Which of the following statements is not true about an animal's circadian rhythm?
a. animals have special adaptations depending on whether they are nocturnal or diurnal
b. it's not influenced by genetics, only the time of day
c. it can be adjusted or overcome with time and effort
d. it's influenced by genetics and the time of day
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B. it's not influenced by genetics, only the time of day.

Explanation:

Circadian rhythm is a natural process that take place in animals, plants, fungi etc. It regulates cycles of sleep and wake, it repeats after 24 hours. Various genes are involved in this cycle so, to say that it's not influenced by genetics is wrong.

e.g. in Drosophila two factors that contribute mainly in its circadian clock are "tim" and "per" both are genetic factor, both regulate each others function. They regulate the 24 hour cycle in drosophila. In morning 'tim' is degraded due to light, and in absence of 'tim' 'per' is also degraded. while in evening, both assembled and translocated in the nucleus, and their binding with transcription factors results in the inhibition of transcription activity.