FISHY FRIENDS
 Clownfish. Photo Source: Leanne Guenther |
What distinguishes fish from the other animal classes?Fish
are a class of aquatic vertebrates. The combination of gills, fins and
the fact that they live only in the water make fish different from all
other animals. |
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Fish spend all of their lives in the water and are cold-blooded with the exception of Tuna family and the Mackerel shark family. |  And some...not so much. Photo Source: Corel Web Gallery |
 Yes! A seahorse is a fish. Photo Source: Corel Web Gallery |
Scientists believe that there are more than 24,000 |
 Lion Fish or Scorpion fish Photo Source: Corel Web Gallery |
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They range in size from the largest, Whale shark at 16 m (51 ft) long, to the smallest the 8 mm (1/4 in.) Stout Infantfish. |
 The Whale Shark is the largest member of the fish family. Photo Source: Corel Web Gallery |
 Shark skeletons are made of cartilage, not bone. Photo Source: Corel Web Gallery |
Most fish have a skeleton made of bone but some, like sharks, have a skeleton made of cartilage. |
The
25,000 known species of fish are divided into three main groups.
They are the jawless, the cartilaginous (KAR-ti-LAJ-i-nus)
and the bony fish. Jawless
fish are the last survivors of the world's first vertebrate
(VUR-ta-bret)
animals, which means "back-boned".
They lack both scales and jaws.
Dating from over 5000 million years ago, only the hagfish
and lampreys remain.
Cartilaginous
fish developed about 100 million years later, ancestors of today's
sharks. The skeleton
of these fish is made of cartilage (KART-laj), which is not as
hard as bone. These fish have jaws, as well as teeth which are usually hard
and sharp. Their
bodies are covered with hard scales.
Bony
fish—fish with bony skeletons—appeared at the
same time as cartilaginous fish.
They are the largest group, with about 20,000 species.
These fish have an organ called a swim bladder which gives the
animal buoyancy (BOY-en-see), the ability to float.
All fish live in water and breathe with gills. Fish are cold-blooded, which means their internal body temperature changes as the surrounding temperature changes.
Fast Fish Facts:
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All fish
have a backbone. |
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All fish are
cold-blooded.
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There are
three classes of fish:
jawless, cartilaginous, and bony..
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Fish have
been around for 500 million years.
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There are
about 25,000 different species of fish alive today.
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There are about 20,000 different species of bony fish alive today. |
