Grade level: 6-8 subject area: Earth Science credit

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Birth of the Earth


Two class periods



Earth Science

Bryan Goehring, Earth science teacher, Blair Middle School, Silver Spring, Maryland; Brewster Bartlett, science/ecology teacher, Pinkerton Academy, Derry, New Hampshire; and Michele Bartlett, science teacher, Rundlett Middle School, Concord, New Hampshire.


Students will understand the following:

1. Earth is estimated to be 4.6 billion years old.

2. Certain major events have occurred during this period that are considered important milestones in Earth's development.

3. Early Earth was very different from our planet as we know it today.

4. Earth has existed as we know it today for only a very short time, relative to the number of years since its origin.


For this lesson, you will need:

Computer with Internet access
Books and articles concerning the birth and development of the Earth
Forty-six sheets of white paper

1. Tell the students that they will be creating a time scale of Earth's history. Introduce the following background information to the class:

- Scientists estimate that Earth formed approximately 4.6 billion (4,600,000,000) years ago.

- Our planet began as a lifeless sphere, surrounded by hydrogen and methane and devoid of water; it was nothing like the planet we call our home today.

- Certain important events are considered milestones in Earth's history.

2. Write the following chronology and major geologic events on the chalkboard, and have students record them:

- 4.6 billion years ago: Earth was created.

- 4.5 billion years ago: Earth's moon was formed.

- 3.8 billion years ago: Bacteria arose.

- 3.6 billion years ago: A cooling process began on Earth.

- 3.0 billion years ago: Clouds formed.

- 2.0 billion years ago: Eukaryotic cells (single cells with a nucleus) evolved.

- 0.5 billion year ago: Oxygen began to saturate the atmosphere.

Point out to students that the Earth's atmosphere has contained oxygen for only the most recent 10 percent of our planet's history. Announce that they are about to discover more surprising facts about Earth's geologic history.

3. Invite students to use the materials you have provided to research the development of Earth so that they can answer the following questions about additional important milestones in Earth's geologic history:

- When did primordial oceans form?

- When did plant life begin to appear on Earth?

- When did animal life begin to appear in the oceans?

- When did the first land animals evolve?

- When did humanlike life appear on Earth?

4. Have students share their findings by adding to the list of geologic events on the chalkboard.

5. Have volunteers help you to tape the 46 sheets of paper around the room, explaining that each sheet represents 100 million years of Earth's history. Students should use markers to label the sheets: “4.6 billion years ago,” “4.5 billion years ago,” and so on.

6. Have additional volunteers work to transfer onto the appropriate sheets of paper the list of geologic events that you and the class have developed. If possible, involve each student in creating the geologic time scale.

7. Discuss with students what the time scale they have created reveals:
- Which time period shows the most developments?

- For approximately what fraction of the Earth's total history have animals existed?

- What about human beings?

- How much space would an average human life span cover on the scale?

8. Ask students if creating the time scale has made them think in any new ways about our planet or about the relative place of human history in the bigger scheme of geologic history.


Adaptations for Older Students:

Have each student or students working in groups write more detailed reports on one of their findings that particularly interests them.

1. Describe the organic, geologic, and atmospheric events that led to the formation of oxygen-enriched oceans.
2. Discuss the reasons life on Earth developed more slowly than life in the seas.
3. Many scientists consider the theory of natural selection the primary mechanism for the evolution of organisms. Describe how natural selection was evident during the development of early organisms like bacteria and cyanobacteria.
4. Discuss what is meant by the statement “DNA is a genetic library; etched in its code is the history of life on this planet.”
5. Describe the relationship between hard-shelled bacteria and the mitochondria, and soft-membrane bacteria and the nucleus. Discuss how these relationships led to the formation of eukaryotic cells—cells with a well-defined nucleus.
6. Describe how geology has influenced the formation and development of life. Think about geothermal energy, plate tectonics, tides, mountain formation, and atmospheric conditions.
7. Describe several ways the formation and presence of the moon changed life on Earth.

You can evaluate your students on their research using the following three-point rubric:
- Three points:significant additions to the given list of geologic events; accurate dating of events

- Two points:some additions to the given list of geologic events; accurate dating of events

- One point:few additions to the given list of geologic events; some inaccuracies

You can ask your students to contribute to the assessment rubric by determining how many additions to the given list of geologic events constitutes a significant number.

Microstudy of Protozoans
Provide your students with the following background information:

Protozoans are unicellular organisms that have a true nucleus.

They live in fresh water and salt water.

  Some live independently, whereas others live in colonies.

Most protozoans are heterotrophs, whereas others are autotrophs.

