Transcript Evolution and the History of Life

Evolution and the History of
Life
Part 3
MLK
Fall 2005
M.Elizabeth
www.marric.us/teaching
Chapter 9: The History of Life on Earth
I.
Chapter 9.1: Evidence of the Past
A. Fossils
B. The Age of Fossils
Relative Dating
Absolute Dating
C. The Geologic Time Scale
Division of the Geologic Time Scale
Mass Extinctions
D.The Changing Earth
Pangaea
Do the Continents Move
Adaptations in Slow Motion
Fossils
• Fossils are traces or imprints of living
things. Fossils are found most often
Sedimentary rocks
found in _____________________.
•So what is a rock.
•The rock cycle describes how rocks are
formed. But sometimes there area
complications
3 types of rocks
• Igneous Rock
• Sedimentary Rock
• Metamorphic Rock
Rocks are classified
according to how
they were formed.
Rock Cycle
is a sequence of events involving the
formation, alteration, destruction, and
reformation of rocks as a result of
natural processes ...
Glossary of Geology, Bates & Jackson, AGI
The Rock Cycle is…
• A process in which rocks change
form from one type to another
type. Any of the three classes of
rock can be changed into any other
class.
• Igneous Rock- Formed from cooled magma
• Sedimentary Rock- Formed from sediments
compacted and cemented together
• Metamorphic Rock- formed by changes in
heat and pressure
• Metamorphic Rock
The Rock Cycle explains
how Rocks and Natural Processes
are related
compaction,
cementation
Sedimentary
weathering
Metamorphic
Igneous
Types of Rocks
Igneous Rocks
Metamorphic
Rocks
Sedimentary Rocks
Igneous Rocks
What are They?
• Fire Rocks
• Formed underground
by trapped, cooled
magma
Intrusive
• Formed above ground
when volcanoes erupt
and magma cools Extrusive
Examples?
Sierra Nevada Granite
Intrusive igneous ____________________
Hawaiian Lava
Extrusive igneous _____________
Catastrophic Event: Eruption of Mount Vesuvius,
Italy, 79 AD
excavated ruins
Volcanic ash
layer
Effects: Mass human mortality in Pompeii and Herculaneum
Atoms make up elements.
Elements combine to form
the natural compounds.
.
Natural compounds
and elements combine
to form minerals.
Minerals make up rocks.
Rocks make up the Earth.
This is a hierarchy of
the elements of Geology
Well back to Dating Fossils
The Age of Fossils
• Relative Dating
– the law of superposition.
• Absolute Dating
– the law of radioactive decay
Relative Dating
• Relative Dating: the law of superposition.
• Older rocks are on the bottom and newer
layers are on the top, unless there has
been folding, faulting or uplift.
• This method of dating fossils or layers
relative to each other is called relative
dating.
• Exact ages cannot be determined with
relative dating.
Examples of complications when reading
sedimentary rocks
Absolute Dating
• Absolute Dating: the law of radioactive decay.
Atoms are made of neutrons, protons, and
electrons.
• Isotopes are atoms of the same element but
with different numbers of neutrons. Some
isotopes are not stable – unstable isotopes –
release energy by decaying radioactively.
• Each time an isotope decays it becomes another
element that may or may not be stable.
Eventually, a stable isotope will be formed.
Absolute Dating
• Each isotope decays at a particular rate.
The time it takes for one-half of the
unstable isotopes (parent isotopes) to
decay (into daughter isotopes) is its halflife.
• By measuring the ratio of parent isotopes
to daughter isotopes is how the age of
rock and fossils in the rock can be
determined. Remember the Geology lab$$
• Absolute dating is how exact ages can be
determined.
Example problems
• Thorioum-232 has a half life of 14.1 billion
years. How much of an 8 mg sample will be
unchanged after one half-life? _____.
4 mg How
much after two half-lives?_______.
How much
2 mg
1 mg
after three half-lives?_______.
How much
after four half-lives?________.
0.5 mg
• Carbon-14, an isotope of carbon, has a half-life
of 5780 years. How much of the original sample
will be left after 11560 years? 25% = 1/4
• After 17190 years? 12.5%= 1/8
Geologic Time Scale
Because
geologic time
is soooo long
a different
type of
calendar is
used to
describe
geologic time
– the geologic
time scale.
Divisions in the Geologic Time Scale
• Paleontologists have divided the time scale
into large blocks of time called eras which
are then subdivided into periods that can
be subdivided again.
• Our four eras are (Papa Pete Makes Cake)
• Precambrian, Paleozoic, Mesozoic, and
Cenozoic.
• Eras are characterized by the type of animal
that dominated the Earth at the time.
Major Era Characteristics
• Precambrian Era – all time up to 540 million years
ago (_____)
mya – prokaryotic (without nucleus) and
eukaryotic (with nucleus) single celled organisms.
• Paleozoic Era began 540 mya to 248 mya – plants
and fishes. Included the largest mass extinction
when 90 percent of marine organisms and 75
percent of terrestrial organisms became extinct.
• Mesozoic Era – 248 mya to 65 mya –dominated
by dinosaurs and other reptiles, and birds until
their mass extinction when the era ended.
Age of the Reptiles.
• Cenozoic Era – 65 mya to now – dominated by
mammals – Age of Mammals.
