When you think of evolution, what comes to mind?
Draw a circle on your paper like the one below. Write down words, thoughts, or what you know (or think you
know) about evolution. At the top write information related to geological evolution. At the bottom, write
down information about biological evolution.
Geological
Evolution
Biological
What is evolution?
What are examples of evolution related to:
1.
2.
3.
4.
5.
6.
Technology
Earth’s Geology
Living Things
Environment
Methodology
Others ……..
Activity: “The Evolution of Technology”
Evolution: Theories & Evidence
Gradual change over time:
Biological evolution:
- Charles Darwin’s “Theory of Evolution”
- natural selection; survival of the fittest;
species/genetic variation
- adaptations (adaptations box activity, Gizmo: Natural Selection, newspaper)
Geological evolution:
- Uniformitarianism
- theory of plate tectonics, continental drift
- Law of Superposition
Environmental evolution:
- ice cores (dissolved gasses), rock layers
Life on Earth, as well as, the shape of Earth’s surface, has a history of change that is called evolution.
Theories of Evolution
Charles Darwin (Biological Evolution)
The 19th century English scientist who carried out the necessary research to
conclusively document that evolution has occurred and then made the idea
acceptable for scientists and the general public. This man did not invent the idea of
evolution. His work led to the theory of natural selection and survival of the fittest.
Lamarck (Chevalier de Lamarck) (Biological Evolution)
Lamarck's explanation for evolution summarizes the idea that evolution occurs as a
result of an organism acquiring a change in body shape due to using or not using
particular body parts during its lifetime and then passing the new trait on to its
offspring.
Uniformitarianism (Geological Evolution)
The theory that the gradual natural forces now changing the shape of the earth's
surface have been operating in the past much the same way. In other words, the
present is the key to understanding the past. From this view, the earth must be very
old. What are some examples of “natural forces” that change earth’s surface?
Compare & Contrast
Darwin’s Theory of Evolution
Lamarck’s Theory of Evolution
Theory of Uniformitarianism
Darwin’s Theory of Evolution
Lamarck’s Theory of Evolution
Theory of Uniformitarianism
Compare & Contrast Theories of:
Charles Darwin’s Theory of Evolution
Lamarck’s Theory of Evolution
Theory of Uniformitarianism
Charles Darwin’s Theory of Evolution
-
-
-
Research included
investigations conducted of
the Galapagos Islands
Concluded that natural
selection occurred by
survival of the fittest
Traits passed genetically
from parent to offspring
- Both Darwin’s theory
and TOU are directly or
indirectly related to
environmental change
- Both have evidence
based on research
Student Feedback: This
is the data put together
by students in classes
3– 6.
Lamarck's Theory of Evolution
-
Darwin & Lamarck
- Related to theories
of biological evolution
-
By either using or not using
body parts in a certain way,
new traits could be acquired
Traits acquired after birth
could be passed to offspring
- All of these are “theories”
- All involve the concept of
“change over time”
Theory of Uniformitarianism (TOU)
- Related to only geological evolution
- States that forces of nature (erosion,
earthquakes, volcanoes, water, wind, etc.) that
changed the shape of earth in the past are
continuing to do so
Theory of Uniformitarianism
Evidence of Evolution of
Organisms and Landforms
* Comparative Anatomy
*Species/Genetic Variations
*Fossils
* The Fossil Record
*Geologic Time Scale
* Plate Tectonics
* Continental Drift
*Law of Superposition
Fossils as Evidence
Fossils are the preserved remains or traces of once living things. Fossils can be
compared to one another and to living organisms according to their similarities
and differences.
1. Mineral replacement/petrification: Minerals in water and soil replace the
living material. (mold, cast)
2. Trace/Imprints: Imprints, footprints are left by the once living organism.
3. Carbonization: A thin layer of carbon is left by the once living organism.
4. Preservation of Actual Remains: (skin, bones, teeth, hair, etc.)
- amber
- ice
- tar (LeBrea Tar Pits)
- peat preservation
Methods of Fossilization: Lab: “Fossil Identification”
What can scientists learn by studying fossils?
“Analyzing Trace Fossils” activity
The Relationship Between Sedimentation and Fossilization
Sediments, sand and smaller particles are gradually buried and cemented together to form solid rock.
More recently deposited rock layers are more likely to contain fossils resembling existing species.
