Chapter 14The History of Life
Section 14.1 The Record of Life
Early History of Earth
-The Earth is 4.1- 4.2 billion years old
-Life originated in Earth’s oceans
between 3.4 - 3.9 billion years ago
History in Rocks
Fossils—Clues to the
past
- A fossil
(化石 ) is evidence of an
organism that lived
long ago
Fossil formation ( P 371 )- For fossils to form, organisms usually have to be
buried in mud, sand, or clay soon after they die.
- These particles are compressed over time and
harden into a type of rock called sedimentary rock
( 沉积岩 ).
History in Rocks
Trace fossil-
Foot prints, nests/dens, or fossilized feces (poop)
Tell scientists about the activities going on at that time
History in Rocks
Mold-
Organism dies in soft mold and leaves an imprint of it’s body
History in Rocks
Cast-
Starts as a mold, but over time a mixture of water and minerals fill in the mold
Makes a 3D model of the organism
History in Rocks
Petrified/ Permineralized fossil-Minerals invade and replace organism’s parts as it dies
Makes very detailed skeletons
Body is turned to stone
History in Rocks
Amber-preserved fossil
-Organism lands on a tree and gets stuck in the tree sap
-Over time the sap changes to Amber stone
-Organism is often perfectly preserved
History in Rocks
Relative dating ( 相对定年法 )
-As layers of sediment rock build on top of each other, the fossils in the deepest layers of rock most be older than those above them.
-General age of fossil, cannot be exact
History in Rocks
Radiometric dating ( 放射性定年法 )
-Using radioactive isotopes to age fossils
-Carbon-14
-Potassium-40
-Chlorine-36
History in Rocks
The geologic time scale
- The Precambrian ( 前寒武纪 )
- The Paleozoic Era( 古生代 )
- The Mesozoic Era( 中生代 )
- The Cenozoic Era( 新生代 )
Each era( 代 ) is subdivided into periods( 纪 )
Geological Calendar:
All of Time in just 1 year!
Formation of the Earth is
00:00 on 1/1
A Trip Through Geologic Time
The Precambrian Era
A Trip Through Geologic Time
4570 – 542 million year ago1)Life Begins2)Prokaryotes form3)Eukaryotes form4)Invertebrates appear -complex organisms with no backbones
Geological Calendar: 2/25- 11/18
Life during the Precambrian
Unicellular prokaryote appear
(4000- 3400 million years ago)
A Trip Through Geologic Time
Life during the Precambrian
More complex eukaryotic organism
appeared (2500 – 2100 million years ago)
A Trip Through Geologic Time
Life during the Precambrian
Multicellular eukaryotes, such as sponges and
jellyfishes, and invertebrates diversified and
filled the oceans (543 million years ago)
A Trip Through Geologic Time
A Trip Through Geologic TimeThe Paleozoic Era:542-251 million years ago
-First Vertebrates
-First Fish
-First Land Plants
-First Amphibians
-First Reptiles
-First TreesGeological Calendar:
11/18- 12/12
Cambrian explosion ( 寒武纪大爆发,535 to 525 million years ago)
Dramatic increase in number of species
A Trip Through Geologic Time
Permian extinction (二叠纪大灭绝)“The Great Dying”
-End of the Paleozoic Era
96% of Marine species
70% of vertebrates
83% of Insect species
-Caused by climate
change
-Hotter temperatures
-volcano activity
-Ice Age
-Dust reflects sunlight
The Mesozoic Era:200-65 million years ago
-First dinosaurs
-First mammals
-First flowers
-First birds
Geological Calendar:
12/12 – 12/26
A Trip Through Geologic Time
Mesozoic Mass Extinction:Second largest extinction
Caused by an asteroid impact and increased volcanic activity
Known as the K-T Extinction
Continental Drift
(板块漂移)
Movement of tectonic plates
The Cenozoic Era:65 million years ago – Present day
-Domination of
mammals
-Evolution of
Humans
-Modern Society
Geological Calendar:
12/26 – 12/31
A Trip Through Geologic Time
Geological Time Line Homework:Create your own representation of the Geological Time
- Work in Groups of 2 or 3
- Must show the ratio used
- Must show all events listed on p.376
- Creative designs can get bonus points
- You will present your time line next class
- MiniLab 14.2 on p.376 will help you;
You do not have to follow MiniLab 14.2!!
SHARE the work!
P 390
Section 14.2 The Origin of Life
Spontaneous generation
The idea that nonliving material can produce life
Origins: The Early Ideas
Spontaneous generation is disproved by Francesco Redi:
Origins: The Early Ideas
• Maggots only grow on meat exposed to flies
• What about microbes?
• There are bacteria everywhere?! How they must appear from a life force in the air…
Louis Pasteur:
Origins: The Early Ideas
• French Scientist• One of the creators of Microbiology
and did experiments that supported Germ Theory
1) Germs cause disease2) Germs do not spontaneous
generate
• Biogenesis ( 生源论 )
• The idea that living organisms
come only from other living
organisms
Simple organic molecules formed
In the 1930s, a Russian scientist, Alexander
Oparin, hypothesized that life began in the
oceans that formed on early Earth.
Origins: The Modern Ideas
Simple organic molecules formedIn 1953, two American scientists, Stanley Miller and Harold Urey, tested Oparin’s hypothesis by simulating the conditions of early Earth in the laboratory.
Origins: The Modern Ideas
The formation of protocells
A protocell( 原细胞 ) is a large, ordered
structure, enclosed by a membrane, that
carries out some life activities, such as growth
and division.
Origins: The Modern Ideas
Archaebacteria:
Early Life Forms
• First forms of complex life; Can only survive in extreme environments
• Used abundant organic molecules for food
• Evolved to produce glucose through chemo-synthesis
Photosynthesizing prokaryotes
Origins: The Modern Ideas
Death By Oxygen!
Origins: The Modern Ideas
• Most species up to this point were anaerobic prokaryotes
• Creation of an oxygen rich atmosphere changed environment
• Dramatic shift in microbe evolution
The Endosymbiont theory( 内共生理论 )Eukaryotes evolved through a symbiotic relationship between ancient prokaryotes.
Origins: The Modern Ideas
Experimental evidence shows:
- Chloroplasts/Mitochondria
contain DNA that is similar
to the DNA in prokaryotes
- Chloroplasts/Mitochondria
have their own ribosomes
- Chloroplasts/Mitochondria
reproduce independently
Origins: The Modern Ideas
That’s all