UNIT 12
VERTEBRATES
READING:
Chapter 32
Chapter 33
Chapter 34
Chapter 35
Chapter 36
Introduction to Vertebrates
Fishes and Amphibians
Reptiles and Birds
Mammals
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
I.
UNIT 12
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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D.
E.
F.
G.
H.
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.
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.
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
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.
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
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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I.
12. Crimson-spotted Newt
a. Has 3 different forms during its life time
1) Gill-breathing aquatic larva - hatches in May
2) Land-dwellers with lungs - after about 2 months - is coral red - Called a Red Eft
3) Aquatic; respires through skin - after about 2 years
Order Anura
1. Name means "without a tail"
2. Inhabit a variety of habitats - live on every continent except Antarctica
a. Deserts
d. Rivers
b. Mountains
e. Ponds
c. Rain Forests
3. Frogs
a. Have smooth, moist skin.
b. Have long hind legs - excellent jumpers
c. Live in or near water
d. Tree Frogs
1) Live in trees.
2) Have special suction disks on toes - aid in climbing and clinging to branches.
e. Bullfrog
1) Named for loud bellowing it makes
2) One of the most aquatic of all frogs.
3) Legs may be 10 inches long.
4) Excellent swimmers
5) Eat insects, worms, crayfish, small fish, small birds
4. Toads
a. Have dry, bumpy skin
b. Body stocky; legs short - useful for digging as well as leaping.
c. True toads belong to the Family Bufonidae
d. Term "toad" used for any anuran adapted to dry environments.
e. Live in loose, moist soil - common in gardens
f. Color and texture of skin provides good camouflage.
g. Poison glands on skin - secrete irritating, foul-tasting substance.
h. May inflate body to escape being eaten by snakes.
i. Feed on insects, worms, and other animals harmful to plants - called "gardener's friend"
5. Reproduction
a. Sex organs internal in both sexes
1) Male
a) TESTES - 2; bean-shaped, creamy white/yellowish organs located near kidney
b) During mating season, sperm passes through tubes to kidney and urinary duct.
c) Sperm leaves body through cloacal opening.
2) Female
a) OVARIES - 2; large lobed organs containing eggs; near kidney.
b) Mature eggs burst through ovary walls - cilia move eggs to opening of oviduct.
c) As egg passes through oviduct, it receives protective coat of jellylike material
d) Exit through cloacal opening
b. Breeding/Fertilization
1) Breed once a year - usually in spring
2) Males establish territories; call to female - air driven back and forth between mouth and
lungs vibrate the vocal cord; Vocal Sacs in male amplify sound
3) Male climbs onto female's back - grasps her firmly; Embrace is called AMPLEXUS - may
last for days.
4) Female releases eggs; male discharges sperm - fertilization is external.
5) Eggs hatch into TADPOLES (larval swimming form) in about 12 days.
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c. Metamorphosis
1) Newly hatched tadpole lives off of yolk stored in body.
2) Breathes by gills; have 2 chambered heart.
3) Mouth eventually opens - feeds on plant material
4) Tadpoles can regenerate lost parts (leg or tail) - ability lost in adult
5) Legs begin to grow; tail disappears
6) Mouth broadens - develops teeth and jaws
7) Sac-like bladder in throat divides to become 2 lungs
8) Heart develops third chamber.
9) Emerges from water for life on land.
VII.Reptilian Evolution
A. First group of vertebrates to make complete transition to land.
1. Forces leading to transition.
a. Increased competition for food and space in aquatic environments.
b. Limited competition for food (insects and plants) on land.
2. Adaptations that made transition to land possible.
a. Amniote Egg
1) Amphibians forced to reproduce in water.
2) Reptiles, birds and mammals have special reproductive structure that allows reproduction
on land - AMNIOTE EGG.
a) Egg with protective membranes and porous shell enclosing embryo.
b) Self-contained "nursery"
3) Has 4 specialized membranes
a) AMNION - thin membrane enclosing salty fluid in which embryo floats
b) YOLK SAC - encloses yolk - protein rich food supply for embryo.
c) ALLANTOIS - stores nitrogenous waste from embryo until egg hatches.
d) CHORION - lines outer shell; encloses all other membranes and embryo; regulates gas
exchange between environment and egg.
