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Microbial Cultures
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NASA Sci Files segment explaining how to test for microbial presence and controls and variables in tesing.
I wonder where Dr. D is?
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Well, you never know with Dr. D.
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Wow, someone's in the aquarium.
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Dr. D?
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Dr. D?
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Dr. D, what were you doing swimming in the aquarium?
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I was helping clean the Chesapeake Bay Aquarium here at the Virginia Marine Science Museum.
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I understand you're trying to help Jacob stay well before he goes on his vacation.
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Yes, we've learned about all kinds of ways that diseases can be transmitted.
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So Jacob quarantined himself in the treehouse.
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I've got just the thing for you to test your treehouse.
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Test it for what?
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This will be a test to see if the treehouse is free from airborne microbes.
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What's a microbe?
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Microbes are very small organisms, too small to see without a microscope.
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Microbes like bacteria, fungi, and viruses sometimes cause disease.
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So how do we do the test?
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This is called a Petri dish.
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All you have to do is take it to the treehouse and leave it open for 10 minutes.
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What's the stuff at the bottom of the dish?
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It's called nutrient agar. It's food for microbes.
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When microbes like bacteria or fungi land in the dish, they multiply and grow.
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Each microbe will grow into a colony.
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Wow, will we be able to tell what grows in the dish?
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Yes, let the microbes grow until tomorrow.
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You'll be able to go by and see my friend Mr. Frank, a biologist at Tidewater Community College.
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He'll be able to show you what microbial colonies look like and help you count the colonies.
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I have an idea.
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Can I have a second dish to take to Jacob's house
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so we can see if the treehouse has more or less microbes and he will get it home?
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Sure, that's an excellent idea.
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But how do we know that the Petri dish doesn't already have microbes growing in it right now?
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Good question.
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What you need is a third dish that you never open.
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This will serve as a control.
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In any experiment, you need to have only one variable.
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We'll need to keep the exposure times the same in both Petri dishes
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and use the same kind of microbe food.
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That's nutrient alkaline.
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Right, and make sure nothing is already growing in the dish.
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Then you'll have a carefully controlled experiment.
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If we can prove that there are no airborne microbes that can cause illness
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and keep all infected people out...
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Then we can be totally sure that Jacob will stay well.
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Now wait a minute, totally sure?
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I don't think you can do that.
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What do you mean?
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Sometimes if you miss a small detail, it can become a major problem.
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This is called the butterfly effect.
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Butterfly effect?
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Yes, Edward Lorenz, who was a pioneer in chaos theory,
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once gave a talk entitled,
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Predictability, as the flap of a butterfly's wing in Brazil set off a tornado in Texas.
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Let me show you.
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I'm going to try to release this ball exactly the same way each time.
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Now let's try it again.
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Look at how little variations in the beginning make a big difference in the end.
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Does that mean that our mission to keep Jacob well is impossible?
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No, it just means it's not as easy as you think to have complete control.
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You can stay away from crowds, but for example, you can't stop breathing.
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Oh, I get it. There are just so many factors.
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There are also a lot of internal things to consider, like how the body fights diseases.
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You mean like whether or not we've had a disease before.
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And whether we've taken any medications.
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And if we have good genes.
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Yes, those are a few.
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Thanks, Dr. D. It sounds like we need to investigate this a little more.
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You're welcome. Let's go get some more Petri dishes.
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- Idioma/s:
- Niveles educativos:
- ▼ Mostrar / ocultar niveles
- Nivel Intermedio
- Autor/es:
- Office of Education
- Subido por:
- EducaMadrid
- Licencia:
- Reconocimiento - No comercial - Sin obra derivada
- Visualizaciones:
- 466
- Fecha:
- 28 de mayo de 2007 - 15:32
- Visibilidad:
- Público
- Enlace Relacionado:
- NASAs center for distance learning
- Duración:
- 03′ 45″
- Relación de aspecto:
- 4:3 Hasta 2009 fue el estándar utilizado en la televisión PAL; muchas pantallas de ordenador y televisores usan este estándar, erróneamente llamado cuadrado, cuando en la realidad es rectangular o wide.
- Resolución:
- 480x360 píxeles
- Tamaño:
- 22.56 MBytes
