Select all the correct statements:
1. In birds, placenta develops from the chorion and extends into the uterine lining.
2. In humans, placenta develops from the chorion and extends into the uterine lining.
3. In humans, the placenta (originating from the chorion) allows for the exchange of oxygen and metabolic wastes.
4. In birds, the placenta (originating from the chorion) allows for the exchange of oxygen and metabolic wastes.
5. In birds, the chorion is involved in gas exchange
6. In humans, the chorion is involved in gas exchange
7. In birds, the chorion combines with the allantois (an extra-embryonic membrane) rather than with the mother's tissues
8. In humans, the chorion combines with the allantois (an extra-embryonic membrane) rather than with the mother's tissues