Mammals

Biological diversity - mammals

• subphylum Vertebrata: class Mammalia
• provide young - milk via mammary glands
• mammal skin = highly glandular
• mammary glands - simple secretory glands - monotreme mammary patch - more complex breasts
• presence - monotremes - early evolution 

• skin covered - hair/fur
• hairs = multiple intertwined filaments - keratin
• hair keratin unique - mammals (recently found - Anole lizard claws)

• endothermy
• importance - insulating layer - naked mole rat = moderate body temperature via behavioural regulation+microhabitiat selection (inefficient endotherms not ectotherms)

• proportionally larger brains
• increased metabolic rates, better memory, social behaviour

• modifications - skull structure
• bony palate
• inner ear bones

• subphylum Vertebrata: class Synapsida
• mammalian origins. divergence - modern mammals early - amniotes. 320 mya
• classified - synapsid skull
• early synapsid pelycosaurs (+Dimetrodon)
• mammal like reptiles: the Therapsids (lion/dog size carnivores) - derived palate, ear bones+heterodonty

• class Synapsidae: order Therapsidae
• mammalian origins - late Permian (260 mya): diverse Cynodonts - fossil record 
• derived palate, ear bones, heterodonty, structures skull - endothermy (blood vessel density+turbinal bones)
• laid eggs - burrows

• subphylum Vertebrata: class Mammalia
• 1st true mammals - generic, small shrew like creatures - survived age - dinosaurs - nocturnal
• ACTUALLY great diversity concurrent - dinosaurs

• 2 subclasses, 6000 species 
• Prototheria (Monotremes: echidna+platypus, 5 species)
• Theria (2 infraclasses)
  • Metatheria (Marsupials, 300 species, 7 orders) - koalas, kangaroos, quolls, wombats, numbat
• characterised - maintaining offspring - pouch (born very early stages - development) (decreased gestation, increased lactation)

• 2 subclasses, 6000 species 
  • Prototheria (Monotremes: echidna+platypus, 6 species)
  • Theria (2 infraclasses)
    • Metatheria (Marsupials, 300 species, 7 orders)
    • Eutheria (Placentals, 5000+ species, 26 orders)

• class Mammalia: infraclass Eutheria
• 4 superorders
  • Xenarthia (anteaters, sloths, armadillos)
  • Afrotheria (tenrecs, elephant shrews, hyraxes, elephants)
  • Laurasiatheria (shrews, bats, ungulates, carnivores)
  • Euarchontoglires (rodents, lagomorphs, tree shrews, primates)

• placental mammals
• diverse - share reproductive strategies: long internal gestation period vs lactation 
• embryo retained - uterus
• external shape = lost+embryo maintained - amniotic sac, nourished via elaborated extra embryonic membranes (placenta)

• marsupials vs placentals
• Eutherian diversity outstrips marsupial diversity. not - marsupials don't compete well - same resources
• Australia - occupy similar range - ecological niches - placentals not highly specialised 
• constraints - reproductive mode - marsupials

• modern phylogeny 
• taxonomy - placentals - long been contentious
• convergent evolution - distantly related groups leads - similar body forms
• morphology grouped shrews+elephant shrews - class…