Transcript Document 7518991

Phylum Chordata
the “chordates”
Chordata Characteristics
Triploblastic
Organ level of organization
Bilateral symmetry
Cephalization
Eucoelomate
Deuterostome
Chordata Characteristics
Complete digestive system
Closed circulatory system
Endoskeleton
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
mouth
basic chordate body plan
anus
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
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
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
Chordata Characteristics
Postanal tail
• located posterior to the anus
• associated with somatic musculature
• provides motility in the aquatic environment
segmented myotomes
anchored to notochord
Phylum Chordata
Subphylum Urochordata
Subphylum Cephalochordata
Subphylum Vertebrata
Subphylum Urochordata
tunicates, ascidians, sea squirts, etc.
Subphylum Urochordata
• swimming “tadpole larva”possesses all 4 chordate
characteristics
• sessile adults have lost all chordate characteristics
except pharyngeal gill slits
Subphylum Urochordata
Larval Anatomy
anus
mouth
Postanal tail
gill slits
notochord
pharynx
dorsal nerve cord
Subphylum Urochordata
Adult Anatomy
incurrent siphon
mouth
excurrent siphon
pharynx
anus
intestine
gill slits
used for filtering food
Subphylum Cephalochordata
the lancelets (amphioxus)
Subphylum
Cephalochordata
• have all 4 chordate characteristics throughout the
lifecycle
dorsal nerve cord
notochord
gill slits
postanal tail
Subphylum Vertebrata
the vertebrates
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
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
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
Class Agnatha
jawless fish
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
Class Chondrichthyes
the sharks and rays
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
Class Chondrichthyes
• skin is covered with dermal scales which are also
modified to form teeth
Class Chondrichthyes
• although many sharks are feared predators, some
are harmless filter feeders
Class Osteichthyes
the “bony” fish
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
Class Osteichthyes
• some species of fish are sequential
hermaphrodites  they may change sex during their
life
Class Amphibia
frogs, toads, and salamanders
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)
Class Amphibia
• metamorphosis usually occurs from a gill
breathing larva to a lung breathing adult
• soft eggs tie amphibians to water
Class Amphibia
• many amphibians have amazing parental
behavior
Subphylum Vertebrata
Class Agnatha
Class Chondrichthyes
Class Osteichthyes
Class Amphibia
Class Reptilia
Class Aves
Class Mammalia
Amniotes
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
Class Reptilia
lizards, snakes, turtles,
alligators, and crocodiles
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
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
Class Reptilia
• some snakes retain their eggs internally and
give live birth
Class Aves
birds
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
Class Aves
• endothermic (body temperature is regulated
metabolically)
• flow-through respiratory system (air only goes
through the lungs once)
Class Aves
• males often have exaggerated traits used to attract
females
Class Mammalia
the mammals
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
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
Class Mammalia
• although we often only think of insects and birds
as pollinators, many mammals are essential
pollinators and seed-dispersers
How does Chordata fit in?
Urochordata
Echinodermata
Bryozoa
Mollusca
Nematoda
Rotifera Arthropoda
Annelida
Nemertea
Platyhelminthes
Porifera
Cnidaria
unknown
common ancestor
Cephalochordata
Vertebrata