20 Questions
What is the function of the sebum secreted by sebaceous glands associated with hair roots?
To waterproof hair
What is the temperature of a monotreme's body?
30 degrees
What is the function of the placenta in mammalian development?
To provide oxygen and nutrients to the developing embryo
What is the characteristic of the jaw articulation in modern mammals?
Dentary-squamosal connection
What is the function of the mammary glands in mammalian mothers?
To nourish the baby with milk
What is the characteristic of the lower jaw in modern mammals?
Formed of a single bone
What is the function of the quadrate and articular bones in modern mammals?
To form the hammer and anvil in the ear
What is the characteristic of hair in mammals?
Made of keratin protein
What is the benefit of the new jaw attachments in modern mammals?
Allows for greater digestion within the mouth
What is the characteristic of the subclass Theria?
Subclass Theria
What is the primary function of the alpha keratin protein in mammals?
To insulate the body
What is the primary difference between the body temperatures of monotremes and placentals?
Monotremes have a lower body temperature
What is the purpose of the umbilical cord in mammalian development?
To supply oxygen and nutrients to the developing embryo
What is the result of the quadrate and articular bones losing their function in jaw articulation?
They became smaller and eventually migrated into the ear region
What is the characteristic of the hair found in mammals?
It is made of the protein alpha keratin
What is the primary function of the squamosal and dentary bones in modern mammals?
To make the connection with the lower jaw
What is the primary difference between the jaw articulation of modern mammals and that of reptiles and amphibians?
Modern mammals use the dentary-squamosal connection
What is the benefit of the modification of hair in mammals?
It provides greater insulation to the body
What is the characteristic of the subclass Prototheria?
It includes monotremes
What is the primary function of parental care in mammals?
To provide nourishment to the young
Study Notes
Mammalian Classification
- Mammals are classified into subclass Prototheria (monotremes) and subclass Theria, which is further divided into infraclass Marsupialia (marsupials) and infraclass Placentalia (placentals/eutherians)
Mammalian Characteristics
- Mammals have hair made from the protein alpha keratin, which helps to insulate the body
- Endothermy allows for different body temperatures, e.g., monotremes (30°C), armadillos (32°C), marsupials and hedgehogs (35°C), humans (37°C), and rabbits and cats (39°C)
- Hair is often composed of guard and soft underfur and is waterproofed by sebum, the oily secretions of sebaceous glands associated with their roots
- Hair can be modified to serve various functions
Parental Care
- Mammalian mothers nourish their babies with milk produced from mammary glands
- Each baby in the uterus is attached via an umbilical cord to the placenta, which supplies oxygen and nutrients to the developing embryo
- Mammals have a longer gestation period compared to other animals
Skull and Jaw Evolution
- Modern mammals use the squamosal and dentary bones to make the connection between the skull and lower jaw
- The quadrate and articular bones, which were used in reptiles, amphibians, and earliest synapsids, have become smaller and migrated into the ear region, forming the 'hammer' and 'anvil' of the ear
- The new jaw attachments allow for greater digestion within the mouth, enabling a higher metabolic rate and maintenance of a high body temperature
Dental Characteristics
- Mammals have teeth that come in a variety of shapes and sizes, adapted for biting and chewing many kinds of food
- Mammals are diphyodontic, meaning they have two sets of teeth: milk/deciduous and adult
- Mammals are heterodontic, meaning their teeth are diversified in function, typically consisting of incisors, canines, premolars, and molars
Test your knowledge of mammalian characteristics, including hair composition, body temperature regulation, and adaptations such as waterproofing. Learn about the different types of mammals, including monotremes, marsupials, and placentals. Discover the unique features that define mammals.
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