Mammals- Overview, Structure, and Function Study Guide


Mammals are widely distributed and are more adaptable compared to other organisms. The ability of mammals to adapt to different continental regions is attributed largely to their ability to regulate their body temperatures in excessive heat conditions and severe cold.

Mammals overview

  • There are more than 5,500 species of living mammals habituated to different environments, including the ocean, underground, and on land.

Types of mammals

Mammals are broadly divided into three types based on how they give birth and care for their young.

  • Placental Mammals are characterized by the presence of a placenta, such as humans, lions, and whales.

  • Marsupials are mammals that carry their young in a pouch, such as kangaroos, koalas, and opossums.

  • Monotremes are mammals that lay eggs, such as platypuses and edchidnas.

Largest and Smallest Mammals

  • The largest mammal is the Blue Whale. Blue whales live in the ocean and can grow over 80 feet long.

  • The largest land mammal is the elephant, followed by the rhino and the hippo (which spend a lot of time in the water).

  • The smallest mammal is Kitty’s hog-nosed bat.

Mammal Intelligence

  • Mammals have unique brains and are often very intelligent.

  • Humans are the most intelligent. Other intelligent mammals include the dolphin, the elephant, the chimpanzee, and the pig.

Herbivores, Carnivores, and Omnivores

  • Mammals that eat meat are called Carnivores. Carnivores include lions, tigers, and seals. The largest carnivore mammal is the polar bear.

  • Plants eating mammals are called Herbivores. Some herbivores are cows, elephants, and giraffes.

  • Mammals that eat both meat and plants are called Omnivores. Humans are an example of an omnivore.

Structure of mammals and their functions

The structure of a mammal is made up of different body parts, each with a unique function. They are critical to their sustenance and adaptation to their immediate environment, and include the hair, skin, skeletal system, teeth, heart, kidneys, and brain.

Hair: Hair is a mammal key feature, although it is not seen in whales. Hair helps perform several important functions in mammals, including:

  • Heat retention
  • Sensory mechanism
  • Protective coloration
  • Social signaling to other animals

Skin: Mammalian skin has secretory glands.

  • Sebaceous Glands produce sebum (a lipid mixture), which is secreted onto the hair and skin and helps provide water resistance and lubrication.

  • Eccrine Glands produce sweat or perspiration.

Skeletal System: The mammal’s skeletal system is unique in many ways.

  • The lower jaw has a single bone called Dentary.

  • The adductor muscle comprises two muscles, and these enable sideways movement of the jaw, ensuring chewing and jaw closure.

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Teeth: Mammalian teeth act as guides for chewing and tools for initiating and moving food items. They vary in form and structure based on the proterties of the food the species has evolved to eat.

  • Most mammals have two sets of teeth – the baby teeth during infancy to early years, and then the permanent teeth.

Heart: Mammals have a four-chambered heart.

Kidneys: Mammalian kidneys produce urine with a high concentration of solutes compared to solutes present in the blood.

Brain: Mammalian brains are unique compared to other Vertebrates. Mammal brains have a unique layer of nerve cells covering the cerebrum. This layer is called the neocortex. The neocortex plays an important role in many complex brain functions.

Structure of mammalian brain:

The three main parts of the mammal brain are Cerebrum, Cerebellum, and Brainstem. The brainstem connects them with the spinal cord.

The Limbic System of this mammalian brain is the center of emotion and learning. It regulates the motivations and emotions that we now associate with feeding, reproduction, and attachment behaviors.

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The cerebrum, which lies in front or on top of the brainstem, is the largest in a mammalian brain. It is the newest structure in the phylogenetic sense, and the largest and most developed among all species.

The neomammalian brain is one of three aspects of Paul MacLean’s Triune Theory of the human brain. The key functions of the neomammalian brain include analysis, sensory processing, learning and memory, motor control, decision-making, reasoning, and problem-solving.


  • Mammals are a class of vertebrate animals named after their distinguishing feature: mammary glands.

  • Mammary glands produce milk for feeding the young ones.

  • Mammals give birth to their young ones and have a gestational period.

  • Another special feature of the mammals is that they have fur, a neocortex in their brains and three ear bones.


1. What is mammal structure?

Mammals are vertebrates that possess hair and mammary glands. The mammalian integument includes various secretory glands, including sebaceous glands, eccrine glands, apocrine glands, and mammary glands.

2. What are the three types of mammals?

Mammals are broadly divided into three groups – Monotremes, Marsupials, and Placentals. These are based on how they give birth and take care of their young.

3. What are the 5 characteristics of a mammal?

The seven characteristics of mammals are:

  1. The presence of hair or fur.
  2. Sweat glands.
  3. Their offspring are fed milk, which is produced by the mother’s mammary
  4. Three middle ear bones.
  5. Have a complex brain.
  6. Specialized teeth.
  7. Mammals have a four-chambered heart.

4. What are the defining characteristics of mammals?

The defining characteristics of a mammal include:

  • Presence of hair or fur,
  • Warm-blooded,
  • Viviparous, as in born live and completely developed,
  • Mammary glands and
  • Complex brain – Mammals have a large and more complex brain than any animal group.

5. Why are whales called mammals?

Whales are mammals because, like humans and other land mammals, they have hair, breathe air, and the females produce milk through mammary glands to feed their offspring.

6. What are the 5 characteristics of amphibians?

  • Unshelled Eggs -Living amphibians produce many different eggs than strictly terrestrial organisms as reptiles do.
  • Permeable Skin – While caecilians have scales similar to fish, most other amphibians have moist, permeable skin.
  • Carnivorous Adults
  • Distribution
  • Courtship Rituals.

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  1. Mammals. . Accessed 4 Dec, 2021.
  2. Mammals. Accessed 4 Dec, 2021.
  3. Mammalian dental function and wear: A review. Accessed 4 Dec, 2021.
  4. Vertebrate. Accessed 4 Dec, 2021.
  5. Mammal Structure and Function. Accessed 4 Dec, 2021.

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