FishesAmphibians Fishes and Amphibians Chapter 28

FishesFishes and AmphibiansAmphibians

Chapter 28

• Fishes, like all vertebrates, are classified in the phylum Chordata.

• Fishes belong to the subphylum Vertebrata.

What is a fish?What is a fish?

Section 28.1


• In addition to fishes, subphylum Vertebrata includes amphibians, reptiles, birds, and mammals.

• In vertebrates, the embryo’s notochord is replaced by a backbone in adult animals.

• All vertebrates are bilaterally symmetrical, coelomates that have endoskeletons,( made of cartilage or bone) closed circulatory systems, nervous systems with complex brains and sense organs, and efficient respiratory systems.

• * is a tough, flexible material


Neural Crest

A neural crest is a group of cells that develop from the nerve cord in vertebrates.

Fishes and Amphibians

Portions of the brain and skull, certain sense organs, and some nerve fibers are some of the structures that develop from the neural crest.

Fishes

Section 1

• Despite the variation – all fish have Gills, single loop blood circulation, and a backbone.

1.Fish breathe using gills

• Fish have gills made up of feathery gill gill filamentsfilaments that contain tiny blood vessels through which gases enter and leave the blood.

Key Characteristics of Modern FishesKey Characteristics of Modern FishesKey Characteristics of Modern FishesKey Characteristics of Modern Fishes

Gill Filaments

• As a fish takes water in through its mouth, water passes over the gills and then out through gill slitsgill slits at the side of the fish.

• Gill cover= operculum

Fishes breathe using gillsFishes breathe using gills

Gill Filaments

Capillary networksin filament Gill

filaments

Water

Water

Artery

Vein

• Oxygen and carbon dioxide are exchanged through the capillaries in the gill filaments. In a countercurrent flowcountercurrent flow.(=blood flows in one direction and water in the opposite direction.)

2. Single-loop blood circulation-

• Blood is pumped from the heart to the capillaries in the gills.

• From the gillsgills, blood passes to the rest of the body and then returns to the Heart.

• a.) Sinus Venous- collection chamber- reduces the resistance of blood flow into the heart.

• b.) Atrium- delivers blood to ventricle• c.) Ventricle- forces blood to flow through the gills and

eventually to the rest of the body.• d.) Conus arteriosus- smoothes the pulsations and

adds still more force. • Lungfishes are an exception they have a double loop.

Fishes have two-chambered heartsFishes have two-chambered hearts

Heart

Gills

Aorta

Capillary network

• Although the method may vary, all fishes reproduce sexually.

5. Reproduction5. Reproduction

• Fertilization and development is external in most fishes.

• Eggs and sperm can be released directly into the water, or deposited in more protected areas, such as on floating aquatic plants.

• A yolk sac within each egg contains nutrients the developing embryo will need for growth.

• Most bony fishes have external fertilization and development.

Fishes reproduce sexuallyFishes reproduce sexually

• This type of external reproduction in fishes and some other animals is called spawning.

Salmon spawning

• Cartilaginous fishes have internal fertilization.


• Skates deposit fertilized eggs on the ocean floor.

• Some female sharks and rays carry developing young inside their bodies.

• A few species of sharks lay eggs.

• During mating, the male uses two organs called claspers to insert sperm into the female.

• In some bony fishes, such as guppies and mollies, fertilization and development is internal.


• Most fishes that produce millions of eggs provide no care for their offspring after spawning.

• Some fishes, such as the mouth-brooding cichlids, stay with their young after they hatch.

• Fishes in the classes Chondrichthyes and Osteichthyes have paired fins.

Most fishes have paired finsMost fishes have paired fins

• Fins are fan-shaped membranes that are used for balance, swimming, and steering.

3. Vertebral column (backbone)Vertebral column (backbone)• made of either cartilage or bone• Surrounds the spinal cord• Brain is encased with the skull or cranium.4. Kidneys-Kidneys- NephronsNephrons- - are tube-like units that regulate the

body’s salt and water balance and remove metabolic wastes from the blood.Freshwater fish excrete large amounts of urine compared to marine fish due to osmosis and ion ion exchange.

