Transcript Chapter 12 Notes - Ms. Irwin`s Website

The History of Life
The Fossil Record
Types of Fossils
 Permineralized fossils
 Natural casts
 Trace fossils
 Amber-preserved fossils
 Preserved remains
Permineralization
 Minerals carried by water are deposited around
a hard structure or may replace hard structure.
 Most common form of fossil
Natural casts
 Flowing water removes all of original tissue or
bone, leaving an impression
 Minerals fill mold to recreate shape of organism
Trace fossils
 Record activity of an organism
 Include nests, burrows, imprints
of leaves or footprints
Amber-preserved fossils
 Organisms trapped in tree resin that hardens into
amber
Preserved remains
 Entire organism becomes encased in
material such as ice, volcanic ash or
immersed in bogs.
Fossils
 You and your partner will be given a
fossil. You job is to:
 Describe the type of fossil it is
 What living thing was fossilized
 When you are finished, trade with
another group until you have described
three different fossils.
How are some fossils
formed?
 Mainly form in sedimentary rock
 Many layers of small rock particles (clay, silt, sand)
 1.) After organism dies, must be buried by sand, sediment,
mud or tar
 2.) Water fills in spaces of organism and minerals are
deposited
 Tissue is replaced by hard minerals
 3.) More and more layers continue to build up and pressure
compresses bodies
Journal Question
Is the fossil record complete?
In other words, is there fossil
evidence for every living thing
that has existed? Why or why
not?
Relative Dating
 Estimation of time which organism
existed
 Compares location of fossils in different
layers
 Law of Superposition
 Allows scientists to determine the order
(sequence) of species groups that
existed
 NOT ACTUAL AGES OF FOSSILS
Radiometric Dating
 Absolute age
 Use natural decay (break down) of
radioactive isotopes found in dead materials
 When nucleus is unstable, it decays (breaks
down) over time – known as “half-life”
 Half-life
 Amount of time it takes for half of the
isotope to decay into another isotope
 Example: carbon-14 decays into nitrogen14 with half life of about 5,700 years
Radiocarbon dating
 While organism is alive, it breathes in carbon14.
 When organism dies, carbon-14 continues to
decay
 If carbon-14 has half-life of 5,700 years, a 5,700
year old fossil will have half of its C-14
decayed into N-14.
 After 11,400 years (two half-lives) ____ percent
will have decayed?
 75%
 25% of the original remains
Radioisotopes used to
determine Earth’s Age
Radiometric dating used to
determine the age of Earth
Based on radioisotopes from
meteorites, Earth is about 4.6 billion
years old.
Geologic Time Scale
Index Fossils
Fossils of organisms that existed
only during specific spans of
time over large geographic
areas.
Helps to determine the age of
rock layers
Geologic Time Scale
 Shows history of Earth, and is divided into
eras and periods
 Era:
 Tens to hundreds of millions of years
 Consist of two or more periods
 Periods:
 Last tens of millions of years.
 Associated with particular type of rock
Paleozoic Era
Paleo = ancient
Cambrian Period
544-505 mya
Variety of animals developed very
quickly
All life was found in water
“Cambrian Explosion”
Ordovician Period
505-440 mya
Marine invertebrates evolved
First vertebrates evolved
Glaciers formed sea level
dropped  MASS EXTINCTION to
marine life
MASS EXTINCTION
 Mass extinction:
 When a large number of organisms
become extinct over a relatively short
period of geologic time
 Glaciers caused global cooling
 Killed organisms that are adapted to
warmer climates
Silurian Period
440-410 mya
Land plants arose
Glaciers melted  seas formed
Jawless and freshwater fish
evolved
Devonian Period
410-360 mya
Fish became more diverse
Sharks, amphibians and insects
appeared
Trees and forests arose
MASS EXTINCTION
 Global cooling due to glaciers
 Another 50% of organisms die
Carboniferous Period
360-286 mya
Coal forming sediments in swamps
Fish became more diverse
Amphibians, winged insects,
conifers (ex. Pine trees) and small
reptiles
Permian Period
286-248 mya
Modern pine trees appeared
Pangaea supercontinent was
formed as land masses joined
MASS EXTINCTION
 Largest mass extinction in the history of life
on Earth
 “Permo-Triassic Extinction”
 95 % of species die
 Less water available for life
 Sea level changed
Mesozoic Era
Meso = middle
Triassic Period
248-213 mya
Dinosaurs evolved
Fern plants and cycads evolved
Mammals and flying reptiles arose
Jurassic Period
213-145 mya
Dinosaurs diversified
Trees became more similar to trees
today
Oceans were very diverse with fish
and squid
Birds arose
Cretaceous Period
145-65 mya
Dinosaurs peaked, then went
extinct
Birds survived
Flowering plants arose
MASS EXTINCTION
 Large meteorite (10km in diameter) hit
Yucatan Peninsula
 Adding dust into the atmosphere
 Blocking UV light needed for life
 Massive volcanic activity also added to the
dust in atmosphere
Cenozoic Era
Ceno = recent
Tertiary Period
65-1.8 mya
 Mammals
 Flowering plants
 Grasslands
 Insects
 Fish
 Birds
 Primates
Quaternary Period
1.8 mya-PRESENT
Continues today
Includes all modern forms of life
Plate Tectonics
Plate Tectonics
 Study of the formation and
movement of the plates
 Plates: rigid, moving pieces of
Earth’s surface
 Plates are either moving past each
other, moving apart, or moving
together (colliding)
Evidence for Plate Tectonics
Diverging Boundaries
Also known as spreading centers
Places where two plates are
moving apart
Sliding Boundaries
 Plates are sliding past each other
 San Andreas Fault in California
 Fault: break or crack in Earth’s crust
where movement has occurred
 Likely places for earthquakes
Converging Boundaries:
Collision
 Two plates are coming together
(converge)
 Collision refers to the plates being
pushed upward
 Mountain range
 Himalayan Mountains
Converging Boundaries:
Subduction
Plates come together
One plate plunges down under
another plate
Deep-sea trenches usually found in
oceans