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Fishes

Table of Contents

Section 1 Introduction to Vertebrates

Section 2 Jawless and Cartilaginous Fishes

Section 3 Bony Fishes

Chapter 39



Section 1 Introduction to

Vertebrates Chapter 39

Objectives

• Identify the distinguishing characteristics of

vertebrates.

• List an example for each of the nine classes of

vertebrates.

• Describe the characteristics of the early vertebrates.

• Explain the importance of jaws and paired fins for

fishes.





Characteristics

Vertebrates are members of the subphylum

Vertebrata, within the phylum Chordata.

All Chordates share the following characteristics.

• Notochord

• Dorsal hollow nerve cord

• Pharyngeal gill slits

• Post-anal tail





Characteristics, continued

Vertebrates are distinguished from chordates by:

• Vertebrae - bones or cartilage that surround the

dorsal nerve cord and form the spine.

• A cranium - a skull that protects the brain

• An endoskeleton - an internal skeleton made of

bone or cartilage






Vertebrates are divided into nine classes: • Myxini - hagfishes • Cephalaspidomorphi - lampreys • Chondrichthyes - sharks, rays, skates, and

ratfishes • Actinopterygii - ray-finned fishes • Sarcopterygii - lobe-finned fishes • Amphibia - frogs, toads, salamanders, and

caecilians • Reptilia - lizards, snakes, and turtles • Aves - birds • Mammalia - mammals



Chapter 39

Evolutionary

Relationships

Among

Chordates


Vertebrates





Vertebrate Evolution

• Most biologists think that vertebrates originated

about 560 million years ago.

• The first fish were jawless.

• About 450 million years ago, the first fishes with

jaws and paired fins appeared.

• Jaws are thought to have evolved from the first

pair of gill arches, the skeletal elements that

support the pharynx.



Chapter 39

Evolution of Jaws


Vertebrates





Vertebrate Evolution, continued

The advantages to jaws and paired fins:

• Paired fins increased fishes’ stability and

maneuverability in water

• Jaws allowed fishes to seize and manipulate prey



Chapter 39

Origin of Jaws


Vertebrates



Chapter 39

Advantage of Paired Fins


Vertebrates



Section 2 Jawless and

Cartilaginous Fishes Chapter 39

Objectives

• Identify three characteristics that make fishes well suited to aquatic life.

• Describe three sensory systems in fish.

• Evaluate the similarities between jawless fishes and

early vertebrates. • Identify two characteristics of cartilaginous fishes. • Contrast reproduction in lampreys with reproduction

in cartilaginous fishes.





Fish Adaptations

Fish have several adaptations that make them well

suited to life in water:

• Streamlined body plan - allows fish to move

rapidly in water

• Adaptations for buoyancy - stored gases or lipids

help maintain vertical position in water

• Efficient respiration - internal gills exchange

gases efficiently





Fish Adaptations, continued

Adaptations for salt and water homeostasis -

• The concentration of solutes in a fish’s body

usually differs from the concentration of solutes

in the water.

• Fish have adaptations to maintain ion and water

homeostasis.






Sensory adaptations - Fish have a variety of organs that allow them to sense their environment.

• Sight: fish eyes are similar to eyes of land vertebrates

• Sound: fish have internal ears sensitive to sound

• Chemoreception: the ability to detect chemicals in the environment includes the senses of smell and taste. Fish have nostrils and tastebuds. Tastebuds may be located in their mouths, on their lips, fins, and skin, and on whisker-like organs called barbels.






Unique senses:

• Lateral line: the lateral line is a system of canals in the skin that allow fish to sense vibration in the water

• Ampulae of Lorenzini: cartilaginous fishes have sense organs called ampulae of Lorenzini that can detect weak electrical fields

• Electroreception and Magnetoreception: some fish have the ability to detect electrical and magnetic fields



Chapter 39

Lateral

Line in

Fishes


Cartilaginous Fishes



Chapter 39

Lateral Line System





Chapter 39

Characteristics of Fish







Jawless Fishes

Only two classes of jawless fishes are alive today:

• Hagfishes (class Myxini) Hagfishes are bottom-

dwellers that feed on dead and dying fish.

• Lampreys (class Cephalaspidomorphi) Lampreys

can be free-living or parasitic. Parasitic lampreys

attach themselves to their host with disc-shaped

mouths and feed on the blood and body fluids of

other fishes. All lampreys breed in fresh water.

Fertilization occurs outside the body - external

fertilization.






All cartilaginous fishes:

• belong to the class Chondrichthyes.

• have skeletons made of cartilage - a flexible lightweight material made of cells surrounded by tough fibers of protein.

• have skin covered with placoid scales - small, toothlike spines that feel like sandpaper. Placoid scales probably reduce turbulence and increase swimming efficiency.





