6.2: Fossils
Background Information
The history of life on Earth began around 3.5 billion years ago with the emergence of single-celled microorganisms, called prokaryotes. Over time, these evolved into more complex cells, including eukaryotes, which eventually led to the formation of multicellular organisms. Around 540 million years ago, the first complex life forms appeared in the oceans, including invertebrates and early fish. During the next 400 million years, life continued to evolve and diversify, leading to the emergence of land plants and animals, including dinosaurs. The extinction of dinosaurs 65 million years ago paved the way for the rise of mammals, including primates and eventually humans. Over the past 200,000 years, humans have developed complex civilizations, languages, and technology.
A fossil forms when an organism's remains or imprint are preserved in rock or other material. This typically happens when the remains are covered in sediment, such as sand, ash, or mud, which eventually hardens into rock. Over time, the organic material decays, leaving behind an impression or mold in the rock. In most cases, minerals replace the organic material, preserving it as a mineral cast. Fossils can also form from preserved tracks or burrows made by an organism, or from preserved body parts, such as leaves, shells, or bones. The process of fossilization can take millions of years, and the conditions must be just right for preservation to occur.
FOSSIL CRINOID. A MARINE ANIMAL, FLOWERLIKE, ANCHORED BY A STALK. GRCA 14466. 26 MAR 1993. QUINN, NPS. CCBY 2.0
Soft tissues, such as muscles, organs, and skin, are not typically preserved in fossils. However, in rare cases, conditions may exist that allow for the preservation of soft tissues. One way this can happen is through rapid burial, which helps prevent decay and the destruction of soft tissue by scavengers. Another way is through the process of mummification, which occurs in dry, arid environments where low humidity slows down decay. In recent years, researchers have discovered many examples of fossilized soft tissues, such as dinosaur skin and feathers, body impressions, stomach contents, as well as many other exciting things. These fossils provide important insights into the anatomy and biology of ancient organisms.
Evolutionary history of life. Montage by Sciencia58 is based on works by Richie Diesterheft, JJ Harrison ( jjharrison89@facebook.com ), Ghedoghedo, Fritz Geller-Grimm and others., CC BY-SA 4.0 < https://creativecommons.org/licenses/by-sa/4.0 >, via Wikimedia Commons
Materials needed
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Fossil specimens (real or replicas)
- 4-6 specimens per 3 students
- Magnifying glass or dissection microscope
- Sketchbook and pencil
- Reference materials (books, websites, etc.)
- Rulers
- Device with photographing capability
- Device with internet access
Procedure :
- Obtain a fossil specimen from your instructor. There should be some basic information included with it such as where it was found, type of rock, the general age of rock, and a general description of the species. Also, obtain a magnifying glass or other magnifying device.
- Observe each fossil specimen with a magnifying glass and examine its physical characteristics. Take note of any noticeable details, such as the type of rock it is found in, any visible imprints or textures, and the overall shape of the fossil.
- Make detailed sketches of your fossil in the space below. Be sure to include a description of what you observed, measurements, and any other observations you have made.
- After sketching, take a picture of your fossil along with a ruler to show scale. Insert the picture beneath your sketch.
- Research the type of fossil you have found. Use the basic information that was provided to you as a starting point. Use reference books or online resources to identify its age, the species it belonged to, and the environment in which it lived.
- Record your observations and research in a lab report. Include sketches of the fossils and describe their physical characteristics and the environment in which they were formed. (OPTIONAL)
- As a class, discuss the findings and how they relate to the Earth's history. 8. On the timeline and table below, correctly write in the fossils to the date.
Draw your fossil sketch and notes in this space. Include any comments or observations you make here as well.
Insert photo with scale here:
● The record of major past glaciations during Earth’s history. Source: Steven Earle (2015) CC BY 4.0 view source
The importance of fossils in providing evidence of the Earth's past are invaluable and help us piece together the history of life on our planet.