Standards - Question #3 (1997)

#3. A scientist working with Bursatella leachi, a sea slug that lives in an intertidal habitat in the coastal waters of Puerto Rico, gathered the following information about the distribution of the sea slugs within a ten-meter square plot over a 10-day period.

DISTRIBUTION OF SLUGS WITHIN A TEN-METER SQUARE PLOT

Time of Day Average Distance Between Individuals (cm)

Midnight 8.0

4 A.M. 8.9

8 A.M. 44.8

NOON 174.0

4 P.M. 350.5

8 P.M. 60.5

Midnight 8.0

a. For the data above, provide information on each of the following.

Summarize the pattern

Identify THREE physiological or environmental variables that could cause the slugs to vary their distance from each other.

Explain how each variable could bring about the observed pattern of distribution

b. Choose ONE of the variables that you identified and design a controlled experiment to test your hypothetical explanation. Describe results that would support or refute your hypothesis.

(A) From the data MAX for Part A = 6 points (B) Controlled experiment for one variable

1 pt - summarize pattern (dispersal - day / clumped - night) 1 pt - Control - constants (explicit)

1 pt - Manipulation of variable

1 pt - 3 physiological or environmental variables (1st three only and TESTABLE) 1 pt - Measurement (quantitative

1 pt - Verification (sample size / repetition)

carbon dioxide light rhythms 1 pt - Hypothesis (if:then) TESTABLE

competition mating salinity 1 pt - Statistical analysis of data

desiccation metabolism taxis 1 pt - Results as related to hypothesis

endogenous oxygen temperature

feeding pH tidal exchange 1 pt - Elaboration

foraging predation water depth

hormonal protection (Others possible)

MAX for Part B = 6 points

1 pt each - for a clear and plausible explanation of variable as it influences the observed

(3 max) distribution pattern (vary)

1 pt - Elaboration

Only ONE extra elaboration point may be earned in either Part A or Part B - for extensive, unique, or exceptional effort