Help with APBio Energy Dynamics

[Paula]

Hello all,

Mostly I just lurk around the discussions so thanks for all of past support.

   I am planning on preforming Investigation 10 Energy dynamics in  September and am having a problem. For the life of me I can not figure out how to calculate the ratio for the dry/wet Larvae and the ratio for the plant percent biomass. The manual gives it as 0.15 for both ratios. Where are these ratio coming from? I have lost sleep over this one so any help would be awesome.

 

Thanks

Paula

[Cynthia Lingo]

Hey Paula - I am trying to conduct this experiment. We have grown the fastplants successfully in the bottles.  They are about 10 days old.  We have massed the plants, and because they are so small got a very tiny measurement on an electronic scale.  Then we dehydrated them in an incubator and were not able to get any weight at all - bomb.  So now I am at a loss.  Can you tell me how you are doing the NPP of the fast plants.

 

Now we have put our butterfly larve on the other fast plants that are left.

 

I really need help with this lab - is there a teacher's guide out there somewhere?? Thanks for any feedback

[Paula]

Hi Cynthia,
My larvae and eggs are arriving Wed. 9/12.
As far as the mass issue, I think you need a scale that is sensitive to the .001 g.
I will be "stealing mine from my the chem department.

I have been using the energy dynamics teachers guide on the apcentral.collegeboard.com/apc/members/courses/teachers_corner/218954.html website.

To measure the NPP of the plants I am going to find the average dry mass per 10 plants X 4.35 kcal.
so if I have at day 7 an averge mass of 4.2 g. I would multiply that by 4.35 kcal. Giving me 18.27 kcal
Now I can get the NPP per day per plant. 18.25 kcal/10/ 7day = 0.26 kcal/day.

I will be doing the same thing for growth on day 14.

Then to estimate the flow of energy between plants and larvea we will transfer the larvea to the plants when they are at about the 4th instar. I think this is where you are at the moment.

I hope to walk them through the energy transfer on data table 3 on page T185. I still am trying to figure out where the 0.15 percent larae bio mass ( dry /wet) comes from , but am willing to use it. Since I do not want to dry out live caterpillars anyway.

Once we go through the table we will know energy used in repiration for the larvae, the frass energy and we can then find the difference to calculate the energy in biomass.

Then I am going to do the inquiry part. Who knows where that is going to lead???

I have only been teaching AP bio for 2 years so if anyone finds any mistakes above , please let know, I would be grateful for any corrections or suggestions.

Let me know how its going,
Paula

[Cynthia Lingo]

actually they are butterfly eggs - I hope to have larve tomorrow when we return.