Placental eutherians, marsupials, and monotremes. Marsupials, like the

Placental mammals are a specialized type of mammal.

In this lesson, we’ll learn about some of the characteristics of placental mammals and go over some examples.

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It’s All Relative

What would you think if I told you that you and an African elephant are relatives? Or if I told you that while in the womb, it would be hard to tell the difference between you and a cat? You and every other human are related to elephants, cats, dogs, arctic foxes, and many other animals. Humans aren’t relatives of these animals as in brothers and sisters or cousins and uncles, but relatives as in similar types of animals.For example, humans and dogs both belong to the same kingdom, which is a level of classification used by scientists.

Along with other mammals, they’re part of Kingdom Animalia, which is broken into many categories. Today, you’ll learn about one category of mammals: placental mammals.

What Are Mammals?

First, though, let’s look at mammals in general.

Mammals are all vertebrates, which means they have a backbone. They also have hair or fur and nourish their young with milk produced by the mother. Mammals are warm-blooded animals, which means their temperature is not dependent on the environmental temperature. This means a dog, which is a warm-blooded animal, doesn’t have to sun itself on a rock like a snake, which is a cold-blooded animal, to keep its body warm.

Mammals are further broken down into three groups: eutherians, marsupials, and monotremes. Eutherians are mammals that are attached to a placenta early on during their development: for example, dogs, cats, and monkeys. Marsupials are mammals that carry their young in a pouch early on in their development, such as kangaroos and opossums. And monotremes are the most primitive type of mammals; their young hatch from eggs. Examples of monotremes include the duck-billed platypus and the spiny anteater.

Now, let’s focus on eutherians, the placental mammals.

Placental Mammals

Placental mammals are mammals whose young are nourished for an extended period of time by a placenta. A placenta is an organ in the womb that allows a mother to exchange nutrients with a developing offspring and get rid of waste. Because of the placenta, eutherians develop longer in the womb than other mammals and so are more independent at birth.Mammals that don’t have the advantage of developing with a placenta in utero must constantly remain with their mother for physical protection and nourishment.

Placental mammals aren’t as fragile and can be left by their mothers for short periods.Placental mammals are much more common than non-placental mammals and are more widespread across the globe. There are more than 4,000 species of placental mammals, including humans, elephants, aardvarks, baboons, hippos, and squirrels.

Lesson Summary

Mammals are a group of animals that are warm-blooded (meaning they generate their own body temperature), have fur or hair, produce milk for their young, and are vertebrates (meaning they have a backbone).Mammals are further broken down into three groups: eutherians, marsupials, and monotremes. Marsupials, like the opossum and kangaroo, are mammals that carry their young in a pouch.

Monotremes, like the spiny anteater, are the most primitive type of mammals; their young hatch from eggs. Eutheria, or placental mammals, are mammals whose young are nourished in the womb for an extended period of time by a placenta.Unlike other mammals, placental mammals do much of their development in the womb. Just some examples of the more than 4,000 placental mammals are squirrels, hippos, and us!

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