Final answer:
The clear noncellular layer of an ovum that influences fertilization rate due to its thickness and needs to be penetrated by sperm is indeed the thick glycoprotein membrane known as the zona pellucida.
Step-by-step explanation:
The zona pellucida is indeed a thick, gel-like glycoprotein membrane that coats the oocyte (egg cell). Its primary function is to protect the oocyte and must be penetrated by sperm for fertilization to occur. This clear, noncellular layer plays a vital role in the fertilization process.
The thickness of the zona pellucida affects the ability of the sperm to penetrate and fertilize the egg, influencing the fertilization rate.
Upon contact with the oocyte, capacitated sperm release digestive enzymes in a process known as the acrosomal reaction, allowing them to attach and burrow through the zona pellucida.
Successful penetration by a sperm results in the release of its haploid nucleus into the oocyte, and the subsequent cortical reaction prevents any further penetration by other sperm, forming a protective fertilization membrane and completing fertilization. The fusion of the haploid nuclei from the male and female gametes then forms the diploid cell known as a zygote.