Script for
Fossils

This slideshow is designed for all grades.  The instructor should decide the level and purpose for their class.  It establishes the type of fossils and preservation.  It gives an example of shark fossils.

Slide 1: What is a fossil?

·       Introduce that fossils are part of the Earth Sciences called Paleontology. A scientist that studies fossils is called a Paleontologist.

·       Paleontologist have to understand the living organisms in order to understand fossils. Many people can walk by a fossil and just think it is a rock (which it is – a sedimentary rock).

·       Is the specimen in this photograph a fossil? Ask students if picture #1 (shell fossil) or picture #2 (modern shells) is a fossil. Point out some differences between modern shells and fossils. The fossils do not have any color or pattern that we can see. Fossils often look like they are attached to rocks. You can point out that we can compare the fossils to the modern organisms to learn about the fossils. Ask students to see what modern day specimen in the second image can be used to compare to the fossil in the first.

·       Introduce to students that fossilization just does not pertain to bones, and remind the audience that many things leave evidence. Bones, shells, footprints, imprints, coprolites, and many other specimens fossilize. The first slide is a great way to establish the direction of your lecture. Be clear that in this slide to inform your audience that you will be discussing and observing fossils from the Paleozoic (before the dinosaur) all the way to the Cenozoic (present time).

Slide 2: Fossilization process- This slide demonstrates how an organism becomes a fossil.

·       First an organism has to die. All the “gooey” soft stuff will be eaten away either by animals or bacteria, and a hard part will remain. It is then buried. The fossil is then exposed either by erosion or someone excavating the site. Notice that fish can be identified but if you look at the snail shell, it had a hermit crab inside. Fossils help paleontologists tell a story, but sometimes the clues do not tell the entire story.

Slide 3: The easy way to become a fossil

·       This slide repeats and expands upon the previous one.

·       To become a fossil first you need a hard part like a shell, bone or tooth. Pick up the jellyfish model and ask if this can easily become a fossil. No it lacks a hard part. (Jellyfish can be preserved via impressions or carbonization, but it is much harder for a jellyfish/soft organism to be preserved overall.)

·       Second you need to be buried rapidly by soft sediments to help preserve features. The fossilization process for animals that die on land is more difficult. The bones are often not buried rapidly and the parts may be eaten or scattered by scavengers.

·       Once a bone or shell is buried chemistry takes place. Different minerals can harden a fossil specimen and even replace it. Chemistry has to do its “magic.”

·       Students may believe an organism becomes a fossil overnight instead of realizing the unique process of fossilization takes time. Once a fossil becomes a rock, it alive forever.

Slide 4. Environments, types of fossilization

After your students understand how an organism becomes a fossil, transition into the types of environments in which specimens can be preserved and the different types of fossilization. Depending on the grade level of your class, it is my recommendation to discuss mummification, amber, mold/cast, and impression. You can state that carbonization, per-mineralization, recrystallization, and replacement are other ways specimens can be preserved but the concepts may be too complicated for grade school science.

·        Mummification: These slides explain the process of mummification for Lyuba (Russian: Люба), a female woolly mammoth calf (Mammuthus primigenius) who died c. 41,800 years ago at the age of 30 to 35 days. She is by far the best preserved mammoth mummy in the world. Her intestines still contained adult mammoth feces, showing that she followed the same behaviour as her elephant cousins, eating her mother’s feces to fill her gut with microbes, to prepare her body to digest grass.

·       Amber: Another example is an insect which has been trapped in tree resin. The tree resin keeps oxygen out. When the resin fossilizes to form amber, it preserves the insect. Plants, insects, and small vertebrates can be preserved this way.

·       Mold and Cast: This is a form of indirect fossil preservation – the organism is not preserved, but traces of the organism are. These traces provide clues about an organism’s life. The most common indirect fossils are molds and casts. After the remains of an organism have been buried in sediments, water moving through the sediment dissolves the fossil. A cavity in the rock remains and is called a mold. A cast forms when the mold fills up with another material. In some cases, minerals such as calcite or quartz precipitate in the mold. Sediment may also fill the void. The formation of a cast is similar to putting Jell-O in a mold. When you remove the mold, you are actually seeing a cast. 

·       Impression: An impression is when an organism leaves an imprint or impression in soft sediment. The sediment then turns into a rock preserving the outline and any detail of the organism.

