1) In reptiles, the eggs enter the oviduct, where they are covered with protein and shell, and are laid 12–20 days after fertilization. The fetus receives all the necessary nutrients from stocks of eggs.
2) Small eggs (ovules) of mammals have few nutrients. Internal fertilization occurs in paired oviducts.
3) Oviducts open into a special organ – the uterus. A fertilized egg is attached to the wall of the uterus, where the fetus develops. At the site of attachment of the egg to the wall of the uterus, the placenta develops. The fetus is connected to the placenta by the umbilical cord, inside of which pass its blood vessels. Through the walls of blood vessels from the mother’s blood, nutrients and oxygen enter the blood of the embryo, carbon dioxide and other waste products harmful to the embryo are removed. Mammals are characterized by live births.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.