fishes agnatha chondrichthyes osteichthyes. general characteristics ectothermic vertebrates have...
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FISHES
Agnatha
Chondrichthyes
Osteichthyes
General Characteristics
Ectothermic Vertebrates Have scales Swim with fins Almost all exclusively aquatic Filter oxygen from water over gills
Classes of Fish
Agnatha – Jawless FishChondrichthyes –
Cartilagenous FishOsteichthyes – Bony Fish
Question #1:
What is the name for a person who studies fishes?
Ichthyologist
Early Fish
Earliest - Filter feeders, no jaws, no fins
Ostracoderms – jawless, heavy bony plates
Lobe finned fishes – Coelocanths
Fish Anatomy
Fins
Caudal – propels fish forward Dorsal – stabilizer Anal – stabilizer Pectoral – hold fish steady, maneuvering Pelvic – hold fish steady, maneuvering
Scale Types
Cycloid – smooth surface, on bony fish – Carp– Salmon
Ctenoid – teeth along ridge (rough to touch), on bony fish– Bass– Bluegill– Perch
Scale Types
Placoid – Look like tiny teeth, feel like sandpaper, on cartilagenous fish– Sharks– Rays
Ganoid – hard, interlocking, diamond-shaped, on primitive fish– Gar
Question #2:
What is the purpose of a fish’s scales? Shield against injury, help to move through the
water
Maintaining Buoyancy
Swim bladder – Uses air– Most bony fishes– Can be used as a second “lung”
Liver– Uses oil– Sharks– Most sharks must constantly swim to avoid
sinking
Locomotion
Use fins and body wall to push against water
Forked tails reduce drag in the waterMuscles in a zig-zag shape
– Each contraction moves large parts of the body wall
Gills
Obtain oxygen Give off carbon dioxide Most have an operculum Oxygen dropped into circulatory system
pumped by 2-chambered heart
Gas Exchange
Pump ventilationRam ventilationExchange of gases occurs in capillary
network in gill lamellae; water and blood flow in opposite directions over lamellae = Countercurrent Exchange
Countercurrent Exchange System
Excretion and Osmoregulation
Freshwater fishes – never drink– Lots of
nephrons– Ions are
reabsorbed
Marine fishes– Drink constantly– Less blood is
filtered– Water is
reabsorbed
Senses
Limited vision, focus by moving lens back and forth
Olfactory receptorsMagnetic receptorsTouch
Sense (cont.)
Hearing – sound conducted through skull
Lateral line system – senses movement of other organisms around them
Electroreception – sense electrical impulses generated by muscle twitches
Reproduction
Oviparous (most fish)– Release eggs, young develop outside mom
Ovoviviparous (some cartilaginous fishes)– Eggs remain inside mom– Eggs at a later stage of development before they
are released
Viviparous (a few sharks)– Young born alive
Class Agnatha
CartilagenousSimplest and oldest vertebratesJawlessNo scalesScavengers or parasitesLamprey, hagfish
Class Chondrichthyes
Hinged jawPaired finsScalesMuscles attached to skin, not
skeletonCartilagenous skeleton
Sharks
Jaws not attached to brain case– Can protrude during attack– 20 tons per square inch for an 8’ shark
Size varies (few inches to over 40 feet)
Variable body shapes
Skates and Rays
Wing-like pectoralsMost live on sea bedsSome have poison spines on backs
or tails (stingrays)
Class Osteichthyes
Largest group of fishesSkeleton made of bone and cartilageHinged jawsPaired finsHard, protective scalesCovered gills (operculum)
Major Groups of Osteichthyes
Subclass Sarcopterygii– Lobe-finned fishes (Coelocanth)– Lungfishes
Subclass Actinopterygii – – Ray-finned fishes
BassTunaGuppies
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