Fossil Dating
What is a Fossil?
How do we know what extinct organisms looked like when they were alive? While we will never know exactly what every part of their body was like, we can take a very good guess by using fossil evidence.
A fossil is a preserved remain of an organism from the past. It is actually very difficult for an organism's body parts to be fossilized. To become a fossil, there must be a perfect combination of body part and external condition.
A fossil is a preserved remain of an organism from the past. It is actually very difficult for an organism's body parts to be fossilized. To become a fossil, there must be a perfect combination of body part and external condition.
Only certain body parts can become fossilized. For example, bones, teeth, and shells can easily be fossilized due to their rigid structure. Body parts such as skin, hair, muscle tissue, and other internal organs are extremely difficult to fossilize or preserve.
To become fossilized, a body part must be subject to a perfect mix of environmental conditions. The body part must be buried, pressurized, and remain still in an area of almost no moisture or erosion for a very long period of time.
To become fossilized, a body part must be subject to a perfect mix of environmental conditions. The body part must be buried, pressurized, and remain still in an area of almost no moisture or erosion for a very long period of time.
Types of Fossil Dating
There are two ways that scientists use fossils to determine the evolutionary history of organisms. They are called Relative Dating, and Absolute Dating.
In relative dating, scientists can observe how deep a fossil is buried, and what it is buried around. This can help in making a rough estimate of the fossil's age.
Scientists have long known that generally, the deeper a fossil is buried, the older the fossil is. So, they can order the age of fossils based on what depth they are buried in relation to other fossils. Scientists can also observe what fossils are buried around. If a fossil is buried in a layer of sediment that is 500 million years old, scientists can guess that the fossil is about the same age. Also, a fossil's age can be guessed if it is buried near other fossils whose ages are known by scientists. |
All matter on earth is made up of atoms. Along with normal, stable atoms, the earth is also full of radioactive, unstable atoms. These atoms fall apart, or decay, at a fixed rate. Scientists have determined exactly how fast many of these atoms decay.
In absolute dating, scientists can test the chemical composition of atoms found in or around certain fossils. Scientists know that the more decayed an atom is, the older it is. By knowing the age of decay (also known as half-life) of certain atoms, scientists can isolate these in order to determine how old a fossil actually is. |
What About Whales?
In relation to fossils, we will look at one specific whale species. The fossil remains of the transitional species Maiacetus inuus have been discovered by scientists. By using relative and absolute dating, scientists have learned much about this animal.
The bones of Maiacetus look as if they may be that of a land mammal. By using relative dating, scientists can estimate what era this fossil was from. By doing this, and finding that Maiacetus was surrounded by fossils of aquatic life, it can be determined that Maiacetus was in fact an animal that lived most of its life in the water.
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To figure out that Maiacetus lived about 47.5 million years ago, scientists can use absolute dating of the rocks surrounding the fossil. By isolating and dating the decay of certain atoms found around the remains, the scientists can determine the age of the organism.
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Afterwards, go back and review the main types of evidence for evolution. You will need to know these!
Please notify the teacher and return your laptop to the correct location.
Afterwards, go back and review the main types of evidence for evolution. You will need to know these!