Vocabulary
If you are talking about the entire community of trillions of microscopic organisms living inside a human stomach, what scientific term are you referring to?
Microbiome
Place these three biological structures in order from largest to smallest: Bacteria, Human Skin Cell, Water Molecule.
Human Skin Cell --> Bacteria --> Water Molecule
What was the condition of Patient 23's gut microbiome before taking any medication or catching an infection in Week 1
Healthy and fully populated with a diverse community of bacteria
In the lab experiment with mice and Salmonella, why did 20 out of 20 low-bacteria mice get sick compared to only 3 out of 20 normal mice?
the normal mice had helpful bacteria defending the space, while the low-bacteria mice had no competition against the pathogen
In the mouse experiment testing Salmonella, what was the independent variable (the condition changed by the researchers)?
level of bacteria in the mice's gut microbiome
What is the fundamental, smallest structure of a living organism that can carry out life processes on its own?
Cell
While both require a microscope to be seen, why is a single cell considered significantly larger than a single protein molecule?
cells are made up of millions of molecules packed together
What unintended side effect occurred when Patient 23 took broad-spectrum antibiotics to clear his initial illness?
It killed both the bad bacteria and the good bacteria, wiping out most of his microbiome
Why would taking a broad-spectrum antibiotic when you are not sick actually increase your risk of getting a severe gut infection later?
it clears out helpful gut bacteria, creating empty space for invading pathogens to colonize?
What was the dependent variable measured in the controlled mouse experiment?
how many mice got severely sick from the Salmonella infection
"Taking broad-spectrum antibiotics makes a patient more likely to catch a secondary gut infection." What part of a CER framework does this sentence represent?
Claim
Arrange these units of measurement in order from largest to smallest: Micrometer, Meter, Nanometer, Millimeter.
Meter --> Millimeter --> Micrometer --> Nanometer
Why did C. difficile bacteria easily multiply and make Patient 23 severely ill in Week 7, whereas a healthy person's body would usually fight it off?
the antibiotic treatment left open space and unconsumed food in the gut, leaving no helpful bacteria to compete against C. difficile
What piece of evidence proves that bacteria are living organisms that compete for survival rather than non-living particles?
require food/nutrients and physical space to reproduce
Why was it important for researchers to keep the amount of Salmonella given to both groups of mice exactly the same?
ensure a fair, controlled experiment so any difference in sickness was caused only by the gut bacteria, not the amount of pathogen
What general label do scientists give to single-celled organisms like E. coli or C. difficile?
Bacteria (or Microorganisms)
Why can't a doctor see a single bacterial cell on a patient's skin with the naked eye, but can see a bacterial colony growing on an agar plate?
a single cell is microscopic, but an agar culture multiplies into millions of cells clustered together
How does introducing 75 to 80 trillion helpful bacteria through a fecal transplant cure a C. difficile infection?
crowding out the harmful bacteria and taking away their available food and space
If two patients are exposed to the exact same amount of harmful bacteria, why might Patient A get sick while Patient B shows no symptoms at all?
Patient B has a dense, healthy microbiome that blocks the harmful bacteria from getting food and space
What statistical data from the mouse study serves as direct quantitative evidence that gut bacteria protect against infection?
100% (20 out of 20) of low-bacteria mice got sick, compared to only 15% (3 out of 20) of normal mice
When a student explains why a lab dataset proves their scientific hypothesis using biological principles, what key component of CER are they providing?
Reasoning
What primary resources does the human body provide that allow both helpful and harmful gut bacteria to survive and multiply?
Food and Space
By Week 9 post-treatment, what change in Patient 23's gut allowed his health symptoms to disappear completely?
his gut microbiome returned to a normal, high-bacteria state, fully suppressing harmful invader
What is the main scientific mechanism that allows a fecal transplant to succeed when strong antibiotics fail to eliminate a recurrent gut infection?
outcompetition (helpful bacteria fill the ecological niche and starve/crowd out the pathogens)
How does the mouse experiment help doctors make a medical decision about treating human patients like Patient 23?
proves in a controlled setting that having fewer gut bacteria directly increases infection risk, supporting treatments like fecal transplants that restore bacteria levels