Describe the events by which depolarization of a smooth muscle cell results in contraction and explain why smooth muscle contractions are slow and sustained.

The depolarization of the smooth muscle cell membranes triggers the potential for contraction action, since the endoplasmic reticulum releases calcium in the intraplasmic zone, causing myosin and actin to unite, generating a sweeping movement and bringing the z lines of the sarcomero.

Smooth muscle contractions are more sustained over time by the distribution and type of muscle fiber, as they are more tapered.

Explanation:

The smooth muscle is that muscle that controls non-voluntary contractions, that is, controlled by the somatic nervous system, and is not related to locomotion but rather to involuntary movements such as intestinal motility, vascular contraction, etc.

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.

1. is geographic distribution

2 is increasing complexity

3 is transitional forms