Thousands of layers of sedimentary rock not only provide evidence of the history of Earth itself, but
also of changes in organisms.
Rock Cycle
1. Why are fossils more likely to be found in sedimentary rock?
2. Why are fossils never found in igneous rock?
3. How can studying fossils in rock layers provide evidence of biological evolution?
“FossilofFun”
What process may lead to the discovery
fossils?
http://www.abc.net.au/beasts/fossilfun/makingfossils/default.htm “Fossil Fun” online activity
3
2
1
Which rock layer do you think is the oldest, 1, 2 or 3?
Igneous Intrusions cool inside Earth’s surface.
Igneous Extrusions cool outside Earth’s surface.
The Rock Cycle
Why are fossils more likely to be found
in sedimentary rock?
Mineralization/Petrification: Minerals in water and soil replace the living
material.
Dinosaur skull
Petrified wood
Trilobites and ammonites are used as “index fossils”.
trilobite
Index fossils
ammonite
Trace or Imprint Fossils: Imprints, footprints are left by the once living
organism
1
3
What can be inferred by studying each of these fossils?
2
4
“Traces of Tracks” Activity
1.
1.
What can you infer about
picture #1?
2.
2.
What can you infer about
picture #2?
Carbonization: A thin layer of carbon is left by the once living organism. Use the
concept of “comparative anatomy” to infer what each organism is.
1
1.
2.
2
What can be inferred by studying each of these fossils?
How did you use the concept of “comparative anatomy” to reach your conclusions?
3
4
Actual Remains of Organisms
Fossils Preserved in Ice
1
2
3
4
How does ice allow for the preservation of actual remains?
Actual Remains of Organisms
Fossils Preserved in Amber
3a
1
2
3
4
3b
1.
2.
How does this method of preservation allow actual remains to be present?
Based on “comparative anatomy” , what living organisms of today may they be descendants of?
Actual Remains of Organisms: Preserved in Tar The La Brea Tar Pits are a group of tar
pits around which Hancock Park was formed, in urban Los Angeles. Asphaltum or tar
(brea in Spanish) has seeped up from the ground in this area for tens of thousands of
years. The tar is often covered with dust, leaves, or water. Over many centuries, the
bones of animals that were trapped in the tar were preserved.
2
1
3
How did this method of preservation preserve the actual remains?
http://www.youtube.com/watch?v=G7FK59waeo0
“La Brea Tar Pits: An Urban Mystery” 6:08 min.
The Bog Bodies of Iron Age Europe
http://topractice.wikispaces.com/1+-+Arch.+of+Complex+Societies+Bog+bodies+term+paper (3:51 min.)
Bog bodies have been found in many locations in northwestern Europe: mostly in Ireland, England, Germany, and Denmark.
Generally, these countries have poor preservation conditions, but the bogs are an exception to the rule.
How did this method of preservation allow for the preservation of the actual remains?
http://www.abc.net.au/beasts/fossilfun/
On-line Activity : “Fossil Fun”
Burying Bodies
Pitfall
Skeleton Jigsaws
Making Fossils
Color and Camouflage
Footprints Game
Carbon-14 dating is a way of determining the
absolute age of certain objects of a biological
origin(actual remains) up to about 50,000 years old.
It is used in dating things such as bone, cloth, wood,
skin and plant fibers. This will be discussed when we
Based on what scientists have learned from the
fossil record, they have developed the
Eons
Eras
Periods
Epochs
Largest…….……………. To………….………. Smallest
Geologic Time Scale http://www.youtube.com/watch?v=7PQURsc2SYs “Geologic Timeline Music Video”
1. Which time periods are the longest?
4:23
2. Which time periods are the shortest
Mass Extinction: Meteor hits Earth
leads to environmental change
Mass Extinction: Continental drift leads
to environmental change
Precambrian Eon
bacteria: single-celled organisms
Coach Lesson 29
Eons are not shown.
Cont. Geologic Time Scale
Compare to an annual calendar.
http://www.esse.ou.edu/fund_concepts/Fundamental_Concepts4/Geologic_Time_Scale.html
Using the Geologic Time Scale, answer the questions.
1. Which included the longest amount of time:
eons, eras, periods, epochs?
2. In which era are we living?
3. In which period are we living?
4. Which organism evolved first, the first land
plants or the first reptiles?
