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Vertebrates
- -have backbone
- -varying enormously in characteristics, such as body mass
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Chordata
- -chordates are bilateral
- -belong to Deuterostomia
- -includes echinoderms
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Notochord
- -longitudinal, flexible rod located between the digestive tube and the nerve cord
- -fluid-filled cells in stiff, fibrous tissue
- -provide skeletal support = firm but flexible
- -in humans, it is reduced to gelatinous disks in between the vertebrae
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Dorsal, Hollow Nerve Cord
- -unique to chordates
- -hollow; developed from a plate of ectoderm that rolls up located dorsal to the notochord
- -develops into central nervous system: brain and spinal cord
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Pharyngeal slits or clefts
- -alongside the pharynx, there are a series of grooves (clefts) that develop into slits that open up to the outside body
- -slits allow water to enter the mouth and exit the body without going through the digestive tract
- -function as suspension feeding devices
- -function in gas exchange
- -in tetrapods, they don't develop into slits; develop into ear and structures in head and neck
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muscular, post-anal tail
-it helps propel many aquatic species in the water
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Lancelets (Cephalochordata)
- -most basal group of living chordates; invertebrates
- -larvae feed on plankton
- -wriggles backward into the sand, with anterior end sticking up
- -mucus secreted by slits removes tiny food particles from the water
- -gas exchange occurs more over entire body
- -serial arrangement of muscles allow it to contract side to side in swimming - evidence of segmentation
- -muscle develops from blocks of mesoderm = somites
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Tunicates (Urochordates)
- -4 characteristics of chordates in larvae
- -swims until it finds substrate
- -metamorphosis- disappearing chordate characteristics
- -organs rotate 90 degrees
- -incurrent siphon
- -large atrium
- -"sea squirts" = jet themselves from the excurrent siphon
- -9 Hox genes
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Chordate evolution
- -lancelets provide useful clues to these evolutionary changes
- -they have slightly swollen tip ("brain") at the anterior end of dorsal nerve cord
- -Hox genes that organize regions of the brain correspond themselves in small clusters of cells
- -turnicates have a completely sequenced genome (special genes that determine organs such as the heart and thyroid)
- -turnicates lack genes like long range nerve impulses
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craniates
- -origin of head, dorsal nerve cord, eyes and sensory organs
- -skull
- -duplicated genes from the divergence sequence led to genetic complexity
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Neural crest
- -a collection of cells that appear near the dorsal margins of the closing neural tube in an embryo
- -these cells give rise to teeth, bones, cartilage in the skull, dermis of the face, neurons, and sensory capsules
- -aquatic craniates: clefts evolved into slits = gills
- -associated with pumping water through
- -facilitates gas exchange
- -higher metabolic rates, more muscles
- -heart with 2 chambers; blood cells and hemoglobin
- -kidneys
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origin of craniates
- -Haikouella = resembled lancelet
- -had brain, small eyes, and muscle segments
- -respiratory gills, no skull or ear organs
- -Myllokunmingia = had ear capsules, eye capsules, and skull
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Hagfish (Myxini)
- -cartilage skull
- -lack jaws and vertebrae
- -keratin "teeth", segmented muscles
- -secrete slime as protection from predators
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vertebrates are craniates that have a backbone
- -capturing food
- -avoiding being eaten
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Dlx Family
- -a group of transcription factor genes
- -nervous system, skeleton, skull, and backbone
- -aquatic vertebrates acquired fins and more efficient gas exchange through gills
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Lampreys (Petromyzontida)
- -most are parasites that clamp jawless mouths onto the flank of a fish
- -ingest the blood
- -resemble lancelets in larval state
- -devastated the fish in the Great Lakes
- -cartilage lacks collagen
- -have a flexible sheath around notochord (different from hagfish)
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Conodonts
- -soft-bodied vertebrates with prominent eyes
- -barbed hooks at anterior of mouth; mineralized with calcium
- -their abundance 300 mya that today their fossils are used in petroleum
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mineralization hypotheses
- -mineralization was associated with a transition in feeding mechanisms
- -may have begun in the mouth and later was incorporated into protective armor
- -then skull
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gnathostomes
- -jawed vertebrates
- -sharks, ray-finned fish, lobe-finned fish, amphibians, reptiles and mammals
- -enlarged forebrain (for sight and smell)
- -in aquatic, lateral line system = organs form a row along each side of the body and are sensitive to vibrations
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gnathostome hypothesis
- -jaws evolved by modification of the skeletal rods that had previously supported the anterior pharyngeal slits
- -the gnathostome common ancestor underwent a duplicated Hox gene; entire genome duplicated
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gnathostome fossils
- -survival: fins and tails allowed them to swim fast; jaws let them cut flesh
- -placoderms
- -extinct, "plate-skinned"
- -acanthodians
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Chondrichthyans
- -sharks, rays, and skates
- -skeleton made of cartilage
