Final answer:
Fertilization is the process where a sperm and an egg combine to form a zygote, which then develops into a new individual. This takes place in the female reproductive tract and involves the sperm penetrating the protective layers of the egg.
Step-by-step explanation:
The process by which a sperm cell combines with an egg cell is known as fertilization. This vital process in sexual reproduction involves the fusion of haploid gametes - the male sperm and the female egg - to form a diploid zygote. Each gamete carries a single set of chromosomes, and through fertilization, these sets come together to form one complete diploid set, which is essential for producing genetically diverse offspring with the full requisite number of chromosomes.
Fertilization typically occurs within the female reproductive tract, where the sperm travels through the vagina and uterus into the fallopian tubes, which is the common site for the fertilization of the egg. The complexity of this process is evident when considering the protective layers surrounding the egg, like the zona pellucida, which sperm must penetrate. This is achieved through the acrosomal reaction, whereby the sperm releases enzymes to break down the glycoprotein matrix of the zona pellucida, allowing the sperm to reach and fuse with the egg membrane. Consequently, the sperm transfers its nucleus into the ovum, where the haploid sperm and egg genomes combine to form a diploid zygote, marking the beginning of a new individual's development.