What may occur if a zygote forms but does not survive?

When a zygote forms but does not survive, the phenomenon described is specifically known as zygote mortality. This occurs when the fertilized egg fails to develop properly or undergoes processes that prevent it from progressing to the next stages of embryonic development. This can happen due to various intrinsic or extrinsic factors, such as genetic incompatibility, environmental stressors, or inadequate nutrients, preventing successful division and growth.

In contrast, the other options do not accurately represent the scenario of the zygote's failure to survive. Gamete mortality generally refers to the death of sperm or egg cells before fertilization occurs. Hybrid sterility describes a condition in which hybrids (offspring from two different species) are formed but are unable to reproduce successfully, which is a step beyond zygote formation. Pre-reproductive barriers involve factors that impede the formation of a zygote in the first place, such as geographical separation or temporal differences in reproduction. Thus, these concepts do not apply to the situation where a zygote has already formed yet fails to survive.