Transcript Chordates and Fishes - Fulton County Schools

CHORDATES AND
FISHES
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Chordate Characteristics
Characteristics of Chordates
• A chordate is an animal that in some stage
of development has:
1. Notochord- dorsal rod of specialized nerves
2. A dorsal hollow nerve cord- tube just above
the notochord
3. Pharyngeal pouches- small out pockets of
the anterior gut (may become gills in some
animals)
4. Postanal Tail-a tail that extends beyond the
anus
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Characteristics Continued
Notochord exists only in the embryo
Notochord replaced by an endoskeleton
In lower chordates (fishes amphibians)
pharyngeal pouches evolved into gill slits
In terrestrial vertebrates pharyngeal
pouches evolved into structures in throat
and ear
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Classification
Phylum Chordata has 3 subphyla
1. Urochordata-Tunicates
2. Cephalochordata-Lancelets
3. Vertebrata
Subphylum Urochordata
Hollow barrel shaped Urochordates
are commonly called Tunicates and
Sea Squirts
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Subphylum Cephalochordata
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Marine organism (usually shallow water)
Best represented by a blade-shaped, animal
called a
lancelet
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Subphylum Vertebrata
• Brain protected by an outer skull and spinal
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cord protected by vertebrae
Organs of vertebrates are organized into 10
systems
Skeletal, muscular, integumentary, digestive,
respiratory,
circulatory, excretory,
immune, nervous, and
reproductive
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Characteristics of All
Vertebrates
 Bilateral symmetry
 Two pairs of jointed appendages such as
limbs or fins
 Cephalization with complex brains and
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sense organs
True coelom lined with mesoderm
Closed circulatory system-blood in vessels
and heart
Chambered heart
Either ectothermic (cold blooded) or
endothermic (warm blooded)
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Vertebrate Classes
 Fish
 Amphibians
 Reptiles
 Birds
 Mammals
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Classes of Fish
1.Agnatha-Jawless Fish
2.Chondrichthyes-Sharks
Skates and Rays
3. Osteichthyes-bony fish
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Fishes are the most numerous of all
vertebrates and most widespread
in their distribution
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Adaptations of Fishes
Swimbladder-adaptation for
buoyancy- traps gas inside their
body: gas swim bladder is used to
regulate their vertical position
Single Loop Blood CirculationBlood goes to the gills, is
oxygenated and sent to all parts of
the body
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Gills
 Made of gill filaments where gases enter
and leave the blood (Oxygen and Carbon
Dioxide)
 Gill slit-opening at the rear of the cheek
 Countercurrent flow - the water passing
over the gills and the blood flow inside the
gills is in the opposite directions-this
increases the gill’s efficiency
 Fish can extract 85 % of the oxygen passing
over the gills
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Circulation of Blood in Fish
Single loop circulation in fish
Atrium-chamber with thin,
muscular walls
Ventricle-a thick walled
pump with much force
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Excretory Organ-Kidneys
 Kidneys are organs made up of
thousands of nephrons
 Nephrons are tubelike units that
regulate salt and water balance
and remove metabolic wastes
from the blood
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Reproduction in Fish
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Separate sexes in most fishes
Usually external fertilization
Yolk sac in egg contains nutrients
Large numbers of eggs are fertilized
during spawning
 Sharks, Skates and Rays fertilization is
internal-most are born live
 Some sharks lay eggs
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Adaptations of Fishes
Scales limit chemical exchanges through
the skin; exchanges occur through the
membranes of the gills
Lateral line system consists of a row of
sensory structures that run the length of
the body and connected by nerves to the
brain; detects vibrations
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Agnatha “jawless”
• Examples:Lampreys and hagfish live in the
ocean
• Lampreys attach to fish-parasites
• No lateral line system
• Have “round mouths”- no scales
• Have Notochord, a
cartilaginous skeleton,
and unpaired fins
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Hagfish
• Bottom dwellers in cold marine waters
• Scavengers of dead and dying fish on ocean
bottom
• When not feeding they remain
hidden in burrows on the
ocean floor
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Chondrichthyes
 CHONDRICHTHYES-SHARKES, SKATES AND
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RAYS
chrondros=cartilage
ichthyes=fish
movable jaws
no swim bladder
cartilage strengthened by calcium carbonate or
bone
placoid scales
Teeth-modified scales
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Sharks
• Sharks are scavengers
• The shark’s mouth has 6 to 20 rows of
backward-pointing teeth
• They can detect blood from an injured
animal as far as 500 miles away
• They swim with a side-to-side motion of
their asymmetric tail fins.
• Gas exchange requires a continuous
passage of water over a shark’s gills
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Osteichthyes
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Osteon=bone
ichthyes=fish
Skeletons rigid, calcium bases
Movable jaws
Gill cover or operculum
Scales
Most have swim bladders
Most have separate sexes-fertilization
external
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Types of Osteichthyes
or Bony Fish
1. The Lungfish resembles a short-bodied
eel- Lungfishes have gills where gas
exchange normally takes place
2. During dry periods they burrow unto
the mud and cover themselves in mucus
to stay moist until the pond refills
 Their "lung" is a modified swim bladder,
which also absorbs oxygen and
removes wastes during this dry time
 The various species are found in the
lakes and rivers of South America,
Africa and Australia
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Osteichthyes Continued
2. Lobe-finned fishes-have paddle like fins
with fleshy bases.
3. Ray-finned fishes have fins that are
supported by the long bones called raysMost familiar fishes and include snake-like
eels, salmon, trout, bass, herring, and
lantern fish
(most fish we eat)
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Morphology of a Bony Fish
or Osteichthyes
External Anatomy
1. Distinct head, trunk, and tail regions
2. Each side of head is operculumHard plate that opens at rear and covers
and protects gills
1. Strong muscles along dorsal backbone
thrust tail from side to side
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Fin Characteristics
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Thin fan-shaped membranes
Richly supplied with blood
By raising and lowering fins,
regulate body temperature
Supported by rays or spines
1. Rays- bony yet flexible
2. Spines- bony and rigid
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Scales
1. Skin covered with scales-highly
modified bone that grow from pockets
of skin
2. Overlap like roof shingles, all pointing
toward tail to minimize friction
3. Grow during entire life of fish
4. Scales grow quickly when food is
abundant and slowly when scarce
5. Skin contains pigmented
chromatophores-which
create various color patterns
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Circulatory System
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Adapted for rapid swimming and other highperformance activities
Consists of:
Two-chambered heart
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Atrium- collecting chambers
Ventricle- pumping chambers
Blood vessels
Blood-red and white blood cells
Heart pumps blood to  arteries  capillaries
in gills blood picks up oxygen gas and
releases carbon dioxide into water blood
moves to body tissues, where nutrients and
wastes are exchanged blood returns by veins
to heart
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Respiratory and Excretory
Systems Work Together
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Gills adapted for gas exchange
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Each has double row of thin projections called gill
filaments richly supplied with capillaries
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Large surface area allows rapid gas exchange
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Gills also excrete nitrogenous wastes from body, but
task carried out primarily by kidneys
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Kidney’s filter out dissolved chemical wastes from
blood
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