From cute and furry to huge and ferocious, God has painted a beautiful world
filled with an amazing variety of mammals.
Today there are over 5,000 types of mammals in existence.
All mammals are animals, but not all animals are mammals. The animal kingdom is divided into many different
classes such as birds, fish, and reptiles, each class sharing similar characteristics.
Mammals are just one of the classes of the animal kingdom. In order to be classified as a mammal, certain traits
must be present, though some of these traits are not limited to only mammals.
For example, like birds, mammals are endotherms meaning they are warm-blooded. They can generate and regulate
their own body heat because they have a very fast metabolism, which also means they need to eat a lot and often.
Mammals eat more than the cold-blooded reptiles of the same size and the food they eat
gets converted into energy, which is like fuel to keep their body temperatures regulated.
This fast metabolism requires a high amount of oxygen, so mammals respiratory and circulatory systems must be efficient.
With specially designed lungs that are filled with grape-shaped air sacs, called alveoli,
mammals are well equipped to collect more oxygen. The air sacs shape provides more
surface area, allowing plenty of oxygen to pass through to the surrounding blood vessels. A four
chambered heart helps pump the oxygen-rich blood through the mammals body. As part of the Chordata
phylum of vertebrates, mammals have a spinal column, also known as a backbone. Having a backbone gives
the mammal structure. Notice this worm doesn't have a backbone but with vertebrates, backbones
allow for standing up straight and walking or other movement. Can you think of other animals
that are not mammals that also have backbones? Birds, fish, and reptiles are examples of other
animals that are also vertebrates. From this, we can conclude that having a backbone, among other
features, can't be reserved to just mammals. Here are characteristics found just in mammals.
Most mammals do not lay eggs and wait for them to hatch and all mammals develop from eggs within
their mother. Mammalian babies that come from eggs that aren't laid will be carried within
the mother until the baby has grown enough and is prepared to be born. Even after they
are born, newborn mammals rely on their mothers for nutrition, shelter, protection, and care for a period of time.
The word mammal comes from the Latin word, "mama" meaning breast. Many mammals
have mammary glands and some of these glands are located on the breast, while other mammals have
them on other parts of their bodies. For example, a cat has two rows of mammary glands on their under
bellies. Mammary glands produce milk which feed the mothers new young. Interestingly, only the Mammalia
class can do this. The mother nurses or feeds her young until they are developed enough to eat solid
food. During this time of nursing the baby receives plenty of nourishment from it's mother, as well as
learning through example an interaction of how to function as a new animal. All mammals have three
bones in the middle ear. This special design allows mammals to have sharper hearing and sound waves go
through more easily. Each bone is linked to the previous bone like a chain, so these sound waves
which form vibrations in the mammalian ear can be clearly transmitted. Many groups of animals have
teeth so teeth are not unique to only mammals. For example, some fish and reptiles have teeth.
However, most mammals typically have two sets of teeth. Baby teeth present themselves first and later permanent
teeth come in. Permanent teeth can replace baby teeth or just come in on their own.
This means that some teeth in some mammals do not fall out and some teeth come in later without a first set
of baby teeth to replace. Each species of mammal has a specific tooth structure and makeup, based
on their diet and the way they eat their food. All mammals have hair growing from some part of
their body at least during some point in their lives. Some mammals have large amounts of thick
fur or hair, while others have very little. If you are to examine a big whale swimming in the ocean.
which is a mammal, you might not find any hair but whales do have a small amount of hair during their earliest stage of development.
Wouldn't it look a little funny if we, as human mammals, grew as much hair as a bear?
Thankfully, how much hair or fur a mammal has and where it grows depends on the type of mammal.
While other vertebrates have jaws made from multiple bones, mammals uniquely have a
lower jawbone that is one single piece directly connected to the jaw. The two muscles that move a
mammals jaw allows the jaw to move up and down or side to side. This feature gives mammals the
distinguishing ability to purposefully chew our food. Only Mammalian brains have a neocortex which
is found in a section of the brain called the cerebral cortex. The neocortex is what
gives mammals higher functioning abilities, like to perceive and become aware of things through their
senses. The ability to reason when approaching a problem and to have conscious thought are
also special abilities of the neocortex. For us as humans communicating is performed in
the neocortex as well. Also in the human brain, the neocortex is quite large which is why we are more
advanced and have the ability to do and think much more than other species. Get ready to explore the
amazing world of mammals in this science unit as we recognize God's creativity and majesty
in designing such unique, amazing, funny, intelligent, sweet, useful, beautiful, and even peculiar creatures.