Mass Extinctions
• When a species is extinct it does not reappear.
• There have been five major extinctions in the
Earth’s history. These extinction events are
called mass extinctions.
• There are many possible reasons for these mass
extinctions, a possible explanation for the
dinosaur extinction is a meteorite hit that
caused a brief changes in climate or atmospheric
composition - Catastrophic.
• It is thought that man’s activities may be the
source of the rapid extinctions that are
occurring today.
• Is this the sixth mass extinction?
Name of
Extinction
Episode
Percent of
species
lost
MYA
Affected Species
Ordovician
(Paleozoic)
85%
440
mya
Marine species
Devonian
(Paleozoic)
83%
360
mya
Meteor impact,
Many fish and marine volcanism, glaciation,
invertebrates die out. oxygen depletion
Permian
95%
250
mya
Trilobites and other
marine species, but
some land plants,
amphibians, and
reptiles
(Paleozoic
Era ends)
Tropical areas are hit
hardest.
No terrestrial
vertebrates have
evolved yet
Hypotheses
Glaciation, oxygen
depletion
Marine species
Greatest mass
extinction ever.
Volcanism, meteor
impact, sea level
change, global
warming glaciations
Name of
Extinction
Episode
Percent
species
lost
MYA
Affected
Species
Hypotheses
Triassic
80%
213
mya
Mostly
marine
species,
some land
animals
Global cooling, meteor
impact, sea-level change,
oxygen depletion
Cretaceous/
Tertiary
aka
KT Extinction
76%
66
mya
Affected
both land
and marine
species.
Meteor impact, volcanism,
continental drift, mammal
competition.
Quaternary
70%
(Dinosaurs and
mammals had just
recently evolved;
both live through
this extinction.)
Mesozoic Era
ends
Findings from a
United Nations
Report of 1,100
scientists in 2002)
NOW
+ 30
years
Dinosaurs
become
extinct
65 million of years after
this mass extinction, early
humans evolve.
Affected
both land
and marine
species.
Anthropogenic -Human
caused effects such as
pollution, over population,
global warming, over
fishing, and deforestation.
Geologic Period
at
Qu
ce
ou
s
na
ry
er
ta
Cr
e
Tr
ias
sic
an
mi
vo
nia
n
Pe
r
De
an
Or
do
vic
i
Percentage of Species Lost
100
90
80
70
60
50
40
30
20
10
0
Questions
1. Which hypotheses is the most common
over all the mass extinctions?
Meteor Impacts
2. Which mass extinction is the greatest?
Permian
3. Which mass extinction is the least?
Quaternary – What is occurring now
due to human activities
4. After each mass extinction new species
evolved, what is this process called?
SPECIATION
5. Has the number of species on Earth
remained the same or changed over the
history of the Earth?
The number of species on Earth has
changed with speciation and
extinctions occurring over Earth’s
history
6. Extinction normally occurs at what rate?
10-100 species per year – VERY SLOWLY
7. If the scientists are correct and trends
continue, should we worry about
extinctions today? Why?
Losing 70% of all species would be one of
the great mass extinctions of the
planet and we are the cause. The
conditions that cause the loss will also
affect our ability to live as well.
We are
not
alone
The Changing Earth
• Example of the results from a changing earth:
– Marsupials – mammals that carry their young in
pouches are found in Australia almost exclusively,
although there are some in South America and one
in North America.
– Why is a question that requires careful thought not
just a “because”.
– The answer that geophysicists have developed is
called plate tectonics which explains why Australia
is so different.
– Australia separated from the main landmass of the
earth’s early beginning.
http://www.ucmp.berkeley.edu/mammal/marsupial/marsupial.html
Opossum
Pangaea
• Pangaea is the name given to the Earth’s early
landmass by Alfred Wegner.
• Wegener published his theory called Continental
Drift in his 1915 book, On the Origin of
Continents and Oceans.
• In it he also proposed the existence of the
supercontinent Pangaea, and named it (Pangaea
means "all the land" in Greek).
• The evidence Wegener used included the shapes
of continents, the fossils of plants and animals
at coastal margins, and that there has been
drastic changes in the climates of continents.
Do the Continents Move?
• Plate Tectonics – the outer crust is
underlain by a semi-molten material that
circulates and in doing so creates
convection currents that move the
overlying crustal plates.
Adaptations in Slow Motion
• Tectonic plates move slowly, slowly enough
for adaptations to occur.
Converging/Diverging
Plates
Glacial Striations
• How to “track” a glacier………..
Striations help determine which
direction the ice was flowing as it
moved across an area.
http://nsidc.org/
glaciers/gallery/
grooves.html
Homo sapiens
• The modern species of humans, the only
extant species of the primate family
Hominidae.
• Thought to have originated in Africa.
• ETYMOLOGY:New Latin Hom sapi ns,
species name : Latin hom , man + Latin sapi
ns, wise, rational, present participle of
sapere, to be wise.
That’s All Folks
What is the
Rock Cycle ?
The Rock Cycle
Gypsum (Mg Ca Carbonate)
Minerals
Sulfur
Beryl
Be3Al2(Si6O18)
Pyrite
Fools Gold (FeS2)
Metamorphic Grade - Foliated
Metamorphic