Source: Evgeniia, "A fish with wide open mouth and big eyes, Surprised, shocked or amazed face front view", PublicDomainPictures.net, (Link to Page)

Classification

1. Jawless Fishes
• Skeleton made of cartilage(strong fibrous connective tissue)
• Retain notochord into adulthood
• Only vertebrate with no backbone


Source: Andrei Nekrassov, "Lamprey Fish", PublicDomainPictures.net, (Link to Page)



2. Cartilaginous Fishes
• Pair fin and jaw
• Cartilage strengthened by calcium carbonate
• Sharks
• Streamlined body make for fast movement through the water
• 6 - 10 row of teeth(modified scales)
• When they lose a tooth a new one comes forward
• Use more than 20,000 teeth in their lifetime
• Shark are predators but the largest shark the whale shark consume plankton instead
• Skate and Fishes
• Flattened bodies
• Rays are 1 m long, and skates are smaller
• Flattened teeth to crush prey
• Manta rays strain plankton from the water
• Some rays can discharge a powerful electric shock(stun prey or scare off predators)


Source: prochym, "blue shark, prionace glauca", PublicDomainPictures.net, (Link to Page)



3. Bony Fishes
• Majority of fish are in this group
• Possibly the most successful vertebrate
• strong endoskeleton(made of bones)


Source: aquapix, "Gelbkopf Schnapper - Snapper - Macolor macularis", PublicDomainPictures.net, (Link to Page)

Characteristics of Fishes

1. Endoskeleton: an internal skeleton made of cartilage or bone


2. Gills: a respiratory structure for fishes to obtain oxygen from the water which enter through the gill slit


3. Closed-loop circulation: 2 chambered heart that pumps blood in a single loop


4. Kidneys: maintain a fish's salt and water balance, and also metabolic waste


5. Fins: pair fin use to move in the water, and unpair fin use for stability


6. Swim bladder: Gas filled sac in bony fishes to control buoyancy


7. Lateral Line: a small canals like system that detect vibration in the water


8. Lateral Line: makes fish aware of his position and rate of movement, and also detects movement in the water


9. Opercula: a hard plate that cover the gills on each side of the head so that the fish doesn't have to keep moving to breath like the shark

More Information

• Salt and Water Balance
• Homeostasis: maintain water balance
• Salt Water Fish: they drink sea water and pump the salt out from the gills
• Fresh Water Fish: they take in salt fro their environment
• The reason that salt and freshwater fish can not go in each other's environment is that how they take in the salt and water are different.
• P.S. Salmon can be both salt and Fresh water fish


• Sexual Reproduction
• Most fish reproduce through external fertilization
• Spawning: male and female gamete are realised near one or a group in the water
• Predator may eat many of the hatchlings, but because of the large number some many survive
• Sharks, Skates, and Rays eggs are fertilized inside the female's body, and they hatch inside so that they are less likely to be eaten by other predators


• Ray-finned Fishes
• Most bony fish are Ray-finned
• Fins a supported by bony structure called rays
• Teleosts
• Mobile fin
• Thin scales
• Completely symmetrical tail(95% of all fish)
• They are successful for the fact that they suck their food toward their mouth


• Lobe-finned Fishes
• 7 species exist
• coelacanth and 6 species of lungfish
• fin are fleshy
• muscular structures supported by bones and attached to muscles