Chap 14: The History of Life

14.1 The Record of LifeEarly 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.

.

.

Formation of universe

The “BIG BANG” 12-15 billion years

ago

Sudden expansion & explosion of all matter & energy.

Early Earth

Formation of Earth4.5 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

Theories1. Divine Origins2. Meteorites3. 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?

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 atmosphereWater, Ammonia, & Methane, Hydrogen

gasesElectrical CurrentCooled & 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

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 2.TRACKS, IMPRESSIONS, ORGANISMS TRAPPED IN TRAPPED IN

TREE SAPTREE 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. 1. Most fossils are not complete Most fossils are not complete organismsorganisms

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 isotopesUse radioactive isotopes Radioactive elements decay at known Radioactive elements decay at known

rates.rates. Measure the rate of radioactive decay of a

particular radioactive atoms. called half-life Half-lifeHalf-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 Carbon Dating: Carbon 14 : Date younger fossils. (50younger 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 --1909 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 LifeMesozoic Era-Middle LifeCenozoic Era-Recent Life

Precambrian Time4.5 billion to 545 million

years agoFormation of the EarthFirst Life on EarthAll life was in the seas

Earliest Fossils-3.5 billion years old; found in Stromatolites

The Precambrian Era

First Life—prokaryotes 3.5 byaEvidence: found in stromatolitesEarly 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