4) Egg may be enclosed in shell - leathery - reptiles; hard - birds; missing - most mammals.
a) Requires INTERNAL FERTILIZATION - places sperm inside female before shell forms
b) Internal fertilization makes water transport of sperm unnecessary
b. Waterproof skin
1) Dry body covering of horny scales or plates - protects reptile
2) Scaly covering develops as surface cells filled with keratin - also forms nails and feathers.
3) Scales prevent water loss; protect reptiles from rugged terrestrial environments.
c. External Structural Adaptations for Movement
1) Claws on toes - aid in climbing, digging, and moving.
2) Suction cups - aid in climbing; modified toes
3) Snakes depend on scaly skin and well developed skeletal and muscular system to crawl.
d. Lungs - located inside body; kept moist even in driest environments.
e. Circulatory system more complex
1) Double circulation
2) 3 chambered heart in most species
a) Partial division of ventricle
b) Crocodilians have 4-chambered heart
f. Excrete nitrogenous wastes in dry or pasty form as crystals of uric acid.
g. Temperature Regulation
1) Metabolic rate controlled in part by body temperature
2) In reptiles body temperature determined by surroundings
a) ECTOTHERMIC - coldblooded; animals in which body temperature is determined by
environment - fish, amphibians, and reptiles
b) ENDOTHERMIC - warmblooded; animals in which body temperature remains constant - birds
and mammals
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3) Reptiles regulate body temperature by behavior
a) Bask in sun to warm up - increases metabolic rate
b) Seek shade to prevent overheating.
B. Origin and Evolution
1. Believed to have ancestral reptiles called Cotylosaurs
2. Permian Period (280 to 225 million years ago) - cotylosaurs begin to adapt.
a. Gave rise to new reptilian forms
1) Pterosaurs - flying reptiles
2) Ichythyosaurs and Plesiosaurs - marine reptiles
3) Thecodonts - small, lizard-like carnivores
b. Thecodonts were first ARCHOSAURS - "ruling reptiles"
c. Thecodonts later included early crocodiles, dinosaurs, and reptiles that evolved into birds.
3. Mesozoic Era (225 to 65 million years ago) - Age of Reptiles
a. Reptiles especially dinosaurs dominate earth
b. Term Dinosaur means "terrible lizard"
1) Remembered mostly for their large size - most were small.
2) 300 genera identified from fossils - adapted to many environments and ways of life.
3) Major question is their extinction 65 million years ago - many theories exist
a) Gradual climate changes
b) Catastrophic cosmic event - asteroid hitting earth.
VIII.Modern Reptiles
A. Characteristics - share traits that are adaptations to land survival
1. Have amniote egg to help protect developing embryo
2. Have internal fertilization that replaces water transport of sperm
3. Dry body covered by scales or plates.
4. Limbs with claws or pads to aid in movement
5. Respiration throughout life by use of lungs.
6. Heart with 3 or 4 chambers
a. 3-chambered has ventricle with partial division
b. Helps supply body with more oxygen.
7. Ectothermic temperature regulation controls metabolic rate
B. Occur worldwide except in coldest regions - due to ectothermy
C. Classification
1. Reptiles classified into 16 orders - 12 are extinct
2. 4 surviving orders include about 6000 species
3. 4 living orders of reptiles
a. Rhynchocephalia - Tuatara
b. Chelonia - Turtles and Tortoises
c. Crocodilia - Crocodiles and Alligators
d. Squamata - Snakes and Lizards
D. Order Rhynchocephalia
1. Ancient order - only 1 living species Sphenodon punctatus, Tuatara
2. Lives on small islands off New Zealand
3. Looks like large lizard
4. Has "third eye" on top of head - PARIETAL EYE
a. Under thin layer of scales
b. Has lens, retina and nerves connecting eye to brain
c. Appears to function as thermostat
5. Most active at low temperatures - different from most reptiles
6. Burrows during day; active at night
7. Feeds on insects, worms and small animals
E. Order Chelonia
1. Includes about 265 species of turtles and tortoises
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2. Terminology
a. TORTOISE - terrestrial members of Order Chelonia
b. TURTLE - aquatic members of Order Chelonia
c. TERRAPIN - Oriental freshwater turtles as well as a few salt-marsh species of eastern U.S.
