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Source-This post on Placenta Mammals has been created based on the article “Marsupials key to discovering the origin of heater organs in mammals” published in “Phys.org” on 8 June 2024.
Why in News?
Researchers at Stockholm University have found that brown fat, the typical mammalian heater organ, has evolved exclusively in modern placental mammals.
About Placenta Mammals:
1. About Placenta Mammals: A placental mammal is an animal that has a placenta.
2. The placenta is a special organ that forms during pregnancy in female mammals (except for monotremes and marsupials). It is made from both the mother’s and the fetus’s tissues.
3. The placenta helps by:
i) Transporting nutrients from the mother to the fetus.
ii) Removing waste products from the fetus.
4. Fetal Development:
i) Placental mammals carry their fetus in the uterus until it is born at an advanced stage.
ii) The fetus gets nourishment through the placenta before birth.
iii) The placenta delivers nutrients and oxygen to the fetus in the uterus.
iv) This allows a long period of fetal growth in the uterus, so the fetus can become large and mature before birth.
5. Classification: Placental mammals are classified under the subclass Eutheria. There are 4,000 identified species of placental mammals.
6. Evolution: Fossil evidence shows that the first placental mammals evolved between 163 million and 157 million years ago during the Jurassic Period.
7. Diversity: Placental mammals include all living mammals except marsupials and monotremes (egg-laying mammals). Marsupials and monotremes have a less-developed and less-efficient type of placenta that limits the gestation period.
About Marsupials
1. About Marsupials: Marsupials are a group of mammals known for giving birth to relatively undeveloped young.
2. Reproduction:
i) Marsupials have a short-lived placenta that nourishes their young for just a few days before they are born.
ii) After birth, the young continue to grow and develop outside the womb, usually in a pouch.
iii) The young get their nutrition from the mother’s teats inside the pouch.
3. Anatomy: Marsupials have an extra pubic bone called the epipubic bone to support their pouch.
4. Species: There are over 330 species of marsupials. About two-thirds of them live in Australia and the other third mostly live in South America. Examples: Kangaroos, Koalas, Opossums, etc
UPSC Syllabus: Science & Technology
