Question

When comparing life-history traits across animal species, which one of the following relationships is LEAST expected under r-selection and K-selection theory?

• A. Development time is positively correlated with age at first reproduction
• B. Development time is negatively correlated with lifespan
• C. Lifespan is positively correlated with body size
• D. Lifespan is negatively correlated with number of offspring per breeding attempt

Hint:

r and K selected traits cluster together on a fast-slow spectrum; look for the one pair placed on opposite sides that the theory actually groups on the same side.

Answer 1

The Correct Option is B

Step 1: Recall the r-K selection framework.
r-selection and K-selection describe two ends of a continuum of life-history strategies. r-selected species grow fast, mature early, live short lives, stay small, and produce many offspring each time they breed. K-selected species grow slowly, mature late, live long lives, grow large, and produce few offspring each time they breed.

Step 2: Notice that these traits travel together.
The theory predicts that these traits cluster: slow development, late reproduction, long lifespan, large body size, and low offspring number all sit on the K-selected end together, while their opposites sit on the r-selected end together. So most pairs of these traits should be positively correlated across species, since a species that is K-selected in one trait tends to be K-selected in the others too.

Step 3: Check option (A).
Development time and age at first reproduction should move together, since an animal cannot reproduce before it finishes developing. Long development time goes with late first reproduction, so this is a positive correlation, exactly as the theory expects.

Step 4: Check option (B).
Development time and lifespan are both K-selected traits when they run long, and both are r-selected traits when they run short. So they should be positively correlated across species, not negatively correlated. A negative correlation here would mean species with long development somehow have short lives, which goes against the whole logic of the theory.

Step 5: Check option (C).
Larger body size generally goes with slower metabolism and longer lifespan, a well-supported positive correlation across many taxa, matching K-selected expectations.

Step 6: Check option (D).
Long-lived, K-selected species usually produce few offspring per breeding attempt, while short-lived, r-selected species produce many. This is a negative correlation between lifespan and offspring number, exactly as the theory predicts.

Step 7: Identify the odd one out.
Option (B) is the only relationship that runs against how r-K traits are expected to cluster.

Final Answer:
\[ \boxed{\text{Development time is negatively correlated with lifespan}} \]