1. Wednesday, Sept 13th, 2017 Agenda: Go over homework definitions Becoming a fossil video and discussion Laetoli Footprints Radiometic dating HW: Complete a question in your “I wonder” Journal Complete the vocabulary worksheet with the words habitat and fossil record (Due on Thursday, Sept 14th)

2. Vocabulary Competition Predation
the activity or condition of competing.
interaction between organisms where their survival depends on gaining a share of a limited environmental resource
--the preying of one animal on others (Like a fox hunting a chicken)

3. Becoming a fossil (PBS-2:34 mins)
Why do most living things not leave?
How are fossils formed?
How are fossils found?

5. Laetoli Footprints (lay tolli)
What was the unusual series of circumstances that caused the Laetoli footprints to be preserved?
What do the footprints at Laetoli tell scientists about the way the creatures that made them moved?
The Laetoli footprints were formed and preserved by a chance combination of events—a volcanic eruption, a rainstorm, and another ashfall. When they were found in 1976, these hominid tracks, at least 3.6 million years old, were some of the oldest evidence then known for upright bipedal walking, a major milestone in human evolution. 

6. Laetoli Footprints
The Laetoli footprints were formed and preserved by a chance combination of events—a volcanic eruption, a rainstorm, and another ashfall. When they were found in 1976, these hominid tracks, at least 3.6 million years old, were some of the oldest evidence then known for upright bipedal walking, a major milestone in human evolution. 

7. Dating Fossils
Before we answer this question— How do you know how old you are? How does a vet know how old a stray dog is? How do forensic scientists know how long a body has been dead? KEY COMPONENT Using EVIDENCE we collect to compare it to information we know to be accurate.
When dating fossils, scientists rely on the information they know about ATOMS.
(You learned in 6th grade that atoms make up everything– including fossils).

8. Atomic Clocks
An atomic clock keeps perfect time by predictable behavior of electrons.
Atomic clocks are designed to measure the precise length of a second.
The International System of Units (SI) defines
1 sec = 9,192,631,770 oscillations of Cs-133 atom
Several atomic clocks in the world– including one at the  United States Naval Observatory in Washington DC

9. Radioactive “Clocks” These clocks use nuclear reactions to monitor
changes in time.
When atoms undergo a nuclear reaction, they changes from one type of atom to another. Examples:
K-40 Ar-40
Rb-87  Sr-87
U-238  Pb-206
Because these process take a long time to occur they are used for geologic dating (long periods of time).
Calvert Cliffs Nuclear Power Plant

10. Radiometric Dating What is radiometric dating?
How old has scientists determined the earth to be?