Vertebrate Unit 2 - BIOLOGY JUNCTION

Reptile

Reptiles All Materials © Cmassengale

Evolution of Reptiles:

Reptiles were 1st vertebrates to make a complete transition to life on land (more food & space)
Arose from ancestral reptile group called cotylosaurs (small, lizard like reptile)
Cotylosaurs adapted to other environments in Permian period
1. Pterosaurs – flying reptiles
2. Ichthyosaurs & plesiosaurs – marine reptiles
3. Thecodonts – small, land reptiles that walked on back legs
Mesozoic Era called “age of reptiles”

Dinosaurs dominated life on land for 160 million years
Brachiosaurs were largest dinosaurs
Herbivores included Brontosaurus & Diplodocus, while Tyrannosaurus were carnivores
Dinosaurs became extinct at end of Cretaceous period
Mass extinction of many animal species possibly due to impact of huge asteroid with earth; Asteroid Impact Theory
Amniote (shelled) egg allowed reptiles to live & reproduce on land

Amniote Egg:

Egg had protective membranes & porous shell enclosing the embryo
Has 4 specialized membranes — amnion, yolk sac, allantois, & chorion
Amnion is a thin membrane surrounding a salty fluid in which the embryo “floats”
Yolk sac encloses the yolk or protein-rich food supply for embryo
Allantois stores nitrogenous wastes made by embryo until egg hatches
Chorion lines the inside of the shell & regulates oxygen & carbon dioxide exchange
Shell leathery & waterproof
Internal fertilization occurs in female before shell is formed

Section 1 Review

Terrestrial Adaptations:

Dry, watertight skin covered by scales made of a protein called keratin to prevent desiccation (water loss)
Toes with claws to dig & climb
Geckos have toes modified into suction cups to aid climbing
Snakes use scales & well developed muscular & skeletal systems to move
Lungs for respiration
Double circulation of blood through heart to increase oxygen to cells
Partial separation in ventricle to separate oxygenated & deoxygenated blood
Ectothermic – body temperature controlled by environment
May bask or lie in sun to raise body temperature or seek shade to lower body temperature; known as thermoregulation
Water conserved as nitrogen wastes excreted in dry, paste like form of uric acid crystals

Section 2 Review

Modern Reptiles:

Only 4 living orders remain
Found worldwide except in coldest ecosystems
Orders include —– Rhyncocephalia (tuatara lizard), Chelonia (turtles & tortoises), Squamata (lizards & snakes), & Crocodilia (alligators, caimans, and crocodiles)

Rhyncocephalia:

Only one living species, Spenodon punctatus, (tuatara lizard)
Live on islands off the coast of New Zealand

Tuatara
Tuatara

Spiny crest running down back
Grows up to 60 cm in length
Has 3rd eye on top of head (parietal eye) that acts as a thermostat
Most active when temperatures are low (nocturnal)
Often burrow during the day
Feed on insects, worms, & small animals at night

Chelonia:

Includes turtles and tortoises
Aquatic, but lay eggs on land
Body covered with shell composed of hard plates & tough, leathery skin
Carapace or dorsal surface of shell fused with vertebrae & ribs
Plastron is ventral shell surface
Shape of shell modified for habitat
Dome shaped shell helps to retract head & limbs in tortoises

Galapagos Tortoise

Water-dwelling turtles have streamline, disk shaped shell to rapidly move in water

Spotted Turtle

Forelimbs of marine turtles modified into flippers

Green Turtle found on Guernsey 1/2003 (Photograph © by Richard Lord, Guernsey)
Marine Turtle

River & sea turtles migrate to breeding areas where they hatched to lay their eggs on land

Crocodilia:

Includes crocodiles, alligators, caimans, & gavials
Direct descendants of Archosaurs
Carnivorous (wait for prey to come near & then aggressively attack)
Eyes located on top of head so they can see when submerged
Nostrils on top of snout to breathe in water
Valve in back of mouth prevents water from entering airway when feeding underwater
No parental care of young in most species except Nile crocodile that carry young in their jaws & guards nest
Crocodiles are tropical or subtropical, usually nocturnal, reptiles found in Africa, Asia, South America, & southern Florida

