Overview

The Earth contains fossils which date as far back as 3.7 billion years. Today, we will investigate that timeline.

Science Question

How has the structure of living creatures changed to adapt to their environment as that environment changes?

Biology

There are a number of ways in which organic material may be preserved for study:

1. Permineralization: organic material is buried in sediment. Over time, water flows through the material, depositing minerals into the shape of the fossil. Many dinosaur bones were fossilized this way, along with petrified trees.
2. Molds and Casts: organic material is buried, then decays, leaving behind a hollow which is filled by sediments or minerals over time. A lot of shelled creatures, like snails, have been preserved this way.
3. Replacement: Shells or bones in organic materials are dissolved, then slowly filled in with a different mineral, such as quartz. Ammonites are common quartz fossils.
4. Compression: A high pressure on a flat material may create a dark imprint. Ferns and other ancient flora are often preserved this way.
5. Preservation: A material such as amber or ice can capture the organism completely with minimal decay. Amber has preserved insects and small creatures. More recent fossils, such as those of human beings, have occasionally been found inside ice.

Materials: 

• A wide variety of fossils from varying epochs of the Earth’s history

Instructions

Around the room there are seven stations representing different epochs of life on Earth. In your lab groups, please go through the stations (doesn’t have to be in order) and answer the following questions. You can use your notes from class.

STATION 1: PRE-EARTH

1. What materials are on the table? How do they relate to life on Earth?
2. Approximately how old are these items? Do they predate life itself?
3. Draw one item.

STATION 2: THE CAMBRIAN

1. What is a stromatolite?
2. Do trilobites have bones?
3. What notable event happened in this epoch of life on Earth?
4. Draw one fossil. What type of fossil is it?

STATION 3: THE ORDOVICIAN, SILURIAN, AND DEVONIAN

1. Describe the structures of the fossils you see. Are they more sophisticated than the fossils from the previous epoch?
2. Describe what you think a crinoid would look like today.
3. Draw one fossil. What type of fossil is it?

STATION 4: THE CARBONIFEROUS:

1. What important facet of human evolution evolved during the Carboniferous?
2. Why do you think we have a lot of shell-type fossils, but not a lot of fossils of ferns and other plants?
3. Draw one fossil. What type of fossil is it?

STATION 5: THE PERMIAN

1. Fun fact: the coelacanth is still alive today! What type of creature is it?
2. What caused the Permian extinction?
3. Draw one fossil. What type of fossil is it?

STATION 6: THE TRIASSIC/JURASSIC

1. What kind of creatures dominated this epoch of life on Earth?
2. Describe the difference between the Triassic and Jurassic.
3. Describe the Chicxulub Impactor and its effect on the development of life on Earth.
4. Draw one fossil. What type of fossil is it?

STATION 7: THE PALEOGENE:

1. What creature is alive in the bottle? How old is that species? What does it look like in its macroscopic form?
2. What happened to megafauna? Why do we think that there aren’t creatures like mastodons around anymore?
3. Draw one fossil. What type of fossil is it?