Chap 14: The History of Life 14.1 The Record of Life Early History of Earth

What does it look like?

What is the Geological Time Scale? The geological time scale is a scale “used by geologists to describe the timing and relationships between events that have occurred during the history of the Earth”

What does it suggest? The earth is around 5 billion years old The order of different events in the Earth’s history Things have been evolving since the beginning of measurable time

The Geological Time Scale Evidence for Evolution

Divisions of Geological Time Eon Era Period Epoch Age

Geologic Time Scale: Boundaries between Eras and periods correspond to times of great change

How are the eras divided and what are they? Cenozoic, Mesozoic, Paleozoic, Precambrian These are usually determined by major geographical or paleontological events such as mass extinctions Time scale suggests many species came to be and became extinct over millions of years Fossils of things like trilobites and dinosaurs suggest things have been evolving over the millions years

Continental drift. Explains geographic distribution of species.

THE EFFECTS 250 mya: Formation of Pangea Species once isolated faced competition. Total shoreline was reduced. Interior land masses were drier; weather more severe 180 mya Break-up of Pangea Radiation of marsupials

How old are you?? DATING scientists can determine in which order events occurred. 2. relative dating: uses layers of rock sedimentary layers in the earth oldest layers at the bottom, youngest at the top 2. absolute dating like Carbon to Nitrogen and Potassium to Argon

What can we conclude? By looking at fossils from millions of years ago and comparing them to more recent fossils and then again comparing those to even more recent fossils (still within a mere million year time scale) we can see that things have been changing in order to adapt to the ever changing environment.

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Formation of universe The “BIG BANG” billion years ago Sudden expansion & explosion of all matter & energy.

Early Earth

Formation of Earth 4.5 billion yrs. ago, molten, no oxygen 4 billion years ago, oceans formed, as earth began to cool. But how did life appear?

Origin of First Cells 3.9-to-3.4 Billion Years Ago Proposed that life began in the oceans

Origin of Life on Earth p.388 Theories 1. Divine Origins 2. Meteorites 3. Primordial Soup-- abiogenesis

14.2 The Origins of Life The Early Ideas: Spontaneous Generation: ________material can produce life. Redi Louis Pasteur disproves this theory (p. 381)

Origins—The Modern Ideas 2 developments must have preceeded life: 1. Simple Organic Molecules Formed 2. These became organized into complex molecules –like proteins, carbs, nucleic acids

First Cells If the building blocks of cells formed on primitive Earth (or arrived on Earth), could cells self- assemble?

Formation of Macromolecules- From non-living matter Theories: 1. Panspermia: Murcheson Meteorite Australia- colonial microbes similar to cyanobacteria 2 Thermal vents in Ocean: 3. Spontaneous generation of macromolecules—Miller/Urey

Alexander Oparin ‘s hypothesis of the Spontaneous Generation of Macromolecules Life began in oceans in the Early Earth Lots of energy: sun, lightening, Earth’s heat. This triggered chemical reactions in the atmosphere The molecules”rained” into the oceans forming a “primordial soup”

Miller & Urey 1953-test Spontaneous Generation of Macromolecules Simulated early Earth’s atmosphere Water, Ammonia, & Methane, Hydrogen gases Electrical Current Cooled & collected the “rain”

Miller & Urey Exp. Cont. Results: in 1 week formed amino acids other small organic molecules

BUT!!!!! 2 Possible Inaccuracies in Miller & Urey’s Experiment 1. Atmosphere maybe not right: 2. Not enough continuous energy from lightening

How do macromolecules Life? Need proteins to make nucleic acids Need nucleic acids to make proteins WHOA!!!!!!!!! This sounds like the “CHICKEN OR EGG” QUESTION!!!

The Evolution Of Cells ( p. 383) The First True Cells Prokaryote cells Anaerobic Heterotrophs Similar to present-day archaebacteria ASSIGNMENT: RESEARCH ARCHAEBACTERIA; 2 PARAGRAPH SUMMARY.

Oldest fossils 3.4 –3.5 billion years old Photosynthetic prokaryotes

Earliest Fossils found in Stromatolites in Australia

History in Rocks (p. 370) Fossils Help understanding of ancient events, climate, geography Fossil Formations; conditions have to be right: Buried in sand, mud,or clay soon after death; low pressure, low temperature. Compress & harden into sedimentary rock

FOSSILS 1. Traces or remains of dead organisms 2.TRACKS, IMPRESSIONS, ORGANISMS TRAPPED IN TREE SAP TREE SAP 3. Often found embedded in stratified layers of Sedimentary rock.

Fossils 4. Fossil layers used to help construct a geologic time scale. 5. Deepest layers=oldest fossils

FOSSIL FORMATION 1. Most fossils are not complete organisms 2. Conditions have to be right 3. The remains have to be buried in sediment. Shell or bone fossilizes if buried in sediment—mud, tar, lava.

One-celled organisms appeared before multi-celled ones Plants appeared before animals Invertebrates before vertebrates What have We Learned from Fossils?

Relative Dating Age is relative to the order of appearance in the sedimentary rock layer. Older fossils are in the deeper layers Not actual age

Radiometric Dating Use radioactive isotopes Use radioactive isotopes Radioactive elements decay at known rates. Radioactive elements decay at known rates. Measure the rate of radioactive decay of a particular radioactive atoms. called half-life Half-life Half-life—the amount of time it takes for ½ of the radioactive atoms in a sample to decay into a new isotope.

Carbon Dating: Carbon 14 : Date younger fossils. (50 Carbon Dating: Carbon 14 : Date younger fossils. (50,000 yrs).: (4.5 Billion Year H.L.); Potassium 40-half-life of 1.3 billion years Can determine age, because the amount of radioactive decay is constant Earth is about 4.5 billion years old. Earth is about 4.5 billion years old.

The Burgess Shale Yoho National Park, Canada Shale dates to 530 MYA Some of the most well preserved from Cambrian Period—date to the Cambrian Explosion Soft bodied (and these are hard to preserve!!)

A Trip Through Geologic Time The Geologic Time Scale 4 large sections

Precambrian Time Paleozoic Era-Ancient Life Mesozoic Era-Middle Life Cenozoic Era-Recent Life

Precambrian Time 4.5 billion to 545 million years ago Formation of the Earth First Life on Earth All life was in the seas

Earliest Fossils-3.5 billion years old; found in Stromatolites

The Precambrian Era First Life—prokaryotes 3.5 bya Evidence: found in stromatolites Early prokaryotes soon split into 2 kingdoms: 1)Eubacteria (true bacteria) 2)Archaebacteria (ancient)- Eukaryote’s ancestors

. Eukaryotes evolved 1.5 bya—algae Most life- soft-bodied— so few fossils; like sponges, jellyfish