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Zoology Question 51 – AP-EAMCET 2025

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Assertion (A) : Binary fission in Euglena is called symmetrogenic division. Reason (R) : Plane of fission in Euglena is at right angles to the longitudinal axis of the body. Identify the correct option from the following

Recall the different types of binary fission (e.g., irregular, transverse, longitudinal, symmetrogenic) and their characteristics.

Step 1: Analyze Assertion (A)✦ Active

Assertion (A) states that binary fission in Euglena is called symmetrogenic division. Symmetrogenic fission is a type of longitudinal binary fission where the division produces two mirror-image daughter cells. Euglena exhibits longitudinal binary fission, which is indeed symmetrogenic.

💡 Teacher's Secret Hint

Symmetrogenic division is characterized by the formation of two mirror-image daughter cells, typical of flagellates like Euglena.

Step 2: Analyze Reason (R)○ Expand

Reason (R) states that the plane of fission in Euglena is at right angles to the longitudinal axis of the body. In Euglena, binary fission is longitudinal, meaning the plane of division runs parallel to the longitudinal axis of the body, not at right angles to it. If it were at right angles, it would be transverse fission.

💡 Teacher's Secret Hint

Distinguish between longitudinal and transverse fission. Longitudinal fission is parallel to the long axis, while transverse fission is perpendicular.

Step 3: Evaluate Truthfulness of (A) and (R)○ Expand

Based on the analysis: - Assertion (A) is true. - Reason (R) is false.

💡 Teacher's Secret Hint

Always evaluate each statement independently before considering their relationship.

Step 4: Select the Correct Option○ Expand

Since Assertion (A) is true and Reason (R) is false, the correct option is the one that reflects this conclusion.

💡 Teacher's Secret Hint

Match your evaluation of (A) and (R) with the given options carefully.

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