BSCS Biology: A Molecular Approach

Unit 4: Evolution

WebQuest

Introduction
In the 1960s, a scientist named Thomas Brock wanted to conduct some experiments in the hot springs of Yellowstone National Park. Brock was a bacteriologist, a scientist who studies bacteria. As Brock sampled his way up a hot stream, he looked for microbes. He expected to find that as the water got hotter and hotter, he would no longer find anything living in it. He was surprised to discover tiny organisms living in near-boiling water. Brock called these unusual microbes Archaea, a word meaning "ancient."

At first scientists thought Archaea were simply a weird kind of bacteria. But evidence indicates that Archaea differ from bacteria in important ways. Many scientists now consider Archaea to be their own kingdom of life. Since Brock's initial discovery of Archaea in hot springs, scientists have found Archaea living in all sorts of harsh conditions-in the Dead Sea, in sewage sludge, on the ocean floor, in the gut of cows. Studying Archaea has helped scientists expand their definition of where life exists. Research on Archaea is helping scientists in their search for life on other planets.

Task
Your job in this WebQuest is to learn about Archaea. You will learn how Archaea are similar to but distinct from bacteria. You will learn why scientists think eukaryotes may have evolved from Archaea. You will read about evidence that Archaea form a new kingdom in the classification of living things. You will learn about the extreme environments where Archaea are found and how these microbes are expanding the boundaries of where life can survive. You will read why Archaea give us clues about how life evolved on earth. You will discover how the Archaea are guiding the search for life in outer space. When you have completed your research, you will answer a set of questions to demonstrate what you have learned.

Time
2 class periods to answer the set of questions.

Process
First, read through the set of questions before you begin your Internet research. As you explore each site, look for answers to the following questions.

  1. Scientists call organisms that thrive in harsh environments "extremophiles." What are some of the extreme environments in which Archaea have been found?
  2. Archaea look like bacteria under a microscope, but scientists do not consider them to be true bacteria. What traits do Archaea have that are like bacteria? What traits do they have that are different from bacteria? How long ago do scientists think Archaea split off and developed separately from bacteria?
  3. What evidence supports the idea that eukaryotes evolved from Archaea? How long ago do scientists believe eukaryotes split off from Archaea?
  4. What traits do Archaea have that suggest they may be closely related to the first life forms on earth? How are the conditions in which Archaea live similar to what scientists believe ancient earth might have been like?
  5. A type of Archaea known as strain 121 was found in a vent on the floor of the Pacific Ocean at a depth of 1.5 miles. Strain 121 is a hyperthermophile. What is a hyperthermophile? How has Strain 121 redefined the boundaries of life?
  6. Archaea have been found living in communities with other organisms around hydrothermal vents on the ocean floor. How do these Archaea form the basis of the food chain in this habitat? How did the discovery of life around deep sea vents change scientists' views of life on the ocean floor?
  7. Archaea found living in Lidy Hot Springs in Idaho have given scientists hope that life may exist on other planets or moons. What is unique about Lidy Hot Springs that made scientists choose this site to study? What types of microbial community did scientists find there? How are the conditions in Lidy Hot Springs similar to conditions on Mars?

Resources
http://www.microbeworld.org/htm/aboutmicro/microbes/types/archaea.htm

Visit this site to learn about what Archaea are, how they are classified, and where they live.

http://www.microbe.org/microbes/what_is.asp

This Web site contains a good introduction to the different kinds of microbes. Click on "Archaea" to learn more about these unusual microbes.

http://chainreaction.asu.edu/solarsystem/digin/extreme.htm

Visit this site to read an article about extremophiles. Learn why extremophiles may provide clues to earth's early life forms. Read about extremophiles and the search for life on Mars.

http://www.learner.org/channel/courses/biology/textbook/microb/microb_2.html

Go to this site to read about the conditions on ancient earth. Learn why some scientists think life may have begun beneath the earth's surface.

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/Archaea.html

Visit this site to find a lot of useful information about Archaea. Learn about the types of Archaea and where they live. Learn how the Archaea are similar to both bacteria and eukaryotes. Read why they are thought to be little changed from the first forms of life on earth.

http://www.sidwell.edu/us/science/vlb5/Labs/Classification_Lab/Archaea/

This Web site gives an introduction to the Archaea. Read about the evolutionary relationship between Archaea, bacteria, and eukaryotes. Read descriptions of three types of Archaea.

http://library.thinkquest.org/CR0212089/home.htm

Visit this site to view a chart showing the five kingdoms of life. See a diagram of the evolutionary tree of life showing Archaea as a new kingdom. Learn about scientists' attempts to classify the Archaea.

http://serc.carleton.edu/microbelife/extreme/extremophiles01.html

Visit this Web site to read about extremophiles. Read about the different types of extremophiles.

http://www.resa.net/nasa/extreme_chart.htm

Go to this site to view a chart showing the different types of extremophiles and the environments in which these organisms they live.

http://www.divediscover.whoi.edu/vent_cd/vent_discovery/index.html

Go to this site to find a wealth of information about deep sea vents. Read the introduction page, then click on "A Scientific Revolution." Here you will read about the stunning discovery of life around hydrothermal vents. Click on the heading "Vent Biology." There you will learn about the communities of organisms living at deep sea vents.

Find out where, in the absence of sunlight, food webs on the ocean floor get energy. Click on "a changed view of 'life'" at the bottom of the "A Scientific Revolution" page to read how these findings impacted scientists' understanding of ocean life.

http://news.nationalgeographic.com/news/2002/01/0116_020116microbes.html

Visit this National Geographic site to read about experiments done at Lidy Hot Springs, Idaho. Find out why these experiments may give clues to life on other planets.

http://news.nationalgeographic.com/news/2004/05/0521_040521_extremeheat.html

Go to this site to read about the discovery of the hottest life form, a heat-loving microbe called Strain 121.

http://www.pbs.org/lifebeyondearth/alone/habitable.html

Go to this PBS Web site to learn about what scientists who are looking for life on other planets call The Habitable Zone. Click on "extreme environments" to read how extreme life on earth is helping scientists expand their ideas about where life may exist in the universe.

Conclusion
In the process of completing this WebQuest, you've learned about exciting research into the Archaea. You've discovered how the Archaea have overturned many of the old rules about life on earth. You've learned why many scientists consider the Archaea to be an entirely distinct kingdom in the tree of life. You've learned how Archaea give clues to the evolution of eukaryotes. You've learned the relationship of these microbes to the first life forms on earth. You've discovered how research on Archaea is informing the search for life on other planets. In the process of conducting this Internet research, you've increased your knowledge about the diversity of life on earth. You've also gained an inside look into an exciting area of research, one that is causing scientists to change their own ideas about life on earth.

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