READING: Chapter 32 Introduction to Vertebrates Chapter 33 Fishes and Amphibians Chapter

UNIT 12

VERTEBRATES

READING:
Chapter 32 Introduction to Vertebrates
Chapter 33 Fishes and Amphibians
Chapter 34 Reptiles and Birds
Chapter 35 Mammals
Chapter 36 Animal Behavior

OBJECTIVES
At the end of this unit of study the student will be able to:
1. List the characteristics of all Chordates
2. Identify and briefly describe the three Chordate subphyla
3. Name the seven living vertebrate classes and give and example of each one.
4. List the major adaptations that enable fish to live in water.
5. Describe the Class Agnatha and its members.
6. Describe the Class Chondrichthyes and its members.
7. Compare and contrast the three types of bony fish (Class Osteichthyes)
8. List the characteristics of amphibians.
9. List adaptations amphibians have that permit their survival on land.
10. Name and describe the four orders of living amphibians, and give an example of each
11. Describe reproduction and development of frogs.
12. Describe the structure of the amniote egg and explain its importance to life on land.
13. List and describe structural characteristics of reptiles that are adaptations to life on land.
14. List the characteristics of modern reptiles.
15. Name, describe and give an example of the four modern orders of reptiles
16. List the characteristics of birds.
17. Describe the structure of and types of feathers.
18. Describe some adaptations for flight by birds.
19. Summarize reproductive behavior and patterns in birds.
20. List and describe the characteristics of mammals.
21. Name and identify the three major groups of mammals.
22. Describe the Order Monotremata.
23. Describe the Order Marsupialia
24. Describe the characteristics of the placental mammals.
25. Name, describe and give examples of the placental orders of mammals.
26. Describe the mammalian reproduction.

ASSIGNMENTS:
1. 7.

2. 8.

3. 9.

4. 10.

5. 11.

6. 12.

VERTEBRATES UNIT 12

I. Overview of Chordates - Phylum Chordata
A. Early development follows that of echinoderms.
1. Indeterminate radial cleavage
2. Mesoderm arises from outpocketings of endoderm.
3. Both are deuterosomes - anus forms from blastopore; mouth forms from second opening.
B. Characteristics
1. All have a notochord sometime during development.
a. NOTOCHORD - firm, flexible rod of specialized cells located in dorsal part of body
b. Some retain notochord all their lives.
c. In vertebrates - replaced by VERTEBRAL COLUMN - backbone.
d. Replaced by ENDOSKELETON - internal skeleton
1) Supports larger body
2) Grows with the animal; isn't shed periodically
2. Have a hollow dorsal nerve cord just above the notochord.
a. Anterior end of nerve cord is bulbous - develops into brain.
b. Remaining part forms spinal cord.
3. Have pharyngeal pouches - gill slits or clefts.
a. Small outpockets of anterior gut.
b. In fish and larval amphibians the slits act as gills
c. In land chordates - pouches develop into various throat and ear structures - Eustachian Tube.
C. Classification
1. Separated into 3 subphyla
a. Subphylum Urochordata c. Subphylum Vertebrata
b. Subphylum Cephalochordata
2. Subphylum Urochordata
a. Commonly called Tunicates or sea squirts
b. Sessile marine animals enclosed in a tough covering called a TUNIC
c. Larval form usually freeswimming.
d. Adults are filter feeders
e. Only the larval forms have notochord and dorsal nerve cord.
3. Subphylum Cephalochordata
a. Marine organisms - shallow waters of warm, southern region
b. Representative species - Branchiostoma - called amphioxus or lancelet (knifelike)
1) Shows all 3 chordate characteristics
2) Filter feeder - usually buried so only head protrudes
3) Swims in spiral as it moves forward; poorly developed fins
4) Sexes separate - external fertilization.
4. Subphylum Vertebrata
a. Characteristics
1) Have endoskeleton of bone or cartilage, or both - jointed and flexible.
2) Notochord replaced by column of bony or cartilaginous structures called VERTEBRAE - surround dorsal nerve cord.
3) Brain protected by skull or cranium - together with vertebral column forms the
AXIAL SKELETON.
4) Have 2 groups of bones called GIRDLES that attach limbs to axial skeleton.
a) PECTORAL GIRDLE - anterior; attaches arms or forelegs to axial skeleton
b) PELVIC GIRDLE - posterior; attaches the legs or hindlegs to axial skeleton.
5) Have 2 pair of limbs - fins, wings, legs, arms, flippers - girdle and limbs form APPENDICULAR SKELETON.



