Describe some of the various types of fossils including casts and molds, permineralized, carbon film, mummified and trace fossils.
Recognize that fossils form in sedimentary rocks. Explain that the conditions must be absolutely perfect in order for a fossil to form.
Emphasize that the probability of specimens of any species of organisms surviving is small-soft body parts are eaten or decomposed, and hard parts are crushed or dissolved.
Discuss how fossils can be used to explain changes in Earth's life forms and climate over long periods of time. The fossil record provides snapshots of the past. Although the fossil record is not complete, fossil evidence clearly shows that life is old and has changed over time (evolved).
Explain how knowledge gained from the age of the rocks where the fossils are found provides us with the sequence of change that has encompassed the history of life. Samples of the same fossil species or related species can be placed into the order in time that they lived in order to understand the evolutionary history of a group.
Discuss how when scientists examine all of the organisms that come from sequentially ordered fossil beds, they can develop temporal maps and scenarios of the changes that have taken place in ecological communities.
Discuss how scientific knowledge changes over time as new fossils are discovered.
Recognize that fossil evidence is used to support several scientific theories (the theory of evolution and the theory of plate tectonics). Remind students that a theory is not an opinion. A theory is based on empirical evidence and can be altered as new evidence is discovered. Do not cover the basics of either theory at this time. The theory of evolution will be taught in 7th grade. The theory of plate tectonics will be taught in the next unit.
LEQ: Number 2
HOTS: Deductive Reasoning could be used to demonstrate the ET LEQ.
Discuss how geologic time can be estimated by observing rock sequences and using fossils to correlate the sequences at various locations.
Explain that if a scientist knows the age of a certan type of fossil, then the rock that fossil is found in must have formed at the same time.
Recognize that fossils found underneath other fossils tend to be older. More recently deposited rock layers are more likely to contain fossils resembling existing species.
Identify the methods used for determining the age of rocks and fossils including radioactive dating, radiocarbon dating and relative dating techniques.
Explain that scientists use the Law of Superposition to determine the order of events that have occurred within an area (relative dating).
Scientists can also use certain fossils to determine the approximate age of the rock (index fossils).
Use visual diagrams to show the concept of a half-life and explain how knowing the half-life of an isotope scientists can use it to determine the numerical age of a rock or fossil. Apply the use of half-life to radiometric and radiocarbon dating.
LEQ: Number 2
HOTS: Deductive reasoning or error analysis could be used to support the ET LEQ.