Vertebrate Notes
I. Vertebrates = (Chordate Coelomate Deuterostomes)
A. Subphylum Vertebrata
1. About 45,000 extant species of vertebrates are in subphylum Vertebrata.
2. Vertebrates have all four chordate characteristics sometime during their lives.
3. Embryonic notochord is replaced by a vertebral column.
a. Vertebral column is individual vertebrae that surround a dorsal hollow nerve cord.
b. Vertebral column is part of a flexible, strong endoskeleton, is evidence of segmentation.
4. Vertebrate skeleton is living tissue (either cartilage or bone) that grows.
5. Endoskeleton and muscles together permit rapid and efficient movement.
6. Mutations could not have accumulated new genetic information needed to evolve kinds.
7. A skull is anterior component of main axis of vertebrate endoskeleton; it encases the brain.
8. High degree of cephalization in vertebrates is accompanied by complex sense organs.
a. Eyes designed as outgrowths of the brain.
b. Ears – for equilibrium, also sound-wave receivers.
9. They possess a complete digestive system and a large coelom.
10. Circulatory system is closed and respiratory pigments are contained within blood vessels.
11. Gills or lungs provide efficient gas exchange.
12. Kidneys efficiently excrete nitrogenous waste and regulate water.
13. Reproduction is usually sexual with separate sexes.
14. Design of the amnion allow reproduction on land.
15. Placental mammals allow development in the uterus.
B. Fishes
1. Fishes are aquatic, gill-breathing vertebrates that usually have fins and skin covered with scales.
2. Small, jawless, and fin-less ostracoderms are extinct vertebrate (fossils).
a. They were filter feeders also able to move water through their gills by muscular action.
b. Although living jawless fish lack protection, extinct jawless fish had large defensive head shields.
C. Jawless Fishes
1. Jawless fishes are agnathans; 63 species belong to superclass Agnatha.
2. Lampreys and hagfishes are modern jawless fishes; they lack a bony skeleton.
3. They have smooth non-scaly skin; have cylindrical bodies, and are up to a meter long.
4. Hagfishes are scavengers feeding on soft-bodied invertebrates and dead fishes.
5. Many lampreys are filter feeders; others are parasitic with a round muscular mouth equipped with
teeth to attach themselves to fish and suck nutrients from the host’s circulatory system.
6. Marine parasitic lampreys entered the Great Lakes and devastated the trout population in the 1950s.
D. Fishes with Jaws
1. Animals beyond this point are super class gnathostomates, animals with jaws and teeth
2. Placoderms are extinct jawed fishes.
a. They were armored with heavy plates and had strong jaws.
b. Like extant fishes, they had paired pectoral and pelvic fins.
c. Paired fins allow a fish to balance and maneuver well in water; this helps predation.
E. Cartilaginous Fishes
1. 850 species of sharks, rays, and skates are in class Chondrichthyes, the cartilaginous fishes.
2. They have a cartilaginous skeleton rather than bone.
3. Five to seven gill slits are on both sides of the pharynx; they lack gill covers of bony fish.
4. Body is covered by epidermal placoid (tooth-like) scales; teeth of sharks are enlarged scales.
5. Three senses detect: electric currents in water, pressure (a lateral line system), and smell.
6. Largest sharks are filter feeders, not predators; basking and whale sharks eat tons of crustaceans.
7. Most sharks are fast, open-sea predators; a great white shark eats dolphins, sea lions and seals.
8. Rays and skates live on ocean floor; pectoral fins are enlarged into wing-like fins; they swim slowly.
9. Stingrays have a venomous spine.
10. Electric rays feed on fish that have been stunned with electric shock of over 300 volts.
11. Sawfish rays have a large anterior “saw” that they use to slash through schools of fish.
F. Bony Fishes
1. 20,000 species of bony fishes are in class Osteichthyes.
2. Bony fishes have a bony skeleton; most are ray-finned with thin, bony rays supporting fins.
3. A few are lobe-finned fishes.
4. Ray-finned fishes include familiar fishes.
a. They are most successful and diverse of vertebrates.
b. They vary from filter feeders to predaceous carnivores.
c. Their skin is covered by scales formed of bone.
d. The gills do not open separately and instead are covered by an operculum.
e. Swim bladder is a gas-filled sac whose pressure alters to regulate buoyancy and depth.
f. Salmon, trout, and eels migrate between fresh and salt water but adjust kidney and gill function.
g. Sperm and eggs are usually shed into water.
h. For most, fertilization and embryonic development occur outside the female’s body.
