Phylum Chordata Worksheet (Biology) Page 3
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4Phylum Chordata
Class
Main Characteristics
Examples
Approximate #
of species
Agnatha
lack jaws and paired fins
Lamprey, hag fish 10 species
cartilaginous skeleton
Sharks, skates,
600 species
Chondrichthyes
have jaws
cartilaginous skeleton
rays, sawfish
paired fins
have jaws
Most familiar fish
20,000 species
Osteichthyes
bony skeleton
ie perch, tuna,
paired fins
catfish
moist, glandular skin
frogs, toads,
2,000 species
Amphibia
lack scales and claws
salamanders
larvae are aquatic
eggs without shells
dry, scaly skin
snakes, turtles,
5,000 species
Reptilia
breathe by lungs
lizards, crocodiles
leathery shelled eggs
feathers
birds
9,000 species
Aves
wings
warm blooded
hard shelled eggs
hair on part or all of
humans, rodents,
4,500 species
Mammalia
body
whales, bats
warm-blooded
mammary glands to
produce milk
From an evolutionary perspective, there are a number of trends or changes that can be seen in the vertebrates
from class agnatha to class mammalia. Some of these trends are:
1. A switch from a cartilage to a bone skeleton.
2. A move from water to land.
3. An increase in brain size and complexity.
4. An increase in size, number of chambers and complexity of the heart.
5. A change from cold to warm blooded.
6. The evolution of learned behaviors
7. A reduction in the number of offspring (clutch sizes).
8. An increase in parental care.
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