Marsupials are a group of mammals that have a unique way of reproducing. Unlike placental mammals, which give birth to fully developed offspring, marsupials give birth to underdeveloped embryos that crawl into a pouch on the mother's belly and attach to a nipple.
There they continue to grow and develop until they are ready to leave the pouch. Marsupials are found mainly in Australia, New Guinea, and nearby islands, where they make up most of the native mammals, but also in South and Central America, and one species in North America.
Some examples of marsupials are kangaroos, koalas, wombats, opossums, Tasmanian devils, and bandicoots.
Marsupials have evolved more than placental mammals
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Some scientists argue that marsupials might be more evolved than placental mammals because they have changed more from their common ancestor than placentals have, as per Phys.org.
By analyzing the skulls of different mammal species during their early development, researchers have reconstructed how the common ancestor of marsupials and placentals would have looked like and compared it with both groups.
They found that the ancestor was more similar to placentals than to marsupials, meaning that marsupials have modified their method of reproduction more than placentals have.
This challenges the longstanding belief that marsupials are more primitive than placentals and represent an intermediate stage between egg-laying and placental mammals. Instead, it suggests that marsupials are a highly diverse and adaptable group of mammals that have evolved a different way of reproducing than placentals.
In fact, as many as seven different groups of mammals living today have taken to the air separately from each other, and four of them are marsupials: flying squirrels, marsupial possums, colugos (cousins of primates), and bats.
All these flying mammals have a special skin structure between their limbs called a patagium, or flight membrane.
Researchers have discovered that this structure is controlled by a gene called Wnt5a, which is shared by all mammals, even those living on the ground.
This gene regulates the growth and differentiation of the skin cells during early development and determines how big and thick the patagium will be.
This shows that marsupials and other mammals have used the same genetic blueprint for building their wings, but have modified it in different ways to suit their ecological niches.
This is an example of convergent evolution-a tendency for organisms to adapt in similar ways to similar habitats.
Marsupials are a fascinating group of mammals that have evolved a different way of reproducing than placental mammals.
They have changed more from their common ancestor than placentals have and have evolved flight multiple times independently of other mammals.
These findings suggest that marsupials might be more evolved than placental mammals depending on how one defines evolution and what criteria one uses to measure it.
However, one thing is certain: marsupials are an important part of the biodiversity of our planet and deserve our respect and protection.
Despite their advantages, marsupials also face some challenges that limit their distribution and diversity, as per ActiveWild.
One of the main challenges is the competition from placental mammals, which have invaded many regions where marsupials used to live. Some of the reasons why placental mammals might outcompete marsupials are:
Placental mammals have a more efficient metabolism than marsupials, which means they can use less food and oxygen to produce more energy. This gives them an advantage in colder climates and higher altitudes where resources are scarce.
Placental mammals have a more complex brain than marsupials, which means they can learn faster and better from their experiences. This gives them an advantage in solving problems, finding food and avoiding predators.
Placental mammals have a more diverse immune system than marsupials, which means they can resist more infections and parasites. This gives them an advantage in coping with diseases and adapting to new environments.