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6) Organs organized into 11 systems.
a) Integumentary - outer body covering - skin and outgrowths(hair, scales, feathers) - protection and regulates body temperature.
b) Skeletal - bone and cartilage - support and protection
c) Muscular - movement; forms walls of heart and stomach
d) Digestive - mouth, esophagus, stomach, liver - breakdown and absorption of food.
e) Excretory - kidney - removal of nitrogenous waste
f) Respiratory - gills, lungs - gas exchange between body and environment.
g) Circulatory - heart, veins, arteries, blood - transport of materials within the body.
h) Immune - cells and substances in blood - detection and destruction of invaders.
i) Endocrine - glands - secrete hormones that regulate body processes
j) Nervous- brain, spinal cord, nerves, sense organs -provide sensory perception and voluntary/involuntary movement
k) Reproductive - ovaries, testes, and other reproductive organs - production of gametes and reproduction of species.
b. Classification
1) Fossil evidence indicates increasing complexity according to order in which classes evolved.
2) Divided into 7 classes - may be order in which class evolved
a) Agnatha - jawless fish - lamprey and hagfish
b) Chondrichthyes - Cartilage fish - sharks, rays, skates
c) Osteichthyes - Bony fish - trout, goldfish, perch
d) Amphibia - Amphibians - frogs, toads, salamanders
e) Reptilia - Reptiles - snakes, turtles, lizards, crocodilians
f) Aves - Birds - sparrow, pigeon, eagle
g) Mammalia - Mammals - lion, dog, man
II. Fish
A. Encompasses 3 vertebrate classes
1. Agnatha - jawless fish 3. Osteichthyes - bony fish
2. Chondrichthyes - cartilaginous fish
B. Most numerous and most widespread of all vertebrates
C. Adaptations to Aquatic Life
1. Buoyancy
a. Trapping gas inside body
b. Specialized "air bladder"
2. Streamlined shape
3. Muscular tail - enable rapid movement through water.
4. Paired fins - permits maneuvering right/left, up/down, forward/backward
5. Mucus reduces friction
6. Protective scales limit chemical exchange through skin.
7. Exchange of between water and blood occurs across membranes of gills
8. Have well developed sense of smell and touch - LATERAL LINE SYSTEM.
a. In all except members of Class Agnatha
b. Row of sensory structures running length of fish's body on each side - connected by nerves to brain.
c. Detect vibrations and chemicals in water.
D. Evolution
1. First known vertebrate - small, jawless fish - Ostracoderms - covered by heavy, bony plates - appeared about 540 million years ago.
2. Members of Class Agnatha similar to ostracoderms - probably evolved from ostracoderms
3. Bony and cartilaginous fish probably also evolved from ostracoderms -different phylogenetic lines.
4. Evolutionary events important to other vertebrates
a. Evolution of pouch in posterior portion of mouth - functions as a lung
b. Emergence of fins supported by bony lobes projecting from body.
c. These adaptations occur today in lungfish and lobe-finned fish - both bony fish.
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III. Class Agnatha
A. Consists of 45 species of jawless fishes - lamprey and hagfish
1. Name Agnatha means "jawless"
2. Also called Cyclostomes ("round mouth") because of circular mouth
B. Skin slimy - no plates or scales.
C. Retain notochord throughout life - has cartilageous skeleton and unpaired fins.
D. Lamprey
1. Some free-living; most are parasitic.
2. Mostly live in freshwater - marine forms reproduce in freshwater
3. Has thin, cylindrical body
4. Has unpaired fins
5. Head not well defined
6. Fertilization external - eggs laid in shallow nests in river bed - adults die after releasing gametes.
7. Causes extensive damage to economically important fish, Lake Trout.
8. Life Span - About 7 years - adult about 1.5 years
E. Hagfish
1. Bottom dwellers - in cold marine waters
2. Scavenger - lives on dead or dying fish - eats from inside out
3. Extremely supple - can tie body into knot to evade capture; also useful for cleaning.
4. Normally hide in mud burrows on ocean floor.
IV. Class Chondrichthyes
A. Includes Sharks, skates and rays - all are marine dwellers
B. Characteristics
1. Have skeleton of CARTILAGE
a. Tissue made of cells surrounded by flexible protein structure.
b. Cartilaginous skeleton believed to be degenerative - evidence indicates they evolved from bony fish - lost bone over time
2. Have movable jaws and skeleton with paired fins
3. Carnivorous - uses large olfactory organs and lateral lines to track prey.
C. Sharks
1. Among largest living fishes
2. Gray colored skin covered by rows of PLACOID SCALES
a. Point backward; spines covered by enamel
b. Scales along with teeth are only bone-like material on shark body.
c. Skin feels like sandpaper.
3. Body torpedo shaped
a. Swims with side-to-side, wavelike motion
b. Uses paired fins for maneuvering and to maintain balance
c. Asymmetrical tail characteristic of ancient fish - long upper lobe
4. Mouth is horizontal slit on ventral surface of head
a. Jaws lined with rows of razor-sharp teeth - 6 to 20 rows
b. If tooth lost - another one moves forward to replace it
c. Teeth point back - hold food in mouth.
5. Have an acute sense of smell - constantly monitors water for chemicals
a. Paired nostrils on snout have specialized nerve cells connected to olfactory lobes of brain.
b. Can detect blood nearly 3/10 of a mile away
6. Most are predators
7. Water enters mouth as shark moves forward.
a. Passes over gill - gas exchange occurs
b. Water exits through gill slits
c. Some sharks have special muscles to pump water through mouth while stationary
d. For those lacking special muscles, constant motion needed to keep water moving over the gills.
8. Have well developed lateral line system - detects slight changes in water pressure.