* to make up for the water they lose by osmosis, marine fish drink sea water & pump out excess ions out of their bodies.

Most fishes have paired finsMost fishes have paired fins• Fins are attached to and supported by the

endoskeleton and are important in locomotion.

• The paired fins of fishes foreshadowed the development of limbs for movement on land and ultimately of wings for flying.

Most fishes have paired finsMost fishes have paired fins

Caudal fin

Anal fin

Pelvicfins

Pectoralfin

Dorsal fins

Fishes have developed sensory systemsFishes have developed sensory systems• The lateral line system is a line of fluid-filled

canals running along the sides of a fish that enable it to detect movement and vibrations in the water.

Lateral line

Receptor cellsGelatin-like fluid

Nerve

• Fishes have eyes that allow them to see objects and contrasts between light and dark in the water as well.

• Some fishes that live in areas of the ocean where there is no light may have reduced, almost nonfunctional eyes.

Fishes have developed sensory systemsFishes have developed sensory systems

• Some fishes also have an extremely sensitive sense of smell and can detect small amounts of chemicals in the water.

Fishes have developed sensory systemsFishes have developed sensory systems

• Sharks can follow a trail of blood through the water for several hundred meters.

Scales There are four types of fish scales.

Fishes and Amphibians

Ctenoid scales- tooth like a comb

Cycloid scales- made of bone and skin

Placoid scales -made of tooth like material and are rough and heavy (shark)

Ganoid scales-made of enamel and bone

Section 1

• The gill arches evolved to form the jaw!!

Jaws evolved in fishesJaws evolved in fishes

Jawless, filter-feeding fish

Beginning of jaw formation Fish with jaws

Gill arches

Gill slits

Gill slits

Gill arches

Skull Jaws


• Jaws also allowed early fishes to prey on a greater variety of organisms.

• The advantage of jaws is that they enable an animal to grasp and crush its prey with great force

Jawless, filter-feeding fish

Beginning of jaw formation Fish with jaws

Gill arches

Gill slitsGill slitsGill arches

SkullJaws

• Sharks have up to 20 rows of teeth that are continually replaced.


• Their teeth point backwards to prevent prey from escaping once caught.


• Sharks are among the most streamlined of all fishes and are well adapted for life as predators.

• Bony fishes, a successful and widely distributed class, differ greatly in habitat, size, feeding behavior, and shape.

Most fishes have bony skeletonsMost fishes have bony skeletons

Classes of fishesClasses of fishes

Fishes

Class Organisms Characteristics

Myxini

Cephalaspidomorphi

Chondrichthyes

Osteichthyes

Hagfishes

Lampreys

Sharks, skates, rays

Lobe-finned fishes, ray-finned fishes

Jawless, cartilaginous skeleton, gills

Jawless, cartilaginous skeleton, gills

Jaws, cartilaginous skeleton, pairedfins, gills, scales, internal fertilization

Jaws, bony skeleton, paired fins,gills, scales, swim bladder

• The evolution of a backbone composed of separate, hard segments called vertebrae was significant in providing the major support structure of the vertebrate skeleton.

Bony fishes have separate vertebrae that provide flexibilityBony fishes have separate vertebrae that provide flexibility

• Separate vertebrae provide great flexibility.

Swim bladder

Bony fishes evolved swim bladders

Bony fishes evolved swim bladders

• A fish with a swim bladder can control its depth by regulating the amount of gas in the bladder.

• Some fishes remove gases from the swim bladder by expelling them through a special duct that attaches the swim bladder to the esophagus.

Bony fishes evolved swim bladdersBony fishes evolved swim bladders

• In fishes that do not have this duct their swim bladders empty when gases diffuse back into the blood.

A Bony FishA Bony Fish Lateral line system

Swim bladder

Scales

Gills

Fins

Kidney

Urinary bladder

Reproductive organ

Stomach

Intestine

LiverHeart

• Fishes range in size from the tiny dwarf goby that is less than 1 cm long, to the huge whale shark that can reach a length of about 15 m—the length of two school buses.

