Origin of the Earth and of Life by zhouwenjuan


									Origin of the Earth and of Life
Assigned reading: Kump et al., The Earth System (3rd edition): Chapter 10

Learning Objectives

After reading this chapter, students should be able to:
   • Realize that the solar nebula formed from a cloud of interstellar gas
   • Know that the Earth and the other terrestrial planets are 4.55 billion years old
   • Know that the evidence for this age comes from radiometric dating of meteorites
   • Understand how location in the solar nebula determined whether a planet became a
     gas giant or a terrestrial planet.
   • Understand that the moon was formed by a giant impact between the Earth and a
     Mars-sized planetesimal
   • Know how the early atmosphere and ocean formed from volatiles released from
     impacts of comets and asteroids
   • Realize that the Earth’s early atmosphere was drastically different from the present-
     day atmosphere, with extremely low O2 and O3 levels and high CO2 levels.
   • Know there are a number of theories on how life first arose, including a theory of
     chemical evolution that results in an RNA-world.
   • Know how the Urey-Miller experiment created amino acids, and what the
     implications of this experiment were for the chemical evolution theory
   • Realize that the gas mixture used in the Urey-Miller experiment probably does not
     represent the atmosphere of the Earth when life first evolved
   • Know what the RNA-world is and realize that many biologists support such a world
     as a stepping stone towards the development of life because of RNA’s ability to self
     replicate and encode protein production
   • Consider the possibilities for prebiotic synthesis of glucose, and the RNA bases
   • Consider theories for the evolution of life that involve prebiotic chemistry at
     hydrothermal vents and in space
   • Know that that most scientists agree that life had arisen by at least 3.5 billion years
     ago, and that some believe life arose as early as 4.0 billion years ago
   • Know what the Universal Tree of Life is, and its implications for the origin of life
   • Offer multiple hypotheses explaining why methanogens are thought to be amongst
     the earliest forms of life on Earth

Review Questions

   1.) How old is the solar system, and how is this age determined?

   2.) How is the age of Earth determined if no rocks older than 4.1 billion years old
       have been preserved?

   3.) How do Jupiter and the Moon affect the habitability of Earth?

   4.) How and when did the atmosphere and ocean form? Which gases are thought to
       have been present in the early atmosphere?

   5.) In what types of environments might life have originated?

   6.) Why is RNA thought to have preceded DNA in evolution?

   7.) How is the Universal Tree of Life constructed?

   8.) Into what three different domains are modern organisms divided?

   9.) List two possible reasons why organisms near the base of the Tree of Life are

Critical-Thinking Problems

   Write a 1 to 2 page, typed essay on the following question:

   1.) What do you feel is the best theory for how life originated? Do you think that life
       might exist elsewhere besides Earth?

Submit your work to Volker Brüchert (volker.bruchert@geo.su.se).

Resource Guide


Biology & Space Exploration Series: Episode I, “The Origin and Early Evolution of Life”
This is a NASA film that describes the early evolution of life and various theories on how
life first arose. (21 minutes)

If We Had No Moon VHS
Discovery Channel
This program has animations that show how scientists think the Moon formed, and
discusses the effects that the Moon has had on the Earth and the biosphere. It also
discusses the fact that the Earth is slowly losing its grip on the Moon, and considers ways
in which this can be avoided. (50 minutes)

It Came From Outer Space VHS
Discovery Channel

This video discusses the possibility that life on Earth did not originate on Earth. This
theory, called panspermia, claims that life evolved on Mars first and then spread to Earth
via a meteor released during an impact event. (52 minutes)

The Earth and the Moon
Films for the Humanities and Sciences
Although scientists have found evidence of volcanoes, tectonics, and rivers on Mars, only
the Earth, which also has these features, currently sustains life. Why? Scientists have
postulated that the answer somehow lies in the Earth’s relationship to the Moon.
Astronomers are now scanning the galaxy for other habitable planets with the same
configuration as the Earth and the Moon. Original BBC broadcast title: A World Apart.
(50 minutes, color)

Initmate Strangers: Unseen Life on Earth, Episode 1. The Tree of Life
Scientists explore how all living things are related and how microbial life on the planet
has evolved over its 3.8-billion-year history.

Dating the Earth
Films for the Humanities and Sciences
The Book of Genesis states that the Earth, its heavens, water, and land were formed in six
days. But how old is the Earth? Up until the 19th century, experts had ascertained the
time of the creation at 4004 B.C., less than 6000 years earlier. However, by dating rocks,
noting the lack of fossils and bacteria in some areas of the globe, and studying meteorites,
geologists have determined that the Earth’s first landforms emerged 4 billion years ago.
This program travels back in time to uncover the place where life began: volcanoes on the
floor of the primordial ocean. Original BBC broadcast title: The Time Travelers. (50
minutes, color)


Internet Resource Guide for astrobiology

For a student-focused guide to astrobiology from the same site, point to:

NASA’s Astrobiology Webpage:


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