A Microbial Ecologist Is Interested in Whether the Microbial Community

question 9

Multiple Choice

A microbial ecologist is interested in whether the microbial community of a pond changes when it rains. She knows that rainfall will increase the number of bacteria, but she is interested in the pattern of diversity. She collects a water sample from a pond two days before a rainfall and two days after and plates her samples on agar (a method to measure bacteria) and counts the number of colonies she observes for each of three bacteria: E. Coli, Salmonella, and Giardia. In the pre-rain sample she observes 21, 57, and 32 colonies respectively. In the post-rain sample she observes 59, 83, and 88 colonies respectively.
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-To determine whether there appears to be a statistically significant relationship between rainfall and bacterial diversity she would conduct a χ² analysis. When performing this analysis, which of the values below is closest to the contribution to the χ² statistic from the "pre-rainfall : Salmonella" category?

• A) 1.01
• B) 2.02
• C) 3.03
• D) 4.04

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Definitions:

Basilar Membrane

A critical structure in the cochlea of the inner ear, it plays a key role in the mechanical analysis of sound waves for hearing.

Cochlea

A spiral-shaped cavity within the inner ear, playing a crucial role in converting sound waves into electrical signals.

Ossicles

Tiny ossicles located within the middle ear that transfer sound waves from the tympanic membrane to the cochlea.

Human Hearing

The faculty by which humans perceive sound through vibrations detected by the cochlea in the ear.