Phylum Chordata

“Chordates”

Notocord

Pharyngeal

Pouches

In vertebrates the dorsal hollow nerve cord is called the SPINAL CORD. As a vertebrate embryo develops, the FRONT END of the spinal cord grows into A BRAIN.

2 Subphyla of Chordates LACKING a backbone…but having all four characteristics…

Members of this phylum are called chordates. A chordate is an animal that has at least for some part of its life 1.) a dorsal hollow nerve cord; 2.) a notochord; 3.)Pharyngeal pouches; 4.)a tail that extends beyond the anus.

A long supporting rod that runs just below the nerve cord. Most chordates have a notochord only when they are embryos.

Paired structures in the throat (pharynx) region. In some chordates (fish & amphibians) slits develop that connect the pharyngeal pouches to the outside of the body. These slits may then develop gills used for gas exchange.

The backbone, which replaces the notochord in most developing vertebrates, is made of individual segments called VERTEBRAE. The endoskeleton gives SUPPORT, PROTECT’s the animal’s body & provides a place for muscle & ligament attachment. *The endoskeleton grows as the animal grows!

Tunicates & Lancelets are soft-bodied marine animals that are called “Non-vertebrate chordates”

FISHES

3 Groups/Classes of Fish:

Jawless Fish

Lampreys & Hagfish

Class Chondrichthyes

(Cartilaginous Fish)

Sharks, Rays, Skates & uncommon fish such as Sawfish & Chimaeras

Class Osteichthyes

(Bony Fish)

Ray Finned fish you are most familiar with…

ANADROMOUS (SALMON)

CATADROMOUS (EUROPEAN EELS)

FISH REPRODUCTION

OVIPAROUS

OVOVIVIPAROUS

VIVIPAROUS

Aquatic vertebrates; Most have paired fins, scales, & gills.

Fish with no true teeth or jaws. Skeletons are made of fibers & some cartilage. They lack vertebrae & keep their notochord as adults. Lampreys are filter feeders as larva & parasites as adults. Hagfish have pink worm-like bodies & 4 short tentacles around their mouths. They lack eyes. They feed on dead & dying fish by using a toothed tongue to scrape a hole in the fishes side (they can tie themselves in a knot too!)

They have skeletons made up entirely of cartilage. Most have tooth-like scales covering their skin making it feel like sandpaper.

They have skeletons made of hard calcified tissue called bone.

Fish that spend most of their lives in the ocean but migrate to fresh water to breed.

Fish that spend most of their lives in fresh water but migrate to the ocean to breed.

Eggs are fertilized internally or externally; the females lay the eggs & they hatch OUTSIDE the mother’s body. The embryo gets it’s food from the yolk in the egg.

Eggs REMAIN INSIDE the mother’s body after internal fertilization. Each embryo stays inside its egg using the yolk for nourishment. The young are then “born alive” like the young of most mammals.

After internal fertilization, the eggs remain inside the mother’s body & get their nutrients from the mother’s body rather than from material in an egg. The young are then “Born alive”.

AMPHIBIANS-frogs, toads, salamanders, & caecilians

Adaptations that allow amphibians to live part of their lives out of water:

Amphibian

Reproduction

An amphibian is a vertebrate that, with some exceptions, lives in water as a LARVA & on land as an adult, breathes with lungs as an adult, has moist skin that contains mucous glands, & lacks scales & claws.

Bones in the limb & limb girdles became stronger, permitting more efficient movement. Lungs & breathing tubes allowed them to breathe air. Their sternum formed a bony shield that supported & protected their internal organs.

Amphibian eggs do not have shells & tend to dry out if not kept moist. This is why most amphibians must lay their eggs in water. The male usually fertilizes the eggs by external fertilization. In a few species, including most salamanders, eggs are fertilized internally.