Chapter 31Reptiles and Birds

Mrs. Rushing Biology 2

Nonvertebratechordates

FishesAmphibians

ReptilesBirds

Mammals

Invertebrate ancestor

Reptiles Pgs. 797-805

What Is a Reptile?

•Body plan typical to that of other land vertebrates

Well developed skullBackboneTailTwo limb girdlesFour limbs

Characteristics of all Reptiles

•Vertebrate•Dry, scaly skin where scales can be

smooth or rough and most times shed•Lungs•Terrestrial eggs with several membranes

•**Enable reptiles to live their entire lives out of water

Reptilian skin• Dry • Often covered with thick,

protective scales• Smooth or rough• Protection• Helps prevent the loss of

body water

• ***Dry waterproof skin has a disadvantage. Can you think of what this might be?

Body Temperature Control

•Ectotherms –Animal that relies in interactions with the environment to help it control body temperature.

•If they want to get warm they go into the sun and if they want to cool off they get out of the sun

Feeding

•Herbivores – Iguanas•Long digestive systems enable them to

breakdown plant material.

•Carnivores – snakes, crocs, and alligators

•Grab prey with their strong jaws and swalow most meals whole.

Respiration

•To exchange gases with the environment , reptiles have two efficient lungs or, in in the case of certain species of snake, one lung.

•Lungs are more spongy than amphibians for better exchange gases – reptiles can NOT exchange gases through skin

Circulation•Closed, double loop heart system

Loop one- brings blood to and from the lung Loop two- brings blood to and from the rest of the

body

•2 atria and either 1 or 2 ventricles

•Most reptiles don’t have a completed septum

•Crocs and gators have most developed hearts of living reptiles (much like a mammal heart)

Section 31-1

To body

To lungs

From body

From lungs

Right atrium

Left atrium

Incomplete division

Ventricle

Kidney Liver

Heart

LungDigestivetract

BladderCloaca

The Structure of a Turtle’s Heart

Excretion•Urine either contains ammonia or uric acid•If mostly a water animal - ammonia (which

is toxic) is excreted because it can be diluted•If mostly a land animal – uric acid is

excreted (a white paste because water is absorbed in cloaca)

• ****By eliminating wastes that contain little water, a reptile can conserve water.

Response

•Active during the day and have complex eyes and see color very well

•Many snakes have a very good sense of smell and some can detect heat and ground vibrations through bones in their skulls

•Nostrils and sensory organs on roof of mouth that can detect chemicals

•Simple ears with external eardrums and a single bone that conducts sound to the inner ear.

Movement

•Reptiles have legs with larger stronger limbs enabling them to: walk, run, burrow, swim, or climb

•May have rotated legs under the body to carry more weight

•Backbones of reptiles help accomplish most of their movement

Reproduction• Internal fertilization in which male deposits

sperm inside the female’s cloaca• Most male reptiles have a penis• After fertilization, the female’s reproductive

system covers the embryo with several membranes and a leathery shell

• Most reptiles are oviparous, laying eggs that develop outside the mother’s body.

• By carrying her eggs within her body, eggs are protected and kept warm.

Amniotic egg

•Most important adaptation to life on land•Four membranes surround the developing

embryo:•1. amnion•2. yolk sac•3. chorion•4. allantois

Section 31-1

Allantois-Embryo

Shell

-Amnion

Chorion

Yolk sac-

 The Amniotic Egg

The chorion regulatesthe transport ofoxygen from thesurface of the eggto the embryo andthe transport ofcarbon dioxide,one product ofrespiration, in theopposite direction.

This baglike structurecontains a yolk thatserves as a nutrient-richfood supply for the embryo.

The amnion is a fluid-filled sacthat surrounds and cushionsthe developing embryo. Itproduces a protected, wateryenvironment.

--

The allantois stores thewaste produced by theembryo. It also servesas a respiratory organ.

Groups of Reptiles• 1) Lizards and snakes ( Order Squamata)

• 2) Crocodilians – crocs, gators, caimans, and gavials (Order Crocodilia) Alligators live in fresh water while crocodiles live in fresh or salt water

• 3) Turtles and Tortoises (Order Testudines) Turtle lives in water; tortoises on land. Shell consists of dorsal carapace and ventral plastron.

