 2: Bacteria, the simplest organisms, were the first organisms to evolve on Earth. Increasingly complex organisms
followed them.
A. Life on Earth Changes
1. Paleontologists observe that fossils from rock _________ that are touching are more similar to each other than fossils
from widely ______________ layers.
2. Geologists also recognized that the more recently a fossil was formed, the more it ____________ a living _____________.
B. Precambrian Time
1. Fossils are not abundant in ____________________-aged rocks.
2. Minerals found in Precambrian rocks shows the early ___________________ had very little __________________.
3. Stromatolites are mounds of sediment and _________________ cyanobacteria. They contain _______________
of one of the earliest known, ancient organisms called ___________________, a single celled blue-green algae.
4. As organisms increased in ___________________, the first __________________ organisms appeared.
C. The Paleozoic Era
1. An event known as the Cambrian explosion, shows that during a relatively _______ period of time, the number of animals
with ____________ greatly increased. Invertebrates including sponges, __________ and ___________also evolved.
2. Vertebrates, animals with _________________evolved early in the Paleozoic Era.
-During the __________________ period an organism, called an ______________ evolved that could lay its eggs on land.
-Mammals, dinosaurs and __________ all evolved from amniotes.
-During the Ordovician period plants spread onto __________. Ferns and conifers appeared during the _____________.
3. The Paleozoic ended with the late __________ extinction - including 90% of all marine _________ and ___% of land species.
Lesson 3: Life continues to evolve into many forms we see on Earth today.
A. The Mesozoic Era
1. The three periods of the time scale that make up the Mesozoic era are the Triassic, the ___________ and the Cretaceous.
2. In addition to fish, the Mesozoic contained predatory _____________ such as plesiosaurs and mosasaurs.
Amphibians, _____________, reptiles and mammals that lived on land continued to __________.
3. Dinosaurs evolved during the __________. These were _______ at first, but as new species evolved, they grew __________.
4. Mammals evolved during the Triassic, alongside the ___________. As dinosaur species became extinct,
mammals were able to move into the ____________ that dinosaurs once occupied.
5. Plants called ___________________ dominated the plant population of the Mesozoic era.
6. _________________ (flowering plants) evolved near the _______ of the Mesozoic era.
7. One of the most well known _____________ events (the K-T) occurred at the end of the Cretaceous,
almost ___% of all species in the oceans and all the remaining ___________ became extinct. This event marked
the end of the ______________era.
B. The Cenozoic Era
1. The Cenozoic era is divided into seven ____________.
2. During the Cenozoic, marine life began to recover from the cretaceous mass _______________. The offspring of the
organisms that survived make up the present __________ecosystem.
3. Primates, animals with ______________ thumbs and two eyes that look directly forward evolved during the ________epoch.
-about 4.4 mya during the ______________ epoch, hominids evolved. _______________ walk upright on two legs. The .
human species Homo sapiens belongs to the ________ group.
4. Flowering plants evolved near the end of the ______________ era, and have continued to evolve ever since. Today there
are more than ____________ species of flowering plants. Fruits, _____________ and nuts are produced by flowering plants.
5. Grasses are flowering plants and during the __________ epoch supported a large diversity of mammals, and enabled the
mammals to multiply and diversify.
6. Cenozoic mass _________________ events have not occurred on the scale of those previously discussed in this chapter.
7. Fossil _________ for the Archean eon to the Cenozoic era show that ____________ increases over time. Life began as
____________ bacteria, then organisms with ________ evolved. Organisms became diversified and continued to _________
from marine invertebrates to marine and land vertebrates and plants. The _____________ record reveals this change.
1. Life forms of the Precambrian era include mainly____________________________________________________________________.
2. Life forms of the Paleozoic era include mainly ______________________________________________________________________.
3. Mesozoic era life forms include mainly ____________________________________________________________________________.
4. Life forms of the Cenozoic era include mainly _______________________________________________________________________.