Wednesday, Sept 13th, 2017 Agenda: Go over homework definitions Becoming a fossil video and discussion https://mpt.pbslearningmedia.org/resource/tdc02.sci.life.evo.becfossil/becoming-a-fossil/#.WbbjmMiGO1t Laetoli Footprints https://mpt.pbslearningmedia.org/resource/tdc02.sci.life.evo.becfossil/becoming-a-fossil/#.Wbh-lK2lmCR Radiometic dating https://mpt.pbslearningmedia.org/resource/tdc02.sci.phys.matter.radiodating/radiometric-dating/#.Wbh-0a2lmCS 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)

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)

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

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. 

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. 

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).

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

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

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