Mammal Characteristics Section 32.1 Biology II

I. Mammals Have Hair Only mammals have hair. Mammalian hair is made of keratin and is thought to have evolved from scales. Hair provides insulation and waterproofing to conserve body heat. Can also be used for camouflage, signaling danger, or protection (porcupine) Mammals cool off body by panting or sweat glands. Panting releases water from the lungs – loss of body heat Sweating releases water onto skin surface and evaporation cools body.

II. Mammals Nurse Their Young Gland – organ that secretes substances inside or outside the body. Saliva, sweat, digestive enzymes, hormones, mammary glands. Mammary glands secrete milk and mammals nurse their young until mature to find own food. Rhinoceros has one calf and grazes at two months Mice have 4-9 offspring and nurse for a few weeks.

Respiration and Circulation in Mammals Need a high level of energy for heating and cooling the body. Need oxygen to do this. Use a diaphragm to expand and contract chest cavity – it’s a sheet of muscle separating chest and abdominal cavity. Four-chambered heart with separation oxygenated and deoxygenated blood.

Mammals Have Different Types of Teeth Animals have teeth adapted to the type of food they eat. Ex: pointed incisors of mole grasp small prey, chisel-like incisors of beaver for gnawing. Lion’s canines puncture and tear. (carnivores) Premolars, molars shear, crush or grind food. (horses and herbivores) Hoofed animals chew cud to help break down cellulose in plant material for easier digestion. – food is swallowed once and brought back up and chewed again and then swallowed once more.

V. Mammals Have Modified Limbs Modified for a variety of food gathering methods. – bats have elongated fingers that form wings, moles have large claws for digging. Primates have an opposable thumb to grasp objects.

VI. Mammals Can Learn Teach survival skills to young. Can learn and remember things. Primates most intelligent. Chimps can use sign language, work machines and tools. Mammals have complex nervous system and large brains.