Question

The biological clock measures the length at each night by the
A. Relative amount of red absorbing and far red absorbing phytochrome present at dawn
B. Amount of and far red absorbing phytochrome at dusk
C. Relative amount of red absorbing and far red absorbing phytochrome at mid day
D. Rate at which are kind of phytochrome is converted to the other

Answer 1

In order for you to arrive at an answer, try to understand the function of the biological clock. Biological clocks are a group of molecules that interact throughout to maintain important biological functions.

Complete answer:
Biological clocks are an organism's innermost timing device. They are composed of molecules that interact with one another in a very specialized manner. They are found in each of the tissues and organs found in the living systems. It is in synchronization with the solar time. It works on a 24 hours basis and helps the organism to coordinate its behavior. Circadian clocks control the sleep cycle. It is composed of three components.
1. A central biochemical oscillator with a duration of 24 hours that keeps a track of time;
2. A series of input pathways to the present central oscillator to permit entrainment of the clock;
3. A series of output pathways tied to distinct phases of the oscillator that regulate over rhythms in biochemistry, physiology, and behavior of an organism.
The circadian clock is present in association with important cellular and biological processes. The working of the mechanism drastically changes in response to aging. The mechanism is reset when it gets external signals primarily daylight.

Thus, the correct option is (A) Relative amount of red absorbing and far-red absorbing phytochrome present at dawn.

Note:
Circadian clocks are of immense importance in biological systems as they have a direct influence on the sleep cycles, hormone release, temperature, eating habits, digestion, and most importantly on the mood.