Diversity of fishesDiversity of fishes

Whale shark

Section 28.2

• Lampreys and hagfishes belong to the superclass Agnatha.

Agnathans are jawless fishesAgnathans are jawless fishes

• The skeletons of agnathans, as well as of sharks and their relatives, are made of a tough, flexible material called cartilage.

• Lampreys and Hagfish have a notochord in all stages of their life. (even adulthood)

Lamprey

• A hagfish has a toothed mouth and feeds on dead or dying fishes.

Agnathans are jawless fishesAgnathans are jawless fishes

• It can drill a hole into a fish and suck out the blood and insides.

• Parasitic lampreys use their suckerlike mouths to attack other fishes.

• They use their sharp teeth to scrape away the flesh and then suck out the prey’s blood.

• Sharks, skates, and rays belong to the class Chondrichthyes.

Sharks and rays are cartilaginous fishesSharks and rays are cartilaginous fishes

• These fishes, like agnathans, possess skeletons composed entirely of cartilage.

• Sharks are perhaps the most well-known predators of the oceans.

• Like sharks, most rays are predators and feed on or near the ocean floor.

Sharks and rays are cartilaginous fishesSharks and rays are cartilaginous fishes

• Ras have flat bodies and broad pectoral fins on their sides.

Sharks and rays are cartilaginous fishesSharks and rays are cartilaginous fishes• By slowly flapping their toes up and down,

rays can glide as they search for mollusks and crustaceans along the ocean floor.

• Scientists recognize two subclasses of bony fishes—the lobe-finned fishes, including lungfishes, and the ray-finned fishes.

Subclasses of bony fishes (see p. 831)Subclasses of bony fishes (see p. 831)

• The lobe-finned fishes are represented by seven living species: six species of lungfishes, which have both gills and lungs, and the coelacanth.

• Each fin consists of a long, fleshy muscular lobe that is supported by a central core of bones.

• A third group (now extinct) - Is the tetrapod

Subclasses of bony fishesSubclasses of bony fishes• In the ray-finned fishes,

such as catfish, perch, salmon, and cod, fins are fan-shaped membranes supported by stiff spines called rays.

• Teleosts- have highly mobile fins

• Very thin scales

• Completely symmetrical tails

• 95% of all ray finned fish are teleosts.

Perch

Evolution of FishesEvolution of Fishes

• Scientists have identified fossils of fishes that existed during the late Cambrian Period, 500 million years ago.

• At this time, ostracoderms (OHS trah koh durmz), early jawless fishes, were the dominant vertebrates on Earth.

Origins of FishesOrigins of Fishes

Anaspid

Cephalaspid

Heterostracah

Origins of FishesOrigins of Fishes

• Bone provides a place for muscle attachment, which improves locomotion.

• In ancestral fishes, bone that formed into plates provided protection as well.

Origins of FishesOrigins of Fishes• Scientists hypothesize that the jawless

ostracoderms were the common ancestors of all fishes.

• Modern cartilaginous and bony fishes evolved during the mid-Devonian Period.

• Lobe-finned fishes, such as coelacanths (SEE luh kanths), are another ancient group, appearing in the fossil record about 395 million years ago.

• Legs- most have 4, Caecilians have none.

• Amphibians have thin, moist skin (cutaneous respiration)

• Lungs- is an internal , baglike respiratory organ.

-In the larval form they have gills not lungs.

Key Characteristics of AmphibiansKey Characteristics of Amphibians

• Two large veins called pulmonary veins return oxygen rich blood from the lungs to the heart.

4. Double Loop circulation4. Double Loop circulation

• The evolution of the three-chambered heart in amphibians ensured that cells received the proper amount of oxygen.

• Blood from both chambers then moves to the third chamber, (=ventricle) which pump oxygen-rich blood to body tissues and

oxygen-poor blood back to the lungs and skin so it can pick up more oxygen.

