Study Guide -- Chapter 10 Geologic Time
Test Friday, February 19th
Reviewing Main Ideas
Section 1: Life and Geologic Time
1. Geologic time is divided into eons, eras, periods, and epochs.
2. Divisions within the geologic time scale are based largely on major evolutionary
changes in organisms.
3. Plate movements affect organic evolution
Section 2: Early Earth History
1. Cyanobacteria evolved during Precambrian time. Trilobites, fish, and corals were
abundant during the Paleozoic Era.
2. Plants and animals began to move onto land during the middle of the Paleozoic Era.
3. The Paleozoic Era was a time of mountain building. The Appalachian Mountains
formed when several islands and finally Africa collided with North America.
4. At the end of the Paleozoic Era, many marine invertebrates became extinct.
Section 3: Middle and Recent Earth History
1. Reptiles and gymnosperms were dominant land life-forms in the Mesozoic Era.
Mammals and angiosperms began to dominate the land in the Cenozoic Era.
2. Pangaea broke apart during the Mesozoic Era. Many mountain ranges formed during
the Cenozoic Era.
Using Vocabulary
1.
Cenozoic Era – era of recent life that began about 66 million years ago and
continues today; includes the first appearance of Homo sapiens about 400,000 years
ago.
2.
cyanobacteria – chlorophyll-containing, photosynthetic bacteria thought to be one
of Earth’s earliest life forms.
3.
eon – longest subdivision in the geologic time scale that is based on the abundance
of certain types of fossils and is subdivided into eras, periods, and epochs.
4.
epoch – next-smaller division of geologic time after the period; is characterized by
differences in life-forms that may vary regionally.
5.
era – second-longest division of geologic time; is subdivided into periods and is
based on major worldwide changes in types of fossils.
6.
geological time scale – division of Earth’s history into time units based largely on
the types of life-forms that lived only during certain periods.
7.
Mesozoic Era – middle ear of Earth’s history, during which Pangaea broke apart,
dinosaurs appeared, and reptiles and gymnosperms were the dominant life-forms.
8.
natural selection – process by which organisms that are suited to a particular
environment are better able to survive and reproduce than organisms that are not.
9.
organic evolution – change of organisms over geologic time.
10. Paleozoic Era – era of ancient life, which began about 544 million years ago, when
organisms developed hard parts, and ended with mass extinctions about 245 million
years ago.
11.
Pangaea – large, ancient landmass that was composed of all the continents joined
together.
12. period – third longest division in geologic time; is subdivided into epochs and is
characterized by the types of life that existed worldwide.
13. Percambrian time – longest part of Earth’s history, lasting from 4.0 billion to about
544 million years ago.
14. species – group of organisms that reproduces only with other members of their
own group.
15. trilobite – organism with a three-lobed exoskeleton that was abundant in Paleozoic
oceans and is considered an index fossil.
16. fossil – remains, imprints, or traces of prehistoric organisms that can tell when and
where organisms once lived and how they lived.
17. evolution – change in the genetics of a species over time.
18. trace fossil - a fossilized track, trail, burrow, boring, or other structure in
sedimentary rock that records the presence or behavior of the organism that made
it.
19. index fossil – remains of a species that existed on Earth for a relatively short
period of time, were abundant and widespread geographically, and can be used by
geologists to assign the ages of rock layers.
20. relative age – the age of something compared to other things.
21. Law of Superposition – in any undisturbed sequence of rocks deposited in layers,
the youngest layer is on top and the oldest on bottom, each layer being younger than
the one beneath it and older than the one above it.
22. Geologic Time Scale - division of Earth’s history into time units based largely on
the types of life-forms that lived only during certain periods.
23. radioactive dating – process used to calculate the absolute age of rock by
measuring the ratio of parent isotope to daughter product in a mineral and knowing
the half-life of the parent.
24. half-life – time needed for one half of the mass of a sample of radioactive isotope
to decay.
Fill in the blank with the correct word or words.
evolution
1. A change in the hereditary features of a species over a long period isorganic
__________.
Geologic time scale
2. A record of events in Earth history is the ___________________.
organic evolution
eon
3. The largest subdivision of geologic time is the ____________________.
organic evolution
4. The process by which the best-suited individuals survive in their environment is
natural selection
_________________.
organic evolution
5. A group of individuals that normally breed only among themselves is a(n)species
_______.
organic evolution
Checking Concepts
Choose the word or phrase that best completes the sentence.
1. How many millions of years ago did the era in which you live begin?
a. 650
b. 245
c. 1.6
d. 65
2. What is the process by which better-suited organisms survive and reproduce?
a. Endangerment
b. Extinction
c. Gymnosperm
d. Natural selection
3. During what period did the most recent ice age occur?
a. Pennsylvanian
b. Triassic
c. Tertiary
d. Quaternary
4. What is the next smaller division of geologic time after the era?
a. Period
b. Stage
c. Epoch
d. Eon
5. What was one of the earliest forms of life?
a. Gymnosperm
b. Cyanobacterium
c. Angiosperm
d. Dinosaur
6. During which era did the dinosaurs live?
a. Mesozoic
b. Paleozoic
c. Miocene
d. Cenozoic
7. Which type of plant has seeds without protective coverings?
a. Angiosperms
b. Apples
c. Gymnosperms
d. magnolias
8. Which group of plants evolved during the Mesozoic Era and is dominant today?
a. Gymnosperms
b. Angiosperms
c. Ginkogoes
d. Algae
9. In which era did the Ediacaran fauna live?
a. Precambrian
b. Paleozoic
c. Mesozoic
d. Cenozoic
Thinking Critically
1. Infer why plants couldn’t move onto land until an ozone layer formed. Too much
harmful ultraviolet radiation from the Sun reached the Earth’s surface.
2. Discuss why trilobites are classified as index fossils. Trilobites were widespread
and individual species existed for a limited amount of time before becoming extinct.
3. Compare and contrast the most significant difference between Precambrian lifeforms and Paleozoic life-forms. Most organisms of Precambrian age lacked the hard
parts that developed in the Paleozoic Era.
4. Describe how natural selection is related to organic evolution. Evolution occurs
through natural selection, which is the process by which organisms with
characteristics best suited to their environment survive and reproduce.
5. Explain In the earth 1800s, a naturalist proposed that the giraffe species has a long
neck as a result of years of stretching their necks to reach leaves in tall trees.
Why isn’t this true? Acquired traits are not hereditary.
6. Infer Use the outlines of the present-day continents to make a sketch of Pangaea.
7. Form Hypotheses Suggest some reasons why trilobites might have become extinct
at the end of the Paleozoic Era. Possible answers include: plate tectonic processes
that changed the configuration of land and seas, disappearance of shallow seas
where they lived; meteorite impact
8. Interpret Data A student found what she thought was a piece of dinosaur bone in
Pleistocene sediment. How likely is it that she is right? Explain. It is not likely
that she is correct, because dinosaurs became extinct long before the Pleistocene
Epoch.
9. Infer why mammals didn’t become dominant until after the dinosaurs disappeared.
Dinosaurs were better-adapted to the habitat until they became extinct. Mammals
were then best-adapted.