Chapter 30 Fish

360 to 400 million years ago-

These are the most primitive vertebrates. Jawless Fish These are the most primitive vertebrates.              A hagfish.

A sea lamprey.

Lamprey on trout

IV.  Fishes             A.  Vertebrate jaws evolved from skeletal supports of    Jaws and fins allowed fish to become active in pursuit of food and in biting off chunks of flesh. Members of group are chondrichthyes and osteichthyes. They have two pairs of fins.  

Respiratory Structures Gills Made of feathery thread-like structures called filaments. Each filament contains a network of capillaries for the exchange of oxygen and carbon dioxide. Fishes exchange gases by pulling oxygen-rich water in through their mouths, pumping it over their gill filaments, and then pushing oxygen-poor water out through gill openings.

Circulation in fish Two chambered heart

360 to 400 million years ago- the “Age of Fishes”    Two groups are alive today: Class Chondricthyes:  Sharks and Rays have cartilaginous skeletons. Skin made of denticles Nerve center Stream lined body Rigid Pectoral fins used for lift Liver secretes oil to change depth

Shark Skin Shark skin feels like sandpaper because it has small scales known as denticles.  It is often dried and used as a leather product or sandpaper. Denticles are homologous in structure to teeth, and are what gives the skin a rough feeling.

Ampullae Counter shading

Osteichthyes: “bony fishes” Paired fins that move independently swim bladder to change depth quickly lateral line: line of sensitive nerve endings Scales for protection and flexibility Ray finned

Great Lakes Some of the natives Lake trout Whitefish Sturgeon Ray finned Great Lakes Walleye Some of the natives

Lobe finned fishes Coelacanth

Sea to land

Excretion.. Lol c: Kidney Helps control the amount of water in their bodies. Fish in saltwater tend to lose water, so their kidneys concentrate the waste in the form of ammonia, which contains very little water and helps control water loss. Fish in freshwater tend to gain water, so their kidneys produce very dilute urine which contains an abundance of water.

Fish Spawning: females laying eggs and males fertilizing them externally Roe: fertilized fish eggs Milt is the seminal fluid from males that fertilizes The eggs Fry: baby fish

Reproduction Internal or external fertilization. Oviparous- Female lays the eggs and the embryos in the eggs develop and hatch outside her body. Ovoviviparous- The eggs stay in the mother's body after internal fertilization and embryo develops inside egg and obtain nourishment from the egg; the young are “born alive”. Viviparous- The embryos stay inside the mother’s body after internal fertilization and obtain nourishment from mother’s body, not egg; the young are “born alive”.