Transcript Focus On Life Science
Chapter Menu Lesson 1:
Geologic Time and Mass Extinction
Lesson 2:
Early Earth History
Lesson 3:
Middle and Recent Earth History
Click on a hyperlink to view the corresponding lesson.
8.1 Geologic Time and Mass Extinction
index fossil mass extinction catastrophic event
8.1 Geologic Time and Mass Extinctions
Development of the Geologic Time Scale
• The changes that have occurred in Earth’s history are recorded on a time line called the geologic time scale.
• The time scale’s units are uneven because extinctions, growth rates, and environmental changes happen at different rates.
8.1 Geologic Time and Mass Extinctions
Index Fossils
• An
index fossil
is the remains of a species that existed over vast regions of Earth for a short period of time.
• Special criteria are used to identify index fossils.
Index Fossils
(cont.) 8.1 Geologic Time and Mass Extinctions
8.1 Geologic Time and Mass Extinctions
Divisions of the Geologic Time Scale
• No two divisions of time have the same number of years.
• The largest divisions are eons, then eras, periods, and epochs.
8.1 Geologic Time and Mass Extinctions
Eras
• The Phanerozoic eon is divided into three eras.
– Paleozoic era: dominated by invertebrate marine organisms – Mesozoic era: dinosaurs and mammals lived on land – Cenozoic era: humans evolved, continues today
Phanerozoic Eon Part A Part B Part C Part D
8.1 Geologic Time and Mass Extinctions
Periods and Epochs
• The Cenozoic era is divided into the Paleogene, Neogene, and Quaternary periods.
– The Quaternary period began 1.8 million years ago and is divided into epochs.
– The Pleistocene epoch ended about 8,000 years ago, and we now live in the Holocene epoch.
What are mass extinctions?
8.1 Geologic Time and Mass Extinctions
•
Mass extinction
is the dying off of many species at one time.
• A greater abundance of fossils in one rock layer compared to other layers indicates a mass extinction.
• Mass extinctions happen over a great span of time.
8.1 Geologic Time and Mass Extinctions
Possible Causes of Mass Extinctions
• A
catastrophic event
causes drastic change in the numbers of organisms of species over a short period in geologic time. • Not all catastrophic events cause mass extinction.
• Types of events that can cause mass extinction include changes in climate, volcanic eruptions, and asteroid impacts.
8.1 Geologic Time and Mass Extinctions
Climate Change
• There is evidence that some mass extinctions were caused by sudden climate change.
• Species that cannot survive a change in climate become extinct.
• Climate change can be caused by volcanic eruptions or asteroid impacts, and can result in global warming or cooling.
8.1 Geologic Time and Mass Extinctions
Global Warming
• Greenhouse gases in the atmosphere may contribute to global warming —a global increase in atmospheric temperature.
• Global warming causes a decrease in oxygen levels in water, and an increase in sea levels.
– May have been the cause for the Devonian mass extinction
8.1 Geologic Time and Mass Extinctions
Global Cooling
• Global cooling could lower sea levels as more water is frozen in glacial ice.
• Less water means fewer warm, shallow water environments.
– May have initiated the Ordovician mass extinction
8.1 Geologic Time and Mass Extinctions
Volcanoes
• Eruptions can be explosive or non-explosive.
– The dust, ash, lava, and gas emitted from volcanic eruptions can affect climate and organisms.
– A volcanic eruption is one hypothesis proposed to explain the mass extinction at the end of the Cretaceous period.
8.1 Geologic Time and Mass Extinctions
Basalt Flows
• Non-explosive floods of molten basalt emit the largest volume of matter of any eruptions.
• Geologic evidence shows that large basalt flows occurred during the Permian and Cretaceous mass extinctions.
8.1 Geologic Time and Mass Extinctions
Volcanic Haze
• The gases produced by basalt flows cause a volcanic haze effect.
• Sulfur dioxide gas is released and acid clouds form, preventing the Sun’s ultraviolet rays from reaching Earth.
• Global cooling occurs over months and years.
• Heat becomes trapped in the atmosphere and global temperatures increase.
8.1 Geologic Time and Mass Extinctions
Asteroid Impacts
• Scientists believe an asteroid impact in Mexico may have contributed to the Cretaceous mass extinction.
8.1 Geologic Time and Mass Extinctions
Asteroid Impacts
(cont.)
• Scientists propose that this impact sent enough dust and materials into the atmosphere to block sunlight.
• Global cooling after the impact turned to global warming as carbon dioxide was released from burning plants.
8.1 Geologic Time and Mass Extinctions
The Debate
• Evidence supports the idea that many species became extinct at the end of the Cretaceous period because of asteroids.