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9. Reproduction
a. Eggs fertilized internally
b. During mating male grasps female with modified fins called CLASPER
c. Sperm runs from male to female through grooves in clasper.
d. In most species, eggs develop inside female's body; nourished by yolk of egg, pups born alive - called OVOVIPAROUS
e. A few species lay large, yolky eggs right after fertilization -develop outside mother's body - called OVIPAROUS
D. Rays and Skates
1. Have flattened bodies with wing-like, paired pectoral fins - some have whiplike tails.
a. Rays - diamond or disk shaped bodies
b. Skates - triangular bodies
2. Primarily bottom dwellers
3. Move in undulating or wavy motion
4. Feed on mollusks and crustaceans
5. Respire through spiracles on top of head - moves in through spiracles, goes into pharynx, runs over gills, exits through ventral gill slits
6. Sting Rays have tail with venomous barbed spine
V. Class Osteichthyes - Bony Fish
A. Comprise 95% of all known species of fish
B. Adapted to a variety of aquatic environments - because of skeleton, scaly skin, sense organs, fins, and reproductive patterns
C. Divided into 3 groups
1. Lobe-finned Fishes - Coelacanths
a. Have paddle-like fins with fleshy bases
b. Believed to have been extinct for 70 million years
1) South African fisherman caught one in 1938
2) Recognized by local museum curator
3) Several have been caught since 1938.
c. Probably related to ancestors of first amphibians
2. Lungfishes
a. Have lungs - internal respiratory organs where gas exchange takes place between air and blood.
b. Also have gills
c. Live in shallow, tropical ponds - dry up in summer
d. Fish burrows in mud and cover themselves with mucus to stay moist - may crawl to other pond.
3. Ray-finned Fishes
a. Fins supported by long bones called RAYS
b. Diverse in appearance, behavior and habitats
c. Includes most familiar fish - trout, perch, etc.
VI. Class Amphibia
A. Name means "double life" - spend part of life on land and part in water.
B. Evolution
1. Believed to have evolved from lobe-finned fishes called Crossopterygians.
2. Amphibians appeared during late Devonian Period - 345 million years ago.
3. During Permian Period - evolutionary line of amphibians diverged into amphibians and reptiles.
4. Geologic record has evidence of environmental changes that may have lead to movement of animals onto land.
C. Characteristics
1. Undergo metamorphosis from aquatic larval stage to the terrestrial adult form.
2. Have smooth, moist, thin skin - no scales, fur, or feathers.
3. Feet, if present, are often webbed; toes soft and lack claws
4. Larval form usually herbivorous (plant eater) while adults are carnivorous (meat eater)
5. Respiration through gills, lungs, skin, and mouth cavity.

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6. Larva have 2-chambered heart; adults have 3-chambered heart; well developed circulatory system.
7. Eggs lack membrane or shell - usually laid in water (or moist area) - fertilization external.
D. Adaptation to life on land
1. Legs - difficult to move on fins on land.
2. Lungs - gills stick together and dry out on land.
3. Stronger bones and muscles
4. Skin contains keratin - reduces water loss
5. Necks - permitted better seeing and easier feeding.
6. Oral glands - moisten food to be eaten.
7. Adaptation to changes in body temperature - Amphibians are COLD-BLOODED - body temperature rises and falls with surrounding temperature.
a. TORPOR - state of dormancy; bury themselves in mud or leave when conditions unfavorable.
1) HIBERNATION - inactive state that occurs in winter.
2) ESTIVATION - inactive state that occurs in summer.
b. Cold-blooded organisms affected by slight changes in external temperature.
E. Classification
1. Classified into 4 orders
2. Amphibian Orders
a. Order Anura - Frogs and toads
b. Order Urodela - Salamanders
c. Order Apoda - Caecilians
d. Order Trachystoma - Sirens
F. Order Apoda
1. Name means "without legs"
2. Wormlike organisms called caecilians
3. Highly specialized group of tropical burrowing amphibians
4. Average about 1 foot long but may grow up to 4 feet long.
5. Have very small eyes - often blind.
6. Eat worms and other invertebrates
7. Internal fertilization - female bears live young.
G. Order Trachystoma
1. Name means "rough mouth"
2. Consists of only 3 living species of Sirens or Mud Eels
3. Live in eastern U.S. and southern Europe
4. Have minute forelimbs; no hindlimbs
H. Order Urodela
1. Name means "visible tail"
2. Order that includes salamanders
3. Have elongate bodies; long tail; smooth, moist skin; short legs and clawless toes
4. Vary in length from few centimeters to 1.5 meters
5. Less able to live on dry land - remain inactive during day
a. May live in either water or marshy areas.
b. Live under logs and stones
6. Many lay eggs in water - some reproduce in damp land environments.
7. Some exhibit a type of internal fertilization - female picks up sperm packet deposited by male.
a. Give birth to live, fully metamorphosed young.
8. Some have skin glands that secrete bad-tasting substances - some change color.
9. Newts - small, landliving salamanders
10. Largest in U.S. - American Hellbender - up to 2 feet long.
11. Mud Puppy
a. Found in American Midwest
b. May reach 2 feet in length
c. Retain gills (external) throughout life - located just behind the head.

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