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