Fish Daniel Lee
What is a fish? • Fishes are limbless aquatic vertebrates. Most fish are cold-blooded and have paired fins, scales, and gills. • Phylum: Chordata • Pharyngeal slits(gills) • Dorsal nerve cord- bundle of nerve fibers that run down the back. • Notochord- cartilaginous rod the runs underneath the nerve chord. • Post-anal tail- an extension of the body past the anus.
Evolution of Fishes • The First Fishes- were odd looking, jawless creatures whose bodies were armored with bony plates. They lived in the oceans during the Cambrian period(510 m.y.a), and kept the same body plan for the next 100 m.y.a.
Evolution of Fishes • The Age of Fishes- During the Ordovician and Silurian Periods (505-400 m.y.a), fishes went under a major adaptive radiation. The species to emerge from this ruled during the Devonian Period, which is often called the Age of Fishes. Doryaspis Hemicyclaspis Pteraspis
Evolution of Fishes • Arrival of Jaws and Paired Fins- Fishes evolved to have jaws, which made it possible for them to nibble on plants and munch on other animals. • The evolution of jaws was accompanied with the evolution of paired pectoral(anterior) and pelvic(posterior) fins. The fins gave a fish stronger control over its body movement.
Evolution of Fishes • Modern Fishes- The jawed fishes disappeared and left behind two major groups that continued to evolve and survive today: the ancestors of modern sharks and rays (skeletons made of cartilage), and skeletons made of true bone.
Feeding • Fishes consist of herbivores, carnivores, parasites, filter feeders, and detritus feeders. • Fish use their mouths to feed. For example, certain carp eat algae, aquatic plants, worms, mollusks, arthropods, dead fish, and detritus. Other fishes, such as barracuda, are highly specialized carnivores.
Respiration • Most fishes exchange gases using gills located on either side of the pharynx. The gills are made up of feathery, threadlike structures called filaments that have a large surface area for the exchange of Oxygen and Carbon Dioxide. • Some fishes such as sharks have several gill openings.
Circulation • Fishes have closed circulatory systems with a heart that pumps blood around the body in a single loop- from the heart to the gills, from the gills to the rest of the body, and back to the heart.
Excretion • Fishes rid themselves of waste in the form of ammonia. Some waters diffuse through the gills into the surrounding water. • Others are removed by kidneys, which are excretory organs that filter wastes from the blood.
Response • Fishes have well developed nervous systems around their brain. Olfactory bulbs are involved with the fish’s smelling, and the optic lobes process information from the eyes. The cerebellum coordinates body movements, and the medulla oblongata controls the functioning of many internal organs. • Many fishes also have specialized cells called chemoreceptor that are responsible for their extraordinary senses of taste and smell. Also, fishes can detect gentle currents and vibrations in the water with sensitive receptors that for the lateral line system.
Movement • Fish alternately contract paired sets of muscles on either side of the backbone. This creates a series of S-shaped curves that move down the fish’s body. The fins are used as stabilizers, and they also give a boost of speed. Many bony fishes also have a swim bladder (internal gas-filled organ) that adjusts their buoyancy.
Reproduction • Internal and external fertilization
Groups of fishes • Jawless fish • Sharks and their relatives • Boney fish
Jawless fish • Consists of hagfish and lampreys. Filter feeders and decomposers.
Sharks and their relatives • Skeletons that are entirely cartilage. Consists of filter feeders and carnivores.
Boney fish • Skeletons of Bony fish are made up of hard, calcified tissue called bone.