Respiration Prac (copy)

Research Question

What effect does the state of seeds have on the amount of carbon dioxide produced as the result of cellular respiration?

Independent Variable

Treatment of the seed. (dried, boiled or soaked)

Dependant Variable

Amount of respiration as measured by carbon dioxide that causes water to rise in the tube.

Controlled Variables

0\.5g hydroxide powder, time left in water, amount of seeds in each tube (6)

Aim

To investigate the effect of states of seeds from dormant to able to germinate on the amount of respiration that occurs as measured by the amount of water that rises in the test tube.

Hypothesis

If the amount of respiration as measured by carbon dioxide that causes water to rise in the tube is related to the state of the seed (dried, boiled or soaked) the water will rise the highest in the soaked seeds tube. The boiled seeds will not raise the water at all as the enzymes in the chemical pathway would have been denatured at the high temperature. The dry seeds will also not produce carbon dioxide as they are still dormant and respire at very low rates.

biological concepts

As indicated by the height of the water rising the most in the soaked seeds (30.94mm) due to carbon dioxide being produced during cellular respiration. This is due to the oxygen in the tube being used as an input, thus being used and replaced with the output of the process carbon dioxide, this makes the water rise in the tube due to the air pressure declining. Cellular respiration is the process of metabolising stored sugars and occurs at a higher rate when the seed is exiting dormancy.

Limitations

errors

random errors such as environmental conditions, observer bias and movement and angling of the tubes. Systematic errors such as size of peas, test tubes and measurement bias if the meniscus.

validity

This calls into question the validity of the experiment as these values contradict each other as they are expected to be 0 and some groups got this while others didn’t. While the experiment investigated the overall impact of seed treatment on respiration, the values recorded did not reflect the trend of soaked having the most, then dry and then boiled, making the experiment invalid.

accuracy

The values for the soaked seeds in this experiment were accurate as with a final height of 30.94mm, the soaked seeds displayed the highest amount of respiration. All individual groups had a value for the soaked seeds higher than any of their other seeds. The dry seeds value of 2.88 is not inaccurate as dry seeds are dormant and respire at low rates and all groups had a value that was equal or slightly greater than the control group measurement, indicating a low amount of respiration. The boiled seed value however, is inaccurate with a 4.25mm average, the second highest the results would indicate a greater amount of respiration than the dried seeds which should not be the case due to the enzymes in the chemical pathway being denatured from the high temperatures of boiling. It should be noted that two groups had values indicative of this (0mm).

precision

The values in this experiment are not very precise, while the values for the soaked seeds were within 8mm of each other and the dry within 7mm. The values for boiled and controlled contradicted each other. 2 groups got 0mm for boiled while others ranged from 3-7mm and 4 groups got 0mm for control while the others got from 1-4 mm.

improvements

could include measuring test tubes and cotton wool to ensure they are the same size, as well as weighing peas for the same purpose