Ch 43 Mammals

1. Ch 43 Mammals

2. Six Major Characteristics • Endothermy=control body temp through metabolism, insulation, reguln of heat loss • Hair = keratin, insulation • Fully divided 4 chambered heart = efficient, no mixing of oxy and deoxy • Milk = fat, protein, sugar mix from mammary glands • Single Jawbone = lower jaw is single bone. • Specialized Teeth = bite, cut, slice, crush, grind

3. Mammal Evolution • Amniotes split about 300 mya into two groups • Dinos, bird, reptiles • Synapsids which evolved into mammals • Unique skull structure used to ID synapsids • First synapsids small lizard like • During Permian a diversity of sizes of synapsids evolved. • Synapsids had specialized teeth.

4. Therapsids • A subset of synapsids directly gave rise to mammals • Therapsids exist in fossil record until 144mya (end of Jurassic) • Many transitional fossils show a range of physical changes. • Therapsids had limbs directly under body and may have had hair.

5. Early Mammals • Dinos and mammals coexist for approx 150my • Mouse like. Large eyes suggest nocturnal. • Teeth adapted insect eating. • Above avoided comp with Dinos • Mammary tissue is similar in many groups of mammals suggesting that milk production evolved early

6. Diversification of Mammals • 3 major grps of Mammals by 100mya • Monotremes – oviparous (egg laying) • Marsupials – viviparous (live young), pouch • Placental Mammals – fetus stays in mother longer and is nourished through blood-rich structure called “placenta”

7. CHARACTERISTICS GREATER DETAIL

8. Endothermy • Heat from food digestion is conserved and heat is regulated. • Can live in cold climates and can undergo strenuous activity EX long migrations • Hair/fur/fat to insulate • Circ/digestive system adapted to fit demands of higher metabolism.

9. Circulatory System • Heart split into 4 separate chambers • 2 atria & 2 ventricles (Reptile heart 3rd chamber is only partially divided) • Double loop circulation • 4 chambers mean oxy and deoxy blood NEVER mix.

10. Respiratory System • A huge no. of tiny sacs, alveoli, provide a massive surface area for gas exchange. (human lung has approxtennis court of surf. area) • Breath in by increasing size of thorax and thus creating negative pressure to suck air in. • Diaphragm muscles does most of work @ rest.

11. Feeding & Digestion • Chewing – incisors, canines, premolars, molars • Baleen whales – no teeth, plates of keratin by which they filter feed from water Herbivores • Cellulose is very difficult to digest • Ruminants (cows, sheep, goats, giraffes etc) • Regurgitate and chew the “cud” • 4 chambered stomach. In rumen micro-org’s aid with digestion of cellulose.

12. Feeding & Digestion contd • Horses, zebras, rodents, rabbits, elephants. • Micro-orgs in cecum complete digestion • Cecum is a pouch of the small intestine • No “cud” chewing required.

13. Nervous System • Brain >15 times that of sim. Size fish/reptile • Humans have very high brain to body size ratio • Large cerebrum – input from sense organs, cntrl movement, behavior, memory, & learning • 5 senses • Use of sense depends on env/niche EX Echolocation in Bats

14. Development • Monotremes = one or two eggs, immature young nurtured and fed by mother. • Marsupials = Immature born and develop in mother’s pouch. Feed from single nipple. Months of further development in Kangaroo’s. • Placental Mammals = Long development period leads to birth of mature young. - Placenta connects blood of young to mothers. - Food/oxy from mom. Waste/CO2 to mom.

15. DIVERSITY OF MAMMALS • Typical organization = 26 phyla • One order of Monotremes • Seven orders of Marsupials • 18 orders of placental mammals

16. Monotremes (Prototheria) • Egg laying. Old. Evolved b4 other mammals. • Platypus and 2 echidna species. Australia • Platypus. Fur. Webbed feet. Wide flat bill for finding/eating inverts in water. • Female digs den. Lays & incubates eggs. • Echidna. Spines. Sticky tongue for insect eating. • Eggs incubated in pouch on belly.

17. Marsupials • 7 orders grouped into one super-order. • Most live in Australia. Some in Americas. • Evolved in isolation as Australia/New Guinea as Pangaea contd. its break up. • Marsupials were common in S.Am. But were replaced by Placental mammals from N. Am. • Why were marsupials successful in Australia?

18. Create a Cladogram for Mammals • Where would each of the 3 groups go on a cladogram line? • What would the derived characters be?

19. 12 major placental orders

20. Xenarthra = “strange joints” • Sloths, armadillos, anteaters. • N. Am, Cent Am, S. Am • No teeth (edentates). • Mouths adapted to insect eating

21. Lagomorpha • Rabbits, hares, pika. • Double row of upper incisors • Herbivores – key adaptation – teeth grow throughout life.

22. Rodentia • 1800 species. 40% of mammals • Every cont. exc Antarctica • Squirrels, marmots, mice, rats etc • Many young per litter • Two pairs of sharp incisors for gnawing that continue to grow throughout life.