Australian photographs - crocodile
Australian Crocodile

Alligators are found in China & the southern United States

American Alligator

Caimans are native to Central America & resemble alligators

Black Caiman

Gavials, living only in India & Burma, are fish eating reptiles with very slender, long snouts

Gavial

Squamata:

Includes snakes & lizards
Snakes probably evolved from lizards during the Cretaceous period
Snakes have 100-400 vertebrae each with a pair of ribs & attached muscles for movement
Interaction of bone, muscles, & skin of snakes allows them 3 ways to move — lateral, rectilinear, & side winding
Lateral undulations:
1. Most common
2. Head moves side to side causing wave of muscular contractions
3. Snake uses sides of its body to push off of ground
4. Snake moves forward in S-shaped path
Rectilinear Movements:
1. Muscular force applied to belly & not sides of snake
2. Scutes or scales on belly catch on rough surfaces
3. Body relaxes & then moves forward slowly
Sidewinding:
1. Used by some desert snakes
2. Sideways movement of body
3. Head vigorously flung from side to side
4. Whiplike motion moves body along
Do not hear or see well but locate prey using forked tongue that gathers chemical scents
Swallow prey whole:
1. Jaws unhinge for mouth to stretch
2. Small teeth used to hold prey in mouth
3. Windpipe thrust into throat while swallowing so snake can swallow & breathe
4. Swallowing may take several hours
5. Saliva begins digestion during swallowing
Constrictors wrap body around prey & squeeze them to death (boas, pythons, etc.)
Snakes may inject venom or poison:
1. Hemotoxin – poisonous proteins attacking red blood cells (water moccasin & rattlesnake)
2. Neurotoxin – poison that works on nervous system affecting heart rate & breathing (copperhead)
Venomous snakes with 3 types of fangs — rear-fanged, front-fanged, & hinge- fanged snakes
Rear-fanged snakes bite prey & use grooved back teeth to guide venom into puncture (boomslang)
Front-fanged snakes inject poison through 2 small front fangs that act like a hypodermic needle (cobra)

Spitting Cobra

Hinged- fang snakes have hinged fangs in roof of mouth that swing forward to inject poison (rattlesnake, water moccasin, copperhead)


Rattlesnake	Water Moccasin

Often camouflaged for defense
May use signals such as cobra expanding its hood, rattlesnake shaking its rattle, or hissing for defense
Most snakes locate females by scent
Internal fertilization with no parental care
May be oviparous (eggs hatch outside body) or ovoviviparous (eggs held inside body until hatch)
Lizards:
1. Four limbs
2. Includes iguanas, geckos, skinks, chameleons, etc.
3. Rely on speed, agility, & camouflage to catch prey
4. Feed on insects & small worms
5. Some, such as anole & chameleon, can change colors for protection
6. May use active displays such as squirting blood, hissing, or inflating bodies
7. Some show autotomy (breaking off tail to escape predators)
8. Two poisonous U.S. species include Gila Monster & Beaded Lizard

Gila Monster

Komodo dragon of Indonesia is largest lizard reaching 3 meters in length

Section 3 Review

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Introduction
Mammals have four-chambered hearts and double circulation. The heart of a bird or mammal has two atria and two completely separated ventricles. The double-loop circulation is similar to amphibians and reptiles, but the oxygen-rich blood is completely separated from oxygen-poor blood. The left side of the heart handles only oxygenated blood, and the right side receives and pumps only deoxygenated blood. With no mixing of the two kinds of blood, and with a double circulation that restores pressure after blood has passed through the lung capillaries, delivery of oxygen to all parts of the body for cellular respiration is enhanced. As endotherms, which use heat released from metabolism to warm the body, mammals require more oxygen per gram of body weight than other vertebrates of equal size. Birds and mammals descended from different reptilian ancestors, and their four-chambered hearts evolved independently – an example of convergent evolution.

Objective
Using a pig heart, students will observe the major chambers, valves, and vessels of the heart and be able to describe the circulation of blood through the heart to the lungs and back and out to the rest of the body. (The pig heart is used because it is very similar to the human heart in structure, size, & function.)

