Features Favorable for Fossilization

Investigating the influences of structure and predation on the fossil record

 

COMPARING STRUCTURE AND PREDATION USING A FOOD WEB

Objectives: As a result of these exercises, students should be able to analyze the characterisics of a specific organism and describe how these characteristics influence whether or not it has a potential for fosslization. In addition, students will apply their knowledge about what types of things get fossilized, to speculate and understand the seeming absence of organisms that live in the same ecosystems but are not seen in the fossil record.

Background/Rationale: Many factors about an organism may make it more or less susceptible to fossilizatoin. The fossil specimens that do exist are therefore valuable in terms of considering specific aspects of earth's history in relation to that fossil. Geologists use fossils in numerous ways when deciphering the histiory of the earth. For example, fossils can be used to correllate stratigraphic (rock) units that are geographically separate from eachother. Locating a fossil in two different areas suggests that either the environment in those two areas was comparable and therefore a particular organism lived in both places, or on the other hand, it may indicate that one or both of the fossilized remains were carried away from their living environment by some sort of interaction, whether it be with another living organism or the result of an earth process such as flooding. The following exercises will help students to examine how structure and predation play a role in the creation of the fossil record.

Materials needed: Internet access or library access, for students to find information on different food chains

Instructions:

1. Begin by asking the students create a list of things that they think are fossils. Try as a group to come with criteria for fossilzation, and discuss why certain things are fossilized or not.

Favorable characteristics for fossilization include hard parts (bones, teeth, shells, exoskeletons etc.), and abundance (number of organisms around, eg. mosquitos), environment, and lack of predators.

2. Now, have the students split up into groups. Each group will be responsible for finding and learning about a food chain within a specific ecosystem. Here's a list of possible ecosystems from which students can find different food chains, and most importantly animals with different types of fossilization potential.

1. Desert

3. Mountainous

5. Deep sea

7. Woods

2. Near shore salt water

4. Lake

6. Prairie

8. Rainforest

3. Next, have the students investigate each of the organisms within their food chain, and determine the fossilization potential for each one based on the organism's sturucture.

Click here for examples of this activity

4. Have students conpare the total number of organisms in their food web with the number that are likely to get fossilized, then have the students look at the relationships between these animals in the food web. Are there any predator-prey interactions that could influence the list of probable fossils?

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5. Reflect with students on the appearance of some fossilis in the record and the seeming absence of others. Compare how many organisms the class would have seen preserved or not preserved based upon these two criteria alone.

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To investigate further characteristics that influence fossilization such as environment and location, click here.

Assessment: There are several ways in which this exercise could be assessed possibilities include

1. Have students report to the class the fossilization potential of the organisms in their food chain, and then discuss the implications of each of the group's findings, as well as whether or not the class agrees with the choices the students made about fossilization potential.

3. Have students roll play, pretending that they are a particular organism and have them tell a story about how or why they will become a famous fossil someday.

2. Create a worksheet or test question that has students compare the fossilization potential of a couple of organisms on the basis of characteristics covered in this lesson; structure and predation.

4. Present a scenario where fossils of one or two organisms are included and ask the students to speculate about the world that the organisms lived in, taking into account how structure and predation may have allowed them to become fossils.

 

Standards addressed: From the National Science Education Standards grades 5-8.

Life Science

a. structire of living things

The human organism has systems for digestion, respiration, reproduction, circulation, excretion, movement, control, and coordination, and for protection from disease. These systems interact with one another.

b. regulation and behavior

An organism's behavior evolves through adaptation to its environment. How a species moves, obtains food, reproduces, and responds to danger are based in the species' evolutionary history.

c. populations and ecosystems

Populations of organisms can be categorized by the function they serve in an ecosystem. Plants and some micro-organisms are producers--they make their own food. All animals, including humans, are consumers, which obtain food by eating other organisms. Decomposers, primarily bacteria and fungi, are consumers that use waste materials and dead organisms for food. Food webs identify the relationships among producers, consumers, and decomposers in an ecosystem.

d. Diversity and adaptations (lack there of = extinction)

Extinction of a species occurs when the environment changes and the adaptive characteristics of a species are insufficient to allow its survival. Fossils indicate that many organisms that lived long ago are extinct. Extinction of species is common; most of the species that have lived on the earth no longer exist.

Earth and Space Science

a. Earth's history

Fossils provide important evidence of how life and environmental conditions have changed

 

 

 

To sample activities on structure

 

 

To sample activities on predation

 

 

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