5. Lobe-finned fishes include six species of lungfishes and one species of coelacanth.
a. Fleshy fins that are supported by central bones.
b. Lungfishes live in stagnant water or ponds that dry up; found in Africa, South America, & Australia.
c. Coelacanths live in deep oceans; once considered extinct, more than 200 have been captured since
1938 near the Comoros Islands, with recent finds near Malaysia.
G. Amphibians
1. Animals from this point on have four limbs and are Tetrapods.
2. Land animals use limbs to support the body since air is less buoyant than water.
4. About 3,900 species of amphibians belong to class Amphibia.
5. Diversity of Amphibians
a. Modern amphibians include frogs and toads, salamanders and newts, and caecilians.
b. Salamanders and newts have a long body and tail, and two pair of legs
c. S-shaped locomotion is similar to a fish.
d. Salamanders and newts are carnivorous, feeding on insects, snails, etc.
e. Practice internal fertilization; males produce a spermatophore that females receive with the cloaca.
f. Frogs and toads are tailless as adults; the hind limbs are specialized for jumping.
g. Frogs and toads have head and trunk fused; frogs live near fresh water, toads live in damp places
away from water.
h. Caecilians are legless; most burrow in soil and feed on worms, etc.
i. Reproduction involves use of water; “amphibian” refers to two life styles.
1) They shed eggs into the water for external fertilization.
2) Generally, eggs are protected by a coat of jelly but not by a shell.
3) Young hatch into aquatic larvae with gills (tadpoles).
4) The aquatic larvae usually undergo metamorphosis to develop into a terrestrial adult.
6. Anatomy and Physiology of Amphibians
a. A tongue is used for catching prey.
b. Eyelids keep eyes moist.
c. Ears are adapted for detecting sound waves and a larynx produces calls.
d. Their brain is larger than that of fishes; cerebral cortex is more developed.
e. Amphibians usually have small lungs supplemented by gas exchange across porous skin.
f. Single-loop circulatory path of fish is replaced by a closed double-loop circulatory system.
g. A three-chambered heart pumps mixed blood before and after it has gone to the lungs.
h. Skin is thin, smooth, and non-scaly, and contains numerous mucous glands; skin plays an active
role in osmotic balance and respiration.
i. Amphibians are ectothermic, depending upon external heat to regulate body temperature.
j. If winter temperature drops too low, ectotherms become inactive and enter torpor.
H. Reptiles
1. Reptiles practice internal fertilization through copulation and lay eggs with a leathery shell.
2. Amniote egg contains extra-embryonic membranes.
3. Extra-embryonic membranes are not part of embryo and are disposed of after development.
4. They protect the embryo, remove nitrogenous wastes, and provide oxygen, food, and water.
5. Amnion is one extra-embryonic membrane; it fills with fluid to provide a “pond” for embryo to develop.
6. About 6,000 species of reptiles are in class Reptilia.
7. Extinct reptiles (stem reptiles) gave rise to several lineages; each adapted to different ways of life.
a. Pelycosaurs (sail lizards).
b. Some were aquatic; ichthyosaurs were fish-like, plesiosaurs had a long neck.
8. Dinosaurs varied in size and behavior; some had a bipedal stance.
9. Dinosaurs were taken on the Ark (Hebrew = Box) and died out later due to lack of vegetation, cold, etc.
10. Diversity of Reptiles
a. Most live in tropics or subtropics; lizards and snakes live on soil; turtles and alligators live in water.
b. Tuataras are lizard-like and identical to fossils supposedly dated at 200 million years old.
c. Crocodiles and alligators are largely aquatic, feeding on fishes and other animals.
1) Powerful jaws have numerous teeth; a muscular tail is a paddle to swim and a weapon.
2) Male crocodiles bellow to attract mates; some species protect eggs and young.
d. Turtles have a heavy shell fused to the ribs and thoracic vertebrae.
1) Turtles lack teeth but use a sharp beak.
2) Sea turtles must return to lay eggs onshore.
e. Lizards have four clawed legs and are carnivorous.
1) Marine iguanas on the Galapagos are adapted to spend time in the sea.
