15. Mammals Flashcards
Didelphimorphia “Opossums”
Speciel feature - They play death as a defence mechanism.
Originated in south america, but invaded North America when the two continents connected again.
Paucituberculata “Shrew opossums”
It´s not a shrew, only named like that.
Microbiotheria
Only one extantant specie.
A relative of this animal, was the orginal ancestor of all marsupials in Australia.
Notorycitade “marsupial mole”
No eyes or external ears because it lives underground.
Swim in loose sand
Dasyuromorphia
Includes most of Australias carnivorous marsupials.
fx the asutralian devil and the extinct thylacine, which some scientist try to bring back.
Peramelemorphia
Small mouse looking marsupial, which is a digging omnivores from Australia and New Guinea
Diprotodontia
Includes fx koala, wombats, kangaroos.
Diprotodontia characteristics
Diprodont “two front teeth”
Syndactyly means that toes 2 and 3 are fused together, number 4 are enlarged and 5 is small.
There was a giant marsupial in Australia, so they haven´t always been small.
Eutheria (clade of placentals)
All mammals with a placenta.
Diversified after the extinction event
Eutheria characteristics
Chorioallantoic placenta
- The size and shape of the placenta differ. This type of Chorioallantoic placenta have a lot of benefits.
Pelvis (hips) are bigger so they can give birth to developed young. In contrast to marsupials.
Have 3 pairs of molars and 4 pairs of premolars.
4 chambered heart, which is more efficient than reptiles.
Diaphragm, which is a kind of layer int the bottom of our longs, there controls our breathing.
Finctions of the placenta
Gas exhcange
Excretion of waste
Endocrine - some hormoens that cordinate the development of the mother and the fetus.
Immunity - the placenta forms a selective barrier, which only allows accepted viruses and antibodies to cross.
Immunological barrier - Whitout it the mothers immunesystem would reject the fetus.
