Digestive System Design Lab Essay Sample

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The purpose of this lab is for students to see and understand the affect of temperature on a healthy brown rat’s (Rattus norvegicus) digestive system.


-five healthy, medium-sized, middle aged, male, brown rats (Rattus norvegicus) (about 10in long and weigh 350g)

-three cups of uncooked red-rice

-three cups of water

-five plastic reseal-able bags

-five clear, plastic boxes, with a lid (length=1m width=50cm height=30cm) with holes at the bottom (approximate size of the holes=1.5cm-2cm and the holes should be 3cm apart from each other)

-five clear, plastic boxes without a lid (length=85cm width=35cm height=15cm)

-five rooms, each 15 square feet

the first room should be set at -2 oC

the second room should be set at 5 oC

the third room should be set at 15 oC

the fourth room should be set at 25 oC

the fifth room should be set at 35 oC

-five small camcorders (make sure they work and have a zoom in and out function)

-scooper (to collect the rat feces)

-ten metal bowls

-electric balance



-paper and pencil

**Note that the rate of digestion is equal to:

temperature + (6.23 x weight in pounds) + (12.7 x height in inches)

number of times waste is excreted


I. Controlled Variables

The type of rat being used in the experiment

What the rat will be eating.

The temperature in which the rats will be in.

The size of the environment that the rats will be in.

II. Independent Variables

Temperature that the rat will be in

III. Dependant Variables

How much food the rats will be eating from the 1/2 cup of rice given to them.

How often the rats will digest their food.

How much waste will be secreted by the rats.


1. Place the rat and the two silver bowls into the plastic box and gently place the lid on this box.

2. Take the cardboard box, which is slightly a bit smaller then the plastic box, and place it under the plastic box. The placement of the boxes should look like so:

3. Leave the rat inside the plastic box for four hours without any food. This is to get all the food that was already in the rat’s system out. (Do not worry that the rat will starve and die, because rats can live up to a full without any food.)

4. After four hours, check the cardboard box for any waste excreted by the rat and throw it away.

5. Now, take 1/2 cup of the scrambled eggs and 1/2 cup of water and put them separately into the two silver bowls.

6. Close the plastic box’s lid and place the boxes in a -2oC environment. Observe the rat for four hours.

7. Sit next to the box and take note of how often the rat excretes wastes. Jot down the time whenever the rat excretes, and with the aid of the scooper, count approximately how much droppings are being dropped each time.

8. After four hours has passed, take the remaining food out of the bowl and weigh it in order to see how much the rat ate and spill the eggs and the water out.

9. Also take the wastes excreted by the rat and put it into the small reseal-able bag and label the bag “-2oC”.

10. Repeat steps 5-9 for these temperatures: 5oC, 15oC, 25oC, and 35oC and make sure that you write the correct temperature on each corresponding reseal-able bag.

11. Write down all observations in a similar chart:


of times of excretion

of droppings

Other observations






12. Make observations to see if there is a possible connection between temperature and how often the rat digests.

13. Now that you have completed the lab, throw the cardboard box, clean the two silver bowls, and the plastic box, and put back all the other equipment into their designated areas.

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