Phylum Chordata Worksheet (Biology) printable pdf download

Classes Found In The Phylum- Chordata

All chordates have a number of structures in common:

A notochord (noto = the back; chord = string) is present in all embryos, and may be present or absent/reduced in adults.

This is the structure for which the phylum was named. The notochord is a rod-like structure that forms the supporting axis

of the embryo and gives birth to the vertebral column in vertebrates.

Chordates are sometimes referred to as “vertebrates” because most possess a backbone with vertebrae. Most also possess

the following characteristics; four limbs, aerobic respiration, get rid of waste via kidneys, reproduce sexually.

1-Class Agnatha

(a- = not, without; gnatho = jaw) which is the lampreys. They do not have jaws, are eel-shaped, prey on fish, and

have larval forms which are different from the adults.

2-Class Amphibia

(amphi = on both sides, double; bios = life) is frogs, newts, and salamanders. They were the first land

vertebrates. Frogs, especially, go through metamorphosis. Their eggs have no egg shells, so the sperm can swim through the water

to the eggs, and the embryos must develop in water. Amphibians are exothermic (exo = out, outside), that is they maintain their

body temperature through external means such as the sun or the water.

3-Class Aves

(avi = a bird) is the birds. It is thought that birds are descended from dinosaurs, as evidenced, in part, by the scales

on their feet. Also, feathers are modified scales: a key characteristic of birds is that they have feathers. Birds’ bones are light weight

for flight. Birds are endothermic (endo = within, inner), that is, they control their body temperature from within (they’re “warm-

blooded”). Birds’ vision is the best of all vertebrates: soaring hawks can spot small mice scrambling through the grass in a field far

below them. Birds have shelled eggs and so must have internal fertilization — the egg much be fertilized before the hen’s

reproductive tract secretes an eggshell. Generally, mating is accompanied by an elaborate courtship ritual. Eggs and often young

birds are more exothermic (are not able to control their body temperatures from within) and so must be brooded/incubated by

parents.

Phylum Chordata Worksheet (Biology)