Honors Biology Final Practice Exam 2026 - Free Honors Biology Practice Questions and Study Guide

The fertilized egg is called a zygote. This single cell forms when a sperm fuses with an egg, restoring the diploid chromosome number and carrying genetic material from both parents. From there, the zygote undergoes rapid mitotic divisions (cleavage) and begins the journey of development toward becoming an embryo. The term embryo refers to the developing organism after fertilization as cell divisions and differentiation proceed. A morula is an earlier cleavage stage, a solid ball of cells formed before the hollow blastula stage. A gamete is the sperm or egg itself—the haploid reproductive cell that joins with its counterpart to form the zygote.