Non-vertebrate Chordates, Fishes, and AmphibiansChapter 30

Phylum Chordata

Contains three sub-phyla:– Vertebrata– Urochordata– Cephalochordata

All chordates at some point in their life span must possess four characteristics:

1) A hollow, dorsal nerve cord

2) A notochord (supporting rod)

3) Pharyngeal gill slits

4) A tail that extends beyond the anus

Also known as the tunicates or “sea squirts”

Basically a sack with two siphons.

Examples: amphioxus and lancelets

Vertebrates

Most numerous chordates Anterior, large brain Jointed internal skeleton Usually two pairs of appendages and

some type of tail Closed circulatory system Gills or lungs and a chambered heart

7 major classes of vertebrates

Jawless fishes, cartilaginous fishes, bony fishes, amphibians, reptiles, birds, mammals

Ectotherms = “cold-blooded” body temp changes with the environment.

Endotherms = “warm blooded” body tem remains fairly constant

FISH or FISHES

Both words can be used for the plural of a fish.

“Fishes” is often used when talking about taxonomy or classification.

1. Class Agnatha “jawless fishes” Most primitive vertebrates No scales nor fins Cartilage skeleton No jaws Both fresh and salt water varieties. examples: lampreys and hagfish

LAMPREY

Both fresh and salt water. (parasitic)

Possess a tongue with teeth that gnaw a hole in its victim then sucks out the blood.

Can be harmful to fish populations.

HAGFISH

Only found in salt water. scavengers

Also known as “slime eels”

Produce great amounts of slime for defense. Can tie themselves in a knot

2. Class Chondricthyes

Chondros (Gr. Cartilage) Ichthys (Gr. Fish) Mostly marine 2 chambered heart Movable upper and lower jaws ex. Sharks, skates, and rays

Skates and rays

Flattened body (countershading) Eat worms, mollusks, and other

invertebrates Can be specialized for defense

– Stingers– Electric rays

SHARKSInternal fertilization.

Viviparous = live birth

Need to be constantly swimming to keep water moving over the gills

Very highly developed sense of smell.

Covered with sandpaper-like scales called placoid scales.

Medicinal uses

Currently shark cartilage is being tested as a possible cure for cancer.

3. Class Osteicthyes

Osteo- Gr. Meaning “bone”Known as the bony fishesLargest class of vertebrates.Vary in size, shape, and structure.Complex nervous system (lateral lines)Very specialized.

Electric eel, pufferfish, angler fish, butterfly fish

Wide Variety

Structure of a bony fish

Usually four pairs of gills covered by a bony flap (operculum)

2 chambered heart Many have scales and fins Swim bladder = gas-filled sac which is

used for buoyancy (maintain depth)

Reproduction

External.A female will lay upto

500,000 eggs.The male usually swims over

the eggs depositing milt (sperm containing fluid)

The Coelacanth

A special fleshy-lobed finned fish thought to be extinct.

1938 one was caught off the southern coast of Africa.

4. Class Amphibia “from water to land” Reproduction and development must

take place in or near water. Thin moist skin Two pairs of limbs, one pair of nostrils 3 chambered heart Young show a distinct larval form.

Examples:

Frog anatomy and function

Large powerful hind legs for jumping. 2 large movable eyes Tympanic membrane 3 eyelids

– Upper– Lower– Nictitating membrane (transparent; used

for underwater sight.

digestion

Large mouth. Long sticky spade-shaped tongue Teeth along upper jaw. A pair of vomerine teeth used to hold

prey in mouth Esophagus...stomach...small

intestine(site of absorption)..large intestine...cloaca…anal opening.

Circulatory system

Oxygenated blood enters left atrium from lungs. Deoxygenated blood enters right atrium from rest of body.

Both empty into ventricle where a mixture of oxygen and non-oxygen blood is pumped out

Respiratory system

Tadpoles use gills to breathe. Adult frog uses three structures for

respiration.

Nervous system

Possess both a cranial and peripheral nervous system

Multi-lobed brain Olfactory(smell) Optic(sight) Cerebrum(voluntary muscles) Cerebellum(coordination) Medulla(involuntary muscle action)

Excretory system

CO2 excreted through the skin, other wastes filtered through the kidneys.

Urine is stored in urinary bladder then passed into cloaca and out of the body.

Reproduction

External fertilization

amplexus = male grasps female, eggs are released then quickly fertilized by the male.

Order Urodela

Salamanders and newts

Long bodies and tails

Live in dark, moist places.

Orders Anura & Apoda

ANURA Frogs and toads

APODA Caecilians Legless amphibians

Assignment

Pages 793-794

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