1. Viviparity: Most placental mammals give birth to live young. The developing embryo/fetus receives nourishment and oxygen through the placenta, which connects the mother's uterine wall to the fetal membranes. The placenta allows for the exchange of nutrients and waste products between the mother and the fetus. The mother gives birth to fully developed, live offspring that are capable of breathing, feeding, and moving on their own.
2. Gestation Length: The duration of gestation varies significantly among placental mammals. For instance, the human gestation period is around nine months, while the gestation period for elephants can be up to 22 months.
3. Number of Offspring: Placental mammals usually give birth to one or a small number of offspring at a time (multiple births can occur but are less common). The number of offspring can vary depending on the species, reproductive strategies, and availability of resources.
4. Parturition: The process of giving birth in placental mammals is known as parturition. It is triggered by hormonal signals, such as oxytocin, which cause uterine contractions and the dilation of the birth canal (cervix). The mother experiences intense contractions that push the fetus out of the uterus and through the birth canal.
5. Maternal Instincts: Placental mammals generally display strong maternal instincts and care for their offspring after birth. This care may include providing nourishment through breastfeeding, protection, warmth, and teaching essential life skills. The maternal behavior varies across species but is aimed at ensuring the survival and well-being of the newborn.
6. Postnatal Development: After birth, newborn placental mammals undergo rapid growth and development. They rely on their mother's milk for nutrition during the early stages of life. Over time, they develop the ability to ingest and digest solid foods and become more independent.
7. Placenta Delivery: Following the birth of the offspring, the placenta is also expelled from the mother's body. This process is known as placental expulsion or afterbirth. The placenta, which has fulfilled its role in supporting fetal development, is no longer needed and is shed by the mother's body.