2) Chameleons live in trees; have a long sticky tongue to catch insects, and change color.
3) Frilled lizards have a collar to scare predators.
f. Snakes.
1) Their jaws can readily dislocate to engulf large food.
2) A tongue collects airborne molecules to transfer them to Jacobson’s organ for tasting.
3) Some snakes that are poisonous have special fangs.
g. Reptiles have a thick, scaly skin that is keratinized and impermeable to water.
1) Keratin is protein found also in hair, fingernails, and feathers.
2) This protective skin prevents water loss but requires several molts a year.
h. Lungs are more developed than in amphibians; air rhythmically moves in and out of lungs due
to an expandable rib cage, except in turtles.
i. Most have a nearly four-chambered heart, except the crocodile is completely four-chambered;
oxygenated blood is more fully separated from deoxygenated.
j. Well-developed kidneys excrete uric acid; less water is lost in excretion.
k. Reptiles are ectothermic.
1) They require a fraction of the food per body weight of birds and mammals.
2) They are behaviorally adapted to warm their body temperature by sunbathing.
I. Birds
1. About 9,000 species of birds are in the class Aves.
2. Most lack teeth.
3. Birds also lay an egg, but it is hard-shelled rather than leathery.
4. Ancestry of birds is in dispute. Evolutionists continually revise their theories and assumptions.
5. Bird classification is based on beak and foot types, and some habitats and behaviors.
a. Birds of prey have notched beaks and sharp talons.
b. Shorebirds have long slender bills and long legs.
c. Waterfowl have webbed toes and broad bills.
6. Birds are the only modern (extant) animals to have feathers.
a. Feathers are NOT modified reptilian scales. Are composed of keratin, and occur as two types.
b. Contour feathers overlap to produce a broad, flat lifting surface.
c. Down feathers provide excellent insulation against loss of body heat.
7. Birds are homeothermic; they have ability to maintain a constant, relatively high body temperature.
a. Homeothermy enables an animal to be continuously active in cold weather.
b. Feathers serve for insulation and for flight.
8. Bird forelimbs are modified as wings for flying with hollow, light bones laced with air cavities.
9. Beak composed of keratin.
10. Keeled breastbone anchors muscles used in flight.
11. Respiratory air sacs are extensive, even extending into some larger bones.
a. Using a one-way flow of air, air sacs maximize gas exchange and oxygenation of blood.
b. Efficient supply of oxygen to muscles is vital for level of muscle activity needed for flight.
12. Birds possess a four-chambered heart; a double-loop circulatory system separates oxygenated blood.
13. Flight requires well-developed sense organs and nervous system.
a. Birds have very acute vision and excellent muscle reflexes.
b. Complex behavioral responses including hormonal regulation are required in bird behavior.
c. Bird flight allows migration and use of widespread food sources.
J. Mammals
1. About 4,500 species of mammals belong to class Mammalia.
2. Chief characteristics of mammals are hair and mammary glands.
3. Mammals are homeothermic; they produce heat and maintain a constant body temperature.
4. Many adaptations of mammals are related to temperature control.
5. Hair provides insulation against heat loss; allows mammals to be active in cold weather.
6. Gas exchange is efficiently accomplished by lungs.
7. Mammals possess a four-chambered heart and a double-loop circulatory system.
8. Mammary glands enable females to feed young without deserting them to obtain food.
9. Nursing creates bond between mother and offspring to ensure parental care while young are helpless.
10. In most mammals, young are born alive after a period of development in uterus.
Yet marsupials use pouches and a monotremes lay eggs.
11. Mammals That Lay Eggs
a. Monotremes are mammals that have a cloaca and lay hard-shelled amniote eggs.
b. They are represented by duckbill platypus and spiny anteater of Australia.
c. Female duckbill platypus lays her eggs in a burrow in the ground where she incubates them.
d. After hatching, young lick milk seeping from modified sweat glands on abdomen of males and females.
e. Spiny anteater has a pouch formed by swollen mammary glands and muscle; egg moves from cloaca
to pouch and hatches; young remain for 53 days and live in burrow where mother feeds them.
12. Mammals That Have Pouches
a. Marsupials begin development inside mother’s body but are then born in a very immature state.
b. Newborns crawl up into a pouch on their mother’s abdomen.
c. Inside a pouch they attach to nipples of mother’s mammary glands and continue to develop.
d. Today, most marsupials are found in Australia where they underwent adaptive radiation without competition from placental mammals introduced recently.