5. Put the following organisms in order from
oldest to youngest.
first amphibians, first birds, first flowering plants,
first mammals
6. Scientists believe that Earth is approximately how old?
You may use the Geologic Time Scale at your table to
answer the questions.
Distribute student copies.
*Anatomical similarities and differences between organisms living
today and between them and organisms in the fossil record
enable the reconstruction of evolutionary history and inference of
lines of evolutionary descent.
Eon
Extinction of Species
1. Most species that have lived on the earth are now extinct (99%).
2. Extinction occurs when the environment changes and organisms do
not have traits necessary to survive and reproduce.
3. Some organisms that lived long ago are similar to existing organisms,
but some are quite different.
4. Extinction of species is apparent in the fossil record.
5. Mass extinctions occurred at the end of each era.
6. Scientists believe that 99% of all organisms that ever lived on Earth
have become extinct.
Environmental Changes: Natural process and human
activities result in environmental changes.
• Natural Processes:
• Human Factors:
- earthquakes
- movement of ice sheets
- volcanoes
- plate tectonics/
continental drift =
change
in sea levels,
changes of
height of
land, changes in
climate,
- pollution = less air and
water quality
- deforestation = increased
erosion,
- global warming = increased
temp. = melting of ice
caps
= change in sea
levels,
The Fossil Record
The collection of fossils and their placement in chronological
order (through location of sedimentary layers in which they
are found or through radioactive dating) is known as the
“fossil record”.
What have scientists learned by studying the fossil record?
Existence of organisms
- Diversity of organisms
- Relationship between organisms
- Time of mass extinctions
- Evolution of organisms
- Adaptions of organisms
- Climate changes
- Links to geological evolution
Student Geologic Timeline Project
Geological Evolution: Find the link. 
http://www.youtube.com/watch?v=YgE-dSx-fPc “Grand Canyon Superposition” 5:51 min
Law of Superposition
In undisturbed
rock layers, the
oldest rock layers
are on the
bottom and the
youngest layers
are on the top.
An “unconformity” is a
disruption in a rock layer. This
may be caused by geologic
forces or erosion from wind,
water, etc..
The Law of Superposition
“Who Dun it?” Activity
http://www.jbole.com/worksheets/WhoDunit.pdf
Someone took the last cookie in the cookies jar last night. The last person to leave the
scene is the culprit. Who was it?
Someone took the last cookie in
the cookie jar last night.
The last person to leave the
scene is the culprit. Who was it?
Clues:
The Butler walks to work.
The Handyman rides a bike.
The Cook rides a motorcycle.
The Maid drives a car.
The Nephew has a seeing-eye
dog.
Use the clues to solve the mystery.  Good luck.
1. Who took the last cookie?
2. Explain your reasoning using the concept of the Law of Superposition.
3. Put the people in order from 1 to 5 with 1 being who arrived at the scene first and 5 as who arrived last.
Unconformities
The red layer is an example of a ______.
1.
What is evidence of an
unconformity?
2.
What may have caused
the unconformity?
3.
What is evidence of
sedimentation?
4.
In “Time 2” what is the
oldest layer?
5.
In “Time 3” what is the
oldest layer?
6.
In “Time 4” what is the
oldest layer?
SG: “The Relative Age of Rocks”
1. Which rock layer is the
oldest? Explain.
2. Which rock layer is the
youngest? Explain.
3. Does this tell the absolute
or relative age? Explain.
Even through “folding” has occurred, the
layers are in their original order.
4. In which type of rock can
absolute age be
determined?
Intrusions
-
areas in Earth’s crust where magma has cooled before it
reached the surface forming an igneous intrusion
Intrusions are always younger than the rock layers they
go
through. (put on study guide)
Igneous intrusion
1
5
2
3
4
“Finding Clues to Rock Layers”
Put the layers in order from
oldest to youngest.
1
2
3
4
6
1. Which layer is the igneous
intrusion? Explain.
2. Put layers 1 – 6 in order from
oldest to youngest.
5
1.
2.
3.
4.
How old are layers 3 and 4? (Provide quantitative data.)
Layer 2 is __________________ than layer 1.
Layer 3 is __________________ than layer 4.
Does this provide “absolute” or
Layer 1 is __________________ than layer 2. “relative” age? Explain.
http://www.youtube.com/watch?v=Xs4yNL1M8Gg “How The Earth Was Made: Ring of Fire” 43:37 min.
