Page 25 - Science Course 2 (Book 1)

Mo1-L3b: What are the Groups of Chordates?

Let’s Begin Bony Fish
All other fish have a bony skeleton, as well as paired
fins and jaws. Bony fish, such as goldfish, also have
a special sac called a swim bladder that the fish can
Vertebrate Chordates fill with gas. This helps the fish move up and down in
All fish are vertebrate chordates that live in water the water. Sea horses are unique bony fish because
and use gills for breathing. the males carry the young in their bodies as they
develop.
Gills are organs that exchange
carbon dioxide for oxygen in the
water.

A tetrapod is a vertebrate animal with four limbs.

Amphibians are a group of tetrapods that live on
land but still depend on water to survive and
reproduce.

The three major groups of fish are jawless fish,
sharks and rays, and bony fish.

Jawless Fish Salamanders and newts have tails and move by
Lampreys are jawless fish. The skeleton of jawless bending their bodies side-to-side.
fish is made of cartilage. The tip of your nose and
the flaps of your ears are made of cartilage. Some
jawless fish get their nutrition from other fish. They
have a circle of teeth that attach to the sides of other
fish and make a wound. They then slowly suck out
blood and other body fluid from the fish.
Frogs and toads do not have tails as adults but they
do have long legs that enable them to jump.

Sharks and Rays
Most of the skeleton of sharks and rays is made of
cartilage. However, shark skulls are made of bone.
Sharks have paired fins. They are fast swimmers and Caecilians, a group of amphibians with no legs,
also have a powerful jaws. Their jaws make them look similar to earthworms and move by twisting
dangerous predators of other animals, especially their bodies back and forth like a snake.
other fish.

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