BIOL 101 Quiz 6 pt 1

What was Archaeopteryx?

• Earliest bird, ~150 million years (from Germany)

• Therapod like – long bony tail and teeth

• Bird like – asymmetric flight feathers

If forelimbs of birds are modified for flying, how do they catch food?

Using their beaks which are modified for feeding (no teeth, but vary in shape)

Discuss wing mechanics (how do they work?)

• Lift is maintained by cross-sectional area plus constant angle of attack adjustment

• Air moves faster over wing, lowering air pressure

• Birds don’t “flap” their wings – flight stroke

Discuss the origin of flight (“Ground-up” Hypothesis)

• Hind limbs developed for speed. Forelimbs lengthened for grasping prey - similar motion to a flight stroke

• Feathers on forelimbs (already present) would provide lift

Which features of birds are adaptation(s) for flight and which are exaptation(s)?

Adaptations:

• Kneeled sternum

Exaptations:

• Furcula

• Hollow Bones

• Feathers

• Endothermy

Kneeled Sternum

• adaptation for powered flight

• Sternum is the breast bone – in us it’s flat, in birds it’s keeled for muscle attachment, only seen in birds with flight

Furcula

• exaptation for powered flight

• Fused collarbones, “wishbone”

  • Stabilizes the shoulder

• Present in dinosaurs that couldn’t fly

Hollow bones

• exaptation for powered flight

• May lighten the skeleton for flying, but really part of respiratory system

Feathers

• exaptation for powered flight

• Asymmetric feathers important for flying

  • Asymmetric in the sense that the barbs are different lengths on either side of the shaft

• Symmetric contour and down feathers important for thermoregulation and display

  • Symmetric in the sense that the barbs are the same length on either side of the shaft

• Many non-flying dinosaurs had symmetrical feathers

Endothermy

• exaptation

• living birds are endothermic

• Most evidence suggests non-bird dinosaurs were endothermic

Respiration in Birds

• Unidirectional thru lungs

• Gas exchange occurs in lungs, posterior and anterior air sacs act as bellows (no gas exchange)

• Inhalation: Fresh air brought into posterior sacs, stale air from lungs drawn into anterior sacs

• Exhalation: Fresh air pushed into lungs from posterior sacs, stale air pushed out of trachea from anterior lungs

Respiration in Mammals

• Inhalation: Fresh air brought into lungs

• Exhalation: stale air pushed out of lungs through windpipe (trachea)

Identify the major clades of mammals (there’s three)

• monotremes

• marsupials

• placentals

monotremes

• Name refers to the cloaca (common anal and urogenital opening; seen also in reptiles)

• 3 species – 1 platypus and 2 echidnas; s. hemiph.

• Sprawling to semi-erect stature (like some reptiles)

• Oviparous and produce milk, but no nipple

marsupials

• Bear live young (viviparous)

• Some have pouches (marsupium), but not all (e.g., numbat)

• Young born altricial (early) and migrate to pouch to suckle on nipple

• Development finishes in the marsupium

• Placenta is generated from the yolk sac (“yolk sac” placenta); does not implant into uterus

• Embryo absorbs nutrients from uterine wall through vascularized yolk sac

• Embryo is born hairless and blind - must find its own way to the pouch

• Baby latches onto nipple and it completely fills its mouth

• Gestation period is short, lactation period is long

placentals

• Placenta links embryo to mother

• Book also calls these Eutherians (the same for all intents and purposes in this class)

• Young born precocial (late stage of development)

• Dominant group of mammals today

Three major clades of placentals

• Afrotheria (elephants, manatees, hyraxes, aardvarks)

• Xenarthra (anteaters, armadillos, sloths)

• Boreoeutheria (rodents, rabbits, carnivores, bats, whales, hoofed mammals, primates)

Afrotheria

• Mammals that originated in Africa

• Proboscidea – elephants (Africa and Asia; extinct species in Europe and North America)

• Sirenia – manatees and dugongs (coastal habitats)

• Other species – aardvarks (Africa only), hyraxes (Africa only)

Proboscidea

• Elephants - largest land animal

• 3 living species, all herbivorous

• Two upper incisors are modified as tusks

• Big ears used for thermoregulation (large surfaces for heat loss)

• Trunk allows the animals to smell the ground without bending over (as well as used as an appendage

• Trunk is muscular (no bones)

Sirenia

• Manatees (Sirenia) – one of two groups of exclusively aquatic mammals (may look a little like whales, but more closely related to elephants)

• Lack hind limbs

• Forelimbs are flippers, tail is a fluke

• Strictly herbivorous

• Very docile; easily injured by boats

• Body covered with vibrissae

Xenarthra

• Primarily S. American, although one recent N. American immigrant (armadillo)

• Many species are toothless (edentulous) – e.g., anteaters

• Other species have simple, peg-like teeth - e.g., armadillo (homodont); sloths (heterodont)

• Armadillos have bony armor with keratinized (horny) covering - roll into ball as a defensive mechanism

Boreoeutheria

• Rodentia

• Chiroptera

• Artiodactyla

• Cetacea

Rodentia

• Rats, mice, guinea pigs, beavers, capybaras, gerbils, hamsters, and squirrels (among other) – most speciose group of mammals (~2,300 species; >40%)

• Upper and lower incisors enlarges for chewing and gnawing that are ever-growing

• Most are herbivorous, some are carnivorous (e.g., grasshopper mice), some are scavengers (e.g., ground squirrels)

Chiroptera

• Bats – only true flying (volant) mammals

• Wing of bats – long fingers supporting a webbed membrane (skin)

• Some bats (but not all; e.g., fruit bats and “flying foxes” use echolocation for navigation and hunting

• Vampire bats use their incisors (not canine fangs) to draw blood; lap blood don’t suck)

Artiodactyla

• Even-toed ungulates (pigs, deer, cattle, hippos, camels, sheep, goats); mostly herbivores

• Cattle, sheep, and goats have horns – permanent ornamental structures

• Deer and relatives have antlers shed and regrown annually

• Antlers only in males (...in most species)

• Horns have horny sheath, bony core; not shed

Cetacea

• dolphins , porpoises, whales

• Exclusively aquatic (hind limbs lost; tails modified as flukes)

• Terrestrial ancestry well-documented (from terrestrial artiodactyls)

• Two major groups:

  • Odontocets (toothed whales)

  • Mysticetes (baleen whales)

• Bulk engulfment feeding – they open their mouths and strain large volumes of krill and fish-filled water

• Some species have throat pouches that extend all the way to their belly buttons

Odontocetes

toothed whales, including dolphins; carnivorous (use echolocation)

Mysticetes

baleen whales, including blue, gray, and humpback; edentulous in adulthood, but instead have baleen