Chapter 34Reptiles and Birds

Section 1The Reptilian Body

Key Characteristics of ReptilesRelatives of dinosaurs

Important members of ecosystemsKill insect pests and

small rodents

Some are poisonous/dangerous

Many go unnoticed

Can’t live in cold climatesNot conducive to

ectothermic organisms

Bony skeleton and 2 pairs of limbsExcepts snakes and

some lizards

Toes with claws

Small brains in relation to their body

Ectothermic MetabolismMust absorb heat from their surroundings

Metabolism is too slow to generate enough heat to warm their bodies

Use the sun to warm their bodies and shade to cool their bodies

Become very sluggishduring cold periods

Temperature is majorlimiting factor on theirrange

Water RetentionAmphibians must spend time in water to

compensate for extra water loss, reproduce and developNot fully terrestrial

Reptiles have evolutionary adaptations to avoid thisWatertight skinWatertight eggs

Watertight SkinTerrestrial animals are susceptible to water loss

through their skin

Reptiles have skin of light, flexible scalesScales overlap to form a nearly watertight skinDecreases amount of water lost through skin

Watertight EggsSperm and eggs dry out without watery environment

Fertilized eggs require a moist environment

Amniotic eggContain a water and food supply Shell is essentially watertight

Does not dry outMost reptiles, birds and some mammals utilize the

amniotic eggAmniotic egg suggests that birds, reptiles and mammals

evolved from a common ancestor

RespirationUsually more active than

amphibiansRequire greater metabolic processes to obtain

oxygen

Utilize lungs and heart

LungsScaly skin does not allow gas exchange

Can’t use skin as additional respiratory surface like amphibians

Lungs of reptiles have internal folds that increase the surface area/capacity

Reptiles have large muscles that attach to their rib cageMuscle help move air in and out, increasing efficiency

HeartOxygen-rich and poor blood mix in an amphibians

ventricle

Reptiles have a septum that allows for the separation of bloodOxygen is delivered to the body more efficiently

Crocodiles have a completely divided heartAllows for even greater efficiency

p. 776 – fig. 5

ReproductionEggs fertilized within females

OviparousYoung hatch from eggsSusceptible to predators

OvoviviparousFemale retains the eggs within their body until right

before hatching or until egg hatchesLess susceptible to predators

Section 2Today’s Reptiles

LizardOrder Squamata

Include iguanas, chameleons, geckos, horned lizards

Most are carnivores

1 – 10 ft. long

Can regenerate tail

SnakesOrder: Squamata

Lack moveable eyelids and external ears

Molt periodically

Flexible jaw5 points of movement

ConstrictorsSqueeze prey until

they suffocate

No teeth for cutting or chewingSwallow prey whole

Some contain venomous fangs

Turtles and Tortoises Order: Chelonia

Body encased in hard protective shell Consists of 2 parts

Carapace – dorsal side of shell

Plastron – ventral side of shell

Able to pull limbs inside shell for protection

Shell shaped due to habitat

Lack teeth, but jaws are covered by sharp plates

Most are herbivores Snapping turtle is carnivorous

CrocodilesOrder: Crocodilia

Most closely related to dinosaurs

Aggressive carnivoresReach as long as 20 ft.

in some areas

Very stealthyOften sneak up on prey

Eyes and snout on top of headCan see and breath

while body is submerged

Care for young after hatching

Tuataras Order: Rynchocephalia

Native to New Zealand

Lizard-like reptiles

Reach up to 2 ft.

Most active during cooler temperatures

Nearly unchanged for the last 150 million years

Numbers are currently declining

Section 3Characteristics and Diversity of Birds

Key Characteristics of Birds Members of class Aves

Some species can’t fly

Usually lack teeth

Lay amniotic eggs

Feet and legs covered with scales

Presence of feathers and modification of forelimb into wings

Body covered with feathers

Lightweight bones

Endothermic metabolism

Very efficient respiratory system

Completely divided ventricle

FeathersModified reptilian scales

Birds molt and replace their feathers Usually doesn’t happen at once

2 main types: Contour

Cover birds body and give them their shape Provide lift for flight

Down Cover young birds and found under contour feathers

Preening Linking of barbs of feathers

Preen gland Secretes oil that cleans and waterproofs feathers

Strong, Lightweight SkeletonBones are thin and hollow

Many bones are fused, making the skeleton very rigid

Large breast muscles Provide power for flight and swimming

Fused collarbone and keeled breastbone

Endothermic MetabolismWarm-blooded

Metabolism generates enough heat to warm body

104-108 F

High temp. due to high rate of metabolism required to produce energy for flightHummingbirds – range 20-80 wing beats per

second

Completely Divided VentricleVentricle completely divided by septum

Keeps oxygen-rich and oxygen-poor blood separateOxygen is delivered to the body more efficiently

Hummingbirds may have ~1000 heart beats per minute

Highly Efficient LungsBirds require large amounts of energy during

flight

One-way oxygen flowMade possible by air sacs connected to their lungsSacs are a holding tanks of airp. 787 – figure 18

2 advantages of one-way air flowLungs exposed to air that is nearly entirely oxygenatedBlood and oxygen flowing in opposite directions

increases absorption

Adaptations of BirdsMade possible by differences in beaks, legs, and

feetTalons for grasping preyBeaks for shoveling mud or moving waterWebbed feet for swimmingBeaks for crushing seedsCurved feet for grasping branches

Wings modified for swimmingAdaptations allow birds to utilize various resources

Other AdaptationsSeagulls body shape allows them to fly over

waterStreamlined

Owls eyesight allows them to hunt at nightNocturnal