Question

Given below are two statements: Statement (I): Characteristics repeated in space are chiefly structural. Statement (II): Repeatability does not express the importance of temporary environment on a performance trait. In light of the above statements, choose the most appropriate answer from the options given below:

• A. Both Statement (I) and Statement (II) are correct.
• B. Both Statement (I) and Statement (II) are incorrect.
• C. Statement (I) is correct but Statement (II) is incorrect.
• D. Statement (I) is incorrect but Statement (II) is correct.

Hint:

The proportion of phenotypic variance due to temporary environmental effects is exactly equal to \( 1 - r \).
Thus, repeatability directly quantifies the impact of the temporary environment.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Repeatability (\( r \)) measures the correlation between repeated measurements of a trait on the same individual.
Phenotypic variance (\( V_P \)) is partitioned into:
\[ V_P = V_G + V_{Ep} + V_{Et} \]
where:
\( V_G \) is genetic variance,
\( V_{Ep} \) is permanent environmental variance,
\( V_{Et} \) is temporary environmental variance.
Repeatability is defined as:
\[ r = \frac{V_G + V_{Ep}}{V_P} \]

Step 2: Detailed Explanation:
Let us analyze both statements.
- Statement (I) discusses traits repeated in space.
Repeated measurements can occur in time (e.g., milk yield in different lactations) or in space (e.g., teat number, segment count, or leaf shape at different nodes).
Traits repeated in space are typically anatomical or structural characteristics of the organism.
Thus, Statement (I) is correct.
- Statement (II) discusses repeatability and the temporary environment.
From the definition of repeatability, we can derive:
\[ 1 - r = \frac{V_{Et}}{V_P} \]
This shows that the remainder of the phenotypic variance (\( 1 - r \)) is caused entirely by temporary environmental effects.
Therefore, repeatability directly indicates the importance of the temporary environment.
A high repeatability means the temporary environment has a small effect, whereas a low repeatability means the temporary environment has a large effect.
Thus, Statement (II) is incorrect.
Therefore, Statement (I) is correct and Statement (II) is incorrect.

Step 3: Final Answer:
Statement (I) is correct but Statement (II) is incorrect, corresponding to option 3.