Question

Pick the mammal with true placenta.
A. Kangaroo
B. Echidna
C. Platypus
D. Mongoose

Answer 1

Hint: Placenta is a characteristic of mammals which provide nutrition to the growing foetus and remove waste which is produced during the growth of the foetus. Placenta is present in all mammals but it is not present in the marsupials and monotremes.

Complete answer:
Placenta is an organ which develops during the pregnancy, when a new organism is developing inside the womb of mother in mammals. This is characteristic of mammals only. It develops in the uterus and helps in completing all requirements of the developing foetus. It provides oxygen and nutrition, and removes all waste generated from the foetus.
Placenta can produce hormones as well. First hormone which is produced by placenta is human chorionic gonadotropin hormone. And other hormones which help in successful pregnancy.
Placenta is connected to the walls of the uterus of the mother and umbilical cord of the foetus. This organ is usually connected to the top, side, front or back of the uterus, in some rare cases it may present in the lower back of the uterus.
There are some factors which affects the placental health:
Mother’s age: Old age women may face problems in their placental development.
High blood pressure.
If someone is pregnant.
Blood-clotting disorders will also increase the chances of placental disorders.
Placenta is removed from the mother’s body after the birth of the foetus. Placental expulsion begins just after the birth of a child and it is known as “third stage of labour”.
Thus, we can conclude that mongoose are the mammals among the available options, which have placenta during their pregnancy.

And option ‘D’ is the correct option.

Note:
IgG antibodies are produced in the mother’s body, which have the unique property of crossing placenta, while other antibodies cannot cross the placenta. Thus, IgG helps in the protection of the foetus from bacterial and other infections.