• But the impact did not cause all the extinctions.
• Many species became extinct before the impact, and the rate of extinction was increasing before the impact.
8.1 Geologic Time and Mass Extinctions
1.
2.
3.
4.
A B C D
Which describes the divisions of the geologic time scale in order of longest to shortest units of time?
A
eons, eras, periods, epochs
B
eons, epochs, eras, periods
C D
epochs, eons, periods, eras epochs, eons, eras, periods
A 0% B 0% C 0% 0% D
Lesson 1 Review
8.1 Geologic Time and Mass Extinctions
1.
2.
3.
4.
A B C D
What is the likely immediate outcome of an explosive volcanic eruption that sends dust into the atmosphere?
A
global warming
B
global cooling
C
basalt flows
D
volcanic haze
0% 0% 0% 0% A B C D
Lesson 1 Review
8.1 Geologic Time and Mass Extinctions
1.
2.
3.
4.
A B C D
What type of eruption emits the largest volume of matter?
A
basalt flows
B
explosive eruptions
C
non-explosive eruptions
D
volcanic haze
A 0% 0% 0% 0% B C D
Lesson 1 Review
End of Lesson 1
8.2 Early Earth History
cyanobacteria vertebrate amniote
8.2 Early Earth History
Life on Earth Changes
• Paleontologists discovered that the system used to classify modern organisms could be used to classify fossils.
• Fossils from rock layers that are touching are more similar than fossils from widely separated layers.
• The more recent a fossil was formed, the more it resembles a living organism.
Life on Earth Changes
(cont.) 8.2 Early Earth History
8.2 Early Earth History
Precambrian Time
• Precambrian rocks are difficult to study because they have undergone metamorphism or been destroyed.
• Precambrian fossils are not abundant but provide a lot of information about Earth’s early atmosphere and environment.
8.2 Early Earth History
The Precambrian Atmosphere
• Archean sediments contain large amounts of pyrite and uraninite.
• Today’s atmosphere contains oxygen that quickly destroys these minerals through oxidation.
• Earth’s early atmosphere had very little oxygen.
8.2 Early Earth History
Ozone
• The absence of oxygen suggests there was no ozone layer during Precambrian time.
• Without ozone, ultraviolet rays cause death or mutations in cells.
• Changes in one gene in an organism could result in new life forms many generations later.
8.2 Early Earth History
The First Organisms
•
Cyanobacteria
—one of the earliest organisms.
• Stromatolites are mounds of alternating thin-layered sediments and photosynthetic cyanobacteria that take in carbon dioxide and release oxygen.
8.2 Early Earth History
A Changing Environment
• Oxygen levels rose slowly as cyanobacteria and other early-life forms released oxygen.
• Natural selection favored organisms that could tolerate or use oxygen.
• The amount of ozone in the atmosphere increased.
8.2 Early Earth History
Soft-Bodied Organisms
• The first invertebrate organisms—animals without backbones —appeared during the Proterozoic eon.
– Ediacaran fauna
8.2 Early Earth History
The Paleozoic Era
• The first appearance of fossils of organisms made from hard parts marks the end of the Proterozoic eon.
• Because hard parts fossilize easier, fossils are easier to find in Paleozoic rocks than Precambrian rocks.
8.2 Early Earth History
The Cambrian Explosion
• During a relatively short period of time, the number of animals with shells greatly increased.
• Invertebrates—sponges, jellies, corals—also evolved during the Cambrian explosion.
8.2 Early Earth History
Invertebrates of the Paleozoic Era
• Throughout the Paleozoic era, the oceans contained a wide variety of invertebrate organisms.
• Corals, brachiopods, crinoids, bryozoans • Ordovician period, Silurian period
8.2 Early Earth History
Vertebrates of the Paleozoic Era
•
Vertebrates
—animals with backbones— evolved during the early Paleozoic era.
• The first of these lived in the oceans.
– Bony fish with bony rays that supported their fins – Bony fish with thick fins supported by large bones and muscles
8.2 Early Earth History
A New Egg
• A new organism that could lay its eggs on land evolved during the early Pennsylvanian period.
•
Amniotes
laid water-tight, amniotic eggs and could spend all their time on land.
– Mammals, dinosaurs, and reptiles evolved from amniotes.
8.2 Early Earth History
Plants of the Paleozoic Era
• During the Ordovician period, plants began spreading onto land.
• Early land plants were small and lived in moist areas because they could not move water to all their parts.
8.2 Early Earth History
Plants of the Paleozoic Era
(cont.)
• Plants with vascular systems that could move nutrients between roots and leaves then evolved.
