Cress seeds investigation Essay
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Test tube 6: Number germinated: 0/10 Height of seedlings: 0 I then took the averages of the height of the seedlings in each test tube. Average height in test tube 1: 49. 9mm Average height in test tube 2: 45. 25mm Average height in test tube 3: 9. 9mm Average height in test tube 4: 11. 5mm Average height in test tube 5: 5. 8mm Average height in test tube 6: 0mm This is a graph to show the average height of the seedlings in each test tube: OBSERVATIONS: Test tube number 1 contained the cress seedlings that had grown the best.
This was the control test tube, and had no acid in it.
The cress in this test tube was a healthy green colour, and was almost perfectly straight. The cress seedlings were the worst in test tube number 5. This tube contained 4 drops of acid, and the cress in it had hardly grown at all. It was a pale, sickly green colour, and very short. The leaves drooped down, and the roots were very short.
Although test tube number 6 contained the most acid, the seedlings in this did not grow at all. I also took results from another group, who had conducted the same investigation as me. Their results are as follows: Test tube 1: Number germinated: 9/13.
Height of seedlings: 1 ; 1 ; 2 ; 3 ; 3 ; 10 ; 22 ; 34 ; 34 Test tube 2: Number germinated: 10/13 Height of seedlings: 4 ; 5 ; 8 ; 14 ; 15 ; 15 ; 22 ; 24 ; 25 ; 33 Test tube 3: Number germinated: 12/13 Height of seedlings: 1 ; 4 ; 4 ; 5 ; 9 ; 10 ; 12 ; 12 ; 14 ; 14 ; 16 ; 16 Test tube 4: Number germinated: 0/13 Height of seedlings: 0 Test tube 5: Number germinated: 0/13 Height of seedlings: 0 Test tube 6: Number germinated: 8/13 Height of seedlings: 1 ; 2 ; 3 ; 3 ; 4 ; 4 ; 5 ; 5 Average height in test tube 1: 12. 2mm Average height in test tube 2: 16. 5mm Average height in test tube 3: 9.
8mm Average height in test tube 4: 0mm Average height in test tube 5: 0mm Average height in test tube 6: 3. 4mm This graph shows the average height of the seedlings in each test tube belonging to the other group: This graph shows the average height of both the other group’s seedlings and mine. ANALYSIS: From my results I can tell that the more sulphuric acid the cress was grown in, the less the seedlings grew. For example, in my investigation, the cress in the control test tube grew to an average of 49. 9mm, whereas in the test tube with 5 drops of acid, the cress did not grow at all.
In both mine and the other group’s results, the average height of the seedlings went up slightly in one test tube – the other group’s by 6. 7mm in test tube 3, and mine by 1. mm in test tube 4. CONCLUSION: From this investigation I have drawn the conclusion that acid rain does indeed affect plant growth. My seedlings grew best in the control test tube, and the worst in the tube that contained the most acid. In the control test tube, the seedlings had long roots, whereas in the test tube with 5 drops of acid, the roots were weak and very short.
This shows that the acid had affected the way the cress seeds had germinated, and had eaten away at the roots of the seedlings. My results support the original prediction that I made. I said that the cress would grow best in the control test tube, and as the results show, it did. I also said that the test tube containing the most acid would produce the worst seedlings, which was also correct. EVALUATING EVIDENCE: My results were not completely accurate. Although the basic trend showed that the more acid the seedlings were put in, the less they grew, my average heights went up slightly when, theoretically, they should have gone down.
For example, they went up from 9. 9mm to 11. 5mm, and then down again to 5. 4mm. Therefore, the graph that I drew does not have a completely accurate curve. This is also true for the other set of results that I gathered. I could improve the accuracy of this investigation by doing several things differently. I could use more test tubes, giving me a wider range of results, and I could also use a smaller amount of acid per test tube – for example, I could increase the acid by . 5 of a drop per tube.
This would give me more accurate results. Because my results were slightly anomalous, they are not sufficient enough to support a firm conclusion. Because the results did not follow a set pattern, they are not entirely reliable. To improve on this, and make my results more accurate, I could be very meticulous when measuring out the acid, and also make sure that I treat all the test tubes equally. I feel that this investigation went quite well although my results could have been slightly more accurate.