Phylum Chordata

Subphylum Vertebrata

Body Structure

external image fishana1.gif Even though the body structures of each fish depends on the environment of the fish, here are a few common parts.... Eye - The fish eye helps the fish see. Helps it see food or any predators. There are three locations of the mouth in fish that tells the fish's feeding habits. Surface feeding fish usually have an undershot, upturned mouth for feeding on insects. Fish that feed in mid water have a terminal mouth which is usually considered the “normal” fish mouth. Predatory fish usually have a wide mouth, while fish that eat plants have smaller mouths. Bottom feeding fish generally have an underslung or inferior mouth. Often, bottom feeding fish are also equipped with barbels (“whiskers”), which are used for locating food in dark or muddy waters. Some fish that live on the bottom of the ocean, especially the Loricarids , have a suction-cup like mouth used to scrape algae, wood, plants, or mud (for small food). Scales - Most fish are covered with scales which protect the body. Some fish such as catfish have bony plates which do the same thing. Other species have very small scales or no scales at all. They are covered with scales and provided with two sets of paired and many unpaired fins. Gills -The gills of a fish act like lungs. The gills Fish-Anatomy.jpgtake gases that are exchanged between the fish and the surrounding water. Through the gills, fish are able to take in carbon oxygen and carbon. Swimbladder -The swimbladder is a unique organ found only in fish and is sometimes called the 'air bladder.' It is a smooth, gas-filled organ found in the abdomen of most fish. A fish will either add to or decrease the amount of air in the bladder to help it move up or down in the water. Without the air bladder, the fish would have to swim continuously to keep from sinking to the bottom. By adjusting the amount of air in the bladder, fish can adjust the depth at which they float and extend very little energy in the process. One other benefit of the air bladder in some species is that it can be used to receive or emit sounds.
Color - Color is made by the pigment of the fish and the light reflection. Fish with solid, dark coloration usually have pigmented skin, while species with silvery iridescence rely on light reflection. Some species are able to change their coloration, while some fish use different coloration at night. Healthy fish are almost always more colorful than unhealthy one. Some fish are one solid color, but some also have spots or stripes.

Obtaining Food

Most species of fish swim to their prey and then they consume it. Some fish such as halibut lie on the bottom of the ocean floor, cover themselves with sand, and wait to strike their prey. Smaller, herbivorous fish, feed on kelp or other plants they can find. Fish swallow their meal whole. Sharks usually tear off bites and swallow their meal. Seahorses use their mouths like a straw to suck up little shrimp and fish. Some fish surprise prey with a giant gulp of their huge mouth that sucks the prey in instantly.


Fish reproduce by external fertilization. In most fish the mom lays about 100 eggs and then the dad comes and fertilizes it with his sperm in the water nearby. To protect their eggs some fish build a nest and others keep the fish in there mouths. The water provides lots of dissolved oxygen and nutrients. Lots of the new born fish don't live to be adults because they have many prey and are often eaten. The eggs contain a material that will give the young fish nourishment in their first stages of life.


The fish has to rely on many things in order for the fish to swim. Its needs its skeleton to keep its body in a good framework. It needs its muscles to give the fish its power,and the muscles are 80% of the fish. The last thing a fish needs in order to swim it needs fins to keep it going in a good direction and for thrust. The density of the water is very hard to swim through but fish can move smoothly and fast through the water. Fins also help guide the fish through the water.


There are many different types of adaptations for fish. One of then is to blow up like the puffer fish, have very sharp spikes that have poison in them like the stingray and the lion fish.Some fish have a very hard skeleton so when something hits there body they will not get hurt. Some fish are immune to stinging cells.

Importance to Humans

Fish are important to humans in a big way we use them for food, pets and lots of other products we use in our every day lives. Like the Yellow tail tuna is a favorite in seafood restaurants all over the world. Every day people will have a fish in a bowl. Fish take up a lot of the ocean, and keep the food chain maintained. Without fish, other organisms would overpopulate the ocean, and our entire ecosystem would collapse. Fish are a big part of our lives.


images.jpegOsteichthyes (Bony Fish)

Osteichthyes fish include ray-finned fish and lobe finned fish. The majority of fish are Osteichthyes consisting of 29,000 different kinds of species.

images-1.jpegChondrichthyes (Cartilaginous Fish)

Cartilaginous fish include Stingrays and Sharks.
They have paired fins, paired nostrils, scales, two chambered hearts, and skeletons made of cartilage.

r609hagfish_532.jpgAgnatha (Jawless Fish)

There are not many types of jawless fish (two to be exact). There is the lamprey and the hagfish. They have cartilaginous skin. The Lamprey and the Hagfish are the extent of the groups, but there are about 100 species of jawless fish. Instead of jaws, agnathans have cyclostomic They use this to stick on to prey and suck out the blood. Agnathans also lack an internal skeleton. Their skeleton mainly consists of cartilage.