The mammals are the dominant animals of the world. The name of the group coined by Linnaeus in 1758, refers to the milk producing mammary glands or breast of the mother for suckling the young. They live wherever life is possible.

3.  The mammals are the dominant animals of
the world.
 The name of the group coined by Linnaeus in
1758, refers to the milk producing mammary
glands or breast of the mother for suckling
the young.
 They live wherever life is possible.

5.  BODY FORM
 Body form is divisible in to head, neck, trunk
and tail.
 External ears are present.
 TEMPERATURE
 Homeothermous that is warm blooded animal
have a constant body temperature.

6.  APPENDAGES
 Two pair of pentadactyle limbs variously
adapted for burrowing, leaping, running,
climbing, flying and aquatic.
 Toes are provided with horny claws, nail or
hooks.
 COELOM
 It is divided into anterior thoracic cavity and
posterior abdominal cavity by a muscular
partition called diaphragm.

7.  SKIN
 Skin is glandular and mostly covered with
hair.
 SKELETON
 Skull has two occipital condyles.
 Teeth are heterodont and diphyodont.
 Neck contains seven vertebrae.

8.  DIGESTIVE SYSTEM
 Alimentary canal usually leads directly to the
exterior by anus.
 RESPIRATORY SYSTEM
 Presence of a definite nose.
 Respiration by well developed spongy lungs

9.  CIRCULATORY SYSTEM
 Heart is four chambered.
 Sinus venousus and truncus arteriosus are
absent.
 Only the left systemic heart is present.
 Erythrocytes are non nucleated.

10.  NERVOUS SYSTEM AND SENSE ORGANS
 Corpus callosum connects the two halves of
the cerebrum.
 Optic lobes are divided into corpora
quadrigemina.
 Internal ear has a large coiled cochlea with
an organ of corti.

11.  EXCRETORY SYSTEM
 Kidneys are metanephric.
 REPRODUCTION AND DEVELOPMENT
 Sexes are separate
 Male has copulatory organ.

12.  Mammary glands are well developed in
females.
 Testes usually descend into scrotal sacs.
 Fertilization is internal.
 Viviparous and the egg with little yolk.
 Young ones are nourished on milk .

14.  Echidna (Tachyglossus aculeatus)
 Echidna is the spiny ant eater found in
Australia, Tasmania and New guinea.
 Its body is covered above with strong pointed
spines and hairs.
 Ventral side has hairs but is devoid of spines.
 The spines are the modified hairs.
 The jaw forms a long and a narrow snout and
teeth are absent.

15.  The tongue is long and protrusible and is
used in collecting ants which forms the food
of the animals.
 A pinna which is characteristics of mammals
is absent in echinda.
 The limbs are short, but the digits bear
strong claws for digging.
 The claws of the hind limbs are turned
outward and backward.

17.  Tail is conical and short.
 Female has temporary pouch (only in
breeding season) in which the single egg is
placed, and the young ones remain in the
pouch and sucks the mother’s milk for some
weeks.
 Ant eaters are nocturnal in habitat.
 They live in burrow.

18.  They come out during night for feeding; ant
hills are torn open with claws and the sticky
tongue is thrust into it.
 The ants adhere to the tongue and it is
withdrawn to swallow the food.
 When threatened the animal can roll into a
ball for protection.
 The spiny ant eater is long lived (50years).