Transcript Introduction to Chordates

Chordates
What is a Chordate?
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Chordates are animals that are
characterized by a notochord, a dorsal
hollow nerve chord, and pharyngeal slits
at some stage of their development.
Characteristics
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Notochord:
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Dorsal Nerve Chord:
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Flexible rod of specialized cells along its dorsal
side
Becomes the vertebral column (in vertebrates)
Hollow tube just above the notochord
Eventually becomes the brain and spinal cord
Pharyngeal Slits:
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Eventually becomes gills in aquatic organisms
Becomes throat and ear structures in
terrestrial organisms
Contains 3 subphlya:
Urochordates (inverts)
 Cephalochordates (inverts)
 Vertebrates (verts)
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Invertebrate Chordates: Urochordates
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2,000 species
Have gill slits as larvae and adults
Have notochord and dorsal nerve cord as larvae
Metamorphosis results in loss of notochord and
tail, and the nerve chord shortens
Examples: tunicates (sea squirts)
Invertebrate Chordates: Cephalochordates
28 species
 Small fishlike creatures
 Have notochord, dorsal nerve cord, and
gill slits as adults
 Lancelet is the closest living relative to
early animals
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Vertebrate Chordates: Vertebrates
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41,ooo species – 95% of chordates
Bones or cartilage surround the dorsal nerve cord
Contain skull and endoskeleton
Have organs organized into systems
How Vertebrates Regulate Body
Temperature
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Endothermic – warm-blooded
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An animal that generates its own body heat
Examples – birds and mammals
Ectothermic – cold-blooded
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Body temperature is determined by the environment
Examples – reptiles, fish, and amphibians
Vertebrate Reproductive Development:
How long the eggs remain within the female
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Oviparous – “egg birth”
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Ovoviviparous – “egg-live birth”
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Lay eggs and eggs hatch outside mother’s
body
Examples – Most fish, most reptiles, all birds,
and 3 species of mammals
Fertilized eggs remain inside of mother
Nourished by egg yolk – not the mom
May lay the eggs and then hatch shortly
thereafter OR eggs hatch inside of mother
and young are born live
Examples – Some fish, some reptiles
Viviparous – “live birth”
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Young develop within the uterus
Nourished by placenta
Example – Placental mammals (humans)
Taxonomy of Vertebrates
Class
Major Characteristics
Examples
Agnatha
Jawless fish
Chondrichthyes Cartilaginous fish
Lamprey, hagfish
Sharks, stingrays
Osteichthyes
Amphibians
Flounder, trout, etc.
Frogs, toads,
salamanders
Turtles, alligators,
snakes
Birds
Reptiles
Aves
Mammals
Bony fish
Part life in water, part life
on land
Amniote egg and scales
Feathers, hollow bones
Warm blooded, hair,
produce milk
Humans, primates,
dogs, etc.
Agnatha – Jawless Fish
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AKA cyclostomes (round
mouth)
Most primitive living
vertebrates
Ostracoderms (extinct);
lamprey (extant)
Lack paired appendages
cartilaginous skeleton
rasping mouth to suck
blood
Chondrichthyes – Cartilaginous Fish
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Sharks, skates, rays
Well developed jaws and paired fins; continual
water flow over gills (gas exchange); lateral line
system (detects water pressure changes)
Sexual reproduction with internal fertilization
Osteichthyes – Bony Fish
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Ossified (bony) endoskeleton; scales; operculum
(gill covering); swim bladder (buoyancy); 2
chambered heart with a single circulatory circuit
through body
Most numerous vertebrate
Sexual Reproduction, most with external
fertilization
Amphibians – “Double Life”
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1st tetrapods on land
Frogs, toads, salamanders
3 chambered heart with a
double circulatory circuit
(travels twice through body for
complete trip)
Double life & metamorphosisaquatic (larva) & terrestrial
(adult)
Must have moist skin for gas
exchange
Must use WATER for
reproduction
Reptiles
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Lizards, snakes, turtles, crocs and gators
Amniote (shelled) egg with extraembryonic membranes
(gas exchange, waste storage, nutrient transfer)
Waterproof scales of the protein keratin
Well-developed lungs for gas exchange
Most have 3 1/2 chambered heart; crocodilians have 4
No WATER needed for reproduction- first to truly adapt to
life on land
Aves – Birds (Flighted Reptiles)
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Flight adaptations: wings
(honeycombed bone) and
feathers (keratin)
Toothless
Airfoil wing
Evolved from reptiles
(amniote egg and leg scales)
4-chambered heart – double
circuit
Internal fertilization
Archaeopteryx (evolutionary
link between reptiles &
birds)
Mammals
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Mammary glands that
produce milk
hair (keratin)
4-chambered heart
large brain
teeth differentiation
Monotremes (egg-laying):
duck-billed platypus and
echidnas (spiny anteater),
Marsupials (pouch):
opossums, kangaroos,
koalas
Eutherian (placenta):all
other mammals
Vertebrate Chordates
Endo/Ectotherm
Circulation (#
of chambers)
Respiration
Fertilization
(where sperm
unites w/egg)
Fish
Ectotherms
Single loop (2)
Gills
Internal or
external
Amphibians
Ectotherm
Double loop (3)
Larvae-gills
Adult- lungs &
skin
External
Reptiles
Ectotherm
Double loop
(most 3 1/2
Crocodilians-4)
Lungs
Internal (some
external)
Birds
Endotherm
Double loop (4)
Lungs (more
complex)
Internal
Mammals
Endotherm
Double loop (4)
Lungs (most
complex)
Internal