Materials
Dissecting pan, dissecting kit, safety glasses, lab apron, pig heart, & gloves

Procedure – External Structure

Place a heart in a dissecting pan & rinse off the excess preservative with tap water. Pat the heart dry.
Examine the heart and locate the thin membrane or pericardium that still covers the heart. The pericardium or pericardial sac, is a double-layered closed sac that surrounds the heart and anchors it. The pericardium consists of two tissues layers – the visceral pericardium that covers the surface of the heart & the parietal pericardium covering the inner surface of the parietal sac. These two tissue layers are continuous with each other where the vessels enter or leave the heart. The slender gap between the parietal & visceral surfaces is the pericardial cavity & is filled with fluid to reduce friction between the layers as the heart pumps.
After examining the pericardium, carefully remove this tissue. Located below the pericardium is the muscle of your heart called the myocardium. Most of the myocardium is located in the lower two chambers of the heart called ventricles.
Locate the tip of the heart or the apex. Only the left ventricle extends all the way to the apex.
Place the heart in the dissecting pan so that the front or ventral side is towards you ( the major blood vessels are on the top and the apex is down). The front of the heart is recognized by a groove that extends from the right side of the broad end of the heart diagonally to a point above & to your left of the apex.

Front or Ventral Side of the Heart

The heart is now in the pan in the position it would be in a body as you face the body. Locate the following chambers of the heart from this surface:
- Left atria – upper chamber to your right
- Left ventricle – lower chamber to your right
- Right atria – upper chamber to your left
- Right ventricle – lower chamber to your left

pig heart dissection

While the heart is still in this position in the dissecting pan, locate these blood vessels at the broad end of the heart:

Coronary artery – this blood vessel lies in the groove on the front of the heart & it branches over the front & the back side of the heart to supply fresh blood with oxygen & nutrients to the heart muscle itself.
Pulmonary artery – this blood vessel branches & carries blood to the lungs to receive oxygen & can be found curving out of the right ventricle (upper chamber to your left)
Aorta – major vessel located near the right atria & just behind the pulmonary arteries to the lungs. Locate the curved part of this vessel known as the aortic arch. Branching from the aortic arch is a large artery that supplies blood to the upper body.
Pulmonary veins – these vessels return oxygenated blood from the right & left lungs to the left atrium (upper chamber on your right)
Inferior & Superior Vena Cava – these two blood vessels are located on your left of the heart and connect to the right atrium (upper chamber on your left). Deoxygenated blood enters the body through these vessels into the right receiving chamber. Use your probe to feel down into the right atrium. These vessels do not contain valves to control blood flow.

Procedure – Internal Anatomy:

Use scissors to cut through the side of the pulmonary artery and continue cutting down into the wall of the right ventricle. Be careful to just cut deep enough to go through the wall of the heart chamber. (Your cutting line should be above & parallel to the groove of the coronary artery.)
With your fingers, push open the heart at the cut to examine the internal structure. If there is dried blood inside the chambers, rinse out the heart.
Locate the right atrium. Notice the thinner muscular wall of this receiving chamber.
Find where the inferior & superior vena cava enter this chamber & notice the lack of valves.
Locate the valve that between the right atrium and right ventricle. This is called the tricuspid valve. The valve consists of three leaflets & has long fibers of connective tissue called chordae tendinae that attach it to papillary muscles of the heart. This valve allows blood flow from the right atrium into the right ventricle during diastole (period when the heart is relaxed). When the heart begins to contract (systole phase), ventricular pressure increases until it is greater than the pressure in the atrium causing the tricuspid to snap closed.

Tricuspid Valve

Use your fingers to feel the thickness of the right ventricle and its smooth lining. Also note the network of irregular muscular cords on the inner wall of this chamber.
Find the septum on the right side of the right ventricle. This thick muscular wall separates the right & left pumping ventricles from each other.
Inside the right ventricle, locate the pulmonary artery that carries blood away from this chamber. Find the one-way valve called the pulmonary valve that controls blood flow away from the right ventricle at the entrance to this blood vessel.
Using your scissors, continue to cut open the heart. Start a cut on the outside of the left atrium downward into the left ventricle cutting toward the apex to the septum at the center groove. Push open the heart at this cut with your fingers & rinse out any dried blood with water.
Examine the left atrium. Find the openings of the pulmonary veins form the lungs. Observe the one-way, semi-lunar valves at the entrance to these veins.
Inside this chamber, look for the valve that controls blood flow between the upper left atrium and lower left ventricle. This valve is called the bicuspid or mitral valve. This valve consists of two leaflets & blood flows from the left atrium into the left ventricle during diastole.

