Geologic Time Lesson

Geologic Time Lesson

CP Biology: Evidence for Evolution Unit

Open Ended

List as many facts/vocabulary you know associated with evolution (you must include at least 3 for full credit)

• I can use geology vocabulary correctly to explain how scientists determine past events.

• I can use information from the geologic timescale to describe how life has changed over time.

​Success Criteria

I am learning what scientists have discovered about the history of the Earth and how they know it.

​WHY?

I am learning this to understand ​my place in the history of Earth and to better evaluate scientific evidence of the past

​W

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A

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​HOW

1. Watch the video by following the link on the next slide

2. Define:

   1. Law of Superposition

   2. Principle of Association

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Let's review some basics

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Stratigraphic Principles

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Multiple Choice

The Law of Superposition states that ...

• the youngest layer is on the bottom and the oldest is on the top

• the layers are formed at the same time

• the youngest layer is at the top and the oldest is on the bottom

• there is no way to tell how old a rock layer is

Multiple Choice

The Principle of Association states that ...

• fossils found in the layer were deposited AFTER the layer was deposited

• fossils found in the layer were deposited AT THE SAME TIME the layer was deposited

• fossils found in the layer were deposited BEFORE the layer was deposited

• there is no connection between the fossils and the layer of rock in which they are found

Open Ended

INFER 

Which layers of sedimentary rock at Grand Staircase Escalante National Monument do you think are the oldest?

Use the Law of Superposition to support your claim.

A fossil is the trace or remains of an ancient organism that is preserved in rock or sediment. Fossils include the huge skeletons of dinosaurs, as well as shells, plants, and microscopic bacteria.

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Read on for the steps in fossil formation

Fossil Formation

Explore the fossilization of a dinosaur

​How are fossils made?

Bones, teeth, footprints, and other traces of life can be fossilized or preserved when they are buried in sediment. The processes involved in fossil formation take place on the scale of millions of years.

There are three major steps...

An organism dies and begins to decay. If the organism is not buried soon after death, scavengers may feed on the flesh or microbes may break down carbon-rich molecules in the animal​.

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Step 1

With the soft tissue gone, only hard parts like bones, teeth, and shells remain and are buried within a layer of sediment​. Fossilization of the animal remains then occurs over time.

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Step 2

Years later disturbances of the rock layers by natural processes like erosion, or man-made ones like construction or excavation by archeologists​, reveal the fossil.

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Step 3

Draw

Below are the steps involved involved in the process of fossilization. Number the steps in the correct order.

Why are fossils so rare?

​Uncountable organisms have existed on Earth over time, but very few have been fossilized. Instead, the bodies of most organisms have decomposed, and their footprints and burrows have been washed away. Specific conditions must exist and certain processes must occur for an organism or its traces to become fossilized.

OPTIONAL For more info on fossils, check out this link https://lisbdnet.com/what-are-the-five-main-processes-of-fossilization/

What can we learn from fossils?

In the early 1800s, scientists studying layers of rock in Europe made two very important observations. First, in a set of sedimentary layers, the combination of fossils changes vertically from layer to layer. Second, the groupings of fossils and the order of combinations are mostly consistent from place to place. These observations gave rise to the principle of faunal succession. Scientists soon recognized that they could use this principle to connect layers of rock that are separated by long distances.

Faunal Succession: rock layers (strata) may be identified by the fossils they contain

Draw

scientists can use the specific combinations of fossils in rock layers to correlate layers in different parts of the world. Draw lines connecting the layers that are the same age.

Multiple Select

Index fossils must be (choose all that apply)

• Short lived

• Widespread

• Rare

• Abundant

Draw

Circle the organism(s) that would make good index fossils

Putting the picture together

​Visualizing the Geologic Timescale

Scientists have combined information from fossil evidence all over the world to build a geologic timescale of Earth’s history. The geologic timescale divides Earth’s history into intervals based on evidence found in layers of rock and the appearance and extinctions of organisms. There is no one place on Earth where you can find rocks representing the complete geologic timescale.

geologic timescale time scale representing the history of Earth

Geologists have interpreted the rock and fossil record to show that Earth’s history can be organized like a calendar into time divisions of different lengths. The largest divisions of geologic time are eons, and the first three eons together are sometimes referred to as the Precambrian. Eons are divided into eras, which are smaller time segments. The Paleozoic era, the Mesozoic era, and the Cenozoic era followed Precambrian time. The three eras are divided into periods, which may be further divided into epochs.

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Open Ended

INFER  Some fossils from the Cambrian period are unlike any organisms living today. Do you think the two organisms in the photos belong to the same group? Why or why not? How do you think scientists could determine whether these organisms are actually related?

Multiple Select

Which of the following statements about the principle of faunal succession is true? Select both correct answers.

• It relies on radiometric dating techniques

• It assumes that rock layers are deposited on top of one another.

• It assumes that rock layers are deposited beneath one another.

• It assumes that specific combinations of organisms were living only at a certain time in Earth’s history.

Multiple Choice

Which of the following shows the correct progression of organisms on the planet?

• reptiles, fish, hominins

• fish, reptiles, hominins

• prokaryotes, flowering plants, trees

• flowering plants, mammals, fish

Multiple Choice

Which of the following would make the best index fossil?

• An insect that only existed in one small forest for about 100 million years.

• An aquatic animal that existed all over the world for about 15 million years.

• A single-celled organism that lived in a widespread region for about 25 million years.

• A plant species that lived in a specific geographic region for about 5 million years.