Phylum Chordata
Invertebrate chordates examples
– Urochordata
• Tunicates, sea squirts, ascidians
– Cephalochordata
• lancelets
Share 4 “chordate” characteristics
• Notochord
– Flexible rod-like structure
• Dorsal nerve cord
– Tube for nerves
• Pharyngeal gill slits
– Respiration and feeding
• Post-anal tail
– Reabsorbed in some species
Phylum Chordata, subphylum Vertebrata
• Share the 4 chordate
characters with lancelets
and sea squirts
• Backbone, vertebral
column, spine
– Series of hollow vertebrae
– Protects nerve cord
(spinal cord)
• Bilateral symmetry
• endoskeleton
Agnatha (jawless fishes)
• Lack: paired fins, scales,
& well developed
vertebrae
• Hagfish (slime eels)
– Mucus for protection
– Feed on decaying flesh
• Lampreys
– Parasitic
– Anadromous
• Marine adults, breed in
freshwater
Chondrichthyes (cartilagenous fishes)
• Sharks, rays, skates,
& ratfishes
• Movable jaws of
ventral mouth
• Paired fins
• Placoid scales
– Dentricles (same
composition as teeth)
Sharks
•
•
•
•
•
•
•
Heterocercal caudal fin
Two dorsal fins
Paired pectorals
5-7 gill slits
Many rows of teeth
Oily liver
Diverse examples:
hammerhead, sawfish,
thresher, whale sharks
Rays, Skates, & Ratfishes
• Flattened
• Demersal
• 5 prd ventral gill slits
• Expanded pectorals
Rays vs. skates
rays: reduced or no dorsal fin
– Stingrays
• Venomous defensive spine
– Electric rays
• Upto 200 volts for defense
and predation
– Ratfishes (chimaeras)
• Deep, bottoms, long skinny
tail
• Paired (pelvic) & unpaired
(forehead) male claspers for
copulation & holding female
--seen in rabbitfish
Lateral line
Osteichthyes (bony fishes)
•
•
•
•
Swim bladder
Operculum (gill cover)
Homocercal tail
Scales of bony origin
– Smooth cycloid
– Spiny ctenoid
Circulatory system: 2 chambered heart (“one way
flow”) …ventricle chamber to gills, “fresh” blood to
tissues, back to atrial chamber
Gill function and diffusion of gas
• High surface area
from many folds or
lamellae of gill
filaments
• The water : blood
relationship is in a
counter-current
orientation -enhances diffusion
– higher [Oxygen] in
water than blood
Fish reproduction & development
•
Internal fertilization
–
•
w/specialized copulatory structures
External fertilization
–
Broadcast spawning
•
–
–
•
Some fishes deposit eggs on bottoms
Some bury in sandy shores
Unique examples:
–
Male carriers
•
•
Eggs released, fertilized, developed
externally, lots of yolk
Viviparous
–
•
e.g. At Birch aquarium
Oviparous
–
•
Millions of eggs released as part of
plankton
Internal development, direct
nourishment; birth live young
Ovoviviparous
–
Internal egg development; yolk; birth
live young
Class Amphibia
• First terrestrial
vertebrates (tetrapods)
• Frogs, salamanders,
newts
• “Two lives”-- Transitions
from aquatic to land
– lose post anal tail & gill slits
• Requires moist
environments
– At least for reproduction &
early development
• External fertilization
• Three chamber heart
Class Reptilia
• Dinosaurs, turtles, lizards,
snakes, crocodiles,
alligators
• Evolved from amphibious
ancestor – broke
dependency to aquatic
environment
• Tough, scaly skin
– Prevents desiccation
• First sign of amniotic egg
– Key for transition to land
– Keeps embryo moist
• Internal fertilization
Class Aves (Birds)
• Descendants of
reptiles
• Adapted for flight
–
–
–
–
Feathers
Wings
Light bones
Flight
muscles/breastbone
• Four-chamber heart
• Extensive respiratory
system
Class Mammalia
• Brain sizes are larger per
pound of body weight than
most other animals'.
• Mammals have more efficient
control over their body
temperatures than even birds.
• Hair provides insulation.
• Mammary glands provide milk
to nourish the young.
• Teeth are specialized for
cutting, shearing or grinding;
thick enamel helps prevent
teeth from wearing out.
Order Monotremata
• Egg laying
mammals
– Australia & New
Zealand
– Only 2 extant
Families that
include:
• Platypus
• Echidna
Order Marsupialia
• Pouched mammals
– Born in the
embryonic stage;
finish outside the
mothers body
(pouch)
– Largely Australian
• Koala, Kangaroo,
Tasmanian Devil
– Few North
American
• opossum
Placental Mammals
• Embryos nourished by
placenta for extended
gestation periods
– 9 mos. = human
– 2 yrs. = elephant
• 12 Orders that include:
– Bats, horses, whales,
rodents, cats, dogs, and
primates (monkeys, apes,
& humans)