PROTOTHERIA.pptx

PROTOTHERIA.pptx

1. Structural peculiarities and phylogenetic relations of P rototheria

2. M ammals Mammals evolved from reptiles during triassic period. It is most highly evolved group of animals. Characters of Mammal: Mammary glands on females for suckling the young ones. Hairy skin. Skin richly glandular. Differentiated dentition. Double occipital condyle. Double headed ribs. Constant body temperature. Three ear ossicles. R espiration always by lungs. Increase intelligence.

3. Subclass – Prototheria This include primitive egg laying mammal. They nourish their young with milk from mammary gland. It comprises only one living order. Order- Monotremata Mammary glands without nipples. No external pinna. Females oviparous. Testis are abdominal. Teeth only in the young ones. Heart is four chambered. Example- Ornithorhynchus , Echidna

4. Distinctive characters of Prototheria Distribution - these are distributed in the entire Australian region, including Australia, Tasmania, Newguinea and neighbouring Island. Habit and habitat- Aquatic or terrestrial Burrowing M ainly insectivorous Nocturnal I ncompletely warm blooded E gg laying mammal

5. External features Body small covered by hair and spines. M uzzel or snout produced into beak. E xternal ear absent. M ammary glands without teats. M ale carries a hollow, horny, tarsal spur on each hindleg connected internally to a poison gland. Ref. – A Textbook of Zoology by Parker & Haswell

6. Body cavity - Divided by a typical mammalian diaphragm. Endoskeleton Skull dicondylic. Malleus and incus relatively large. Lower jaw consist of single bone dentary. Cervical vertebrae 7 Ribs unicephalous. Presence of epipubic bone. A large T-shaped interclavicle is present. Limbs and girdles reptilian like held laterally. Ref.-The life of Vertebrate – J.Z Young

7. Digestive system- teeth develop only in embryo. Respiratory system -respiration pulmonary by lungs. Circulatory system- heart four chambered, right valve incomplete, R.B.C small circular and non-nucleated. Excretory system- Kidney metanephric, ureter open into urinogenital sinus which terminate into common cloaca. Nervous system -brain small without carpus callosum, there are four optic lobes. Receptors - olfactory system of the Platypus is reduced. Eyes and ears are closed under water. Main sensory organs are the mechanoreceptors f the bill. Temperature regulation- body temperature variable.

8. Reproductive system In male testes is abdominal, penis retractile for passing out sperms not urine. In female right ovary is reduced and oviduct lead separately into cloaca. Ref. – www.edu.com

9. Development Eggs large with much yolk and plastic shell. Cleavage is meroblastic. No uterine gestation Newly hatched young are very immature. These are fed on milk in abdominal pouch till fully grown. Ref. – Man & Vertebrates by Romer

10. Phylogenetic relationship Subclass - Prototheria shows its affinity to reptiles and birds with little advance over them. Affinities with class - Reptilia Claws are present. A median T shaped interclavicle present. They can survive during starvation for a longer period. Eggs calcareous, uterine gestation is absent. Testes abdominal. Body temperature is not constant. Vertebrae without epiphysis with cervical ribs. Oviduct separately open into cloaca and vagina absent.

11. Affinities with birds They have following resemblances- Teeth are absent. Feet are webbed. Tarsal region contain spur. Oil gland is present.

12. Affinities with mammals Body covered by hair. Skin richly glandular containing sweat and sebaceous gland. Mammalian diaphragm divides body cavity. Skull dicondylic, presence of four optic lobes, cervical vertebrae seven. Liver is lobed like mammals. Heart is four chambered, only left aortic arch present. R.B.Cs circular and non-nucleated. Presence of milk glands secreting milk.

13. Peculiar characters of Prototheria The following characters are peculiar to Prototheria : Presence of tarsal spur in male. Milk gland derived from sweat glands and without teats. Temporary abdominal mammary pouch in female during breeding season. Jaws elongated forming a beak or rostrum. Marsupial or epipubic bones present. Right ovary smaller and usually functionless .

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