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Phylum Chordata is distinguished by four distinct features:
- a dorsal, hollow nerve cord
- notochord - flexible, supportive, longitudinal rod located between the digestive tract and the nerve cord
- pharyngeal slits located in the pharynx
- muscular post-anal tail
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Tunicates
- invertebrae cordates
- often adgere to rocks and boats
- adult have no trace of chrordate trademarks, but larva do
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Lancelets
- invertebrae cordates
- have all four chordate features
- bury itself in marine sand
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Craniates
all chordates with a head
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Vertebrates distinguished by
more extensive skull and backbone (vertebral column)
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Vertebral Column
- composed of a series of bone called vertebrae
- enclose the one of the main parts of the nervous system the nerve cord
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Tetrapods
- jawed vertebrates with 2 pairs of limbs
- first vertebrates on land
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Amniotes
- tetrapods with terrestrially adapted egg
- completed the transition to land
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List the hierarchy of clades to which mammals belong:
- Chordates
- Craniates
- Vertebrates
- Jawed Vertebrates
- Tetrapods
- Amniotes
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Hagfish
- are not considered vertebrates because they only have a notochord
- considered a craniates
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Chrondrichthyans
- sharks and rays
- have a flexible skeleton made of cartilage
- have a lateral line system
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Lateral Line System
a row of sensory organs running along each side that are sensitive to changes in water pressure and can detect minor vibrations caused by animals swimming nearby
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Ray-Finned Fishes
- have a skeleton made of bone
- fins are supported by thin, flexible skeletal rays
- most have flattened scales that cover their skin
- operculum that covers a chamber housing the gills
- have a gas filled sac - swim bladder
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Lobe Finned Fishes
have a series of rod-shaped bones in their muscular pectoral and pelvic fins
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Amphibians
- include salamanders, frogs, and caecilians
- "living a double life"
- first tetrapods to live on land
- they can live their life on land, but need to lay their eggs in the water
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Where are most amphibians found?
- Damp habitats
- moist skin supplements for gas exchange and many have poison glands for defense
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Amniotes
- Reptiles, birds, and mammals
- major derived character is the amniotic egg, where the embryo develops within a protective, fluid-filled sac (amnion)
- enabled these animals to complete life cycles on land
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Reptiles
- includes lizards, snakes, turtles, and crocodilians, birds (kinda)
- cold-blooded or ectothermic
- adaptations include scales, water-proofed with keratin
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Endothermic
using heat generated by metabolism to maintain a warm, steady body temperature
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Birds
Evolved from a bipedal reptile with feathers
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Feathers
- insulate, allowing enhanced control of body temperature, activity, and endurance
- extensions of feathers on forelimbs and tails led to flight
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Birds play an important role in vast numbers across the hemisphere:
- Essential Services: consumers of insects, pollinators of flowers, and dispersion of seeds
- Barometers of ecosystem health - pristine and altered habitats
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Basic Characters of Birds
- 2-legged (bipedal) vertebrates with backbones
- feathers - soft, filamentous, flexible, lightweight (unlike scales) - need regular replacement and are essential for temperature regulation and flight
- high body temps.
- light weight and strong generating lift and thrust for flight
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Bird Bills
- varies in form and function
- toothless
- horny sheath
- no exact parallel among other vertebrates
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Birds flying:
- structured entirely for flight
- bones lightweight
- spongy
- strutted
- hollow
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Physiology of Birds
- Eggs:
- richly provisioned external eggs
- no species bear live young
- Brains:
- large, well-developed - 6 to 11 times larger than comparable reptiles
- highly developed neural system (communication and navigation)
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Characteristics of Bird Legs
- Have feet that grip tightly
- tendons automatically flex when the bird squats
- locking toes around the branch
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Current Classification
- 30 orders
- 193 families
- 2099 genera
- ~ 9700 species
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Adaptive Radiation
the evolution of additional varied species adapted to different ecologies and behaviors
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Diversity of Birds
- Due to adaptive radiation
- Bill size and shape changes in relation to types of food eaten
- Leg length chang in relation to perching and terrestrial locomotion
- Wing shapes change in relation to patterns of flight
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Differences in feet and legs
correspond to different life styles
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Bird Diversity in Other Aspects
- Season and social behavior
- reproductive rate, life span, and age of maturity
- egg size in relation to body size, agility of new chicks, degree of parental care
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When does avian history begin?
- More than 150 millon years ago
- transformation of reptilian ancestor into feathered birds (with limited flying abilities)
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Extinctions
- Major extinctions have punctuated Earth's history: Class Aves
- starting in late Cretaceous
- at beginning of Pleistoncene (25% loss of existing birds)
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Birds as Reptiles
- Birds evolved from reptiles and have a lot in common:
- lower jaw composed of several bones
- lower jaw articulates on quadrate bone
- single occipital condyle
- single middle-ear bone
- expanded lateral braincase
- sclerotic ring supports eye
- similar leg structure
- scales
- females are heterogametic sex
- nucleated red blood cells
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Archaeopteryx
- the original link
- first solid evidence
- Late Jurassic (155-135 mya)
- central Europe
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Mammals
- endothermic amniotes with hair which insulates the body and mammary glands, which produce milk
- have a relative large brain size compared to other vertebrates and longer parental care
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Three main groups of Mammals:
- Monotremes
- Marsupials
- Eutherians (placental mammals)
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During the Cretaceous Extinction:
mammals underwent adaptive radiation giving rise to terrestrial carnivores and herbivores, bats, aquatic whales and porpoises
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Mammal Charcteristics
- endothermic
- hair
- mammary glands
- differentiation of teeth
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Monotremes
- oldest linage (most primitive)
- egg-laying mammals
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Embryos of Marsupials and Eutherians
are nutured by a placenta within the uterus, which allows nutrients from the mother's blood to diffuse into the embryo's blood
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Marsupials
- brief gestation
- give birth to tiny, embryonic offspring
- offspring complete development attached to the mother's nipples in a pouch or marsupium
- most in Australia and New Zealand
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One Marsupial in North America
Virginia Opposum
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Eutherians bear:
- live young
- commonly called placental mammals b/c their placentas are more complex than marsupials
- young complete development within the mother
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Primates
- includes: lemurs, tarsiers, monkeys, and apes
- most are still arboreal
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Primate Adaptations
- Shoulder and hip joints allow climbing and branchiation
- Grasping hands and feet are high mobile and flexible
- Sensitve hands and feet aid in manipulation
- Short snout and forward-pointing eyes enhance depth perception
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Primates divided into three groups:
- Anthropoids
- Monkeys
- Hominoids (Apes)
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Hominoids
- include - gibbons, orangutans, gorillas, chimpanzees, bonobos, and humans
- nonhuman apes have smaller geographic range
- lack tails and relatively large brain siz and flexible behavior
- Chimps are omnivores
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