Final answer:
Fertilization is the fusion of haploid gametes to form a diploid zygote, while crossing over during meiosis and random chromosome assortment add to genetic variation.
Step-by-step explanation:
The process involved in fertilization is crucial for sexual reproduction and contributes to genetic variance. Fertilization, as shown in the referenced figure, is when haploid gametes (an egg and sperm) unite to form a diploid zygote. However, this is just one part of the diverse processes contributing to genetic variation among offspring from the same parents.
Crossing over is another key event, occurring during prophase I of meiosis, that leads to genetic recombination by exchanging DNA between homologous chromosomes. This mixing of genetic material results in new allele combinations on chromosomes, subsequently increasing genetic diversity in offspring. Additionally, during metaphase I, random chromosome assortment further enriches genetic variability as chromosomes independently align at the equator of the cell with an equal probability of attaching to spindle poles, determining the maternal or paternal origin of each chromosome in the resulting gametes.