Physiology : The Human Excretory System

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Year 11 Biology Physiology: The Human Excretory System Claire Brus Abstract The aim of the practical was to observe the body’s reactions (flow of urination and colour of urination) in the presence of water, caffeine and no liquid during the important stage of reabsorption. Introduction Background Theory ‘The excretory system is a passive biological system that removes excess, unnecessary materials from an organism, so as to help maintain homeostasis within the organism and prevent damage to the body’ (http. 2). The excretory system is composed of two kidneys, two ureters, a bladder and a urethra. What is the excretory system composed of? What is the purpose of the excretory system?  Cleans and filters blood by removal of waste…show more content…
Constants There are numerous conditions that must be kept constant throughout this practical to increase the likelihood of obtaining accurate results. The materials used throughout the practical should be kept constant, especially the bottle/cup, the stopwatch and the toilet. The same bottle/cup should be used to measure the various liquids, as the measurements may be different on other bottles/cups, resulting in inaccurate results. The stopwatch used to record the flow of urination must be kept constant, as other stopwatches may not be calibrated correctly. The toilet used should also be uniform, as the volume of water in the base of the toilet may be significantly larger, resulting in lighter/darker concentration colours. The activities completed during the two hour time period should be relatively similar and not increase nerves, as this may increase the need to urinate. Materials & Method Materials 1 Pencil 1 A4 Sheet of Paper 1 Toilet 1 Watch 1 Stop Watch 1 Timer 250mL Cup/Bottle 250mL Water 250mL Caffeine Method 1. Ensure that all materials listed above are available to use when necessary. 2. Decide upon a two-hour time period during the day when no food is consumed. 3. Go to the toilet and empty the bladder by urinating. 4. Look at the watch and record the time period onto the piece of paper using the pencil. 5. Set timer for two hours. 6. Obtain the 250mL cup/bottle, pour 250mL of water into it and consume
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