What does 'amphimixis' refer to in the process of fertilization?

Amphimixis refers specifically to the combining of genetic material from two parents during the process of fertilization. This term embodies the fundamental concept of sexual reproduction, where the genetic contributions from both the male (sperm) and female (egg) unite to create a zygote, which possesses a mix of alleles from both parents. This process is crucial for increasing genetic diversity in a population, which enhances adaptability and evolution over generations.

The other options, while related to fertilization, do not encapsulate the essence of amphimixis. The stage of cell division pertains to the subsequent developmental processes following fertilization. The block to polyspermy is a mechanism that prevents multiple sperm from fertilizing the same egg, which is an important step in ensuring proper development, but it is not what amphimixis describes. The entry of sperm into the egg describes an aspect of the fertilization process but does not denote the combining of genetic materials that amphimixis specifically refers to. Therefore, the correct answer captures the key concept of genetic combination central to sexual reproduction.