13. Mammals That Have Placentas
a. Placental mammals use a placenta, an organ of exchange between maternal and fetal blood.
b. Placenta supplies nutrients to and removes wastes from blood of developing offspring.
c. Placenta also allows mother to move about while offspring develop.
d. Placenta enables young to be born in a relatively advanced stage of development.
e. Placental mammals are very active animals; possess acute senses and a relatively large brain.
f. Brains of placental animals have cerebral hemispheres proportionately larger than other animals.
g. Young go through a long period of dependency on parents after birth.
h. Placental mammals populate all continents except Antarctica.
i. Most are terrestrial, but some are aquatic, and bats can fly.
14. Classification of mammals is based on mode of locomotion and method of obtaining food.
1. Order Perissodactyla includes 17 species of horses, zebras, tapirs, and rhinoceroses;
Order Artiodactyla includes 185 species of pigs, cattle, deer, buffaloes, giraffes, etc.
a. Both orders are hoofed animals.
b. They have elongated limbs adapted for running across open grassland.
c. They are herbivorous and have large grinding teeth.
2. 270 species are in order Carnivora.
a. Meat-eaters including the dogs, cats, bears, raccoons, and skunks.
b. All have limbs adapted for running.
c. They have a well-developed sense of smell.
d. Canine teeth of meat-eaters are large and conical.
e. Most are terrestrial; some are aquatic (e.g., seals, sea lions, walruses, and otters).
3. Order Primates contains 180 species of lemurs, monkeys, gibbons, chimpanzees, gorillas, and humans.
a. Typical primates are tree-dwelling fruit eaters; some are ground dwellers.
b. They have a freely movable head.
c. Their digits have nails, not claws; thumb in many (and sometimes the big toe) is opposable.
d. Primates, particularly humans, have well-developed brains.
4. Order Cetacea includes about 80 species of whales and dolphins.
a. They lack substantial hair or fur.
b. Blue whales are the largest animal ever to live on this planet.
c. Toothed whales feed on fish and squid; baleen whales strain plankton from the water.
5. Order Chiroptera contains 925 species of nocturnal bats.
a. Wings are layers of skin & connective tissue stretched between elongated bones of the fingers
b. Many species use echolocation to locate their usual insect prey.
c. Bats also eat birds, fish, frogs and plant tissues.
6. Order Rodentia contains rodents (e.g., mice, rats, squirrels, beavers, and porcupines).
a. This is largest order with 1,760 species.
b. Rodents have incisors that grow continuously.
c. Most eat seeds but some are omnivorous or eat insects.
7. Only two extant species are in order Proboscidea: the elephants.
a. Upper lip and nose are elongated and muscularized forming a prehensile trunk.
b. They are herbivores and are largest living land mammals.
8. Order Lagomorpha includes 65 species of rabbits, hares, and pikas.
a. They resemble rodents but have two pairs of continuously growing incisors.
b. Their hind legs are longer than their front legs and they are herbivores.
 II. Phylum Chordata (notochord, nerve chord, pharyngeal pouches)
Subphylum Vertebrata (backbone/vertebrae)
Superclass Agnatha (jawless fishes – lampreys, etc.)
Superclass Gnathostomates (jawed fishes)
Class Chondrichthyes (cartilaginous fishes – sharks, rays, etc.)
Class Osteichthyes (bony fishes)
Class Amphibia (frogs, salamanders, newts, caecilians, etc.)
Class Reptilia (lizards, snakes, turtles, gators, dinosaurs, etc.)
Class Aves (birds)
Class Mammalia (rats, rabbits, cows, dogs, monkeys, apes, man)
Order Perissodactyla (horses, zebras, tapirs, and rhinoceroses)
Order Artiodactyla (pigs, cattle, deer, buffaloes, giraffes)
Order Carnivora (Meat eaters, tigers, wolves, etc.)
Order Primates (lemurs, monkeys, apes, man)
Order Cetacea (dolphins, whales)
Order Chiroptera (bats)
Order Rodentia (rats, mice, squirrels, beavers, porcupines)
Order Proboscidea (elephants, mammoths)
Order Lagomorpha (rabbits, hares, pikas)
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