Zoo 201 Mammals

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Zoo 201 Mammals
2011-06-04 18:00:05
mammals evolution lappin

Evolution of mammals, flashcards for the vertebrae half of zoo 201 with lappin.
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  1. Skull structure of all Mammals
    • Synapsid skull
    • the mammal clade is defined as snyapsid for the skull.
  2. Characteristics of synapsid skull
    • One pair of temporal openings
    • 1st amniote lineage to radiate extensively into terrestrial environment
  3. Importance of pelycosaurs
    • Most basal synapsids
    • diverse-both carnivores and herbivores
    • extinct by the end of Paleozoic (Permian)
    • paraphyletic - therapsid lineage emerged from within pelycosaur lineage (from carnivores)
  4. Importance of therapsids
    • persisted into Mesozoic (Triassic)
    • radiated into many carnivores and herbivorous forms
  5. Importance of cynodonts
    heterodonty - differntiation of tooth types
  6. Importance of cynodonts
    • changes in jaw musculoskeletal structure: enlargement of dentary and reduction of posterior jaw bones
    • paraphyletic group: mammals not included
    • turbinate bones-suggests endothermy
    • more upright posture & greater agility
  7. What group did early mammals arise from?
    within the cynodont lineage 200 million years ago
  8. Dentary characteristics of early mammals
    • diphyodont dentition - teeth replaced one time in life
    • new jaw joint between squamosal & dentary-quadrate & articular incorporated into middle ear
  9. Characteristics of early mammals
    • had hair and probably endothermic
    • had a secondary palate (shared with cynodonts) that separated feeding and breathing pathways that permitted suckling by young
  10. How long did mammals and dinosaurs coexist for?
    140 million years ago
  11. Significance of dinosaur extinction
    • dinosaurs extinct in early Cenozoic, about 65 million years ago
    • mammals diversified into many lineages and many achieved large body size
  12. Characteristics of hair
    • unique structure of mammals
    • made of dead cells impregnated with keratin
    • epidermal structure (hair follicles extend into dermis but is lined with epidermal cells)
  13. Significants of glands
    • mammals have greatest variety of glands among vertebrates (humans have all major types)
    • sweat glands: evaporative cooling
    • scent glands: communication
    • sebaceous glands: expel sebum
    • mammary glands: homologous to sweat glands
  14. How many species are there of extant monotremata?
    3 species (3 in echidnia, and 1 in platypus)
  15. Characteristics of extant metatheria (Marsupials)
    • oviparous -lay yolky eggs and incubate them
    • young fed with maternal milk secretions
    • viviparous with altrical young (early development stage)
    • ~270 species
    • independently and convergently evolved most ecologiical types seen in placental mammals, except powered flight and marine habit
  16. Repruduction in Metatherians (marsupials)
    • females-vagina with two lateral canals and one medial canal (3 passages0
    • males-forked penises fit lateral vaginal canals
    • sperm travel up bifrucated vaginal canals and young pass through medial vaginal canal
    • young born at atrical stage, and hae extended development while nursing
  17. Characteristics of Eutheria (Placentals)
    • viviparous with young born relatively precocial (later stage in development)
    • tremendous variety of forms in almost every habitat
    • worldwide distribution with ~4500 species
    • almost 1/2 are rodents and 1/4 are bats
  18. Reproduction in Eutherians
    • uterus/uteri join single vaginal canal
    • connections between fertlized egg and maternal uterine tissue form placenta (homology). site of gas/nutrient exchange
    • long period of in utero development (compared to metatherians)
  19. Describe first primate apperance
    • first primates had apperance of tree shrews with long snouts, good olfaction, poor diurnal vision
    • appeared ~65 million years ago (Paleocene)
  20. When did primates first adapt to arboreal habitat
    • ~55 million years ago (Eocene)
    • improved diurnal vision (including color vision-reversal)
    • larger brain
    • stereoscopic vision
    • increased capacity for grasping motions
  21. Where did the linage leading to modern humans arise?
  22. When did the hominid ancestor appear?
    • ~14 million years ago (miocene)
    • clade comprising Grade Apes (including humans)-extant and extinct forms
  23. Evoltuion of human traits
    "Uniquely" human traits evolved through the modification of traits that existed in ancestral forms
  24. characteristics of extinct lineages sharing a more recent common ancestor with humans than with extant non-human Great Apes
    • enlargement of cranium (larger brain)
    • more reliance on vision and reduced olfactory capacity
    • paedomorphic characteristics
  25. What is the earlist known hominin fossil?
    dated to 7.6 to 6.0 million years ago
  26. Examples of other hominin fossils spanning the next several million years
    • Ardipithecus (2 speceis) - 5.6 to 4.3 million years ago
    • Australopithecus (4 species) - 4.1 to 3.0 million years ago
  27. When did Homo appear?
    ~2.3 million years ago
  28. Apperance of other homo species
    • H. habilis - 2.3 to 1.4 mya (tools)
    • H. erectus - 1.8 to 0.1 mya (possibly more recent, first Homo to leave Africa to SE Asia
    • H. sapiens (modern humans) appeared ~200k years ago
    • H. neanderthalensis - Near East/Europe to ~30k years ago (replaced by H. sapiens)