Fish…our friends in the water

Porcupine Fish

Great White Shark

Barreleye

Characteristics of Fish• 20,000 species• Found in all types of water• i.e: Fresh, salt, sunless, polluted,

warm, cold, etc.• Ectothermic

Respiration

• Respire using gills• H2O enters mouth. • Water passes over gills• Water then passes out slits on side of

fish• O2 and CO2 are exchanged through

capillaries (small blood vessels) in gills

Circulation• Two-chambered heart• 1-chamber received deoxygenated

blood• 2nd-chamber pumps blood to gills. • Oxygen picked up and dispersed to rest

of body• Carbon dioxide is released• Slow process

Nervous/Reproductive System

• Lateral line---mechanism that detects movements and vibrations.

• Some fish can smell

• Two sexes (male and female)• External fertilization

3 Classes of Fish

•Jawless (Agnatha)•Cartilaginous (Chondrichthyes)

•Bony (Osteichthyes)

Jawless Fish• Sharp teeth used to “drill” hole in

animal• Blood sucked out of hole• Endoskeleton made of cartilage• No scales or paired fins

• Examples: Lamprey, hagfish

Cartilaginous Fish• Endoskeleton made up of cartilage• Skilled predators (typically found near

floor of water source)• Electroreception• Scales

• Examples: Sharks, rays

Bony Fish• Endoskeleton made up of bones• Lateral line system (pressure change and

swim with no light)• Swim bladder (allows fish to float)• Scales (reduces friction)• Majority of fish

• Examples: Salmon, Trout, Catfish