- -mineralized bone is derived characteristic
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sharks
- -streamlined body with fins
- -oil in the liver keeps them buoyant
- -constant swimming keeps gas exchange
- -when they spend time on the ocean floor, they use muscles to pump water
- -spiral valve within intestine which increases surface area and prolongs passage of food
- -sharp vision, no colors
- -smell; sound is transmitted through the entire body
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shark reproduction
- -oviparous = lay eggs that hatch outside of the mother's body
- -ovoviviarous = they retain fertilized egg within the body, hatched within the uterus
- -viviparous = young develops within the uterus and is fed through the placenta
- -excretory and birth leads to cloaca and then released from one hole
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rays
- -bottom dwellers
- -whiplike tail
- -eat mollusks and crustaceans
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osteichthyan
- -ossified endoskeleton
- -made of calcium phosphate
- -the fish have 5 pairs of gills protected by an operculum
- -swim bladder = buoyancy
- -may have had lungs
- -flattened bony scales
- -glands secrete mucus that reduces drag
- -most are oviparous
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ray-finned fish
- -bony rays that support their fins
- -big source of protein for us
- -threats: over fishing cod, building dams block their migration patterns
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lobe-fins
- -rod-shaped bones surrounded by a thick layer of muscle in their pectoral and pelvic fins
- -coalacanths thought to be extinct
- -lungfishes burrow when ponds shrink
- -tetrapods
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Tetrapods
- -have limbs
- -there is a neck, pelvic girdle is fused to backbone
- -no gills
- -Tiktaalik - fins, gills, lungs, covered in scales, ribs, neck, front fin was a limb design
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Amphibians
-salamanders, frogs, caecilians
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salamanders (urodela)
- -walk with a side to side bend of the body
- -paedomorphosis is common, axolotl retains larval features even when sexually mature
- -larvae look like adult and are carnivores
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frogs (anura)
- -powerful hind legs to jump
- -toads are frogs with leathery skin
- -stick their tongue out to get flies
- -distasteful mucus secreted from the body
- -poisonous species are brightly colored
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apodans (caecilians)
- -legless, nearly blind, look like earthworms
- -they lost their legs as adaptations
- -larvae look like adult and are carnivores
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amphibians
- -larval stage of frog is tadpole = lateral line system; herbivore
- -metamorphosis = carnivore, gets legs, lungs, external eardrums
- -some lack lungs and breath through skin
- -lay eggs in water, they lack shells
- -some carry eggs on their backs or in their mouths
- -some are oviparous and viviparous
- -males us vocals to attract mates
- -they are dying out due to: disease from chytrid fungi, habitat loss, climate change and pollution
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amniotes
- -reptiles and mammals
- -amniotic egg which contains amnion, chorion, yolk sac, and allantois
- -egg allowed the embryo to develop on land in its own private pond, reducing dependence to aqueous environments
- -some have shells
- -use ribcage to ventilate lungs, which is more efficient and may have led to less permeable skin
- amnion
- -functions as fluid-filled cavity that cushions mechanical shock
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yolk sac
-stockpile of nutrients
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allantois
-disposal sac for certain metabolic waste
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chorion
-gas exchange membrane
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reptiles
- -tuataras, lizards, snakes, turtles, crocodiles, birds
- -have scales that are made of protein keratin
- -scales protect from desiccation and abrasion
- -fertilization occurs internally, some are viviparous
- -cold-blooded comes actually from behavioral adaptations (basking and seeking shade)
- -ectothermic = absorb heat, allows them to survive on less food
- -birds are endothermic = maintain body temp through metabolic activity
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parareptiles
- -large, stocky, quadrupedal herbivores
- -some had plates on their skin
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diapsids
-a pair of holes on each side of the skill behind the eye socket; muscles pass through this hole to connect to the jaw
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lepidosaurs
- -a lineage of diapsids
- -tuataras, lizards, and snakes
- -mososaurs
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archosaurs
- -lineage of diapsids
- -crocodiles, pterosaurs, dinosaurs
- pterosaurs
- -first tetrapods to show flight
- -different from birds and bats = collagen membrane from hind leg to foreleg
- -fed like birds
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dinosaurs
- -bipeds and quadrupeds
- -ornithschians were herbivores = tail clubs and horned crests
- -most were ectothermic, some were endothermic
- -social, and moved fast
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theropods
- -long necked giants
- -bipedal carnivores
- -T Rex
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tuataras
-threatened by rats in New Zealand
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lizards
- -very diverse
- -jaragua lizard = 16 mm small
- -komodo dragon = hunts deer
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snakes
- -some snakes maintain pelvic and limb bones = evidence of ancestry
- -carnivores, acute chemical sensors
- -sensitive to ground vibrations
- -heat detecting organs that allow them to hunt at night
- -flickering tongue fans odors to the smell organs
