Fish, amphibians, and reptiles

CHAPTER 14
FISH,
AMPHIBIANS,
AND REPTILES

Section 1 Chordates and Vertebrates
A. Chordates have four characteristics present at some stage of their
development: a notochord, postanal tail, nerve cord, and pharyngeal
pouches.
1. The internal notochord extends along the upper part of the body,
supporting it.
a. Also extends into the postanal tail, a muscular structure at the end
of developing chordates.
b. Vertebrates develop backbones that partly or entirely replace the
notochord.
2. The tubelike nerve cord develops into the brain and spinal cord as most
chordates mature.
3. All developing chordates have pharyngeal pouches found in the region
between the mouth and digestive tube.
B. Vertebrates have all chordate characteristics plus distinctive additional ones.
1. Vertebrates have an endoskeleton; part of the endoskeleton is a stack of
vertebrae and cartilage forming the backbone.
a. The backbone protects the spinal nerve cord.
b. A skull protects the brain.
2. Vertebrates are either cold-blooded ectotherms or warm-blooded
endotherms.
3. Vertebrates appeared in various stages beginning with water-dwelling
animals about 420 million years ago to as recently as 38 million years ago,
when modern mammals appeared.

Section 2 Fish
A. Fish are ectotherms with a streamlined shape, a muscular tail, fins
attached to the endoskeleton, and scales that cover and protect the
body.
1. Fish have well-developed sensory systems and a two-chambered
heart.
2. Fish exchange carbon dioxide and oxygen through their gills.
3. Fish use a variety of adaptations for obtaining food including teeth,
beaks, electric shock, and filter feeding.
4. Fish reproduce sexually; some species use external fertilization while
others use internal fertilization.
B. Jawless fish have round, toothed mouths; long tubelike bodies covered
with scaleless, slimy skin; and endoskeletons of cartilage.
C. Sharks, skates, and rays are cartilaginous with skeletons of cartilage,
moveable jaws with well-developed teeth, and tiny scales that make
their skin feel like fine sandpaper.
D. About 95 percent of all fish species are bony fish with skeletons of bone.
1. Most bony fish have a swim bladder that inflates and deflates,
allowing the fish to rise or sink in the water.
2. lobe-finned fish have fins that are lobelike and fleshy.
3. Lungfish have one lung and gills, allowing them to live in shallow
water with little oxygen.
4. Ray-finned fish have fins made of long, thin bones covered with skin;
their body plans show much variety.
E. Fish provide food for many animals and they keep insect populations in
balance; fish evolved from soft-bodied, filter-feeding organisms.

Section 3 Amphibians
A. Amphibians are ectotherms that engage in hibernation in cold
weather and estivation in hot, dry weather.
1. Some amphibians breathe through their skin; others have
small, simple, saclike lungs in the chest cavity.
2. Amphibians have a three-chambered heart.
3. Amphibians need water for reproduction; eggs are fertilized
externally.
4. Most amphibians go through a developmental process called
metamorphosis.
B. Most frogs and toads use a tongue attached to the front of their
mouths to capture prey such as insects, worms, and spiders.
C. salamanders and newts hide during the day and use welldeveloped
senses of smell and vision to hunt worms,
crustaceans, and insects at night.
D. Amphibians help keep insect populations in balance, and
amphibians provide food for other animals.
1. Amphibians are a biological indicator whose overall health
reflects the health of a particular ecosystem.
2. Amphibians are thought to have evolved from lobe-finned fish
about 350 million years ago.

Section 4 Reptiles
A. Reptiles are ectotherms with a thick, dry, waterproof skin covered with scales.
1. Reptiles breathe with lungs.
a. Most reptiles have a three-chambered heart.
b. The three-chambered heart has a partial wall inside the main chamber.
c. Crocodilians have a four-chambered heart that completely separates
oxygen-filled and carbon dioxide-filled blood.
2. Reptiles use internal fertilization and lay eggs with shells; the amniotic egg
provides a complete environment for the embryo’s development.
B. Reptiles live on every continent except Antarctica and in all but polar oceans;
reptiles are divided into three living groups.
1. lizards and snakes have jaws that unhinge so they can swallow their prey
whole.
2. Turtles have a two-part shell made of hard, bony plates that protects against
predators.
3. Crocodilians are lizard-shaped with large, deep scales on their backs.
a. Crocodiles have a narrow head with a triangular-shaped snout while
alligators have a broad head with a rounded snout. Gavials have a slender
snout with a large bump on the end.
b. Crocodilians are among the few reptiles that care for their young.
C. Reptiles are important predators that keep pests under control; reptiles first
appeared in the fossil record about 345 million years ago. Dinosaurs are
descendants of early reptiles.