1
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Hey, Dr. D, look what I brought you.

2
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Terrific.

3
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Looks like you brought something from my terrarium.

4
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Yeah.

5
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Ranger Cortez from Sandy Bottom Park said you would like them.

6
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Thank you.

7
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My terrarium is coming along pretty good.

8
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I'm being very careful to only put plants in that only require the same conditions.

9
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Can you tell us more about how a terrarium works?

10
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Sure.

11
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My sealed terrarium must be self-sufficient.

12
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The only thing that can come into the terrarium is light.

13
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We already learned that light is the basic need of plants.

14
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Water is recycled in a terrarium.

15
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Plants give off water, which collects on the plastic,

16
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runs down the side into the soil where it's collected by the roots and recycled.

17
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Wow, that's pretty neat.

18
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We already talked about how the plants basically just carbon dioxide.

19
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Plants consume carbon dioxide and produce oxygen.

20
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But what replaces the carbon dioxide so the plants don't die?

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Well, animals breathe in oxygen and breathe out carbon dioxide,

22
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but obviously there aren't any animals in there.

23
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That's true, but there are decomposers in the soil like bacteria and fungi.

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They also consume carbon dioxide and produce oxygen.

25
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They also break down dead materials and produce the nutrients that the plants need.

26
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It looks like everything gets recycled.

27
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It turns out that plants use some oxygen to produce the energy they need

28
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and give off carbon dioxide in the process.

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This is called respiration.

30
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Fortunately, plants produce much more oxygen than they consume.

31
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I'm glad about that.

32
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There's a lot going on in that terrarium.

33
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It would be great if we could make our Mars habitat as self-sufficient as your terrarium.

34
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Yeah, just add sunlight.

35
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We've got to get going. We've got a lot of work to do.

36
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Yeah.

37
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Bye, Dr. D.

38
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Bye.