23. Primates • 235 species. Lemurs, tarsiers, monkeys, apes, humans. • Omnivores. Big brains. • Range of sizes (mouse lemur to gorilla) • Forward facing eyes. Grasping hands/feet. • Many are tree dwellers with specific appendage adaptations ex prehensile tail

24. Chiroptera • 900 species of bats • Modified arm with skin stretched between finger bones = wing. Clawed thumb sticks out. • Small eyes. Big ears. Echolocation. • Nocturnal. Insect eaters.

25. Insectivora • Shrews, hedgehogs, moles. • High metabolic rates. Long pointed nose for probing into soil for insects.

26. Carnivora • Dogs, cats, raccoons, hyena, otters, seals • Skilled hunters, strong jaws, long canines, clawed toes. • Skeletal adaptations for fast movement • Pinnipeds – aquatic legs are fins. Streamlined body for rapid swimming.

27. Artiodactyla • Hooved mammals = ungulates • Even toe no. = artiodactyls • Deer, cattle, giraffes, pigs, camels. • Usually herbivores. Molars are large/flat for grinding plant matter. • Usually ruminants.

28. Perissodactyla • Ungulates with ODD TOE no. • Horses, zebras, rhinos, tapirs. • Africa/Asia mostly • Cecum rather than rumen.

29. Cetacea • Whales, dolphins, porpoises. • Forelimbs modified to flippers. No hindlimb. • Aquatic. Breath through modified nostril – blowhole. • Lack hair. Blubber layer. Echolocation. • Toothed Vs Baleen whales.

30. Sirenia • Manatees. • Seas, estuiaries, rivers (tropical) • Close relative to elephant. • No hind limbs. Forelimb mod. to flipper.

31. Proboscidea • Nose mod. To long, boneless trunk. • Asian/african elephant. Upto 6,000Kg • Need to eat up to 18 hrs a day. • Tusks. Trunk. Molars. • Pregnancy 20-22 months. • Fertile until 70. May live upto 80 years *12 other orders make up only 1% of mammals*

32. Primates and Human Origins Lice and Human Evolution http://video.pbs.org/video/1790635347 Homo sapiens – Birth of Humanity http://www.youtube.com/watch?v=Cwc03uAQnxs

33. Primate Characteristics • Opposable thumbs = manipulate objects • Social Org = complex social behaviors • Skeletal struc = arms adapted for hanging/swinging. Bone struc like early mammals. • Infant care = v. immature young req’s extensive parental investment. • Communication = Facial/vocal structure – sounds/expressions • Generalist teeth = can be herb/omnivorous

34. Primate Characteristics • Acute color vision = binocular vision, excellent depth perception and sense of 3D space. • Large brain relative to body size = big brain drives complex abilities – care for young, interpreting sensory info, using hands, interacting socially.

35. Anthropoids • Prosimians. 1st evolved. Lemurs, tarsiers. • Grpincls; gibbons, apes, & humans. • Rotating shoulder/elbow joint. Opposable thumbs • Nonhumans also have grasping feet with opp. Big toe. • Similar teeth; 2 incisors, 1 canine, 2 pre, 3 molars • Great apes – orangutans, gorillas, chimps, bonobos, humans. • Chimp V Human 98% similar DNA. • Common ancestor being pushed back to 8-10mya.

36. Modern Humans • Homo sapiens. Skeleton adapted for bipedalism. • Table of Human V chimp traits. • Shape of pelvis/spine & toe alignment suggest adaptations for walking upright. • Big brain. Large area dedicated to speech.

37. Hominids • Humans and extinct human-like species. • Derived character is bipedal. • Why is bipedalism better than quadrapedalism?

38. Fossil Hominids • Interesting study of the nature of science. Area of major flux. • Constant debate about new fossil finds being new species or not or being in a direct line to humans or not. • Lucy. 3.2mya. Chimp size brain but bipedal bones. • Many sim fossils ranging from 4-2 mya called “Australopithecines”

39. Many hominid species • Our evolution is complicated. • Many lines of hominid evolution arose and became extinct during the past 7 my. • Discovering which particular species led directly to humans is difficult.

40. New find in S. Africa

41. Humans • From about 2mya fossils classified in genus Homo begin to appear. • These are transitional fossils between australopithecines and humans. • H. habilis and H. erectus • Bigger brains. May have been tool users • Hunted animals. H. erectus remains outside of Africa suggest early migrations out of Africa.

42. H. Habilis & H. neanderthalensis • Neanderthals 230K to 30K. • Cavemen. Stone tool users. Sim. brain size to humans. • Interbred with humans. A small portion of our genome matches neanderthal DNA. • Earliest H. sapiens fossils ≈160K in Africa. • “Out of Africa” hypothesis for peopling of planet Supported by Mito DNA and Y chromosome analysis.

43. HW Due Wed 3/6 • Ch 43 SR’s • SR 1 – Q1-4, 7 • SR 2 – Q1-8 • SR 4 – Q1&2 • TEST Ch 39-43 Fri 3/8 • STUDY STUDYSTUDY!! • Big Picture. Derived Char’s. Class characteristics. Char’s as adaptations/disadvantages.