Transcript Chordates and Vertebrates

Chordates and Vertebrates
Chordates
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The notochord is an elongate, rodlike, skeletal structure dorsal to the gut
tube and ventral to the nerve cord.
The notochord should not be confused
with the backbone or vertebral column
of most adult vertebrates.
The notochord appears early in the
embryo and plays an important role in
promoting or organizing the embryonic
development of nearby structures.
In most adult chordates the notochord
disappears
In some non-vertebrate chordates and
fishes the notochord persists as a
laterally flexible but incompressible
skeletal rod that prevents telescopic
collapse of the body during swimming.
Primitive Jawless Fish
 Lamphrey and Hag fish
 The most primitive of the
chordates evident in the fossil
record are the jawless
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Ostracoderms.
They were jawless, bottom feeders
Their endoskeleton was cartilaginous
but the are covered with small bony
plates
 They use a muscular pharynx to
suck food into their mouths and to
exchange gases in respiration.
 Their gill slits were permanently
open
Jawless Fish cont.
 As the fish swam, this fin
configuration drove the animal
down into the bottom where its
food was located.
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The bony plates were useful for
protection but inhibiting when rapid
swimming was required.
They still had no axial skeleton
These animals are long, slender eel
like organisms.
 These animals exist either as
bottom scavengers or parasites of
other fish. (Hag fish top right)
Jawed cartilaginous fish
 The Chondrichthyes are the
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modern cartilaginous fish
The present Chondrichthyes
include the sharks, skates and
rays. (Top left: skate Bottom
left
A ventral jaw with replaceable
teeth. The limited mobility of
the jaw means that the shark
must thrash around to break
up its prey
Sharks must continually swim
to avoid sinking. (Thought this
was interesting!)
The gills are not protected by
an operculum
Cartilagenous Fish
 Cartilage is a soft,
flexible material
 End of your nose, ears
 Cartilagenous fish
have an entire
skeleton made of it
 Class Chondrichthyes
 Sharks, skates and
rays
 First jawed fish
Cartilagenous Fish
 Placoid Scales: tiny
“teeth” that point towards
posterior of animal
 Gill Slits: openings to the
gills
 Skates, rays and some
bottom-dwelling sharks
have gill slits on ventral
side
 Spiracles: openings that
allow water to enter gill
chamber
 Behind eye
 Mouth can be used to
help spiracles pump
water over gills
Cartilagenous Fish
 Fins
 More rigid than bony
fish
 Pectoral fins in sharks
provide lift
 In skates and rays
pectoral fins are more
developed
Skates and Rays
 Many species are
bottom-dwellers
 Stingrays have a
spine at the base of
the tail that can inflict
a stab wound
 Skates do not have
spines
 Both eat crustaceans
and mollusks
Sharks
 Group is more than 300 million years old
 Lateral line organ
 Used to detect motion in the water
 Ampullae of Lorenzini
 Sense electric fields generated by fish
 Teeth
 Constantly replaced
 Many sharks have to swim as they can not pump water over their gills
Sharks
 Reproduction
 Claspers
 Males use claspers to
transfer sperm to
females
 Located between the
pelvic fin and body
 Eggs
 All sharks have eggs
 Some species have
eggs that hatch
internally and are then
born live
 Some species lay an
egg case known as a
Mermaid’s Purse
Bony Fish
 Bony fish
 Skeleton made of
bone
 Have vertebrae
 Have scales covered
with mucus
 Barrier against infection
and reduces friction
with the water
 Found in every aquatic
environment
Bony Fish
 Obtaining oxygen
 Use gills
 Located under a
protective flap called
the operculum
 Mouth and operculum
open at the same time
as water is drawn in by
the mouth and passed
over the gills
Bony Fish
 Locomotion
 Nekton
 As opposed to plankton
 Fins
 Some are paired, others
are single
 Paired: pectoral and pelvic
 movement
 Single: dorsal, anal and
caudal
 Stabilization and thrust
(power)
 Peduncle
 Used as a major marker
for determining species
 Base of caudal fin
Bony Fish
 Pelagic v. Benthic
 Pelagic refers to those
living in the middle of the
water column, open ocean
 Benthic refers to those
living on the bottom
 Speed
 Depends on shape
 Faster fish have more
sharp angles and bigger,
forked caudal fins
Bony Fish
 Temperature
 Bony fish are ectothermic
 Their body temperature
depends on the
temperature of the
environment
 Buoyancy
 Swim bladder
 Neutral buoyancy is when
the fish neither sinks or
floats
 Swim bladder contracts
and fish sinks, bladder
expands and fish rises
Bony Fish
 Feeding
 Parasitic (lamprey)
 Predatory
 Strainers (planktoneaters
 Suckers (use change
in volume to suck prey
into mouth)
 Digestion
 One-way digestive
system coupled with a
closed circulatory
system and 2chambered heart
Bony Fish
 Reproduction
 Takes place during spawning
 Sperm and eggs are released into the water or fertilization takes
place internally
 Eggs develop either floating or attached to a substrate