Answer :
The term 'embryo' refers to a developing human from weeks a) 3 to 8 after fertilization. After week 8, the embryo is referred to as a fetus.
In the field of biology, the development stages of a human from fertilization to birth are classified as the pre-embryonic, embryonic, and fetal stages. The embryonic stage begins once the zygote implants in the uterine wall and lasts from the third through the eighth week after fertilization.
During this period, significant developments occur, including the formation of the basic structures of the head, chest, and abdomen, the start of the heartbeat, and the development of rudimentary organ systems. Consequently, the organism is referred to as an embryo throughout weeks 3-8.
Ultimately, the embryonic stage lays the essential groundwork for subsequent stages of growth, with rapid cell division, migration, and differentiation occurring. By week 9, the embryo is referred to as a fetus as it enters the next phase of prenatal development.