3. Found in most parts of world except Arctic and Antarctic
4. Changed very little in past 200 million years
5. Body design probably has lead to evolutionary stability
a. Body covered by shell of hard plates or tough leathery skin
b. Body parts
1) CARAPACE - top or dorsal covering; in most species it is fused with vertebrae and ribs
2) PLASTRON - Belly or ventral body covering
c. Shell shape modified to environment
1) Tortoises usually have domed carapace into which head, legs and tails can be retracted protective move
2) Turtles - stream-lined shell; permits rapid turning in water
d. Forelimbs of marine turtles modified into flippers for swimming
6. Some sea turtles undergo long migrations
7. Chelonians lay eggs in soft, loose soil or sand
F. Order Crocodilia
1. Composed of about 23 species of large lizard like reptiles
a. Includes crocodiles, alligators, caimans, and gavials
b. Fossil record show they are direct descendants of archosaurs
2. Live near or in water in tropical or subtropical regions
a. Crocodiles - Africa, Asia, and the Americas
b. Alligators - China and southern U.S.
c. Caimans - Central America and now Florida
d. Gavials - India and Burma
3. Carnivorous
4. Lay eggs - in some cases parents guard nest and care for young
5. Comparison of Alligators and Crocodiles
a. Alligator - Broad, rounded snout; Crocodile - narrow, pointed snout
b. Crocodile - 4th tooth protrudes when mouth closed; Alligator - tooth is hidden
G. Order Squamata
1. Consists of about 5700 species of lizards and snakes
2. Distinguishing characteristics
a. Lower jaw not jointed directly to skull
b. Males have paired reproductive organs
3. Lizard generally have legs (a few species are legless); all snakes are legless
4. Groups of Lizards
a. Iguanas - have series of horny spines on head and trunk - includes Anole
b. Skinks - have shiny, cylindrical bodies and weak short legs
c. Gila Monster and Beaded Lizards - only poisonous lizards
d. Geckos - most primitive lizard - has pads on toes to cling.
e. Monitor Lizards - largest lizard in world (up to 3 m)
5. Some lizards have ability to lose tail and then regenerate a new one - trait is called AUTOTOMY permits lizard to escape predators
6. Snakes are believed to have evolved from ancient burrowing lizards.
H. Snakes
1. Movement - 3 basic ways
a. Lateral Undulation - moves head side to side - creates wave of muscular contraction - uses
sides to push off of objects - moves forward in S-shaped path.
b. Rectilinear Movement - muscular force applied to belly not sides - trailing edge of SCUTES
(belly scales) catch on rough surfaces - moves like caterpillar
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2.
3.
4.
5.
c. Sidewinding - moves sideways not forward - flings head to one side - whiplike motion yanks
along rest of body.
Feeding
a. Locating Prey
1) Eyesight and hearing not well developed
2) Uses sense of smell to locate prey - gathers environmental chemicals by flicking its tongue.
3) Tongue transfers chemicals to pits in roof of mouth called JACOBSON'S ORGAN
4) Pit vipers have heat-sensing organs on head to locate warmblooded prey.
b. Killing Prey
1) Nonpoisonous snakes
a) Some hold prey to ground and swallow it alive and whole
b) Constrictors - wrap themselves around prey and squeeze - prey swallowed whole Rat snake, King snake, Boa
2) Poisonous snakes
a) Inject venom or poison through pair of FANGS - hollow teeth at front of mouth; like
hypodermic needle
b) Venom moves from glands on either side of head.
c) 3 families of poisonous snakes
(1) Cobra and Coral Snake - fixed fangs - most venomous snakes
(2) Sea Snakes - fixed fangs
(3) Vipers - fangs fold back in head - Pit Vipers - have heat sensing organs in pits on
head - includes rattlesnakes, copperheads, and water moccasins
d) Poisonous Snakes of U.S.
(1) Rattlesnake
(3) Water Moccasin (Cottonmouth -S.E.U.S.
