Natasha Gupta
AP Biology—Period E
31 August 2015
Experiment 1
I. Introduction a.
Background information: According to the EPA, 44 percent of assessed stream miles, 64 percent of lakes and 30 percent of bay and estuarine areas are considered unhealthy for nearby animal and plant life. The EPA also states that the most common water contaminants in the
United States are bacteria, mercury, phosphorus and nitrogen. b. Purpose: This experiment was conducted to test the effect of chemical pollutants, such as bacteria, mercury, phosphorus, and nitrogen, on the plant life inhabiting contaminated waters. c. Hypothesis: If the water supply of a patch of grass contains a chemical pollutant, then the soil will be more acidic and the grass will be more wilted and discolored than soil and grass with clean, unpolluted tap water.
II. Procedure a. Equipment Used: A control group, a patch of grass watered with unpolluted tap water, and an experimental group, a patch of grass watered with vinegar-contaminated water, were observed for two weeks. Vinegar caused the pH level of the water and soil to drop to 3.5, becoming more acidic than the normal tap water at 7.2.
Both ecosystems received equal amounts of sunlight, were placed in the same temperature, and contained equal amounts of soil. b. Collection of Data: For two weeks, the control and experimental ecosystems were monitored daily, observed for discoloration or wilting. A number 1-5 was assigned to each ecosystem every day: 1=change of color and wilting, 2=same color and wilting, 3=change of color and upright,
4=same color and upright, 5=growth and development. Observations and any other noticeable peculiarities were recorded.
III. Results: a. Tables or Graphs:
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Control on Day 1
Control on Day 14
Experimental on Day 1
Experimental on Day 14
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b. Description of Data: Throughout the entirety of the two weeks, the control ecosystem exhibited no noticeable change in length or color. After 8 days, the experimental ecosystem started exhibiting discoloration (turned yellow and brown) but remained unwilted. On day 12, the experimental ecosystem began to wilt noticeably and remained discolored. On day 14, the experimental ecosystem appeared significantly weaker than it did on the first day, whereas the control ecosystem appeared almost exactly the same.
IV. Discussion a. Support of the Hypothesis: It was hypothesized that, if the water supply of a patch of grass contains a chemical pollutant, then the soil will be more acidic and the grass will be more wilted and discolored than soil and grass with clean, unpolluted tap water.
The data supports the hypothesis because the ecosystem with unpolluted water remained healthy while the ecosystem with chemically polluted water eventually became weaker and noticeably unhealthier. b. Explanation: The results of this experiment proved that chemical pollution in water has significant negative effects on surrounding plant life. A possible explanation for the weakening of the grass when vinegar was added to its water supply is that vinegar is acidic like a chemical pollutant is, thus it is poisonous to the plant’s roots and kills the plant’s nutrient supply. A possible error in this experiment could have been the pH of the experimental ecosystem. The pH of the vinegar-water was approximately 3.5, whereas most chemical pollutants have an average pH of 3.8 to 4. These minute differences in pH may have caused more damage to the experimental ecosystem than real chemical pollutants would damage natural ecosystems. Future
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experiments should use a slightly higher pH level, as well as more acid-resistant plants and even a basic source rather than an acidic source. c. Conclusion: Ecosystems that have a chemically polluted water source and a more acidic pH are negatively affected and weakened over time. It is dangerous for organisms to inhabit areas with water pollution, as living in or consuming polluted water will lead to various ramifications; it can harm the structure, strength, and potentially the function of an organism. Furthermore, a water source so toxic that it kills plant life could potentially be life threatening to animal life who live in or consume that water.
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