Final answer:
Sexual reproduction involves meiosis to produce haploid gametes, followed by fertilization where two gametes combine to form a diploid zygote, which grows into a new organism.
Step-by-step explanation:
Sexual reproduction requires the cellular process of meiosis followed by fertilization. Meiosis is the type of cell division that reduces the chromosome number from diploid to haploid, thus producing gametes, or sex cells. These haploid gametes contain one set of chromosomes, representing one half of the genetic information necessary for the development of a new organism.
During fertilization, two haploid gametes (one from each parent) unite to form a diploid zygote. This zygote contains two sets of chromosomes, one from each parent, resulting in a genetically unique individual. The zygote will undergo mitotic divisions to grow and develop into a mature organism.
In the case of plants, sexual reproduction also involves the alternation of generations, where the life cycle includes both haploid gametophyte and diploid sporophyte stages. Sexual reproduction introduces genetic variation and is a fundamental aspect of the evolutionary success of eukaryotic organisms.