Bicuspid or Mitral Valve

Examine the left ventricle. Notice the thickness of the ventricular wall. This heart chamber is responsible for pumping blood throughout the body.
Using your scissors, cut across the left ventricle toward the aorta & continue cutting to expose the valve.
Count the three flaps or leaflets on this valve leading from the left ventricle into the aorta and note their half-moon shape. This is called the aortic valve.
Using scissors, cut through the aorta and examine the inside. Find the hole or coronary sinus in the wall of this major artery. This leads into the coronary artery which carries blood to and nourishes the heart muscle itself.
Answer the questions on your lab report.

Click here for questions

When you have finished dissecting the heart, dispose of the heart as your teacher advises and clean, dry, and return all dissecting equipment to the lab cart. Wash your hands thoroughly with soap.

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Fish

Fish

All Materials © Cmassengale

Kingdom – Animalia
Phylum – Chordata
Subphylum – Vertebrata

Vertebrates:

	Include fish, amphibians, reptiles, birds, & mammals
	Have a notochord (slim, flexible rod) present in early stages that may be replaced by backbone in adults
	Contain a dorsal, hollow bundle of nerves called the nerve or spinal cord
	Respire through pharyngeal or gill pouches during early development
	Have post-anal tail in early stages
	Endoskeleton made of bone &/or cartilage
	Anterior head with well developed brain & sensory organs (Cephalization)
	Closed circulatory system

Taxonomy of Vertebrates:

Agnatha include hagfish & lamprey with long, eel-like bodies without jaws or paired fins & cartilage skeletons

Chondrichthyes include sharks, rays, & skates with cartilage skeletons, paired fins, & jaws

	Osteichthyes are bony fish with jaws, paired fins, & bone and cartilage in their skeletons
	Amphibia include frogs, toads, & salamanders that go through an aquatic larval or tadpole stage
	Reptilia include snakes, turtles, lizards, & alligators that live on land, are covered with scales, & lay a tough, protective amniote egg
	Aves are birds covered with feathers, adapted for flying, & with hollow bones
	Mammalia have hair or fur & females have mammary or milk-producing glands

Evolution:

	Fossil record shows jawless fish without paired fins appeared first about 550 million years ago
	Ostracoderm was a jawless, bottom-feeding ancestor to the agnathans (modern jawless fish)

	Development of jaws & paired fins allowed better movement & increased ability to capture prey
	Extinct acanthodians or spiny fish were first jawed fish with paired fins

Jaws probably developed from gill arches (bone that supports the pharynx)

Characteristics of Fish:

	Streamlined body & muscular tail for swimming
	Most with paired fins for maneuvering
	Body covered with protective scales & mucus layer to reduce friction when swimming
	Have less dense body tissues & store less dense lipids to help them float
	Respire through gills
	Most have a lateral line system or a row of sensory structures running down each side of the organism to detect changes in water temperature, pressure, current, etc.

	Most with well-developed sense of sight & smell
	Some can detect electrical currents
	Ectotherms (adjust body temperature to environment)
	Two chambered heart (upper atrium receives blood & lower ventricle pumps blood)

Agnatha (Jawless Fish):

	Hagfish (live in oceans) & lampreys (found in marine & freshwater)
	Circular mouths
	Sharp teeth & strong rasp-like tongue to tear hole in prey & suck out blood & body fluids

	Known as cyclostomes
	Eel-shaped body
	Mucus covers body
	Skeleton made of cartilage
	No paired fins
	Gills without bony cover (called operculum)
	Retain their notochord throughout their life
	Hagfish are bottom dwellers in cold marine waters that burrow in mud, scavenge on dead & dying fish, & have tentacles around their mouth
	Lampreys are usually parasites with a keen sense of smell to locate prey, lay their eggs in freshwater streams, & are covered with a poisonous slime

