Geologic Time: Studying Earth’s History and the Evolution of Life

I. The Early Earth The Earth and our solar system formed approx. 4.6 billion years ago. The Earth and our solar system formed approx. 4.6 billion years ago. The early Earth was hot and volatile; as it cooled off the oceans filled with water and the atmosphere formed. The early Earth was hot and volatile; as it cooled off the oceans filled with water and the atmosphere formed. The early atmosphere was composed of primarily CO2; the earliest one-celled organisms that carried on photosynthesis gradually converted it into and oxygen-rich atmosphere. The early atmosphere was composed of primarily CO2; the earliest one-celled organisms that carried on photosynthesis gradually converted it into and oxygen-rich atmosphere.

The Early Earth From Space

The Early Earth’s Surface

What is the Geologic Time Scale? It is a relative time scale based on fossil evidence. It is a relative time scale based on fossil evidence. Geologic time is split into smaller units: Geologic time is split into smaller units: Eons →Eras→Periods→Epochs Present day is located at the top of the chart (0 million years ago) and events go farther back in time as you look towards the bottom of the scale. Present day is located at the top of the chart (0 million years ago) and events go farther back in time as you look towards the bottom of the scale.

II.Geologic Maps Geologists study the geologic time scale for many reasons; one of them being that they want to relate what we find out about the age of the rocks to construct geologic maps. Geologists study the geologic time scale for many reasons; one of them being that they want to relate what we find out about the age of the rocks to construct geologic maps. The Generalized Bedrock Geology Map (Pg. 3 ESRT) and the Generalized Landscape Regions of New York State Map (Pg.2 ESRT) can be used with the geologic time scale to determine the age of the bedrock throughout New York State. The Generalized Bedrock Geology Map (Pg. 3 ESRT) and the Generalized Landscape Regions of New York State Map (Pg.2 ESRT) can be used with the geologic time scale to determine the age of the bedrock throughout New York State. They also can provide general information about local rock types, the ages of bedrock, types of fossils likely to be found, and the geologic history of your community. They also can provide general information about local rock types, the ages of bedrock, types of fossils likely to be found, and the geologic history of your community.

IV. The Columns on the Time Scale 1. Life on Earth: Gives information about what life forms lived on Earth from the beginning until the present day. As you look down the column, keep in mind that life gets simpler as we go back in time. As you look down the column, keep in mind that life gets simpler as we go back in time.Example: Humans→Mammals→Dinosaurs→Reptiles→ Amphibians→Fish→ Soft-bodied marine organisms

2. Rock Record in NYS: Lists information about which time periods are represented by rocks in NYS. 3. Time Distribution of Fossils: Lists several index fossils that are represented in NYS. Each fossil at the bottom of the chart has a letter that corresponds to the group of animals that fossil belongs to and the time when the animal lived on Earth. The bar a fossil sits on represents the group of animals it belongs to, and the length of the bar represents the length of time the group of animals lived on Earth. The bar a fossil sits on represents the group of animals it belongs to, and the length of the bar represents the length of time the group of animals lived on Earth.

4. Important Geologic Events in New York: This column lists major changes to the landscape regions in New York State. This column lists major changes to the landscape regions in New York State. An OROGENY is a period of mountain building. The major orogenies in NY are listed, indicating times of crustal uplift. An OROGENY is a period of mountain building. The major orogenies in NY are listed, indicating times of crustal uplift. 5. Inferred Positions of Earth’s Landmasses: There are five diagrams that show the movement of Earth’s landmasses over time. There are five diagrams that show the movement of Earth’s landmasses over time. Pay special attention to the time periods each diagram represents and where North America is in relation to the equator. Pay special attention to the time periods each diagram represents and where North America is in relation to the equator.

Evolution One of the most important facts illustrated by the Geologic Time Scale is the evolution of life forms over time. One of the most important facts illustrated by the Geologic Time Scale is the evolution of life forms over time. Life has continually evolved, or changed, from very simple life forms to more complex life forms over time. Life has continually evolved, or changed, from very simple life forms to more complex life forms over time. Life on earth continues to evolve. Life on earth continues to evolve.

How do animals change over time? Scientists are not sure how life began on Earth. They know that life on Earth began before the Cambrian Period, but early life forms were one- celled simple creatures that lived in water. Geologists believe that many forms of life may have existed in the Precambrian but they had no hard parts (shells or bones) and therefore left no fossils. As scientists studied the fossil record they found that more complex organisms developed as time went on, and that many organisms disappeared from the fossil record completely.

Explanation for Evolution Scientists looked for an answer that would explain why certain members of a species went extinct, while others seemed to thrive. Scientists looked for an answer that would explain why certain members of a species went extinct, while others seemed to thrive. They found that within each species there are individual variations in size, shape, and other traits, or characteristics. They found that within each species there are individual variations in size, shape, and other traits, or characteristics. Charles Darwin is the scientist credited with proposing the Theory of Organic Evolution. Charles Darwin is the scientist credited with proposing the Theory of Organic Evolution.

What did Darwin Say? Darwin proposed that individuals within a species that have traits that better adapt them to their environment will survive longer and have more offspring. Darwin proposed that individuals within a species that have traits that better adapt them to their environment will survive longer and have more offspring. Their offspring inherit their desirable characteristics and are able to survive in the environment too. Their offspring inherit their desirable characteristics and are able to survive in the environment too. Eventually, an increasing number if individuals in a species will possess the desirable traits. Eventually, an increasing number if individuals in a species will possess the desirable traits. The number of individuals who do not have the desirable traits will decrease, as they can’t survive as well in the environment. The number of individuals who do not have the desirable traits will decrease, as they can’t survive as well in the environment.

Examples of Natural Selection