17.2 FISHES Page 348
May 11, 2015
17.2 FISHESPage 348
Gills
Organs that remove dissolved oxygen from water
Located on either side of fish’s head
Gills
How Gills Work
Water passes over gills as a fish swims
Oxygen in the water diffuses into cells at the surface of the gills
As this happens, carbon dioxide diffuses out of blood vessels into the water
Characteristics of Fish
All fish are ectotherms Most have streamlined bodies
and use fins for movement Most have excellent sense of
smell All have highly developed
nervous systems
3 Classes of Fish
1. Jawless Fish {Agnatha}
2. Cartilaginous Fish {Chondrichthyes}
3. Bony Fish {Osteichthyes}
Jawless Fish
Vertebrates (have backbone) Lack jaws Probably filter feeders Only a few species exist today
› Lampreys & Hagfish Parasites – their mouth is a sucker used to
attach to “hosts” and feed
Jawless Fish
LAMPREY
HAGFISH
Cartilaginous Fish
Cartilage: firm, but flexible, connective tissue
Cartilaginous fish have skeletons made completely of cartilage
Have jaws Most are carnivores – sharp teeth &
senses Some are filter feeders (whale shark)
Cartilaginous Fish
Some are filter feeders (whale shark) Bodies are more dense than water –
must keep swimming to stay off ocean floor
Swimming also creates current of water which passes over gills – supplies fish with oxygen
Cartilaginous Fish Examples
STINGRAY
SHARK
WHALE SHARK
Bony Fish
Greatest number of fish belong to this class
Have skeletons made of bone
Bony Fish Examples
SALMON
CATFISH
GOLDFISH
Bony Fish Anatomy
1. Swim Bladder Helps conserve energy Similar to a balloon Used to adjust their depth Inflating the bladder with right amount of
air keeps fish from sinking
Bony Fish Anatomy
Buoyancy
Buoyancy: force of liquid pushing an object up
If the weight of an object…. Is greater than the buoyant force, it will
sink Is less than buoyant force, it will float Is equal to the buoyant force, it will
stay at any level (FISH)
Buoyancy IllustratedBUOYANCY: force of liquid
pushing an object up
Bony Fish Anatomy…
2. Scales & Fins Outside covered with layer of smooth scales Overlap each other Scales covered with thin layer of mucus
Scales and mucus are adaptations that help fish move through water
Fins are adapted for swimming and guiding the fish
Scales
Scales and mucus are adaptations that
help fish move through water
Gills & Lungs
Bony fish DON’T need to swim to move water over gills (cartilaginous fish DO)
Have ability to pump water through mouth into the gill chamber
MOST bony fish depend only on gills, some on both gills and lungs› These fish must swim to surface of water
for oxygen
Gills & Lungs
The African Lungfish has both gills and lungs