Cartilaginous Fishes, continued

Sharks:

• Sharks have torpedo shaped bodies that reduce turbulence when swimming, called a fusiform body shape.

• Some sharks are filter feeders, and have slender projections on the inner surface of their gills, called gill rakers, that filter the water.

• The mouth of a typical shark has 6 to 20 rows of teeth. When a tooth breaks or wears down, a replacement moves forward. One shark may use more than 20,000 teeth over its lifetime.






Rays and Skates:

• Rays and skates have flattened bodies with

paired wing-like pectoral fins and, in some

species, whip-like tails.

• Rays have diamond- or disk-shaped bodies. Most

skates have triangular bodies.

• Rays and skates are primarily bottom dwellers,

and most feed on mollusks and crustaceans.






Ratfishes:

• Ratfishes are a small group of strange looking fish that have a flap of skin covering their gill slits.

• Ratfishes have long, rat-like tails and feed on crustaceans and mollusks.






Adaptations in Cartilaginous Fishes:

• Some sharks push water through their mouth and over their gills by swimming.

• Most cartilaginous fish pump water over their gills by expanding and contracting their mouth cavity and pharynx.

• When lying on the bottom, rays and skates draw water in to their gills through spiracles, two large openings on the top of the head, behind the eyes.







• Sharks convert ammonia to urea in their bodies.

• Sharks retain large amounts of urea in their bodies to raise the concentration of solutes in their bodies to the same level as that found in sea water.

• Sharks still tend to take up sodium and chloride ions.

• The rectal gland removes excess sodium and chloride ions from the body.







Cartilaginous fishes maintain their position in the water in two ways.

1. The caudal and pectoral fins generate lift, or upward force, as the fish swims.

2. Many cartilaginous fish store large amounts of lipids, usually in the liver. Lipids are less dense than water.






Reproduction in Cartilaginous Fishes:

• Fertilization occurs inside the body of the female, called internal fertilization.

• Some cartilaginous fish lay eggs.

• The eggs of many species develop within the female’s body.

• In some species, the mother nourishes the developing young while they are in her body.




Chapter 39

Objectives

• List three characteristics of bony fishes.

• Distinguish between lobe- finned fishes and ray-finned

fishes.

• Describe three key features of bony fishes’ external

anatomy.

• Summarize the major body systems in bony fishes.

• Describe the function of the swim bladder.

• Discuss reproduction in bony fishes.




Chapter 39

Characteristics of Bony Fishes

Bony fishes have three key features:

• Bone - the skeletons of most bony fishes contain

bone.

• Lungs or swim bladder - early bony fishes had lungs,

organs which exchange gas between the air and

blood. Most bony fishes today have a swim bladder, a

gas-filed sac that is used to control buoyancy.

• Scales - scales protect the body of a bony fish and

reduce friction when swimming.



Chapter 39

Swim Bladder

in Bony Fish




Chapter 39

Swim Bladder





Chapter 39


There are two main groups of bony fishes:

• Lobe-finned fishes - have fleshy fins supported

by a series of bone.

• Ray-finned fishes - have fins that are supported

by long, segmented, flexible bony elements called

rays.



Chapter 39

Characteristics of Bony Fishes




Chapter 39

Ray-Finned Fishes





Chapter 39

External Anatomy

• Operculum Most bony fish have an operculum, a

hard plate that opens at the rear and covers and

protects the gills.

• Fins The fins of most fish are supported by rays or

spines. Rays are flexible, spines are rigid.

• Skin The skin of most bony fish are covered with

scales. Scales are thin, round disks of a bonelike

material that grow from pockets in the skin and

overlap like shingles.



Chapter 39

External Structures of Fish—Yellow Perch




Chapter 39

Anatomy of a Bony Fish





Chapter 39

Internal Anatomy

• Skeleton The major parts of a fish’s skeleton are the

skull, spinal column, pectoral girdle, pelvic girdle, and ribs.




Chapter 39

Internal Anatomy, continued

Digestive system

Food passes from the mouth into the pharynx, through

the esophagus, to the stomach. From the stomach

food passes into the intestine, where nutrients are

absorbed. Undigested material is eliminated through

the anus.



Chapter 39

Internal Structure of Fishes—Yellow Perch





Chapter 39


Circulatory system The circulatory system of a fish delivers oxygen and

nutrients to the cells of the body. The circulatory system consists of a heart, blood

vessels, and blood. The heart pumps blood through arteries to small, thin-

walled vessels called capillaries, in the gills. From the gills, the blood travels to the body tissues, where nutrients and wastes are exchanged. The blood returns to the heart through veins.




Chapter 39


Circulatory system The heart of a bony fish has two chambers in a row, as

shown below. Blood from the body enters the sinus venosus, moves into the atrium, then into the ventricle. From the ventricle it enters the conus arteriosus, and then goes to the gills.



