Biology 6 Chapter 34 Mammals

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Mammals general characteristics

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1) hair or fur
2) mammary glands and milk production
3) four chambered heart and endothermic
4) testes descended into a scrotum
5) mostly viviparous (producing living young instead of eggs from within the body in the manner of nearly all mammals, many reptiles, and a few fishes) and lacking a cloaca (the common cavity into which the intestinal, urinary, and generative canals open in birds, reptiles, amphibians, many fishes, and certain mammals.)
6) limbs carried beneath body

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Mammalia Origins

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a) synapsids- mammal like reptiles that were the precursors to mammals
1) dominant tetrapod during the Permian period
2) wiped out in Permian/ Triassic extinctions 225 mya
ex: dimetrodon

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Morganucodon- Mammal

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b) first true mammal to emerge during Jurassic period (135 mya); shrew-size
c) during the Mesozoic era (135-70 mya) 3 major lineages of mammals emerged

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Monotremes- Mammal

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i. Echidna and platypus, found only in Australia and New Guinea
ii. Oviparous (producing eggs that mature and hatch after being expelled from the body, as birds, most reptiles and fishes, and the monotremes.), cloaca, poison spur (males) (egg laying)
iii. endothermic, fur, milk (females)

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Marsupials Mammals

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i. found in australia and n/s america
ii. higher metabolic rate than monotremes
iii. endothermic, fur, milk (females)
iv. offspring born prematurely, finish development in pouch

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Eutherians (placentals-humans) Mammals : possums and kangaroos

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i. found wold wide
ii. endothermic, fur, milk (females)
iii. longer gestation period than marsupials
iv. offspring complete development in the uterus due to a more developed placenta

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Derived characters of primates (chimpanzee)

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a) hands and feet adapted for grasping
b) nails instead of claws
c) large brain+short jaw= flat face
d) well developed parental care and complex social behaviors
ex: gibbon

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Primates General Characteristics (Tarsier)

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a) earliest primates were arboreal (tree living)
b) hands and feet were adapted for grasping
c) opposable thumbs
d) binocular vision with good eye-hand coordination (helps with depth perception)

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Primata: Old world Monkeys

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i. Africa, Asia, Madagascar
ii. include monkeys and lemurs
iii. arboreal and ground-dwelling
iv. diurnal (active mainly during the day)
ex: mandrill from Lion King

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Primata: New World Monkeys

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i. South America
ii. Monkeys
iii. Arboreal
iv. diurnal
ex: golden lion tamarin

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Primata: Hominoids (great apes)

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i. Africa, Indonesia
ii. include bonobos, chimpanzees, gibbons, gorillas, orangutans, humans
iii. arboreal and ground dwelling
iv. diurnal
v. diverged from old world monkeys 25 mya
vi. long arms, short legs, no tail
vii. most are largest primate
viii. largest brain among primates
ix. behavior is more flexible
ex: chimpanzee

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Hominids (humans and their ancestors)

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i. upright stance, bipedal
ii. reduced jaw bone and muscles
iii. shorter digestive tract (because we eat meat and plants)
iv. largest brain among hominoids
v. language, symbolic thought, and more advanced tool use

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Bipedalism

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a) 10 mya hominids began to rise
b) transitional modes of locomotion evolved
c) changes in environment led to changes in locomotion
d) bipedalism required less energy, freeing hands for other purposes

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Human Evolution: Tool use

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a) simple tool use observed in other hominoids (chimpanzees)
b) more complex tool use first observed in Australoithecines (2.5 mya); cutting tools
ex: young chimpanzee termiting with a stick

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Human evolution: Sahelanthropus tchadensis (6-7 mya) SARAH

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i. reduced canine teeth
ii. relatively flat faces
iii. more upright and bipedal

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Human evolution: Australopithecus sp. (2-4 mya) AUSTIN

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i. smaller heads- smaller brains; tool use
ii. Longer lower jaw
iii. upright and bipedal

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Human Evolution: Homo habilis (1.6-2.4 mya) HECTOR

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i. larger brain- extensive tool use
ii. shorter jaw

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Human evolution: Homo erectus (1.5- 1.9 mya) ERIC

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i. larger brain- extensive stone tool use
ii. shorter jaw, smaller teeth
iii. longer legs, shorter fingers
iv. sexual dimorphism

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Human evolution: Homo neanderthalensis (160k-195 kya) NICK

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i. larger brain- extensive stone/wood tool use
ii. thick boned, heavy
iii. prominent brow ridge
iv. not a direct ancestor of Homo sapiens

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Human Evolution: Homo sapiens (30 k- 600 k) SABRINA

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i. emerged out of Africa, then N & E
ii. language, cognition
iii. Slender body
iv. no prominent brow ridge