1. Fishes

2. Characteristics Most ancient vertebrates Endoskeleton
Gills – gas exchange
Closed-loop circulation
Kidneys

3. Movement & Response Endoskeleton Fins Swim bladder
Made of either cartilage or bone
Fins
Increase stability; help turn, dive, or climb rapidly
Swim bladder
Gas-fill sac that allows them to regulate their vertical position in water
Variety of sensory organs
Sense light, smell, taste, sound, water vibrations
Lateral line (sense organ)
System of small canals lined with sensitive cells that detect vibrations in water

4. Respiration & Circulation
Gill – major respiratory organ
Made up of rows of filaments
Fingerlike projections through which gases enter & leave the blood
Hang between a fish’s mouth & cheeks
Gill slit
Opening at rear of a fish’s cheek
Countercurrent flow
Water passes over the gills in one direction as blood flows in the opposite direction through the gill’s capillaries
Allows oxygen to diffuse into the blood over the entire length of capillaries
Can extract up to 85% of the dissolved oxygen in the water passing over the gills

6. Respiration & Circulation
Single-Loop Blood Circulation
Simple chamber-pump heart
Blood collects in the atrium.
Heart’s ventricle pumps the blood back to the gills, completing a single loop
All fishes, except lungfishes, have single-loop circulation

7. Excretion Gills and kidneys remove nitrogenous waste
Kidney – regulates body’s salt & water balance & removes wastes from the blood
Osmosis causes movement of water through membranes (such as gills & skin) toward regions of higher ion concentration.
Marine fishes lose water to their environment through osmosis
Ion (salt) concentration of sea water is 3 times that of most marine fishes’ tissues
Freshwater fishes have the opposite problem; their bodies contain more salt than surrounding water; taking in water by osmosis, diluting their body salts
Marine fishes excrete only a small amount of urine that has high salt concentration
Freshwater fishes excrete large amounts of dilute urine

8. Reproduction External fertilization Sharks, skates, & rays Spawning
Male & female gametes released near one another in the water
May occur between two individuals or in large groups of males and females
Sharks, skates, & rays
Internal fertilization
Claspers
Male organs used to insert sperm
into the female

9. Groups of Fishes Jawless Fishes Skeletons made of cartilage
Retain their notochord into adulthood
Only modern vertebrates without a backbone
Hagfish
Scavengers, predators that live at great depths
Lampreys
Parasitic, uses suction-cuplike mouth to attach to host

10. Hagfish

11. Lamprey

12. Groups of Fishes Cartilaginous Fishes
Skeletons made of cartilage, strengthened by calcium carbonate
Sharks, skates, rays, ratfishes
Sharks
Teeth are modified scales, triangular in shape, arranged in 6-10 rows
Most are predators
Except whale shark (largest shark) consumes plankton
Skates & Rays
Flattened bodies adapted to life on the sea floor
Flattened teeth used to crush their prey

14. Whale Shark

16. Groups of Fishes Bony Fishes
Strong endoskeleton made completely of bone
Structural adaptations
Lateral lines
Awareness of surroundings & detect objects in its environment
Opercula
Hard plate that covers the gills
Allows fish to move water over gills while remaining in one place
Swim bladder
Adjust the gas content to regulate buoyancy
Maintain or change its depth
Rays
Fins that are supported by bony structures