Chapter 39

Fish Heart Structure




Chapter 39

Fish Heart and Single-Loop Circulation





Chapter 39


Respiratory system • Fish use gills for gas exchange.

• Water flows across the gill filaments in a direction

opposite to blood flow, called countercurrent flow.

• Countercurrent flow allows more oxygen to diffuse into the blood than would be possible if blood and water flowed in the same direction.



Chapter 39

Respiration in Fishes




Chapter 39

Parts of Fish Gills and Countercurrent Flow





Chapter 39


Excretory system • The kidneys filter chemical wastes from the blood to

form urine, a solution containing ammonia, ions such as salts, and water.

• The kidneys help regulate the ion and water balance in fish.

• The gills also allow wastes to diffuse from the blood into the water and help regulate ion and water balance in fish.



Chapter 39

Fish Kidneys




Chapter 39

Parts of a Nephron





Chapter 39


Swim bladder • The swim bladder is a thin-walled sac in the abdominal

cavity that contains a mixture of oxygen, carbon dioxide, and nitrogen obtained from the bloodstream.

• Swim bladders evolved from balloonlike lungs, which ancestral bony fishes may have used to supplement the oxygen absorbed by the gills.

• In some fish the swim bladder is known to amplify sound by vibrating and transmitting sound to the inner ear.




Chapter 39


Nervous system

The nervous system of a bony fish includes the brain, spinal

cord, nerves, and various sensory organs.

The fish brain consists of several parts:

• Olfactory bulb - processes information about smell

• Cerebrum - integrates information from other parts of the

brain

• Optic tectum - processes information about sight and from the

lateral line system

• Cerebellum - coordinates muscle movement and balance

• Medulla oblongata - controls the function of some organs

and relays information from the spinal cord




Chapter 39


Nervous system The fish brain has a well-developed medulla to

coordinate muscle control.




Chapter 39

Reproduction

Spawning • Reproductive behavior in bony fishes is called

spawning.

• Fertilization in most fish takes place outside the body.

• Many species of fishes lay large numbers of eggs.

• Some species of fish carry the eggs within their bodies until the eggs hatch.



Multiple Choice

1. Which of the following is true of sharks and rays?

A. They have lungs.

B. They have placoid scales.

C. Most species live in fresh water.

D. They do not have a lateral line system.

Standardized Test Prep Chapter 39



Multiple Choice, continued

2. Which of the following is not involved in controlling

buoyancy?

F. a fat-filled liver

G. the rectal gland

H. the swim bladder

J. continuous swimming





3. What is the function of the lateral line system?

A. initiates migration

B. detects vibrations

C. acts as camouflage

D. keeps fish moving in a straight line





4. What do sharks use claspers for?

F. startle other fish

G. increase maneuverability

H. transfer sperm while mating

J. hold on to prey while feeding





Interpreting graphics

The table below shows the salinity of fresh water, salt

water, and the body fluids of fish. Use the table to

answer questions 5 and 6.





5. What tendency do freshwater fish have in a

freshwater environment?

A. lose water and salts

B. take on water and salts

C. take on water and lose salts

D. lose water and take on salts





6. What tendency do saltwater fish have in a saltwater

environment?

F. lose water and salts

G. take on water and salts

H. lose water and take on salts

J. take on water and lose salts





7. Bony fishes : Osteichthyes :: Shark :

A. Aves

B. Agnatha

C. Mammalia

D. Chondrichthyes





The figure below shows the external anatomy of a bony

fish. Use the figure to answer the following question.





8. Which of the fins shown on the fish are dorsal fins?

F. 1 & 2

G. 2 & 4

H. 5 & 6

J. 5 & 4




Short Response

Countercurrent flow enhances the diffusion of

oxygen from water into the bloodstream of

fishes.

Explain the meaning of countercurrent flow in gills.




Short Response, continued

Countercurrent flow enhances the diffusion of

oxygen from water into the bloodstream of

fishes.

Explain the meaning of countercurrent flow in gills.

Answer: In countercurrent flow, water flows over

fishes’ gills in a direction opposite to blood flow.

This allows for efficient gas exchange.





Extended Response

Base your answers to parts A & B on the information below.

Humans have a four chambered heart with two ventricles. One ventricle pumps blood to the lungs and the other pumps blood that returns from the lungs to the body.

Part A Compare the structure and blood flow of the fish heart to the human heart.

Part B Which heart is able to pump blood more forcefully around the body? Why?




Extended Response, continued

Answer:

Part A The fish heart has a collecting area, a simple

atrium-ventricle arrangement, and an elastic exit

chamber. Blood with or without O2 is not separated

in the fish heart. The human heart’s two circuits

separate oxygenated and deoxygenated blood.

Part B: The human heart can pump blood more

forcefully since it has essentially two pumps. Since

one pump pumps blood to the lungs, the other can be

dedicated to pumping blood to the rest of the body.

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