characteristics long flexible rod between gut & nerve cord...
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Phylum Chordata
Characteristics
• All chordates possess a notochord.
• Long flexible rod between gut & nerve cord
• Runs most of length of animal
• Possess a dorsal, hollow, nerve cord
• Possess pharyngeal slits
• Muscular post-anal tail
Subphylum Urochordates
• Commonly called tunicates
• Sessile marine animals as adults - Motile as larva
• Larva possess a clear notochord which is less evident in adults
• Filter feed through use of siphon
Subphylum Cephalochordate
• Commonly known as lancelets
• Have all features of the ideal chordate
• Bury selves in sand, and filter-feed through mouth
Subphylum Vertebrata
• Seven extant classes
• First 3 commonly called fishes
• Remaining 4 called tetrapod’s (4 feet)
• All possess some form of segmented vertebra
Class Agnatha
• Commonly known as Jawless Fish
• Include hagfish & Lampreys
• Lack paired appendages
• Lack bony skeleton
• Lack jaws
• Usually have circular sucking mouthparts
• Lampreys parasitize other fish
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Class Chondrichthyes
• Include sharks & skates, & rays
• Very successful class
• Called cartilaginous fishes because skeleton is cartilage not bone
• Approx. 750 species
• Have paired appendages
• Many have acute senses
• Sharks have a lateral-line system
• Allows shark to detect water pressure changes
Class Osteichthyes
• Called Bony fish
• Most diverse of all fish
• Have skeleton made of bone
• Have Cycloid Scales
• Have paired fins
• Allowed evolution of 4 limbed amphibians (tetrapod’s)
• Possess scales for protection
• Have bony flap called operculum
• Allows water to be drawn over gills by fins
• Have Swim bladder
• Gas content can be manipulated allowing for changes in buoyancy
Class Amphibia
• First vertebrates to inhabit land
• Most are 4 limbed (tetrapod’s)
• Include frogs, salamanders & caecilians
• Have 3 chambered heart
• Have more complicated gas exchange organs (often a combination of lungs,
gills and skin)
Order Urodela
• Salamanders & Newts
• Urodela ("tailed ones" - Salamanders)
• More dependent on water
• Many species possess gills as adults
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Class Apoda
• "tail-less ones" - Frogs & toads
• Have more developed lungs than salamanders
• Lack a diaphragm & must “swallow” air
• Most diverse and common of amphibians.
• Toads are the first amphibians to evolve keratinized skin.
This waterproofs the skin preventing water loss
• Toads must still return to water to lay eggs.
• Caecilia "legless ones"
Reproduction and Metamorphosis
• Lack internal fertilization & amniotic eggs
• Reproduction must occur in H2O
• Most species undergo metamorphosis
• Larval stage (tadpole) is usually an aquatic herbivore
• Lacks legs, respiration is through gills
• Develops into tetrapod adult (usually carnivorous)
Class Reptilian
• Includes lizards, snakes, turtles, and crocodilians
• Over 7000 species
• Possess several advanced features over amphibians
• Most adaptations towards independence from H2O
• Possess scales containing keratin
• Keratin is a waterproofing protein which prevents water loss in an
organism
• Possess an amniotic egg.
• Prevents water loss of embryo. Allows for eggs to be laid on dry land
• Combined with internal fertilization, allows reptiles to reproduce
independently of water
• Reptiles are "cold blooded" or ectotherms
• Cannot internally regulate body temperatures
• Reptiles can regulate body temperatures behaviorally (e.g. Basking or
swimming)
• Nutritional requirements are lower than warm blooded animals
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Modern Reptiles
Order Chelonia (Turtles & Tortoises)
• Inhabit aquatic and terrestrial environment.
• Are herbivores, carnivores, and omnivores
• Characterized by possessing a hard-dorsal shell
• Made from bone, extensions of backbone and rib cage
Order Squamata
• Lizards & Snakes
• Most numerous & diverse of the reptiles
• Most relatively small Although monitors and their relatives can grow to 6'
in length
• Herbivores, carnivores & omnivores
• Most able to exhibit some form of hibernation
Order Crocodilian
• Crocodiles, Alligators, & Caimans
• Largest extant reptiles can grow to over 15’ and weigh over a ton
• Primarily aquatic they are true reptiles
• Inhabit warm, tropical climates
• Order most closely related to the dinosaurs
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Class Aves
• The birds
• Evolved from dinosaurs during Mesozoic era.
• Amniotic eggs and scales on legs remnants of reptilian origins
• Almost all adaptations of these animals are made for flight.
• Presence of feathers
• Made of keratin
• Can be used for insulation and flight
• Forelimbs developed into wings
• Honeycombed, light bone structure
• Feathers
• Beak Types
• Absence of some organs
• Females usually have 1 ovary
• Absence of teeth lighten head
• Replaced by gizzard in abdomen & beak
• Beak made of keratin
• Proven very adaptable structure, having a variety of shapes for differing
diets
Modern Birds
• Over 8600 species & 20 orders of birds
• Classified into 2 general groups
• Flightless species including ostrich, emus, & kiwis are known as ratites
o Lack sternal keel on breastbone
o Lack strong breast muscles needed for flight
• Other species capable of supporting flight called carinates
• 60% are "perching birds" called passeriforms
o Possess a sternal keel on breastbone
o Support strong breast muscles required for flight
•
Class Mammalia
• Approx. 4500 species of mammals
• Evolved from mammal-like reptiles called therapsids in the Triassic period
• Diversified greatly following the extinction of dinosaurs
•
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Mammalian Characteristics
• Have Hair
• Made of keratin
• Aids in maintaining body temperature
• Endothermic
o Maintain body temperature internally
• Have efficient respiratory system including a diaphragm
• Efficient circulatory system with a 4-chambered heart
• Most possess placentas and give birth to live young
• Have mammary glands to produce milk for offspring
• All show parental care of offspring
• Have largest brains of all vertebrates
• Have differentiated teeth
• Unlike earlier vertebrates, several different teeth can exist in mammal
jaws
E.g. The molars & incisors in the human jaw
General Types of Mammals
Monotremes
• Early branch from reptilian line
• Include platypuses & echidnas (spiny anteaters)
• Only group to lay eggs (reptilian in structure)
• Have mammary glands to feed young
Marsupials
• Include opossums, kangaroos & koalas
• Mostly found in Australia & New Zealand
• Were isolated in these landmasses when the continents separated and did
not evolve li the same way placental mammals did
• Do not develop placentas
• Give birth to young very early
• Fetuses complete development in pouch called marsupium
• Mammary glands found in pouch nourish young until development is
complete
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Placental Mammals
• Complete embryonic development in uterus
• Joined to parent by organ called placenta
• Only "disposable" mammal organ
• Discarded following birth
• Exchanges gasses, nutrients & waste between mother and fetus