(2) Copperheads
(4) Coral Snake - Red, yellow, black, yellow bands
e) Type of Venoms
(1) HEMOTOXIN - attacks circulatory system; destroys blood cells:prevents clotting
*(2) NEUROTOXIN - attacks nervous system; disrupts respiration and heart functions
Snakes molt or shed skin - allows for some growth - not as much as with arthropods
Excretory system conserves water - nitrogenous wastes released by some as uric acid
Fertilization internal - eggs have leathery shell - some species retain eggs inside - ovoviparous Garter Snake
IX. Birds
A. Origin and Evolution
1. Evidence indicates they evolved from reptiles
2. Archaeopteryx may represent link between birds and reptiles - from Jurassic period
a. Has characteristics of both reptiles and birds
1) Large skull with teeth like reptiles
2) Bones not hollow - like reptile
3) Claws on forelimbs - like reptile
4) Long tail - like reptile
5) Feathers - like birds
6) Has FURCULUM - fused collarbone - "Wishbone" - like bird
b. Probably glided
B. Classification
1. Class Aves
2. Divided into 27 orders on basis of beak, feet, plumage, bone structure, and musculature
C. Characteristics
1. Body covered with feathers
2. Bones thin and hollow
3. In most species forelimbs function as wings - used in flight, not grasping
4. 2 hindlimbs with clawed toes
5. Toothless, horny beak
6. Body temperature generated and regulated internally.
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7. 4-chambered heart with single right aortic arch.
8. Amniote egg with hard, calcium containing shell.
9. Eggs incubated in nest by parents (in most species)
D. Feathers
1. Functions
a. Provides lift for flight
b. Conserves body heat - insulation
2. Structure of a Feather
a. Develops from tiny pits in skin called FOLLICLES
b. QUILL - hollow cylinder filled with jellylike substance - lies in the follicle.
c. SHAFT - Grows out of quill; long central portion of feather.
d. VANES - 2; develop on opposite sides of shaft; branched
e. BARB - thin branch of a vane
f. BARBULES - projections on barbs; have hooks; give feather sturdy but flexible shape.
3. Types
a. Down Feathers
1) Cover body of nestling birds; provides insulating undercoat of adults
2) Has quill and reduced shaft
b. Contour Feathers
1) Most familiar and largest type of feather.
2) Gives bird streamlined shape.
3) Provides coloration and insulation
4) Has quill and long shaft.
5) FLIGHT FEATHERS - specialized contour feathers on wings and tail.
c. Filoplumes or Pinfeathers
1) Resemble fine hair; Has single hairlike shaft that ends with a few barbs
2) May function in controlling feather movement.
3) Grow in groups near follicles of some contour feathers
d. Bristles
1) Hairlike - have short quill
2) Thin shaft with few or no barbs at base
3) Grow around bird's nostrils - filter dust.
4. PREENING - rubbing of oil on feathers by birds using their beaks; oil secreted by Preen Gland
near base of tail.
5. MOLTING - periodic shedding of flight feathers - usually occurs in late summer between breeding
and migration
E. Adaptations to Flight - Physiological/Anatomical
1. Skeleton and Muscles
a. Bones thin and hollow
b. Bones fused for rigidity - provides stability
c. Sternum with keel shape supports large breast muscle - moves the wings
d. Flight muscles may account for 50% of body weight
2. Endothermy
a. Generates and regulates body heat - high metabolic rate
b. Requires rapid breathing and digestion of lots of food
c. Permits inhabitation of hot and cold climates
3. Heart
a. 4-chambered
1) Right side receives blood from body and pumps it to lungs
2) Left side receives blood from lungs and pumps it to body
b. Rapid heartbeat
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4. Respiratory System
a. Efficient
b. 9 air sacs extend from lungs - occupy chest and abdomen; connect with air spaces in bones reduces bird's density.
F. Digestive System
1. Don't have teeth, jawbones, or jaw muscles - can't chew
2. Esophagus has enlargement called CROP - stores and moistens food
3. Stomach has 2 parts
a. PROVENTRICULUS - 1st chamber; gastric fluids begin food breakdown.
b. GIZZARD - muscular organ that kneads and crushes food; may contain small stones.
G. Reproductive Behavior
1. Male anatomy
a. Testes lie below kidney
b. Sperm passes down vas deferens to cloaca
c. During mating, male presses his cloaca near female's and releases sperm.
2. Female anatomy
a. Single ovary on left side - releases egg to long funnel-shaped oviduct where fertilization occurs.
b. Fertilized egg receives protective coating and shell as it moves down oviduct.
c. Shell of calcium carbonate secreted by shell gland.
