Name the three periods of prenatal development, the weeks they occur, and characteristics of development during each period

What will be an ideal response?

A good answer will be similar to the following:
+ Period of the zygote (Weeks 1–2 after conception)
- Begins with fertilization.
- Ends when the fertilized egg (the zygote) implants itself in the wall of the uterus.
- Rapid cell division occurs.
- Implantation begins one week after conception and is complete at two weeks after conception.
+ Period of the embryo (Weeks 3–8 after conception)
- Begins once the zygote is completely embedded in the uterine wall.
- Body structures and internal organs develop.
- At the beginning, consists of three layers; the ectoderm, mesoderm, and endoderm.
- By eight weeks, embryo looks like a human being complete with eyes, jaw, arms, and legs.
- Most of the organs found in a mature human are in place, in some form, by the end of this period.
- Amnion cushions embryo and regulates temperature.
- Umbilical cord and placenta provide nutrients, oxygen, vitamins, and waste products to be exchanged between mother and embryo.
- Growth proceeds according to the cephalocaudal and proximodistal principles.
+ Period of the fetus (Weeks 9–38 after conception)
- Final and longest phase of prenatal development.
- Fetus becomes much larger and its bodily systems begin to work.
- Some simple reflexes are present.
- Reaches the age of viability at about seven months.
- Fetus is able to hear by the last two months of pregnancy.