Fault lines are the breaks in Earth’s crust where tectonic plate boundaries exist.
Plate Tectonics
• The movement of
Earth’s continental
(land) and oceanic
(ocean) plates has
caused mountains
and deep ocean
trenches to form and
continually change
the shape of Earth’s
crust.
• These movements
have caused plates to
pass through different
climatic zones. This
movement of the
continents is called
“continental drift”.
Activity: “Modeling Seafloor Spreading”
http://www.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.plateintro/pla
te-tectonics-an-introduction/ plate tectonics 2:22 min.
Evidence of Continental Drift/Seafloor Spreading
1. Coastline similarities
2. Fossil similarities
3. Glaciers (movement,
concentration of dissolved
gasses and other
substances)
4. Age and types of rocks
5. Rock magnetism
Hotter magma is less dense so it rises. Magma cools as it rises making it more dense. As the
density increases, the magma begins to sink. As the magma moves, so does the plate that is
above it.
http://www.youtube.com/watch?v=Kpoko_l34ZE Convection Currents 1:06
Activity: “Convection Currents”
Convection
Currents
Convection Currents
Green represents continental plates.
Diverging Plates
Converging Plates
Magma cools as it rises to the surface. It becomes more dense and will sink.
Magma near the core is hotter and less dense; therefore, it will rise.
Mid Ocean Ridges
http://www.youtube.com/watch?v=bGye6vlOpbY “The Mid-Atlantic Ridge” 2:53
Activity: “Modeling Seafloor Spreading”
At which location are the rock layers older, A, B or C? Explain.
C
B
A
A
rift valley
B
C
Why does this diagram show a convergent plate boundary and not a divergent plate
boundary?
“Modeling Convergent Plate Movement” activity
Subduction zone
Where is a divergent plate boundary shown?
Where is a convergent plate boundary shown?
Ice Cores: Evidence of Environmental Evolution
http://www.pbs.org/wgbh/nova/warnings/stories/
Record these 8 examples in your notebook.
(Dissolved gasses)
Scientists collect ice cores by driving a hollow
tube deep into the miles-thick ice sheets of
Antarctica and Greenland (and in glaciers
elsewhere).
The long cylinders of ancient ice that they
retrieve provide a detailed record of what
was happening in the world over the past
several ice ages. That's because each layer of
ice in a core corresponds to a single year—or
sometimes even a single season—and most
everything that fell in the snow that year
remains behind, including wind-blown dust,
ash, atmospheric gases, even radioactivity.
What is the relationship between CO2 and
temperature?
Ice Cores Provide Evidence of Radioactivity
1986 - Radioactivity
In April 1986, Russia's nuclear power
station at Chernobyl exploded, killing 250
people and sending radioactive fallout
around the world. Less than two years later,
as the graph indicates, scientists detected
Chernobyl radioactivity in snow at the South
Pole.
In cores from Antarctica and Greenland,
researchers have pinpointed the beginning
of atomic-bomb testing in the mid-1950s.
They have also identified a spike
representing fallout from stepped-up
atmospheric testing that took place just
prior to the 1963 Test Ban Treaty, which
allowed for underground tests only. In the
years following 1965, by which time some
90 countries had signed the treaty, Antarctic
snow revealed a sharp drop in radioactive
fallout.
Ice Cores Provide Evidence of Air Pollution
1900 - Air Pollution
Gases trapped in ice cores show the
dramatic impact that human activities
have had on the planet since the
Industrial Revolution.
The first graph reveals how
atmospheric carbon dioxide, methane,
and nitrous oxides from coal and oil
burning power plants, cars, and other
fossil-fuels (coal, oil, natural gas)
The burning of fossil fuels has climbed
along with the world population, with
as yet unknown effects on the climate
system.
Ice Cores Provide Evidence of Sea Storminess
1400 AD - Sea Storminess
Viking colonies in Greenland abruptly vanished
toward the end of the 14th century. This graph,
which combines results from cores taken in
both Antarctica and Greenland, tracks sodium
levels over the past 1,200 years.
In colder periods, seas become stormier
because of the greater contrast in temperatures
between the tropics and the poles, and so more
sodium—an indicator of sea salt—winds up on
the ice caps.
