1. Fertilization:
* Male: Male mammals produce sperm cells in their testes. These sperm cells are tiny and mobile, containing half the genetic material needed for offspring.
* Female: Female mammals produce egg cells (ova) in their ovaries. These eggs are much larger than sperm and contain the other half of the genetic material.
* Union: During mating, sperm is deposited into the female's reproductive tract. One sperm cell will penetrate and fuse with an egg cell, forming a zygote. This union of sperm and egg is called fertilization.
2. Gestation:
* Implantation: The zygote travels down the fallopian tube and implants itself in the lining of the uterus.
* Development: Once implanted, the zygote begins to divide and develop into an embryo. The embryo grows and develops within a protective sac called the amniotic sac, filled with amniotic fluid.
* Placenta: A specialized organ called the placenta develops, connecting the embryo to the mother's bloodstream. Through the placenta, the embryo receives oxygen and nutrients and releases waste products.
* Fetus: As the embryo grows, it becomes known as a fetus. The fetus continues to develop its organs and systems until it is ready to be born.
3. Birth:
* Labor: When the fetus is fully developed, the mother's body prepares for labor. This involves contractions of the uterus to push the fetus out through the birth canal.
* Delivery: The fetus is born, followed by the placenta (afterbirth).
Key Features of Mammalian Reproduction:
* Live Birth: Most mammals give birth to live young, unlike reptiles, birds, or fish that lay eggs.
* Mammary Glands: Mammals possess mammary glands that produce milk to nourish their young.
* Internal Fertilization: Fertilization occurs inside the female's body.
* Parental Care: Mammals typically exhibit a high level of parental care, including feeding, grooming, and protecting their young.
Variations:
* Monotremes: A small group of mammals, like the platypus and echidna, lay eggs.
* Marsupials: Mammals like kangaroos and koalas give birth to relatively undeveloped young, which continue to develop in a pouch on the mother's abdomen.
This is a simplified overview of mammal reproduction. Many complexities and variations exist depending on the specific species.