1. Chordates and Fishes

2. Chordate Characteristics
Characteristics of Chordates
A chordate is an animal that in some stage of development has:
Notochord- dorsal rod of specialized nerves
A dorsal hollow nerve cord- tube just above the notochord
Pharyngeal pouches- small out pockets of the anterior gut (may become gills in some animals)
Postanal Tail-a tail that extends beyond the anus

3. 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

4. Subphylum Urochordata
Classification
Phylum Chordata has 3 subphyla
Urochordata-Tunicates
Cephalochordata-Lancelets
Vertebrata
Subphylum Urochordata
Hollow barrel shaped Urochordates are commonly called Tunicates and Sea Squirts

5. Subphylum Cephalochordata
Marine organism (usually shallow water)
Best represented by a blade-shaped, animal called a
lancelet

6. Subphylum Vertebrata
Brain protected by an outer skull and spinal cord protected by vertebrae
Organs of vertebrates are organized into 10 systems
Skeletal, muscular, integumentary, digestive, respiratory,
circulatory, excretory,
immune, nervous, and
reproductive

7. Characteristics of All Vertebrates
Bilateral symmetry
Two pairs of jointed appendages such as limbs or fins
Cephalization with complex brains and 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)

8. Vertebrate Classes
Fish
Amphibians
Reptiles
Birds
Mammals

9. 3. Osteichthyes-bony fish
Classes of Fish
Agnatha-Jawless Fish
Chondrichthyes-Sharks
Skates and Rays
3. Osteichthyes-bony fish
Fishes are the most numerous of all vertebrates and most widespread in their distribution

10. 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 Circulation- Blood goes to the gills, is oxygenated and sent to all parts of the body

11. 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

12. Circulation of Blood in Fish
Single loop circulation in fish
Atrium-chamber with thin, muscular walls
Ventricle-a thick walled pump with much force

13. 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

14. Reproduction in Fish 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

15. 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

16. 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

17. 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

18. Chondrichthyes CHONDRICHTHYES-SHARKES, SKATES AND RAYS
chrondros=cartilage ichthyes=fish
movable jaws
no swim bladder
cartilage strengthened by calcium carbonate or bone
placoid scales
Teeth-modified scales

19. 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

20. Osteichthyes 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

21. Types of Osteichthyes or Bony Fish
The Lungfish resembles a short-bodied eel- Lungfishes have gills where gas exchange normally takes place
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

22. 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 rays- Most familiar fishes and include snake-like eels, salmon, trout, bass, herring, and lantern fish
(most fish we eat)

23. Morphology of a Bony Fish or Osteichthyes
External Anatomy
Distinct head, trunk, and tail regions
Each side of head is operculum-
Hard plate that opens at rear and covers and protects gills
Strong muscles along dorsal backbone thrust tail from side to side

24. Fin Characteristics
Thin fan-shaped membranes
Richly supplied with blood
By raising and lowering fins, regulate body temperature
Supported by rays or spines
Rays- bony yet flexible
Spines- bony and rigid

25. Scales
Skin covered with scales-highly modified bone that grow from pockets of skin
Overlap like roof shingles, all pointing toward tail to minimize friction
Grow during entire life of fish
Scales grow quickly when food is abundant and slowly when scarce
Skin contains pigmented chromatophores-which
create various color patterns

26. Circulatory System
Adapted for rapid swimming and other high- performance activities
Consists of:
Two-chambered heart
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

27. Respiratory and Excretory Systems Work Together
Gills adapted for gas exchange
Each has double row of thin projections called gill filaments richly supplied with capillaries
Large surface area allows rapid gas exchange
Gills also excrete nitrogenous wastes from body, but task carried out primarily by kidneys
Kidney’s filter out dissolved chemical wastes from blood