What does the horizontal line between
the male and female represent?

it represents the mating between males and females is shown by a horizontal line between their respective symbols.

Explanation:

Whereas apoptosis is a form of cell death that is generally triggered by normal, healthy processes in the body, necrosis is cell death that is triggered by external factors or disease, such as trauma or infection. Apoptosis, which can also occur as a defense mechanism during healing processes, is almost always normal and beneficial to an organism, while necrosis is always abnormal and harmful. Though necrosis is being researched as a possible form of programmed cell death (that is, a sometimes natural process), it is considered an "unprogrammed" (unnatural) cell death process at this time. As a usually healthy form of a cell's life cycle, apoptosis rarely demands any form of medical treatment, but untreated necrosis can lead to serious injury or even death.