3. Egg
a. Unfertilized egg consists of nucleus, cytoplasm and yolk.
b. When fertilized, embryo becomes suspended in ALBUMIN, egg white.
c. Yolk supported by CHALAZA - rope-like strands of material attached to shell membrane
4. Courtship and Territoriality
a. Male establishes an area he defends against other male birds of the species during breeding
season - called TERRITORIALITY
b. Male attempts to attract 1 or more females to share his territory - COURTSHIP - behavior
designed to attract mate
1) Singing - uses SYRINX or song box
2) Bright colored feathers - Peacock
3) Flight displays
5. Nest Building
a. Holds eggs, conceals young birds, provides shelter, and serves to attract mate.
b. Use a variety of materials
c. Usually well hidden
d. Female lays a CLUTCH or set of eggs - number depends on species
1) Large birds lay egg every 2 or 3 days.
2) Most small birds lay 1 egg per day
3) California Condor - 1 egg every other year.
e. Some birds (Cuckoo) lay eggs in other bird's nests
6. Incubation
a. Eggs must by warmed or INCUBATED
1) Some begin incubation immediately
2) Others wait until all eggs of clutch are laid
b. Incubation time varies - 21 days for chicken; 28 days for ducks
c. Must be warmed to 38o C and turned regularly
d. Incubated by covering with thickening, featherless patch of skin on abdomen -BROOD PATCH.
e. May be performed by either one or both parents
7. Development
a. Zygote forms plate of cells on surface of yolk - forms tissues and organs of embryo.
b. Yolk Sac membrane grows out of embryo's developing digestive tract - surrounds yolk like net.
1) Produces digestive enzymes
2) Blood vessels in yolk sac carry nutrients to embryo.
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c. Allantois also grows from digestive tract.
1) Vascular, netlike sac that attaches to chorion membrane lining the shell.
2) Allantois and Chorion function in respiration and elimination of waste products.
d. Hatching begins when full-term embryo makes crack with scale-like EGG TOOTH on beak
e. Care of Young/Type of Development
1) PRECOCIAL
a) Means "well formed"
b) Young hatch with protective down, are strong and active; can look for some of their food
c) Examples - ducks, quail, chickens
2) ALTRICIAL
a) Helpless at hatching
b) Naked - not covered with down; can't control body heat or feed themselves
c) Parents protect, hunt for food - predigest and regurgitate it into throats of young
d) Examples - woodpecker, hawk, robin, sparrow.
X. Class Mammalia
A. Dominant land vertebrates on earth today
B. Origin
1. Believed to have evolved from group of reptiles call Therapsids.
a. Arose near end of Paleozoic Era - 280 million years ago.
b. Had both reptilian and mammalian characteristics
2. Oldest mammalian fossil - from early Mesozoic Era - 200 million years ago.
C. Evolution
1. Not abundant during Mesozoic
a. Had large eyes
b. Probably active at night - avoid predation by dinosaurs
2. Extinction of dinosaurs open new habitats
a. Mammals dominant by beginning of Paleocene Epoch
b. By end of Eocene Epoch - most modern orders had evolved
c. Cenozoic Era named Age of Mammals
D. Characteristic - (* - Distinguishing Characteristics)
1. Endothermic - permitted mammals to be active day or night; can live in severe environments
*2. Body covered by hair - serves as insulation
3. Heart has 4 chambers - adaptation for endothermy
4. Muscular diaphragm aids in breathing through lungs
a. Adaptation for endothermy
b. Functions for lifetime
5. Single lower jawbone with most species having 4 types of teeth
a. Incisors - chisel-like; bite and cut
b. Canines - pointed; grip, puncture and tear.
c. Bicuspids - 2 points; shear and shred
d. Molars - flattened; grind and crush
6. Viviparous in most species
a. Female carry and nourish young inside body for period of time.
b. Development within uterus
*7. Females secrete milk from mammary glands to feed newborn young
a. Young dependent on mother for food
b. Characteristic that gives class its name.
8. Most mammals have 7 cervical (neck) vertebrae
9. Have highly developed brain - cerebrum/cerebellum more developed than in any animal group.
a. Cerebrum - organ of response, learning and memory
b. Cerebellum - coordinates muscular movement
c. Medulla Oblongata - controls involuntary actions - heartbeat, breathing, etc.
