IB Biology Practice Exam

A zygote is defined as the single cell that results from the fusion of male and female gametes during the process of fertilization. This fusion occurs when a sperm cell from the male combines with an egg cell from the female, resulting in a diploid cell that contains genetic material from both parents. This diploid zygote is the earliest stage of development for organisms that reproduce sexually and will go through several rounds of cell division to develop into an embryo.

The other options do not accurately define what a zygote is. For instance, while meiosis is a process related to producing gametes, a zygote itself does not undergo meiosis; rather, it develops from the outcome of that process. A zygote also cannot be classified as a haploid cell since it is diploid, combining two haploid gametes. Lastly, while the zygote does develop into structures that support embryo development, the term "zygote" itself specifically refers to the initial fertilized cell, not the supportive structures that arise later.