| A | B |
|---|
| cartilage | strong connective tissue that supports the body and is softer and more flexible than bone |
| atrium | large muscular upper chamber of the heart that receives and holds blood that is about to enter the ventricle |
| ventricle | thick-walled lower chamber of the heart that pumps blood out of the heart |
| cerebrum | area of the brain responsible for all voluntary activities of the body |
| cerebellum | region of the brain that coordinates body movements |
| medulla oblongata | area of the brain that controls the functioning of many internal organs |
| lateral line system | sensitive receptor system that enable fish to detect gentle currents and vibrations in the water |
| swim bladder | internal gas-filled organ in many bony fishes that adjusts their buoyancy |
| oviparous | term used to refer to animals whose eggs hatch outside the mother’s body |
| ovoviviparous | term used to refer to animals whose young are born alive after developing in eggs inside the mother’s body |
| viviparous | term used to refer to animals that bear live young that are nourished directly by the mother’s body as they develop |
| operculum | a hard bony flap covering and protecting the gills |
| pyloric ceca | a fingerlike pouch that secretes digestive enzymes and absorbs nutrients from the digested food |
| jawless fish | fish that have no true teeth or jaws. Their skeletons are made up of fibers and cartilage |
| Class Chordrichthyes | this class contains sharks and their relatives; their entire skeleton is built out of cartilage, not bone |
| Class Osteichthyes (bony fish) | fish whose skeletons are made of hard, calcified tissue called bone |
| coelacanth | a lobe-finned, bony fish. it was thought to be extinct until it was caught in the Indian Ocean in 1938 |
| anadromous | fish that spend most of their lives in the ocean but migrate to fresh water to breed |
| catadromous | fish that live most of their lives in fresh water but migrate to the ocean to breed |
| What are the basic characteristics of a fish? | fishes are aquatic vertebrates that are characterized by paired fins, scales, and gills |
| What are the important developments during the evolution of fishes? | the evolution of jaws and the evolution of paired fins |
| How are fishes adapted for life in water? | adaptations to aquatic life include various modes of feeding, specialized structures for gas exchange, and paired fins for locomotion |
| What are the three main groups of fishes? | the jawless fishes, the sharks and their relatives, and bony fishes |