Chondrichthyes

	Includes sharks, rays, & skates
	Endoskeleton of cartilage
	Hinged jaws & paired fins
	Placoid scales & tooth-like dermal spines on scales

	Marine
	Carnivorous
	Sharks are torpedo shaped

Rays & skates have broad, flat bodies with wing-like fins and a tail

Shark Characteristics:

	Fast swimmers
	Large, oily liver (20% of body weight) makes them buoyant
	Tough, leathery skin
	Fierce predators
	Whale shark is largest & filter feeds on plankton

	Ventral mouth with 6-20 rows of sharp, replaceable teeth
	Short, straight intestine with spiral valve to slow food movement
	5-7 pairs of gills for gas exchange
	Kidneys remove wastes & maintain water balance
	Electroreceptors on head help find prey & navigate
	Lateral line along side of body contains sensory cells to detect vibrations & pressure
	Separate sexes with external fertilization

Ray & Skate Characteristics:

	Usually harmless to humans
	Broad, wing-like pectoral fins used to glide through water
	Flattened bodies with ventral mouth
	Both eyes on top of head
	Have protective coloration (darker on top & lighter on bottom)
	Feed on fish & invertebrates
	Stingray with poison spine by tip of tail

	Electric ray gives off strong, electric shock
	Manta ray is largest

Traits of Bony Fish (Osteichthyes)

	Skeleton made of bone
	Hinged jaws
	Paired fins
	Gills for gas exchange
	Lateral line
	Body covered with scales & mucus coating
	Includes lobe-finned, ray-finned, and lung fish

Lobe-finned Fish:

	Muscular, paddle-like fins supported by bone
	Gills
	Known as coelacanths

	Thought to be extinct until 1938 when species found in Africa
	Live in deep oceans

Lungfish:

	Use lungs & gills
	Eel-shaped body

	Live in shallow, tropical rivers of Africa, Australia, & South America
	Come to surface & gulp air when oxygen level is low
	Form mud cocoon & become dormant if stream dries up

Ray-finned Fish:

	Fan-like fins supported by rays
	Includes salmon, perch, catfish, tuna, etc.
	Body covered with round, overlapping cycloid or ctenoid scales & mucus

Four sets of gills covered by bony operculum

	Have movable fins
	Dorsal fin(s) located on top keep fish upright & used for defense
	Caudal fin or tail moves side to side to help steer
	Pectoral fins (paired) on each side behind the operculum
	Pelvic fins (paired) on ventral surface near the head
	Anal fin (single) behind anus

Swim bladder is thin-walled sac in abdomen that creates buoyancy from diffusion of dissolved gas from blood

	Kidneys filter the blood & help maintain water balance
	Ectothermic – body temperature regulated by the environment
	Keen sense of smell (nostrils) & have chemical receptors over the body
	Can detect the earth’s magnetic field as a guide to navigate oceans
	Have separate sexes with external fertilization
	Eggs hatch into fry

Salmon Life Cycle:

	Migrate up to 3200 kilometers following magnetic cues in the ocean
	Follow mucus trails when navigating rivers
	Return to birthplace to spawn
	Males change color & jaw lengthens & develops a hook

	Female uses her tail to build gravel nest & lays up to 10,000 eggs
	Male deposits sperm over eggs
	Adults usually die after spawning
	Pacific salmon return to sea when 15 cm long; while Atlantic salmon may stay in river up to 7 years
	Secrete mucus coating in river as return to sea
	May stay in ocean 6 months to 5 years


Tasmanian Devil	Armadillo
Marsupial	Placental

ARTIODACTYLA	CARNIVORA	CETACEA
CHIROPTERA	EDENTATA	INSECTIVORA
LAGOMORPHA	MARSUPIALIA	MONOTREMATA
PERISSODACTYLA	PRIMATES	PROBOSCIDEA
RODENTIA	SIRENIA

Category: Vertebrate Unit

Reptile

Mammal

Mammal Orders

Pig Heart Dissection

Fish


Echidna	Platypus
Monotremes


Echidna	Platypus
Monotremes


Koala & baby	Opossum


Mole	Shrew