About 1400 AD, the cores at both poles clearly
show a sharp rise in sodium, which some
scientists say marks the onset of the Little Ice
Age, a period of much cooler temperatures that
lasted into the 19th century. For the Vikings, a
series of abnormally cold winters in the late
1300s spelled doom.
Ice Core Evidence of Pollution
1167 AD – Dating
Annual layers of snowfall in ice cores can be counted as easily as tree rings,
allowing precise dating of events such as volcanic eruptions. Distinct annual
layers stand out because, in snow that falls in summer, crystals are larger and
acidity higher than in winter snow. In some cases, scientists can even tell
seasons apart, by using a laser to measure the concentration of dust particles.
(Winds are generally stronger in springtime, meaning more dust gets blown
into the atmosphere.)
In this photograph of an ice core drilled in the Kunlun Mountains of western
China, the thick, lighter bands indicate heavy snowfall during the monsoon
season in the year 1167 AD, while the thinner, darker strips show layers of dust
blown into the snowfield during the dry season.
Ice Core Evidence of Climate Change
12,000 BP (before present) - Rapid Climate
Change
As this graph shows, a jump occurred about
12,000 years ago, as the last glacial period (the
Pleistocene) was giving way to our current warm
"interglacial" period (the Holocene). Suddenly,
possibly in less than five years, average
temperatures, which were slightly cooler than
today's, plunged by about 27°F, returning the
world to near-glacial conditions.
As the graph indicates, calcium levels tend to go
up and snow accumulation down with
temperature.
Ice cores have revealed that global
climate—long thought to change only very
gradually—can shift with frightening speed,
in some cases in a matter of years.
The Younger Dryas, as this freak period is known,
lasted about 1,300 years before it returned—just
as abruptly—to the temperatures typical of the
period immediately preceding it.
Ice Core Evidence of Temperature Change
Background information on isotopes not
necessary to learn as part of the standards.
(Optional)
• Temperature has yo-yoed over the ages
as wildly as it does through any single
year. Like natural thermometers, ice
cores have recorded these fluctuations,
which scientists can "read" by
examining *isotopes of oxygen and
hydrogen in water trapped in the ice.
The data in this graph, gleaned from a core
drilled in central Greenland, shows how
temperatures have risen by more than 20°C
(36°F) since the height of the Ice Age 25,000
years ago.
• Isotope: each of two or more forms of
the same element that contain equal
numbers of protons but different
numbers of neutrons in their nuclei,
and hence differ in relative atomic mass
but not in chemical properties; in
particular, a radioactive form of an
element.
Ice Core Evidence of Volcanic Activity
73,000 BP - Volcanic Eruptions
Approximately 73,000 years ago, an Indonesian
volcano known as Toba erupted with enough
force to send more than 600 cubic miles of
volcanic material into the atmosphere.
Such violent, so-called caldera eruptions can
drastically alter global climate, by spewing so
much ash and sulfur compounds into the
atmosphere as to block sunlight and lower
temperatures worldwide.
Detected on this graph, which displays
volcanic sulfate levels between 20,000 and
110,000 years ago, Toba was the largest
eruption of the past 500,000 years. (The
seemingly larger spike at about 53,000 years
ago involved a series of smaller eruptions on
Iceland, which is far closer than Toba is to
Greenland, where this core was taken.)
Ice cores offer scientists the best means
available to learn how past eruptions have
affected climate—and thus to predict the
impact that future ones might have.
If an eruption on the order of Toba, which
climatologists believe may have led to as much
as several centuries of cold climatic conditions,
were to occur today, it could seriously disrupt
life on Earth. (Yellowstone Nat. Park caldera)
Ice Core Evidence of Global Warming
160,000 BP - Global Warming
Many scientists fear that rising levels of socalled "greenhouse gases" from the burning of
fossil fuels (coal, oil and natural gas) and other
human activities will cause global warming,
with potentially grave consequences for human
agriculture and society.
One of the clearest signs that elevated levels of
greenhouse gases can result in warming comes
from an ice core taken near the Russian Vostok
station in Antarctica.
This graph tracks temperature and atmospheric levels
of carbon dioxide (CO2) and methane (CH4) from the
present back to about 160,000 years ago. (This
represents about 11,350 feet of ice accumulation.) The
graph clearly shows how a rise in gases will mean a rise
in global temperature (though whether rising gases
trigger rising temperatures, or vice versa, remains
unknown). Also note that (though the graph, which has
data up to two decades old, does not show this),
At about 360 parts per million, the amount of
CO2 in the atmosphere today far exceeds levels
at any time in the past 160,000 years—indeed,
in the past few million years. For those worried
about global warming, this is a sobering
statistic.
