general characters of class mammalia

GENERAL CHARACTERS OF CLASS MAMMALIA

Warm blooded, mostly quadruped animals (four legged) Body is divided into head ,neck , trunk and mostly tail Body is covered by hair or fur which is made of keratin.

Hair provides insulation . (Hair absent in Cetaceans Ex. Whale)

Skin has sweat glands and sebaceous gland or oil gland Endothermic or homeothermic, maintain their body

temperature. Head is well developed .Eyes have movable eye lids.

External ears or pinnae present . Mammary glands are present to produce milk to nourish

their young. Functional only in females.

Skull with two occipital condyles . The lower jaw is usually formed by

dentary .Teeth lodged in sockets - (Thecodont) , Heterodont dentition – different types of teeth –incisors, canines, premolars and molars, with two sets of teeth,milk and permanent (diphyodont)

Vertebrae with flat centrum or body (amphiplatyus)

Seven cervical vertebrae present

Cervical 1

Cervical 1

Cervical 7

Trunk bears two pair of limbs which are pentadactyl (five digits each), which bear claws, hooves or nails for protection

Body cavity is a true coelom ,which is divided into two compartments by a muscular partition the diaphragm into anterior thoracic and posterior abdominal cavity

Brain is well developed , cerebrum is large divided into two hemispheres by a median fissure, the two hemispheres are connected internally by corpus callosum .Brain is also characterised by the presence of corpora quadrigemina and pons varolli .

Corpora quadrigemina: functions mainly as a relay center for auditory information and to control visual reflexes.

12 pairs of cranial nerves

Mammalian brain (Section)

Presence of coiled turbinal bone in nasal passage which acts as filter for inspired air.

Three ear ossicles- malleus, incus and stapes Well developed cochlea and organ of corti

Larynx with vocal cords Lungs are organ of respiration .The lungs

of mammals have a spongy and soft texture and are honeycombed with epithelium, having a much larger surface area in total than the outer surface area .Breathing is largely driven by the muscular diaphragm at the bottom of the thorax.

Digestive system complete with associated digestive glands like the salivary glands, pancreas and the liver.

Heart is completely four chambered. Single aortic arch going to the left. Non-nucleated RBC

Endocrine system well developed Meta nephric kidney

Sexes are separate .Fertilization is internal. External sexual dimorphism seen. Males have

copulatory structure penis. Eggs are alecithal (yolk absent) , except in Monotremata

Embryonic membranes amnion, chorion and allantois are present , except in monotremata

Viviparous – Giving birth to living young that develop within the mother's body rather than hatching from eggs

Parental care evident, young ones feed on milk secreted by mammary gland

Credits Wikipedia Chordate Zoology –E.L. Jordan &

P.S.Verma 2004