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Animal rotates on its longitudinal axis....

Animal rotates on its longitudinal axis. The reason behind it is

A

the more vigorous beat of longer cilia present in the oral groove than that of . body surface.

B

the less vigorous beat of longer cilia present in the oral groove than that of body surface.

C

difference in length of cilia is not re- sponsible.

D

more than one of the foregoing.

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The correct Answer is:
To solve the question regarding why an animal rotates on its longitudinal axis, we can follow these steps: ### Step-by-Step Solution: 1. **Understanding the Question**: The question asks for the reason behind the rotation of an animal on its longitudinal axis. This involves understanding the mechanisms of movement in unicellular eukaryotes, particularly those that use cilia for locomotion. 2. **Identifying the Mechanism of Movement**: In many unicellular organisms, such as paramecium, movement is facilitated by cilia. Cilia are hair-like structures that beat in a coordinated manner to propel the organism through its environment. 3. **Analyzing the Options**: - **Option 1**: "The more vigorous beat of longer cilia present in the oral groove than that of body surface." This suggests that if the cilia in the oral groove beat more vigorously, it would lead to a stronger rotational movement. - **Option 2**: "The less vigorous beat of longer cilia present in the oral groove than that of body surface." This implies that a weaker beat would not facilitate rotation effectively. - **Option 3**: "Difference in length of cilia is not responsible." This indicates that the length of cilia does not play a role in the rotation. - **Option 4**: "More than one of the foregoing." This suggests that multiple options could be correct. 4. **Evaluating the Correct Option**: - The key to rotation lies in the beating of cilia. If the cilia in the oral groove beat more vigorously than those on the body surface, it would create a stronger force that could lead to rotation. Therefore, option 1 is the most logical choice. 5. **Conclusion**: The correct answer is option 1: "The more vigorous beat of longer cilia present in the oral groove than that of body surface." ### Final Answer: The reason behind the rotation of the animal on its longitudinal axis is due to the more vigorous beat of longer cilia present in the oral groove than that of the body surface. ---
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