d. ATP is present and the intracellular Ca2+Ca2+ concentration is high.
Explanation:
Myosins are motor proteins that plays a major role in muscle contraction. They depend on ATP and responsible for motility in actin-based substances. Skeletal muscle is composed of myosin and actin fibers. Each myosin thick filament is surrounded by actin thin filaments, and each thin filament is surrounded by thick filaments. There exists a strong attraction between the myosin head and the myosin-binding site of actin which binds them spontaneously. This bond is aided by the presence of ATP and the high concentration of intracellular Ca2+. The myosin protein undergoes a change in its shape.
The vertical migration of <em>Daphnia sp.</em> is their characteristic behaviour.
These organisms migrate to the surface of the water body during night and remain at the bottom during the day.
Behaviorists believe that <em>Daphnia sp. </em>does this to avoid predation.
During the day, it remains at the bottom that lacks light and avoids being noticed by the fishes. But at night when the day light is absent it swims up to feed upon the algae present in the clear surface water.
Thus we can conclude <em>Daphnia</em> population is responding to the clarity of water.