Have your students research the difference between autotrophs and heterotrophs and then list and draw protozoans that fall in each category. Students should be prepared to give a rationale for placing a particular protozoan in a category. Finally, have your students collect water samples to analyze under microscopes. Using reference books to help them identify the protozoans, students should draw and label as well as compare and contrast what they observe.

Biogenesis of Microorganisms

Provide your students with the following background information: Francesco Redi, Lazzaro Spallanzani, and Louis Pasteur made important contributions to science when they provided scientific evidence to disprove the theory of spontaneous generation. False ideas, myths, and superstitions were deeply rooted in the thinking of people at the time.Have students design and conduct their own experiments to disprove spontaneous generation. Your students should follow standard scientific methodology to carry out this inquiry-based lab. Ask them to write up their findings, including the hypothesis, process, and results.

Birth of the Earth

The Incredible Journey to the Beginning of Time

Nicholas Harris. Peter Bedrick Books, 1998.

This book chronicles the history of the Earth by focusing on the same four locations—New York, southwestern France, the Nile Valley, and northern China—through different time periods. The time span covers more than 550 million years.
The Origin and Early Evolution of Life on Earth”

J. Oro, Stanley L. Miller, and Antonio Lazcano. Origins of Planets and Life.edited by H.J. Melosh, Annual Reviews, 1997.

This article focuses on the conditions necessary for life on Earth and on the adaptations of early organisms.

Project Primary

Hands-on science activities provided by Ohio Wesleyan University. Geology activities, particularly “Geological Time and the Evolution of Earth,” are related to theme. Designed for grades K-3; adaptable to other grade levels.
Beginner's Guide to Molecular Biology

Explains molecular biology and cell biology to beginners in an accessible format.
AskERIC Lesson Plans

A wide range of science lessons concerning biology and life sciences. Appropriate for K-12.
Brooks/Cole Earth Science Resource Center

A range of topics including geology, oceanography, and geography.
Living Things

Classroom activities and resources focused on the following concepts in the plant and animal world: individuals, families, neighborhoods, and circle of life.

amino acids

Any of the acids that are the chief components of proteins and are synthesized by living cells or are obtained as essential components of a diet.


Amino acids are necessary for the formation of life; they link to form proteins which act as enzymes and direct cell chemistry.


Any of a group (kingdom Procaryotae or kingdom Monera) of prokaryotic round, spiral, or rod-shaped, single-celled microorganisms that are often aggregated into colonies.


Bacteria are tiny, bar-shaped life forms.


A group of large, photosynthetic bacteria that are blue-green in color.


Cyanobacteria produced oxygen in the ocean.DNA


Any of various nucleic acids that are the molecular basis of heredity, are localized especially in cell nuclei, and are constructed of a double helix held together by hydrogen bonds.


Because DNA stores the cell's genetic information, it is like the blueprint of a living cell.

greenhouse effect

Warming of the surface and lower atmosphere of a planet caused by conversion of solar radiation into heat.


The process of gases trapping heat from the sun in the Earth's atmosphere is called the greenhouse effect.


Relating to hot water—especially to the formation of minerals by hot solutions rising from a cooling magma.


Underwater volcanoes can form hydrothermal chimneys.


Any of various round or long cellular organelles of most eukaryotes that are found outside the nucleus; produce energy for the cell through cellular respiration; and are rich in fats, proteins, and enzymes.


Mitochondria supply the cell with energy by hosting the reaction between glucose and oxygen.


A cellular organelle in eukaryotes that is essential to cell functions, composed of nuclear sap and a nucleoprotein-rich network from which chromosomes arise, and is enclosed in a definite membrane.


Eukaryote cells have a nucleus in their center where the genetic material resides.


First created or developed.


The building blocks of life accumulated in a primordial soup of chemicals.

Grade Level:


Subject Area:

life science


Knows about the diversity and unity that characterize life.


Knows evidence that supports the idea that there is unity among organisms despite the fact that some species look very different (e.g., similarity of internal structures in different organisms, similarity of chemical processes in different organisms, evidence of common ancestry).

Grade Level:


Subject Area:

life science


Understands the basic concepts of the evolution of species.


Knows the history of the origin and evolution of life on Earth (e.g., life on Earth is thought to have begun 3.5 billion to 4 billion years ago as simple, one-celled organisms; during the first 2 billion years, only microorganisms existed; after cells with nuclei developed about a billion years ago, increasingly complex multicellular organisms evolved).

Grade Level:


Subject Area:

Earth science


Understands basic features on Earth.


Knows how life is adapted to conditions on Earth (e.g., force of gravity that enables the planet to retain an adequate atmosphere, intensity of radiation from the sun that allows water to cycle between liquid and vapor).
Copyright 2001

Teachers may reproduce copies of these materials for classroom use only.

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