Introduction to Mammalia:
Class Mammalia is composed of most advanced animals that comprise Man, Rabbit etc. Mammals, of which there are 3 to 4 thousand species, have achieved most complete structural, developmental and physiological adaptations to terrestrial mode of life. They are distinguished by the great activity, high metabolism, intelligence and by display of the parental care -feature in which they are only rivaled by birds. Different mammals dwell in all kinds of habitat from Polar Regions to tropics and from sea to densest forests and driest deserts. Several are of retiring habits or nocturnal so that they are hardly ever seen. They are a leading group and play leading role in present day world. Mammals usually are of great aesthetic interest, few wild species are hunted as game and others for the fur. Few rodents and flesh eaters damage man's crop and livestock and some species are reservoirs of disease-germs. Domestic mammals give man with food clothing and resources of transport. As the matter of fact mammals represent top of evolution of living animals and claim rests roughly exclusively on superiority of the nervous system.
Features of the Mammal:
Characteristics of mammal are given below:
i) They are warm-blooded.
ii) Its skin contains sweat and sebaceous glands and covering of hairs.
iii) It has various kinds of teeth, with each kind performing specific function.
iv) It contains external ears known as pinnae.
v) Its body cavity is divided into two by muscular sheet known as diaphragm. Upper thoracic cavity has the lungs and heart while lower abdominal cavity has alimentary canal, Kidneys and reproductive organs.
vi) It contains well-developed heart and brain.
vii) Fertilization is internal. In many mammals, small fertilized egg grows inside body of female parent for period. In this time, young is joined to mother by placenta, the organ by which it gets nourishment from mother. Young is born alive (Vivipary) and feeds on milk secreted by mother's mammary glands. It is cared by parents until it learns to be self-governing.
External Feature of the Rabbit:
Rabbit, the distinctive example of class mammalian, is taken as suitable kind of mammals for the detailed study. Head of rabbit is large and spherical behind but is pomtal anteriorly to form snout. At sides of snout are long stiff sensory hairs known as whiskers or vibrissae. It has pair of large and protuberant immobile eyes. It has two long erect external ears or pinnae placed at spherical top of head. Head is followed by the very short neck that passes suddenly behind to trunk. Truck comprises of narrow chest or thorax. It has short and rigid fore limbs separated in upper arm, fore arm wrist and hand. Hind limbs are much longer, separated in thigh, shank, ankle, and foot. The anus and urinogenital aperture are there at posterior end of trunk. It has short bush tail at posterior end of trunk.
Adaptation to Ecological Environment:
Wild rabbit has no end of enemies from man to owls, foxes, rats, badgers, jackals, cat, hawks etc. Actually, it has highest number of enemies and so far it is able to live and succeed. Its survival against several odds is not due to its wits, for it is not clever creature, and it is also not due to weapons, for it is not armed and its teeth are not appropriate for biting. Real explanation for its being able to hold out its own is to be found in general habits like:
i) Huge fertility
ii) Burrowing habits
iii) Crepuscular nature, and
iv) Care of young ones and early education by mother.
v) Their great fertility and attachment of mother to its young ones.
vi) Wide field of vision.(large and protuberant immobile eye).
vii) Sharp sense of smell and hearing.
viii) Protective coloration. (Hair or fur)
ix) Their attentiveness in identifying enemies and swiftness and sureness in running.
x) Having 13 pairs of ribs that allow them to breathe better during run for life.
xi) Burrowing habits and crepuscular nature.
xii) Extensive range of appetite.
xiii) Their skill to dwell in different climates.
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