Daily rythms are usually associated with
Or
One of the following endocrine gland functions as a biological clock and a neurosecretory transducer

Options

A. Pituitary
B. Thymus
C. Pineal
D. Hypothalamus.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about daily rhythms and which endocrine gland functions as a biological clock and a neurosecretory transducer.

2. **Identifying the Endocrine Gland**: The pineal gland is the endocrine gland that is primarily associated with regulating daily rhythms, particularly through the secretion of the hormone melatonin.

3. **Function of the Pineal Gland**: The pineal gland is responsible for producing and regulating melatonin, which plays a crucial role in controlling sleep-wake cycles and circadian rhythms.

4. **Role of Melatonin**: Melatonin levels fluctuate based on light exposure. During the day, when there is light, melatonin secretion decreases, and during the night, in the absence of light, melatonin secretion increases, promoting sleep.

5. **Biological Clock**: The pineal gland is often referred to as the biological clock because it helps regulate the body's internal clock by responding to environmental light conditions.

6. **Neurosecretory Function**: The pineal gland acts as a neurosecretory transducer by converting neural signals (light perception) into hormonal signals (melatonin secretion), thus influencing physiological processes like sleep.

7. **Conclusion**: Therefore, the correct answer to the question is that the pineal gland functions as a biological clock and a neurosecretory transducer.

**Final Answer**: The pineal gland.

---