Transcript Fishes
Fish Definition of a Fish • They are aquatic vertebrates that have paired fins, scales and gills. General Characteristics • Vertebrate • Ectothermic—body temperature changes with environmental temperature • Aquatic • Endoskeleton • Integumentary system (body covering) = scales • Paired fins • Gills ECTOTHERMIC “cold blooded” • Body temperature is dependent on surrounding environment Important Definitions • Fins are used for movement. • Scales are used for protection. • Gills are used for respiration (exchanging gases. Adaptations and Evolution • Adaptations to aquatic life include various modes of feeding, specialized structures for gas exchange, and paired fins for locomotion. Integumentary system—body covering system Scalesdecrease water resistance protection growth rings increase with age Body Plan Bilateral symmetry Coloration-darker on top/lighter on bottom Body Shape-streamlined for quick/agile movements RAYS- protection from predators Feeding • All types of feeding exist in fish; herbivores, carnivores, parasites, filter feeds and detritus. Digestive Systems • From the mouth it passes down the esophagus to the stomach where the food is partially broken down. • In a lot of fish the food is broken down again by fingerlike pouches called pyloric ceca (this secretes a digestive enzyme, and also absorbs nutrients. Respiration • Most fish use gills located on either side of the pharynx. • They are feathery structures made up of filaments. • Each filament contains capillaries that provide a large surface area for gas exchange. Circulation • Draw the picture on page 776 in your notes. • Closed circulatory system with a heart that pumps blood around in a single loop. • Heart – Gills – rest of the body – back to the heart. • The heart has four parts to it. Excretion • They excrete ammonia as waste. Some is diffused through the gills, and some is removed from the kidneys. • Kidneys are also used for helping control the amount of water in fishes bodies. Response/Nervous system • They have a well developed nervous system. Draw the basic figure on page 777 • Cerebrum – Responsible for all voluntary actions. • Cerebellum – Coordinates body movement. • Medulla oblongata – controls the functioning of internal organs. Senses • Their eyesight is as good as ours and they can see in color. • They have chemoreceptors that allow them excellent smell and taste. • Their hearing is not well developed, but they can detect currents and vibrations use a lateral line system. Movement • Most fish have muscle which alternately contract causing them to move in a Sshaped movement. • Their body tissue is more dense than water so they have an internal gas filled organ known as a swim bladder. Reproduction • Eggs are fertilized internally or externally depending upon the group of fish. • Oviparous – Eggs hatch outside the mothers body. • Ovoviviparous – Eggs hatch inside of the mother and the fish are born “live”. This is true of our salmon. • Viviparous – young are born live, but they get all the nutrients from their mother not the yolk during their development. Groups of Fish • 24, 000 species of fish. • They are grouped according to body type. • They are classified into three groups: jawless fish, cartilaginous fish and bony fish. Jawless Fish • They have no true teeth or jaws. They lack vertebrae, and have skeletons made of fibers and cartilage. • They are two classes: lampreys and hagfishes. • Lampreys are filter feeds as larvae and parasites as adults. They suck up the tissue and body fluid of their host. • Hagfish have worm like bodies and four to six tentacles around their mouth. They feed on dead or dying fish by scraping a hole in the fishes side and sucking out the contents. Sharks • This phylum contains sharks, rays, skates and sawfishes. • The cartilage is very flexible tissue. The shark is completely made of cartilage. • Most of these species have an enormous number of teeth. Sharks are most carnivorous. Bony Fish • They have skeletons made up of bone.