– New plants developed quickly.
8.2 Early Earth History
Paleozoic Extinctions
• The Paleozoic era ended with the late Permian extinction —90% of marine and 70% of land species.
8.2 Early Earth History
Paleozoic Extinctions
(cont.)
• The uplifting formation of Pangaea, or ash and sulfur released from the Siberian Traps may explain the Permian extinction.
8.2 Early Earth History
1.
2.
3.
4.
A B C D
Which is not a characteristic of Earth’s early atmosphere during the Precambrian time?
A
very little oxygen
B
no ozone layer
C
iron in minerals quickly oxidized
D
organisms were exposed to ultraviolet rays
A 0% B 0% 0% C 0% D
Lesson 2 Review
8.2 Early Earth History
1.
2.
3.
4.
A B C D
What were some of the first vertebrates?
A
brachiopods
B
trilobites
C
edicacaran fauna
D
bony fish
A 0% 0% 0% 0% B C D
Lesson 2 Review
8.2 Early Earth History
1.
2.
3.
4.
A B C D
What ended the Paleozoic era?
A
Ordovician extinction
B
Devonian extinction
C
Permian extinction
D
Cambrian extinction
A 0% 0% 0% 0% B C D
Lesson 2 Review
End of Lesson 2
8.3 Middle and Recent History
pterosaur ectotherm endotherm gymnosperm primate
8.3 Middle and Recent Earth History
A Changing Landscape
• 180 million years ago, Pangaea began to split into Laurasia and Gondwanaland.
• This created a warm, wet climate.
What geologic evidence supports the existence of Pangaea?
8.3 Middle and Recent Earth History
A Changing Landscape
(cont.)
8.3 Middle and Recent Earth History
A Changing Landscape
(cont.)
• The Mesozoic era is known as the Age of Reptiles.
– Dinosaurs dominated midway through the era.
– Toward the era’s end, land began to dry out and the largest dinosaurs became extinct.
– Mammals that had never been larger than a possum, took over as the dinosaurs went extinct.
8.3 Middle and Recent Earth History
Invertebrates of the Mesozoic Era
• Stromatolites increased in number after their predators became extinct at the end of the Paleozoic era.
– Algae and rudistids evolved in the Cretaceous period.
– Reef-building corals replaced rudistids in the Triassic period.
– Insects declined in number and diversity during the Mesozoic era.
8.3 Middle and Recent Earth History
Vertebrates of the Mesozoic Era
• The oceans contained predatory reptiles, and amphibians, reptiles, and mammals that lived on land continued to evolve.
– Frog, turtles, crocodiles, dinosaurs
–
Pterosaurs
—flying reptiles—were different from dinosaurs, not related to birds or bats
8.3 Middle and Recent Earth History
Dinosaurs
• The first dinosaurs were small, but new species evolved into some of the largest animals to walk the Earth.
–
Ectotherms
—animals that rely on their surroundings and behavior to help them regulate their body temperature
–
Endotherms
—animals that generate internal body heat to maintain a constant body temperature
8.3 Middle and Recent Earth History
Dinosaurs
(cont.)
• Scientists think dinosaurs lived more like today’s mammals and birds than like reptiles.
• A dinosaurlike skeleton with fossilized feathers found in Jurassic-aged rocks supports the idea that birds evolved from dinosaurs.
8.3 Middle and Recent Earth History
Mammals
• Early mammals were small and not numerous for most of the Mesozoic era.
• In the Cretaceous period, they began to increase in number and diversity.
8.3 Middle and Recent Earth History
Plants of the Mesozoic Era
•
Gymnosperms
—plants that produce seeds but no flowers —were the dominant plants of the Mesozoic era.
• Angiosperms—flowering plants that bear seeds with hard coverings —evolved near the end of the Mesozoic era.
8.3 Middle and Recent Earth History
Mesozoic Era Extinction Events
• Mass extinctions occurred at the end of the Triassic and Jurassic periods.
• At the end of the Cretaceous period, an extinction event caused 85% of all ocean species and the remaining dinosaurs to become extinct.
• Many mammal species survived.
8.3 Middle and Recent Earth History
The Cenozoic Era
• The Cenozoic era is divided into seven epochs.
• During the Cenozoic era, marine life began to recover from the Cretaceous mass extinction.
• The offspring of organisms that survived the Cretaceous extinction make up today’s marine ecosystems.
8.3 Middle and Recent Earth History
Animals on Land
• Some mammals returned to the ocean during the Eocene epoch, giving rise to marine mammals such as whales.
•
Primates
—animals with opposable thumbs and eyes that look forward —evolved during the Eocene epoch and rapidly diversified.
