The parasympathetic division of the autonomic nervous system regulates erection, whereas ejaculation is triggered by sympathetic impulses. Medical and emotional conditions can cause clinical disorders of erectile dysfunction. Drugs such as Viagra increase erectile function by improving blood flow into penile tissue. Many factors result in poor fertility or infertility in males including hormone imbalances, reproductive tract blockages, decreased sperm concentration, and abnormal sperm.
Fungal reproduction is complex, reflecting the differences in lifestyles and genetic makeup within this diverse kingdom of organisms.  It is estimated that a third of all fungi reproduce using more than one method of propagation; for example, reproduction may occur in two well-differentiated stages within the life cycle of a species, the teleomorph and the anamorph .  Environmental conditions trigger genetically determined developmental states that lead to the creation of specialized structures for sexual or asexual reproduction. These structures aid reproduction by efficiently dispersing spores or spore-containing propagules .