Chapter 14 The 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

History in Rocks 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

A Trip Through Geologic Time 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 4570 – 542 million year ago Life Begins Prokaryotes form Eukaryotes form Invertebrates appear -complex organisms with no backbones Geological Calendar: 2/25- 11/18

A Trip Through Geologic Time 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 The Paleozoic Era: 542-251 million years ago First Vertebrates First Fish First Land Plants First Amphibians First Reptiles First Trees Geological Calendar: 11/18- 12/12

A Trip Through Geologic Time Cambrian explosion (寒武纪大爆发， 535 to 525 million years ago) Dramatic increase in number of species

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

A Trip Through Geologic Time The Mesozoic Era: 200-65 million years ago First dinosaurs First mammals First flowers First birds Geological Calendar: 12/12 – 12/26

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

A Trip Through Geologic Time The Cenozoic Era: 65 million years ago – Present day -Domination of mammals -Evolution of Humans -Modern Society Geological Calendar: 12/26 – 12/31

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

Origins: The Early Ideas Spontaneous generation The idea that nonliving material can produce life

Origins: The Early Ideas Spontaneous generation is disproved by Francesco Redi: 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…

Origins: The Early Ideas Louis Pasteur: French Scientist One of the creators of Microbiology and did experiments that supported Germ Theory Germs cause disease Germs do not spontaneous generate Biogenesis (生源论) The idea that living organisms come only from other living organisms

Origins: The Modern Ideas 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 formed In 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.

Early Life Forms Archaebacteria: First forms of complex life; Can only survive in extreme environments Used abundant organic molecules for food Evolved to produce glucose through chemo-synthesis

Origins: The Modern Ideas Photosynthesizing prokaryotes

Origins: The Modern Ideas Death By Oxygen! Most species up to this point were anaerobic prokaryotes Creation of an oxygen rich atmosphere changed environment Dramatic shift in microbe evolution

Origins: The Modern Ideas 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

That’s all