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E. Classification
1. Divided into 3 major groups.
a. Monotremes - egglaying mammals
b. Marsupials - young born at early stage of development; development completed in pouch in
mother's body.
c. Placental Mammals - young nourished in mother's uterus until an advanced stage of development
2. Divided into 19 orders of modern mammals
a. Order Monotremata - monotremes
b. Order Marsupialia - marsupials
c. 17 orders of placental mammals - named for placenta
3. Order Monotremata
a. Members are oviparous - lay eggs
b. Primitive mammals - have hair and produce milk.
c. Found in Australia, New Guinea, and Tasmania
d. Have some characteristics of reptiles
1) Oviparous
2) Not completely endothermic
3) Large intestine, urinary bladder, and reproductive organs empty into a cloaca.
e. Consists of only 3 species
1) Duck-Billed Platypus
a) Excellent swimmer with webbed forepaws, waterproof fur, partially webbed hindpaws,
and flattened tail.
b) Has flat, sensitive rubbery muzzle - resembles duck's bill - used to grub for worms,
mussels, shrimp and fish.
c) Has poison spur on ankle for defense
d) Mother digs channels in riverbank for laying eggs
e) Curls around eggs to protect and incubate them - hatch in about 2 weeks
f) Young feed on milk from nippleless glands on mother's abdomen
2) Spiny Anteater - Echidnea - 2 species
a) Bristles and quills mingled in with hair
b) Mouth at end of long snout - contains long, sticky tongue for probing anthills
c) Claws used to tear open ant and termite colonies
d) Female deposits 1 or 2 eggs in brood pouch on her abdomen - pouch develops during
breeding season.
e) Glands on female's belly secrete milk.
4. Order Marsupialia
a. Species of order give birth to tiny, immature young
1) Uterus does not stretch - limits development of embryo.
2) Young crawl to pouch on mother's belly after they are born.
a) Attach to milk-secreting nipple
b) Nurse until they are mature enough to survive outside the pouch
b. Inhabit Australia, New Guinea, Tasmania, and the Americas
1) Only North American marsupial is common opossum
2) Most live in Australia - Dominant mammals of that continent
a) Believed to have succeeded because of few competitors
b) Have undergone adaptive radiation - adapted to all environments.
c. Opossum
1) Active dusk till dawn.
2) Eats fruits, insects, and small animals
3) Uses prehensile tail to hang onto tree branches
4) Young develop in uterus for 12 days
5) Litters may be as large as 18 but mother has only 13 nipples - only 13 feed and survive
6) Remain in pouch until fully developed - will remain with mother even after fully developed
riding on her back.
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d. Kangaroo - Australia
1) Live in small herds - many different species and sizes
2) Some such as Large Red and Gray may grow to between 2 and 3 meters tall.
3) Have short forelimbs but long, muscular legs and tail - may travel at speeds of 25 mph.
4) Herbivores
5) At birth they are about 2 cm long - must climb into mother's pouch on its own.
6) Joeys remain in pouch for about 9 months
5. Placental Mammals
a. Comprise about 95% of all mammals
b. Characteristics
1) Carry unborn young in uterus until they can survive in outside world.
2) Mammalian egg contains almost no yolk
3) Embryo nourished by PLACENTA - organ formed from chorion and allantois of mammalian
egg and tissues of uterus.
4) Oxygen and nutrients transferred from mother's blood, through placenta, and then into blood
of unborn - no direct contact between blood systems of mother and child.
c. Classification
1) Classified on basis of what they eat, how they move, and where they live.
2) 17 modern orders.