What are possible consequences of global
warming?
http://video.nationalgeographic.com/video/101-videos/
global-warming-101 “Global Warming : 101“ 3:04
Determining Relative and Absolute Age
Relative Age: the age of a rock or fossil described in
comparison to that of another rock or fossil.
Methods - Law of Superposition
- use of index fossils
Absolute Age: the actual age of a rock or fossil (actual
remains), or how long age it formed
Methods – radiometric/radioactive dating
with
igneous rock or
radiometric/radiocarbon
dating
(with actual remains)
Radioactive Decay
Henri Becquerel
Marie and Pierre Curie
•
Most elements are stable: If they are not part of a
chemical reaction, they do not change.
•
Chemical elements are made of atoms. In stable
elements, the atom stays the same.
•
In the 19th century, Henri Becquerel discovered that
some chemical elements have atoms that change.
During their change they send out a particle. In 1898,
Marie and Pierre Curie called this phenomenon
radioactive decay.
•
The time it takes, on average for half the atoms of a
substance to change/decay is called half-life.
Radioactive/Radiometric Dating: a means of measuring the absolute
age of a material by comparing the amount of a radioactive (unstable)
form of an element with the amount of its decay (stable) element
Radioactive Decay: the spontaneous break down of a
radioactive substance along with the emission of radiation
Radioactive Elements List
http://periodictable.com/Elements/Radioactive/
Radioactive Elements and Half-lives
http://www.buzzle.com/articles/list-of-radioactive-elements.html
Radioactive (unstable) Elements
&
Decay (stable) Elements
1. By what percent does the radioactive element
decrease after each half life?
Radioactive Element (g)
2. What is the relationship between the radioactive
(unstable) element and the decay (stable) element?
1st
Half life
2nd
Half life
3rd
Half life
4th
Half life
Half-life
Mass of
Original
Carbon-14
Remaining (g)
Mass
Of Decay Element
Nitrogen-14
Number of
Years
Carbon 14 is used to determine absolute age of
actual remains.
0
100%
0
0
1
50%
50%
5,730
2
25%
75%
11,460
3
12.5%
87.5%
17,190
4
1.
2.
3.
4.
5.
6.
Complete the data for the 4th half-life.
What is the “stable” element in the above data table? Explain.
What is the “unstable” element in the above data table? Explain.
What is the half-life of carbon-14? Explain.
By what percent does carbon-14 decrease after each half-life?
By what percent does nitrogen-14 increase after each half-life?
How many half-lives must pass before 25% of the carbon-14 is
remaining?
Radiocarbon Dating
Charcoal, wood, twigs and seeds
bone
Marine, estuarine and riverine shell.
Leather
Peat
Coprolites (samples of preserved feces).
Lake muds and sediments.
Soil
Ice cores
Pollen
Hair
Pottery
Metal casting ores
Wall paintings and rock art works
Iron and meteorites
Bird eggshell
Corals and foraminifera
Blood residues
Textiles and fabrics
Paper and parchment
Fish remains
Insect remains
Resins and glues
Antler and horn
Water
Carbon 14 = radioactive (unstable) element
Nitrogen 14 = decay (stable) element
Half-life: the time it takes for half of a radioactive
element to decay
What is the “half-life” of carbon 14?
As the radioactive element _____,
the decay element will ______.
Half-Life: the amount of time it takes for a radioactive element to decay
into its “decay element”
Major Radioactive Elements Used in Radiometric Dating
Radioactive Element
Decay Element
“Absolute age” can only be
determined with materials
that have the radioactive
element in them.
Half-Life of
Radioactive
Element
Effective
Dating Range
(Years)
Minerals and Other
Materials that can
Be Dated
1. How can you tell that the “stable decay element” and the “radioactive material X“ are
correctly labeled?
2. What is the “half-life” of the radioactive (stable) element?
3. How many half-lives will occur before half of the decay element is present?
Twizzler Activity: “Modeling Radioactive Decay”
Practice: “Decay of Radioactive Material”
SG: “Radioactive Dating of Rocks”
Time ( X 10,000 years)