Fishes

Chapter 11 Section 2

Characteristics of Fishes Vertebrate Lives in the water Uses fins to move Ectotherms Obtain oxygen through gills Have scales

Obtaining Oxygen Fishes get oxygen from the water

Fish gulps water (water contains oxygen) Moves through openings in fish’s throat to

the gills Water flows over gills Oxygen moves from water into the fish’s

blood

Circulatory System Closed circulatory system

Heart has two chambers, or inner spaces Pumps blood in one

loopHeart to the gillsGills to rest of the body

Back to heart

Movement

Fins help fish swim Thin membrane

stretched across bony supports

Fin provides large surface to push against the water (canoe paddle)

Movement is related to obtaining food and reproduction

Reproduction External fertilization: the eggs are

fertilized outside the female’s body Male hovers close to female and spreads a cloud of sperm cells over the eggs

Internal fertilization: giving birth to live young Sharks Guppies

Nervous System Nervous system and sense organs of

fishes help them find food and avoid predators

Keen sense of touch, smell, and taste help fishes capture food

Major Groups of Fishes

JawlessCartilaginousBony

Jawless Fishes

No jaws or scales Have mouths instead (scraping, stabbing,

and sucking their food) Cartilage: tissue that is more flexible than bone Examples

Hagfish Look like large, slimy worms

Lampreys Can be parasites Use sharp teeth and suction

cup mouths to feed on other fishes Eel-shaped bodies

Cartilaginous Fishes Have jaws and scales, and

skeletons made of cartilage Most sharks cannot pump water

over their gills, rely on swimming or currents to keep water moving across gills

Rays and skate take in water through small holes located behind their eyes

Usually carnivores Sharks: attack and eat nearly

anything that smells like food, many rows of teeth

Rays and skates: hunt on ocean floor, crushing mollusks, crustaceans, and small fishes with their teeth

Bony Fishes Examples: trout, tuna, goldfish Have jaws, scales, a pocket on each side of the head that holds the gills, and a skeleton made of hard bones

Fins: help the fish stay upright Scales: cover the body by overlapping

each other Gill Pocket: holds the gills Swim Bladder: helps stabilize the fish

at different depths in the water

Diversity of Bony Fishes