• Hominids—animals which walk upright on two legs —evolved from the early primates during the Pliocene epoch.
8.3 Middle and Recent Earth History
Plants of the Cenozoic Era
• Flowering plants have continued to evolve since the Mesozoic era.
• Grasses supported a large diversity of mammals, allowing mammals to multiply and diversify.
8.3 Middle and Recent Earth History
1.
2.
3.
4.
A B C D
Which era is known as the Age of Reptiles?
A
Cretaceous
B
Mesozoic
C
Cenozoic
D
Jurassic
A 0% 0% 0% 0% B C D
Lesson 3 Review
8.3 Middle and Recent Earth History
1.
2.
3.
4.
A B C D
What best describes how dinosaurs are viewed today?
A
ectotherms
B
endotherms
C
reptiles
D
birds
A 0% 0% 0% 0% B C D
Lesson 3 Review
8.3 Middle and Recent Earth History
1.
2.
3.
4.
A B C D
During which epoch did hominids evolve?
A
Pliocene
B
Eocene
C
Cenozoic
D
Cretaceous
A 0% 0% 0% 0% B C D
Lesson 3 Review
End of Lesson 3
Chapter Resources Menu
Science Online
Virtual Lab
Click on a hyperlink to view the corresponding feature.
1.
2.
3.
4.
A B C D
Which is not an effect of an asteroid impact?
A
sunlight blocked by dust
B C
basalt flows causing a complex sequence of events carbon dioxide causing global warming
D
the death of primary producers causing mass extinctions
A 0% B 0% 0% C 0% D
Chapter Assessment 1
1.
2.
3.
4.
A B C D
Why have some paleontologists proposed that asteroid impacts did not cause all the mass extinctions at the end of the Cretaceous period?
A
There is no evidence of an asteroid impact at the end of the Cretaceous period.
B C D
Volcanic haze is a more likely cause.
Many species were already extinct by the time of the impact.
The fossil record does not support a mass extinction at the end of the Cretaceous period.
0% 0% 0% A B C 0% D
Chapter Assessment 2
1.
2.
3.
4.
A B C D
What caused oxygen levels to rise in Earth’s atmosphere?
A
the presence of photosynthetic organisms
B C
the evolution of bacteria-eating organisms an increase in the ozone layer
D
the evolution of organisms that could tolerate or use oxygen
A 0% B 0% 0% C 0% D
Chapter Assessment 3
1.
2.
3.
4.
A B C D
The evolution of amniotic eggs allowed ___.
A
the spreading of organisms into dry land
B
the movement of organisms to shallow-water environments
C D
the evolution of amphibians organisms to live on land and lay eggs in the water
0% 0% 0% 0% A B C D
Chapter Assessment 4
1.
2.
3.
4.
A B C D
Which group declined in number and diversity during the Mesozoic era?
A
stromatolites
B
reef-building corals
C
insects
D
mammals
A 0% 0% 0% 0% B C D
Chapter Assessment 5
SCI 4.g
1.
2.
3.
4.
A B C D
Which is not one of the methods scientists use to divide the geologic time scale into units of time?
A
mass extinctions
B
major changes in life-forms
C
index fossils
D
major changes in climate
0% 0% 0% 0% A B C D
CA Standards Practice 1
SCI 4.g
1.
2.
3.
4.
A B C D
What is not a possible effect of global warming?
A B C D
increase in sea levels decrease in oxygen levels decrease in shallow-water environments rising atmospheric temperatures
A 0% 0% 0% 0% B C D
CA Standards Practice 2
SCI 4.d
1.
2.
3.
4.
A B C D
Which is not a reason Precambrian rocks are difficult to study?
A
many have been destroyed
B C
many have undergone metamorphosis they are difficult to date with radiometric dating
D
they do not provide much information
A 0% B 0% 0% C 0% D
CA Standards Practice 3
SCI 4.g
1.
2.
3.
4.
A B C D
Which does not characterize the Cambrian explosion?
A
an increase in small-shelled organisms
B C
the evolution of amniotes an increase in invertebrates
D
an increase in large-shelled organisms
A 0% B 0% C 0% 0% D
CA Standards Practice 4
1.
2.
3.
4.
A B C D
All remaining dinosaurs became extinct at the end of which period?
A
Triassic
B
Jurassic
C
Cretaceous
D
Mesozoic
SCI 4.b
A 0% 0% 0% 0% B C D
CA Standards Practice 5
Concepts in Motion 1
Image Bank
Interactive Table
Phanerozoic Eon Part A Part B Part C Part D
End of Resources