AP Biology Assignment Question ???PLEASE HELP?

Question

If I grow radish seeds in a germination BAG, (which is basically a plastic bag) is light a major factor in the seed's growth? (there will be 10 seeds in 5 bags each representing a different level of the independent variable, I chose light) The reason I am asking this is because in the teacher 's directions, it says hang the bag on a cabinet door or in another location if the ind. variable requires it. I was going to put the control as the reg. day/ night cycle, one in comple darkness for 10 days, one bag of seeds which gets 1 hr. of sunlight a day, another for 2, etc.. Does this sound ok? And can light be my independent variable if they are grown in bags? If this is not a good idea, what can my independent variable be?

I need 5 LEVELS of the independent variable. READ the WHOLE question!!

Answer 1

Light sounds good to me. What I would do, however, is control the light myself. Find a lamp that will distribute both temp and light equally for the area in which you place the bags. Otherwise, temp could be a confounding factor. Since you're going to do the 1hr/2hr/etc thing anyway, it won't be all that difficult to do.

When they're not in the light, they should be placed in the same location - same amount of darkness, same temp. Since they're in bags, oxygen won't matter so much, and neither will soil type.

If you can't find such a light or think it would be too difficult to do, some other variables you could use would be:
- type of water (ground, tap, distilled, Propel/flavored, etc)
- temp, as said above (but make sure they get the same amount of light! - you could use water baths)
- exposure to the air (you could prop the bags in a box, taping the sides of the bag to the box) vs no air
- seed size

Good luck!

Answer 2

well the control should be a bag of seeds in regular 24 hour light cycle in my opinion, just as you said. one bag should be kept in complete darkness and one perhaps could be placed under a uv plant lamp for the entire duration of the experiment, for the experimental groups. The independent variable would be the amount of light to the seeds, and the dependent variable would be the amount of growth. So yes, light sounds good. As for the outcome of the experiment, light should have little effect on the germination of the seeds. Think about it, they germinate under ground which last time I checked was pitch black, but then again I suppose that all depends on the depth of the seeds. But, you'll find out that answer with the outcome of your experiment. Hope I helped.

Answer 3

I think light is a good independent variable, but you don't have to have so many groups.

Just do two groups: regular day/night cycle compared with complete darkness. That way you can have the groups side-by-side, placing the darkness one in a closed box. The temperatures would be controlled.

You might try taping the bag on the inside of an east-facing or north-facing window that would provide light but not overheat your seeds.

Answer 4

Your idea is not bad. You just have a positive control, regular daylight hours, and a negative control, complete darkness.
Remember to explain what your hypothesis for each control group.
What do expect to happen with the full daylight seeds?
What do expect to happen with the darkness seeds?
I think the above idea of using a lamp to control hours of light is an excellent method. You could even put a twist on it and use different colored lamps, red, blue, or yellow.

As long as you keep everything except amount or color of light EXACTLY the same you should have no problems with this experiment; good luck!

Answer 5

I think temperature would be easier as an independent variable. Keep one set at room temperature, keep one refridgerated, and keep one warm.

Duh, then use FIVE different temperatures, genius.