The Fish

ClassificationThe term “Fish” refers to three different

vertebrate classes: Agnatha—jawless fish Chrondrichthyes—cartilaginous fish Osteichthyes—bony fish

The FishAdaptations that enable fish to be

successful in the water: stream-lined shape muscular tail—move rapidly paired fins—move r and l, up or down,

backward or forward

The Fish unpaired fins on the back and belly—

increase stability mucus secretion—reduces friction

when swimming

The Fish Fish body position:The tissue in a fish’s body are denser

than water and by controlling the amount of gas in their bodies helps to regulate vertical position (swim bladders)

They store lipids, which are less dense than water, to help them float.

HomeostasisHomeostasis—stable internal conditions

of a living thing

Bodies of freshwater fish have a higher concentration of solutes than the surrounding water so the fish tend to gain H2O through osmosis and lose ions, such as Na+ and Cl- through diffusion

HomeostasisSaltwater fish contain lower

concentrations of solutes than their surroundings so the fish tend to lose water and gain ions.

Kidneys and gills play an important role in maintaining homeostasis in the tissues and ridding the body of metabolic wastes

HomeostasisSome fish may move from fresh to salt

water by adjusting kidney functions

Respiration

The presence of scales limit gas exchange through the skin, so fish rely on membranes of the gills for oxygen and carbon dioxide to diffuse

Gills are located on either side of the pharynx and are composed of feathery, threadlike structures called filaments

RespirationEach filament has a network of fine capillaries

that provides a large surface area for the exchange of CO2 and O2.

Fish pull O2 rich water in through their mouths, pumping it over their gill filaments and pushing the O2 poor water out through openings in the sides of the pharynx

RespirationLamprey and shark have several gill

openings, but most have a single gill opening on each side of their bodies.

The opening is hidden beneath a protective bony cover called the operculum.

RespirationLungfish have an adaptation that allows

them to survive in O2 poor water or in areas where bodies of H2O dry up

They have specialized organs that serve as lungs and a tube brings O2 from the air to this organ in their mouth

RespirationSome lungfish are so dependent on O2

from the air that they will suffocate if they don’t reach the surface

Other lungfish can actually burrow into mud, cover itself with mucus and lay dormant for months until rain falls.

Feeding Fish can be herbivores, carnivores,

parasites, filter feeders, or detritus feeders (organic matter). A single fish may exhibit several modes of feeding, depending on what is available.

EX: Carp eat algae, aquatic plants, worms, mollusks, arthropods, dead fish and organic matter.

Feeding EX: Barracudas are highly specialized

carnivores EX: Some lampreys are parasitic.

Digestion From the mouth, food passes through

the esophagus to the stomach where it is partially broken down.

The pyloric ceca, in many fish, are finger-like pouches that further digest food. It secretes digestive enzymes and absorbs nutrients.

Digestion The liver and the pancreas add

enzymes and other digestive chemicals to the food as it moves through the digestive tract.

Intestines complete the process of digestion and absorption of nutrients.

Digestion Undigested material is eliminated

through the anus.

Excretion Nitrogenous wastes are eliminated in

the form of ammonia by diffusion through the gills into the water, or removed by the kidneys, which filter wastes from the blood

Kidneys also help control the amount of H2O in their bodies.

Response Fish have well developed nervous systems,

organized around a brain. The most anterior parts are the olfactory

bulbs, which are involved with the sense of smell, which is the primary sense in the fish.

They are connected to two lobes of the cerebrum. The cerebrum is responsible for all voluntary activities of the body.

Response Optic lobes process info from the eyes.

The cerebellum coordinates body movement.

The medulla oblongata controls the functioning of many internal organs.

Response Most fish have highly developed

sense organs. Almost all fish that are active in

daylight have well developed eyes with color vision that is as good as ours.

Chemoreceptors are responsible for sense of taste and smell.

Response Most fish have ears inside their head,

they may not hear sounds well, but they can detect gentle currents and vibrations with a sensitive receptor called the lateral line system. It is a row of sensory structures that run the length of the body on each side and are connected (by nerves) to the brain

Response Catfish and shark can detect low

levels of electric current.

The electric eel can generates its own electricity.