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turtles
- -hard shell provides for defense
- -earlier turtles could not retract their heads
- -mechanism for retracting head evolved independently in 2 branches of turtles
- -huge leatherbacks feed on jellies
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alligators and crocodiles
- -breath air through upturned nose
- -were small and then evolved bigger
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birds
- -lack urinary bladder, females have one ovary = weight saving modifications
- -toothless = trims weight in head
- -wings = feathers made up of beta keratin
- -flight enhances hunting and scavenging; ready escape
- -endothermic; high metabolism to keep energy for flight
- -efficient lungs with many little tubes that supply oxygen thoroughly
- -acute eyesight
- -internal fertilization, brooding until eggs are hatched
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flight evolution
- -feathers may have enabled small dinosaurs to gain extra lift as they jumped
- -they could have gained traction while running and flapping
- -glided from tree to tree
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bird evolution
- -evolved from theropods
- -first bird = Archaeopteryx
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ratites
- -flightless birds
- -ostrich, rhea, kiwi, cassowary, and emu
- -sternal keel is absent
- -small pectoral muscles
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penguins
- -have powerful pectoral muscles
- -"fly" in the water
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hummingbird
-unique: only bird to hover and fly backwards
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specialized beaks
- -flamengos have filtered beaks
- -parrots have crushing beaks
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mammals
- -mammary glands produce milk
- -hair
- -fat layer to preserve heat
- -endothermic
- -efficient reps oratory and circulatory systems
- -diaphragm
- -long duration of parent care (like birds)
- -larger brain (like birds)
- -differentiated teeth
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synapsids
- -mammals belong to this group
- -distinct feature: single temporal fenestra = hole behind the eye sockets
- -jaw muscle passes through the fenestra and anchor on your temple in humans
- -remodeled jaw
- -2 bones that were in the jaw, became incorporated into middle ear of mammals
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monotremes
- -platypus
- -echidnas (anteaters)
- -lay eggs, lack nipples
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Marsupials
- -opossums, kangaroos, and koalas
- -higher metabolic rates
- -have nipples, and give birth to live young
- -have a placenta
- -born early in its development; stay in marsupium pouch
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Eutherians
- -complex placenta
- -longer pregnancies
- -deer mouse, mole, woodchuck, wolverine, flying squirrel
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primates
- -lemurs, tarsiers, monkey, and apes
- -hands and feet for grasping, flat nails
- -skin ridges on fingers
- -large brain, short jaw, flat face
- -characteristics for tree-dwellers
- -they have big toe widely separated
- -opposable thumb for power grip
- -enhanced depth perception with forward facing eyes
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anthropoids
-monkeys, apes
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living primates
-lemurs, tarsiers, lorises, bush babies
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monkeys
- -new world monkeys are arboreal; have prehensile (spider and squirrel monkeys)
- -old world monkeys are ground-dwelling and arboreal; lack prehensile tail (baboons, mandrils)
- -separate adaptive radiations
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apes
- -gorillas, orangutans, chimps, gibbons, humans
- -diverged from old world monkeys
- -long arms, short legs, no tail
- -gorillas and chimps are highly social
- -larger brain
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human
- -upright and bipedal
- -capable of behavioral differences (language, thought, etc)
- -reduced jaws, shorter intestines
- -1% difference in genes
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hominins
- -sahelanthropus
- -have shared characteristics to humans: reduced canine teeth, flat faces
- -more upright
- -foramen magnum is positioned under the skull
- -earlier hominins were smaller and had smaller brains
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Australopiths
- -walked upright, human hands and feet, teeth
- -1/3 the size of todays brain
- -between 4 and 2 mya
- -Lucy, 4.2 mya
- -long lower jaws, smaller brains
- -paranthropus = sturdy skulls, powerful jaws, and large teeth
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bipedalism
- -hypothesis: tree-dwelling hominins could no longer move through canopy, natural selection favored walking on ground
- -they lived in mixed habitats
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tool use
- -2.5 mya cut marks on animal bones as evidence of tool use
- -used with stone tools
- -first stone tool use = A. garhi
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homo habilis
-larger brain, shorter jaw
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homo ergaster
- -slender legs, hips, short and straight fingers
- -weight difference in male and female became less
- -means more pair-bonding, less competition for women
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homo erectus
-first species to migrate out of africa
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Neanderthals
- -brain equal to humans
- -buried their dead
- -made hunting tools
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homo sapiens
- -h. floresiensis related more to h. erectus
- -isolated islands made a physical shrinkage; dwarfism
- -smaller brains may have resulted from reduced energy consumption
- -h. sapiens may have driven neanderthals to extinction by competition
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