• In the three-chambered heart of amphibians, one chamber receives oxygen-rich blood from the lungs and skin, and another chamber receives oxygen-poor blood from the body tissues. (=atrium) divided into left and right sides.

•A dividing wall known as the septum separates the atrium into a right and left.

5. Partially Divided Heart5. Partially Divided Heart

6. Cutaneous Respiration- amphibians

have thin, moist skin which they

use to supplement their oxygen content.

6. Cutaneous Respiration- amphibians

have thin, moist skin which they

use to supplement their oxygen content.

• Frogs and toads are amphibians with no tails.

Frogs and toads belong to the order AnuraFrogs and toads belong to the order Anura

• Frogs have long hind legs and smooth, moist skin.

FrogToad

• Toads have short legs and bumpy, dry skin.

• Adult frogs and toads are predators that eat invertebrates, such as insects and worms.

(=carnivorous)

FrogToad


• Because the skin of an amphibian must stay moist to exchange gases, most amphibians are limited to life on the water’s edge or other moist areas.

• Most frogs and toads spend part of their life cycle in water and part on land.

• They breathe through lungs or through their thin skins.

• Declining numbers of frog species, or deformities in local frogs, sometimes indicate the presence of pollutants in the environment.


A FrogA Frog Eyes

Tympanic membrane

Tongue

Lungs

Calls

Legs

Vocal cords

Heart

Liver

IntestineFat bodies

Backbone

• Frogs and toads also have vocal cords that are capable of producing a wide range of sounds. Vocal cords are sound-producing bands of tissue in the throat.


• Fertilization in most amphibians is external, and water is needed as a medium for transporting sperm.

Reproduction in FrogsReproduction in Frogs

• Amphibian eggs lack protective membranes and shells and must be laid in water or other moist areas.

Amphibians undergo metamorphosisAmphibians undergo metamorphosis

Fertilized eggs

Young, leglesstadpoles liveoff yolk storedin their bodies.

Tadpoles with legs feed on plants in the water.

Young frogs have structuresneeded for life on land.

Adult frog

Metamorphosis of a Frog

• Tadpole• -Herbivore• -Gills• - tail• -no legs• 2 Chambered

heart

• Adult• -Carnivore• -Lungs• -no tail• -legs• 3 chambered heart

• Young salamanders resemble adults, but, as aquatic larvae, they have gills and usually have a tail fin.


• Most adult salamanders lack gills and fins.

• They breathe through their moist skin or with lungs.

• Completely terrestrial salamander species do not have a larval stage; the young hatch as smaller versions of adults.


• Most salamanders have four legs for moving about, but a few have only two front legs.

• An ectotherm (EK tuh thurm) is an animal that has a variable body temperature and gets its heat from external sources.

Amphibians are ectothermsAmphibians are ectotherms

• Because many biological processes require particular temperature ranges in order to function, amphibians become dormant in regions that are too hot or

cold for part of the year.

Mudpuppy

Salamanders belong to the order CaudataSalamanders belong to the order Caudata

• A salamander has a long, slender body with a neck and tail.

• Salamanders resemble lizards, but have smooth, moist skin and lack claws.

Salamanders belong to the order CaudataSalamanders belong to the order Caudata

• They range in size from a few centimeters in length up to 1.5 m. The young hatch from eggs, look like small salamander adults, and are carnivorous.

Caecilians belong to the order GymnophionaCaecilians belong to the order Gymnophiona

• Caecilians are burrowing amphibians, have no limbs, and have a short, or no tail (=wormlike)

• Caecilians are primarily tropical animals with small eyes that often are blind.

• They eat earthworms and other invertebrates found in the soil.

• All caecilians have internal fertilization.

Challenges of life on landChallenges of life on land• Amphibians first appeared about 360

million years ago.• Amphibians probably evolved

from an aquatic tetrapod around the middle of the Paleozoic Era.

Challenges of life on landChallenges of life on land• Able to breathe through their eyes,

butt, or fingers, amphibians became, for a time, the dominant vertebrates on land.

Challenges of life on landChallenges of life on land

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FishesAmphibians Fishes and Amphibians Chapter 28