Circulation

Fish have a closed circulatory system The heart pumps blood around the

body in a single loop-heart to the gills to rest of the

body and back to the heart

Circulation

The heart consists of four parts (only two chambers) sinus venosus—thin walled sac that

collects blood from the fish’s veins before it flows to the atrium

atrium—large muscular chamber that serves as a one-way compartment for blood that is about enter the ventricle

Circulation

ventricle—thick walled, muscular chamber, the pumping portion

bulbus arteriosus—large, muscular tube, connects to a large blood vessel called the aorta

Movement

Fish move by alternately contracting 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. As the curve travels down the body of the fish it creates a backward force on the surrounding water. This force, along with the action of the fins, propels the fish forward.

Movement

Fins are used to stay on course and adjust direction and provide an extra boost of speed. A swim bladder is used to adjust buoyancy and is located beneath the backbone and is an internal gas-filled organ.

Reproduction

Eggs are fertilized either internally or externally depending on the species.

In many species, females lay the eggs and the embryos in the eggs hatch outside the mother’s body (oviparous). Embryos obtain food from the yolk in the egg. EX: Salmon

Reproduction

In other species, eggs stay in the mother’s body after internal fertilization, each embryo develops inside its own egg, using the yolk for nourishment. The young are born alive (ovoviviparous). EX: guppies

Reproduction A few species of fish, including several

sharks are viviparous, the embryos stay inside the mother’s body, but they receive nourishment directly from the mother’s body and are also born alive.

Fish Classification

Class Agnatha 80 species hagfish and lampreys jawless fish, skin has neither plates nor

scales have an eel-like body and a

cartilaginous skeleton with unpaired fins notochord remains throughout life

Fish Classification Class Chondrichthyes have skeletons composed of cartilage (a

flexible, lightweight material made of cells surrounded by tough fibers of protein)

have moveable jaws have paired fins approx. 800 species of sharks, skates and

rays live in salt water

Fish Classification all species are carnivores (some are

scavengers) that eat many different kinds of food,

including fish, seals, aquatic invertebrates and plankton.

are covered with placoid scales—small, tooth- like spines that feel like sandpaper. These scales reduce turbulence in the water and increase swimming efficiency.

ClassificationSharks Largest sharks, the whale shark, up to 59 ft

in length and the basking shark up to 49 ft in length. They eat plankton.

They have large, curved tails, torpedo-shaped bodies and pointed snouts. Sharks swim in a side to side pattern created by the motion of their asymmetrical tail fin.

Classification Paired pectoral fins are located

behind the head and jut out like the wings of a plane.

Their mouth has 6 to 20 rows of teeth that point inward. When a tooth in a front row breaks or wears down, a replacement moves forward to take its place. They may have more than 2000 teeth over a lifetime.

ClassificationRays and Skates have flattened bodies paired wing-like pectoral fins some species have whip-like tails rays have diamond or disk-shaped

bodies, skates have a triangular body

Classification 3.3 ft long or less bottom dwellers flat shape and coloration are used as

camouflage on the ocean floor feed on mollusks and crustaceans

Bony Fishes-ClassOsteichthyes

Period of Fish is known as the Devonian Period.

Fish were the first vertebrates to evolve and early fish were jawless and covered with bony plates.

Bony Fish are characterized by three features:

Bony Fish Skeleton made of bone Lungs or swim bladder *only a few fish have lungs today (are

called the lung fish) *most have swim bladders (a gas-filled

sac that is used to control buoyancy). Swim bladders are thought to have evolved from the lungs of early bony fishes.

Bony FishScales-most bony fish are covered with

scales protect the fish reduce water resistance

Bony FishBiologists have divided the bony fish

into two main groups: lobe-finned fish ray-finned fish

Bony Fish Lobe-finned fish-have fleshy fins that are

supported by a series of bones, lobes are bony and rigid. Only 7 species exist today. (six species of lungfish and one species of coelacanth)

Lungfish exchange gases through the lungs and gills and live in shallow tropical ponds that periodically dry up, they burrow into the mud and cover themselves with mucus to stay moist until the pond refills.

Bony Fish These fish are important because

extinct lobe-finned fish are thought to be ancestors of amphibians and all other terrestrial vertebrates

Bony Fish Ray-finned fish-have fins that are

supported by long, segmented, flexible bony elements called rays, which are bony yet flexible. Rays probably evolved from scales. These fish are very diverse in appearance, behavior and habitat. (EX. eels, yellow perch, trout, salmon, guppies, bass, herring and darters)

Bony Fish Countercurrent flow-in gills of fish,

an arrangement where water flows away from the head, and blood flows toward the head, if blood and water flowed in the same direction, less O2 would be diffused