CONCEPT: Changes are constantly occurring in and on the earth.
CONTENT OBJECTIVE: 6J1.00 To understand how fossils are formed
INSTRUCTIONAL OBJECTIVES: The learner will:
1.01 define fossil.
1.02 explain how fossils are formed.
OUTLINE OF CONTENT:
I. Formation of fossils
II. Indexing
III. Cast and mold
TN COMPONENT OF SCIENCE: Process of Science
TN GOAL:
To enable students to demonstrate the processes of science by posing questions and investigating phenomena through language, methods and instruments of science.
TN THEME:
COMMUNICATING - An essential aspect of science is the act of accurately and effectively conveying oral, written, graphic or electronic information from the preparer to the user.
TN STANDARD(S): The learner will understand that:
1.6a The sharing and disseminating of results should be done in a clear and concise manner.
BENCHMARK: Human beings learn complicated concepts from others through various methods of communication.
CLASSROOM CONNECTORS
TIME REQUIRED:
Two one-hour periods
MATERIALS:
Plaster of Paris, petroleum jelly, shells, fossils, photos or poster of Grand Canyon, screen and projector
SET:
Today we are going to learn about fossils and how they are formed. We also will learn about fossils and cast and mold fossils.
INSTRUCTION:
(Have photographs of the Grand Canyon, rocks containing fossils Crinoids, trilobites, etc.) (Filmstrips on fossils, shells, petroleum jelly, plaster.) Show students a photograph or poster of the Grand Canyon. Have each student write as many observations as he can about the picture. You may help them by telling them that the rocks at the bottom are igneous and metamorphic. The upper two-thirds the Canyon is sedimentary. Not all sedimentary rocks are made of particles of rock. Sediments may be formed from things that once lived. Fossils are remains, impressions, or any evidence of the former existence of life, as found in rocks. Some fossils that we are going to discuss are index fossils, molds and casts.
Index fossils, which are also called guide fossils, are typical of a particular period of earth history. An index fossil holds the remains of something that lived for only a short period of time, but existed in large numbers. An example of this is an animal called a trilobite which existed 225 to 600 million years ago in oceans all over the world.
Sometimes a fossil shell or bone is dissolved out of the rock in which it was preserved. This leaves a hollow mold. The mold shows what the shape of the fossil had been. When new mineral material fills the mold it forms a cast of the original fossil.
ACTIVE PARTICIPATION:
(Let students bring in fossils that they have collected. Discuss each fossil. Tell the students that fossils can form by petrifaction, preservation in amber, imprint, carbon imprint, cast and molds.)
(Let students make models of fossil casts and molds. Cover the outside of a shell with petroleum jelly. Pour about 75 milliliters of water into a container. Slowly pour plaster of Paris into the water. Mix as you pour. Add plaster until mixture looks like thick cream. Pour plaster of Paris into plastic cup. Tap cup to eliminate air bubbles. Press the greased side of shell into plaster mixture. Let harden overnight. Remove shell.)
CLOSURE:
In our lesson today, we learned about fossils and the different ways they are formed. Write your own definition of a fossil on your paper, then I will let you share your definition with the class. (pause, response, then summarize) (Using a picture of the Grand Canyon or rocks containing fossils. Ask the students to explain the concept of how these were formed.)
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