AP Biology Lab | How Much Water is in a Model Organism

This year I’m taking Advanced Placement biology class to continue my passion for science. Besides listening to presentations by our facilitator, students also go the opportunity to apply our knowledge through labs.

The first lab we did was relating to water in organisms. Water is in every organism; it makes up approximately 60 to 90 percents of every organism. Water is important for various functions including respiration, metabolism, and homeostasis. The objective was to extract water out of model organisms (fruits and vegetable) and figure out how much water is in that organism. We weren’t given an instruction on how we should … our lab, so we needed to invent our own procedures. My partner and I got carrot as our model organism. Below is the procedure we’ve created for our lab:

“The carrot was washed, dried and weighed three times: the average weight was calculated. To ease the process of blending, the carrot was chopped into small pieces. Then, the carrot was blended until it was ground. The paste was placed into a strainer and was squeezed to extract liquid. Finally, extracted juice was weighed three times and the average weight was calculated.”

Fruits and vegetable scraps and juice


The result told us that water made up approximately 45 percents of carrots mass. However, according to the US National Library of Medicine, the amount of water in a carrot is 86 to 89%. Our result was inaccurate because our method was manual so there might be some errors along the way. For instance, there may be parts of carrots that were wasted unnecessarily. Despite the inaccuracy, we can use our data to compare with other organisms that my classmates worked on. For example, we can tell that watermelon contains the most water, while logan contains the least amount of water.

Graph showing percent of water in different organisms, according to our experiment



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