Phylum Chordata the

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Phylum Chordata the chordates
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Chordata Characteristics
Triploblastic
Organ level of organization
Bilateral symmetry
Cephalization
Eucoelomate
Deuterostome
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Chordata Characteristics
Complete digestive system
Closed circulatory system
Endoskeleton
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Chordata Characteristics

• All chordates possess these 4 unique characters
  at some point in their life (even if they
  disappear later on)
• notochord
• dorsal hollow nerve cord
• pharyngeal slits
• postanal tail

basic chordate body plan
mouth
anus
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Chordata Characteristics
Notochord

• a flexible rod-like structure
• extends the length of the body
• an axis for muscle attachment
• in all jawed vertebrates, it is replaced by a
  series of cartilaginous or bony vertebrae

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Chordata Characteristics
Dorsal hollow nerve cord

• a single hollow tube-like nerve cord
• dorsal to the alimentary canal and the notochord
  
• in vertebrates, the anterior end becomes
  enlarged to form the brain

brain
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Chordata Characteristics
Pharyngeal slits

• perforated slit-like openings that connect the
  pharyngeal opening and the outside
• formed by alternating pharyngeal grooves and
  pouches
• in aquatic chordates, they become the gills
• in tetrapod (4 limbed) vertebrates, they become
  parts of the throat and ear cavity

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Chordata Characteristics
Postanal tail

• located posterior to the anus
• associated with somatic musculature
• provides motility in the aquatic environment

segmented myotomes anchored to notochord
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Phylum Chordata
Subphylum Urochordata Subphylum
Cephalochordata Subphylum Vertebrata
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Subphylum Urochordatatunicates, ascidians, sea
squirts, etc.
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Subphylum Urochordata

• swimming tadpole larvapossesses all 4 chordate
  characteristics
• sessile adults have lost all chordate
  characteristics except pharyngeal gill slits

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Subphylum Urochordata
Larval Anatomy
anus
Postanal tail
mouth
gill slits
notochord
pharynx
dorsal nerve cord
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Subphylum Urochordata
Adult Anatomy
incurrent siphon
mouth
excurrent siphon
anus
pharynx
intestine
gill slits
used for filtering food
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Subphylum Cephalochordata the lancelets
(amphioxus)
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Subphylum Cephalochordata

• have all 4 chordate characteristics throughout
  the lifecycle

dorsal nerve cord
notochord
gill slits
postanal tail
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Subphylum Vertebratathe vertebrates
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Subphylum Vertebrata

• have an endoskeleton consisting of a vertebral
  column, and in most classes, limb girdles and
  paired appendages

axial skeleton - consists of skull and vertebral
column
appendicular skeleton - consists of paired limbs
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Subphylum Vertebrata

• outer epidermis (skin) that is modified into
  specialized structures (e.g. hair, scales,
  feathers)
• ventral heart with 2- 4 chambers
• hemoglobin filled blood cells
• paired kidneys
• highly differentiated brain
• endocrine system with glands scattered
  throughout body

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Subphylum Vertebrata
Class Agnatha Class Chondrichthyes Class
Osteichthyes Class Amphibia Class Reptilia Class
Aves Class Mammalia
Note that in your textbook this is a superclass
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Class Agnathajawless fish
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Class Agnatha

• jawless with a sucker-like oral disk containing
  well developed teeth
• fibrous and cartilaginous skeleton with no
  vertebrae
• no scales no paired appendages
• pore-like gill openings
• two chambered heart
• no stomach ? only intestine

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Class Chondrichthyesthe sharks and rays
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Class Chondrichthyes

• cartilaginous skeleton with bony jaws
• paired appendages
• two chambered heart
• heterocercal tail (asymmetrical)
• exposed gill slits (no operculum)
• no swim bladder
• internal fertilization

gill slits
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Class Chondrichthyes

• skin is covered with dermal scales which are
  also modified to form teeth

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Class Chondrichthyes

• although many sharks are feared predators, some
  are harmless filter feeders

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Class Osteichthyesthe bony fish
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Class Osteichthyes

• mostly bony skeleton
• skin covered in dermal scales
• paired appendages
• two chambered heart
• gills supported by bony gill arches and covered
  by an operculum
• most have a homocercal tail (asymmetrical)
• have a swim bladder

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Class Osteichthyes

• some species of fish are sequential
  hermaphrodites ? they may change sex during their
  life

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Class Amphibiafrogs, toads, and salamanders
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Class Amphibia

• mostly bony skeleton
• 4 limbs (tetrapods)
• smooth, moist, glandular skin
• three chambered heart
• gills, lungs, and/or skin respiration
• ectothermic (body temperature matches the
  temperature of the environment)

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Class Amphibia

• metamorphosis usually occurs from a gill
  breathing larva to a lung breathing adult
• soft eggs tie amphibians to water

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Class Amphibia

• many amphibians have amazing parental behavior

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Subphylum Vertebrata
Class Agnatha Class Chondrichthyes Class
Osteichthyes Class Amphibia Class Reptilia Class
Aves Class Mammalia Amniotes
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The Amniotic Egg

• the 3 remaining classes (reptiles, birds, and
  mammals) have amniotic eggs
• amniotic eggs are shelled and contain a
  fluid-filled sac (the amnion) that surrounds the
  embryo
• the evolution of the amniotic egg allowed the
  amniotes to reproduce away from water

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Class Reptilializards, snakes, turtles,
alligators, and crocodiles
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Class Reptilia

• mostly bony skeleton
• 4 limbs (tetrapods)
• body covered by horny, epidermal scales
• few glands
• three chambered heart (except for crocodilians)
• respiration exclusively by lungs
• amniotic egg
• ectothermic

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Class Reptilia

• many reptiles have temperature dependent sex
  determination
• ? The incubation temperature of the nest
  determines the sex of the offspring
• In crocodiles
• high temperatures produce males
• low temperatures produce females
• In turtles
• high temperatures produce females
• low temperatures produce males

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Class Reptilia

• some snakes retain their eggs internally and
  give live birth

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Class Avesbirds
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Class Aves

• mostly bony skeleton with air cavities in the
  bones
• 4 limbs with forelimbs modified into wings
• four chambered heart
• amniotic egg
• in most species, the female only has the left
  ovary
• scales on legs and feathers which are modified
  scales

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Class Aves

• endothermic (body temperature is regulated
  metabolically)
• flow-through respiratory system (air only goes
  through the lungs once)

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Class Aves

• males often have exaggerated traits used to
  attract females

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Class Mammaliathe mammals
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Class Mammalia

• mostly bony skeleton
• 4 limbs (tetrapods)
• body covered by hair (can be modified into
  quills)
• many glands (e.g. mammary, sweat, scent)
• four chambered heart
• respiration exclusively by lungs
• embryos develop in uterus or amniotic egg
• young are nourished with milk
• endothermic

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Class Mammalia

• 3 groups of mammals
• monotremes (echidna and platypus)
• lay eggs
• marsupials
• young are born altricial and complete much of
  their development in a pouch outside the uterus
• eutherians
• ? young complete development in the uterus

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Class Mammalia

• although we often only think of insects and
  birds as pollinators, many mammals are essential
  pollinators and seed-dispersers

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How does Chordata fit in?
Cephalochordata
Urochordata
Echinodermata
Vertebrata
Bryozoa
Mollusca
Nematoda
Arthropoda
Rotifera
Annelida
Nemertea
Platyhelminthes
Cnidaria
Porifera
unknown common ancestor