XI. Important Placental Orders
A. Insectivora - Insect eating mammals
1. Shrews and moles
2. High metabolic rates
3. Have long, pointed nose to grub for insects, worms, and other invertebrates
4. Teeth adapted for picking up and piercing prey.
B. Rodentia - Gnawing mammals
1. Squirrels, chipmunks, gophers, mice, rats, and porcupines
2. Largest mammalian order
3. Have only 2 incisors - grow animal's entire lifetime
4. Incisors sharp from rodents diet of hard seeds, twigs, roots, bark.
C. Lagomorpha - Rodent-like mammals
1. Rabbits and hares
2. Double row of upper incisors; 2 large front backed by 2 smaller ones
3. Teeth grow throughout animal's lifetime
4. Herbivores
D. Edentata - Toothless mammals
1. Anteaters, armadillos, and sloths
2. Name means "without teeth" - only anteaters completely toothless
3. Teeth of armadillo and sloth are peglike; lack enamel
4. Sloths - herbivores; others are insectivores
E. Chiroptera - Flying Mammals
1. Bats
2. Bat's wing is modified front limb; skin membrane stretches between long fingers and hindlegs
3. Clawed thumb on top edge of wing - used for walking, climbing, grasping
4. Navigate and find food by ECHOLOCATION - high frequency sound waves bounce off objects - type
of sonar
5. Divided into insect eaters and fruit eaters
F. Cetacea - Water-dwelling Mammals
1. Whales, dolphins, and porpoises
2. Have fish-like bodies - forelimbs modified as flipper - degenerative evolution
3. Lack hindlimbs - have broad flat tail used to propel them
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4. Divided into two groups
a. Toothed Whales
1) Have hundreds of teeth; prey on fish, squid, seals, and other whales
2) Sperm Whale, Narwhales, Killer Whales, Dolphins, Porpoises
b. Baleen Whales
1) BALEEN - thin plates of fingernail-like material that hang from roof of mouth.
2) Lack teeth - use baleen to strain sea water of shrimp, and other invertebrates
3) Blue Whale, Humpback Whale
Sirenia - Water-dwelling Mammals
1. Manatees and dugongs
2. Herbivores - inhabit tropical seas, estuaries, and rivers
3. Front limbs are flippers; lack hindlimbs - have flattened tail.
Carnivora - Flesh-eating Mammals - Land
1. Dogs, cats, raccoons, bears, hyenas, and otters
2. Most eat meat - some members are omnivores
3. Have long canine teeth, strong jaws, and clawed toes
4. Most have keen senses of smell and vision
Pinnipedia - Flesh-eating Mammals - Water
1. Sea lions, seals, and walruses
2. Water dwelling carnivores
Artiodactyla - Even Toed Hoofed Mammals
1. Deer, bison, cow, sheep, goats, pigs
2. Even toed Ungulates
a. UNGULATES - hoofed mammals
b. Hoof is CLOVEN or split
3. Most are herbivores.
4. Have a storage chamber in stomach called RUMEN - one of four
a. Stores chewed and swallowed plant material; Bacteria breaks down cellulose
b. Partially digested material called CUD is chewed again, swallowed and passed through digestive
system a second time.
c. Double digestion removes more nutrients from grasses
5. Many are domesticated - farm animals
Perissodactyla - Odd Toed Hoofed Mammals
1. Horse, zebra, rhinoceros, tapir
2. Odd toed Ungulates - hoof not split or has 3 toes
3. Herbivores
4. Have a CECUM - blind pouch at end of small intestine - contain bacteria that aid in breakdown of
tough plant material
Proboscidae - Trunknosed Mammals
1. Elephants - only 2 species alive today; Woolly Mammoth - extinct
a. African Elephant - Larger; large fan-like ears, gray bodies
b. Indian or Asian Elephant - Smaller; small ears, tan-gray bodies, "circus" elephants easier trained
2. Characterized by boneless, trunked nose or PROBOSCIS
a. Very sensitive - contains many nerve endings
b. Used to pick up and carry objects
3. Largest land dwellers alive today
4. Have 2 upper incisors and 12 molars
a. Incisors in males develop into tusks - ivory - grow continually
b. Molars grind food.
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M. Primates - Tree dwelling Mammals
1. Lemurs, tarsiers, monkeys, apes, and human
2. Most are omnivores
3. Characteristics
a. Stereoscopic vision
b. Opposable thumb
c. Cerebrum of brain is highly developed.
4. Monkeys
a. Old World Monkeys - Baboon - long tails not used for climbing
b. New World Monkeys - Squirrel Monkey - Prehensile tail curls around branches - used to climb
III. Mammalian Reproduction - Placental Mammals
A. Fertilization is internal 1. Male places sperm inside female by use of penis
a. Contains urethra - tube through which both urine and semen are released to the outside
b. Contains spongy tissue - becomes turgid and erect when filled with blood.
c. Semen - fluid containing sperm and secretions that nourish and protect the sperm
d. Forcibly expelled from body during orgasm by strong muscular contractions of sperm ducts called ejaculation
2. Sperm produced in the testes
a. Oval shaped organs
b. Contained in pouch of skin called scrotum - serves to lower the temperature of the testes
B. Most female mammals go through an ESTROUS CYCLE 1. Series of chemical and physical changes leading up to release of mature eggs
2. Female is in estrous or "heat" - physical and behavioral changes that coincide with egg maturation
3. Male recognizes and interprets changes
4. Female will only mate when mature eggs are present - sometimes only once a year.
5. Ensures proper timing so egg and sperm can unite.
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