·       Carbonization: A chemical reaction where water transforms the organic material of plant or animal to a thin film of carbon. Nitrogen, hydrogen, and oxygen are driven off as gases, leaving an outline of the organism. Organisms often preserved by carbonization include fish, leaves and the woody tissues of plants.

·       Permineralization or petrifaction: Takes place in porous materials such as bones, plants and shells.  The material is buried; later, groundwater percolates through its pore spaces. A solution, commonly supersaturated in either calcium carbonate or silica, precipitates minerals in the spaces. This preserves the original wood or shell-like material.

·       Recrystallization: Occurs when a solution or precipitate changes the internal physical structure of a fossil. Recrystallization changes the microstructure of the original minerals; they often reform as larger crystals. The composition of the mineral does not change, only the crystal structure. For example, many shells originally composed of calcium carbonate in the form of the mineral aragonite recrystallize into the more stable form of calcium carbonate called calcite.

·       Replacement: Involves the complete removal of original hard parts by solution and deposition of a new mineral in its place. The Petrified Forest in Arizona is an excellent example of this type of preservation. Here the original organic material (wood) has been wholly replaced by silica.

Slide 5.  Type of fossils

What types of fossils will you view in our museum?

Explain to the students that there are many different kinds of organisms on Earth, so there are many different types of fossils. Click on each vocabulary term (microfossils, invertebrate, vertebrate, trace fossils, and plants.) After clicking on the term, the slideshow will take you to other information and slides that will help you with the lecture

·       Microfossils: The microfossil slide gives photos of radiolarians. Chert is made out of radiolarians (many, many of them!).  Radiolarian are very small, with diameter of your eyelash.  They are zooplankton and they eat phytoplankton, especially diatoms.  Which have created vast depositions and responsible for raw ingredients of petroleum.  (Olive oil comes from olives; corn oil comes from corn; diatoms have an oil globule that when cooked at right temperature over time produce oil)

·       Invertebrate Fossils: Invertebrates includes animals that do not have bones. This ranges from slugs, to shelled organisms to insects. Remind the students how invertebrates are commonly fossilized (cast, mold, replacement, permineralization, recrystallization, etc.). They can also be fragmented and incorporated into rocks (like the +mollusk fossils they just saw).

Plant fossils: Under the right conditions plants can also be fossilized. This often occurs as impressions or carbonization.    

·       Trace fossils: Trace fossils represent the preservation of an organism’s activities. It is any modification the organism made to the substrate or anything the organism left behind that is not a bone, egg or hard part. Examples of trace fossils are tracks, trails, burrows, nests, poop, root traces, claw marks, holes in shells from predation. Trace fossils help determine how/where an organism lived and also give information about the environment in which the organism lived.

·       Tyrannosaurus rex tracks

·       Dr. Angeline Catena, a paleontologist, holding dung beetle burrows

Slide 6.   What is stratigraphy?

·       Introduce the word stratigraphy to your students. It is the study of sedimentary rocks, their layers (and order of layers) and how they related to geologic time. Explain why the study of stratigraphy is important to the fossil record. Fossils are only found in sedimentary rocks, and stratigraphy helps to understand the environments the organisms lived in, past landscapes, and the and the ages of the fossils. Stress to your group that when discussing fossils it is important to factor in time.

·       Video is an overview of Grand Canyon.

Slide 7.   The country Morocco and fossilization

·       Where is the country Morocco? (Northern Africa)

·       Explain the history with Morocco and fossils. Morocco and much of Northern Africa was once underwater, so many fossils from sea creatures can be found there. Identify the location of Morocco on a map. The students will take a fossil shark tooth souvenir away from this country.

·       Video is of Atlas mountains, and also shows a small town that sells fossils 

Slides 8/9/10. Sharks and fossilization

·       For slides 8, 9, and 10 explain what type of information can be derived from fossils.

·       What is the connection between sharks and fossilization? When modern sharks eat, they lose teeth. The teeth come out of the jaws and are swallowed. Just like everything that goes in one end, the teeth come out of the shark in the form of poop. Since sharks are composed of cartilage (not bone), parts of the skeletons are very, very rarely preserved. The poop and the teeth are thus important, because these are often the only fossils we have of past sharks!

·       Show students the shark jaw and point out the multiple rows of teeth.

·       The video shows a shark that is pooping!