Question

Course Home <Ch 24 HW Scientific Thinking: What Roles Do Diet and the Microbial Community in the Intestines Play in Obesity? Review Fast foods, cookies and ice cream, sodas and energy drinks -Americans eat a lot of processed foods high in fats and simple sugars Not surprisingly, this type of diet can lead to weight gain and is one of the main culprits in the obesity epidemic in thiscountry But, is there more to this story The foods you eat serve as food for the community of microorganisms that inhabit your digestive tract Those microbes have their own food "preferences, " metabolizing different types of food molecules and releasing their byproducts, which your body may absorb. Scientists have hypothesized that a high-fat, high sugar diet actually alters the composition of the microbial community that inhabits the beginning of the large intestine, which contributes to obesity. Because of the difficulties of carrying out experiments on humans, scientists have used mice as an animal model in which to test this hypothesis Part A Designing a controlled experiment In one experiment, scientists raised mice in germ-free conditions so the mice lacked intestinal microbes. The mice were fed a low-fat diet rich in the complex plant polysaccharides, such as cellulose, that are often called fiber When the mice were 12 weeks old, the scientists transplanted the microbial community from the intestine of a single "donor" mouse into all of the germ-free mice. Then they divided the mice randomly into two groups and fed each group a different diet. Group 1 (the control group) continued to eat a low-fat, high-fiber diet. Group 2 (the experimental group) ate a high-fat, high-sugar diet
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Answer 1

Variables include:

• Independent variable: variable which is altered during experiment.
• Dependent variable: Variable whose effect is altered due to the variation in the independent variable.
• Controlled variable: Variable that is constant for the specific experiment.

In this experiment:

Constant:

• Age of the mice.
• Age of the mice will remain the same through the experiment.

Independent variable:

• Initial and final composition of microbial community.
• The composition of microbial community can be maintained by during the experiment and altered.

Dependent variable:

• Weight gain and change in body fat.
• They are dependent on change in composition of microbial flora.