Eighty Years Ago,a Predatory Crab Was Introduced to a Region

question 94

Multiple Choice

Eighty years ago,a predatory crab was introduced to a region it previously did not inhabit and began preying on a species of marine snail.A scientist was able to locate museum specimens of the snail's shells from prior to the crab's introduction and to compare their thickness-an important factor in how protective the shells are-to the thickness of shells from current snails.Based on the graphs of her results (shown here) ,what form of evolution/natural selection has taken place?

• A) nonadaptive evolution
• B) stabilizing selection
• C) directional selection
• D) diversifying selection
• E) neutral selection

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Definitions:

Illusory Correlation

The mistaken perception of a relationship between two events or variables that are actually unrelated.

Positively Correlated

A relationship between two variables where they move in the same direction, meaning as one variable increases, so does the other, and vice versa.

Scatterplot

A type of graph in which the values of two variables are plotted along two axes, the pattern of the resulting points revealing any correlation present.

Normal Curve

A symmetrical, bell-shaped curve representing the distribution of a set of data where most occurrences fall near the average, and fewer are found the farther one moves away from the mean.