Duckweed Population Growth Rate at Different pH of Water (Jennifer Kim)
Research Question and Hypothesis
Research Question- How does different water pH affect the rate of duckweed population growth?
Hypothesis-I believe that a neutral pH will be the best condition for duckweed population growth.
Standards
HS-LS2-6 Evaluate the claims, evidence, and reasoning that the complex interactions in ecosystems maintain relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result in a new ecosystem.
HS-LS2-7 Design, evaluate, and refine a solution for reducing the impacts of human activities on the environment and biodiversity.
Experimental Design
1. Label one plastic cup with pH 7. Label the second plastic cup with pH 4, and label the third plastic cup with pH 10.
2. Place about 200 mL of water in the three different cups with their respective pH levels. I used a special water filter that is able to appropriate pH levels
3. Place the cups in location where they will all be able to get equal amount of sunlight during the day.
4. Put 10 duckweed plants in each of the three labelled cups
5. Record the duckweed population in each of the three cups, once a week for two months. Remember one duckweed "leaf" is actually one duckweed plant.
Independent variable
The independent variable is pH 4, pH 7, and pH 10.
Dependent variables
The dependent variable is the number of duckweed plants.
Series
The series that will be tested is the number of duckweed plants as a function time at various pH levels.
Constants and Controls
The factors that will be held constant are the volume of water and the hours of sunlight exposure.
The control is the duckweed at pH 7.
Materials
3 plastic cups
black sharpie pen
100 mL graduated cylinder
duckweed which can be purchased with Carolina Biological Supply Company (http://www.carolina.com/)
Procedures
1. Label one plastic cup with pH 7. Label the second plastic cup with pH 4, and label the third plastic cup with pH 10.
2. Place about 200 mL of water in the three different cups with their respective pH levels. I used
a special water filter that is able to appropriate pH levels3. Place the cups in location where they will all be able to get equal amount of sunlight during the day.
4. Put 10 duckweed plants in each of the three labelled cups
5. Record the duckweed population in each of the three cups, once a week for two months. Remember one duckweed "leaf" is actually one duckweed plant.
There are two mature fronds and two emerging daughter fronds. A single root can be seen at the top of the photo.
Sample data and graphs
Duckweed Population Growth
Analysis & Conclusions
From this experiment, it seems that duckweed grows the best under basic conditions as seen by the graph above. Strangely enough, the duckweed also seems to grow almost just as well under acidic conditions. Therefore, my hypothesis was proven to be incorrect
Photos & Movies
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