• 4) Tuataras (Order Sphenodonta) Only living member. Lack external ears, scales, and have a third eye located on top of brain

Reptile Review

•Complete Section Assessment pg. 805 1-6

Birds

Nonvertebratechordates

FishesAmphibians

ReptilesBirds

Mammals

Invertebrate ancestor

•Silent Spring

• Rachel Carson wrote the book Silent Spring in the 1960s. As the title suggests, she describes waking up on a spring morning, hearing none of the usual chirping of songbirds and wondering what happened to them. Carson’s book increased awareness of the use of pesticides in the environment. Unfortunately, one of the chemicals that had been used interfered with the formation of the shells of birds’ eggs.

•With a partner, discuss and answer the questions that follow.

•1. What effect would weak eggshells have on the population of birds? How might this cause a “silent spring”?

•2. If you were a legislator, what would you do about the use of chemicals such as pesticides in our environment?

What is a bird?

•Reptilian-like animals•Maintain a constant internal body temp.•Outer covering of feathers•2 legs that are covered with scales and

used for walking or perching•Front limbs modified into wings

•Most of these features are adaptations for flight.

Feathers

•Single most important characteristic that separates birds from living reptiles and other living animals

•Made of protein •Develop from pits in birds skin•Help fly and to keep warm•2 types

1. Contour-provide lifting & balance needed for flight

2. Down-traps air close to body to keep warm

Form, Function, and Flight

•1) Body Temperature Control

▫Endotherms – can generate their own heat

▫High metabolism – which produces heat

▫Feathers insulate body

Form, Function, and Flight

•Adaptations enabling flight:

▫1. Highly efficient digestive, respiratory, and circulatory systems

▫2. Aerodynamic feathers and wings

▫3. Strong chest muscles

How does the bird’s skeletal system enable flight?

•Fused bones provide sturdy attachments for muscles. Cross bracing and air spaces in the bones make them strong and lightweight.

2) Feeding• Pathway of food: mouth, esophagus, crop, stomach,

gizzard, intestines, cloaca

• Any body heat must be regained by eating food. The more food a bird eats, the more energy its metabolism can generate.

• Small birds must eat more because they lose heat faster

• Beaks or bills are adapted to what type food they eat

Beaks or Bills

•Insect-eating birds have short, fine bills•Seed –eaters have short, thick bills•Carnivorous birds long, hooked bills to

shred prey• Long, thin bills gather nectar from

flowers or probing soft mud for worms•Large, long bills help to pick fruit from

branches•Long, flat bills grasp fish

Digestive System• Birds have no teeth and cannot breakdown food

by chewing. Have a crop that stores and moistens the food

• From crop moves to stomach.

If they eat meat- have expandable area where large amounts of food can be stored

If they eat insects or seeds-have a muscular organ called gizzard that helps breakdown food by grinding it

Food moves from here to small intestine where food is absorbed into the body

Wastes leaves the body through the cloaca

Esophagus

Crop

Liver

Firstchamberof stomach

Gizzard Smallintestine Cloaca

Pancreas

Air sac

KidneyHeart

Lung

Brain

When a bird eats,food moves downthe esophagus andis stored in the crop.

1

As digestion continues,the food moves throughthe intestines.

4

Undigested food isexcreted through thecloaca.

5

Large intestine

The muscular wallsof the gizzard squeezethe contents, while small stones grind the food.

3

Moistened food passes to the stomach, a two-part chamber. The first chamber secretes acid and enzymes. The partially digested food moves to the second chamber, the gizzard.

Anatomy of a Pigeon

2

3) Respiration•When a bird inhales, most air enters a large

posterior air sac in the body cavity and bones•Air travels through a series of tubes in a single

direction ensuring that lungs are constantly exposed to oxygen-rich air

•Helps maintain high metabolic rate to maintain body temperature and flight. As well as, allowing birds to fly at oxygen depleted high altitudes

4) Circulation

•Closed, double loop system•Heart has 4 chambers with a complete

septum dividing heart into left and right halves

•Pathway:•Right atrium receives oxygen poor blood

from body and pumps this blood to lungs•Left atrium receives the oxygen rich blood

and pumps this to body

Right atrium

Left atrium

Complete division

Heart

Domestic pigeon

Left ventricle

Right ventricle

Structure of a Bird’s Heart

5) Excretion

•Very similar to reptiles – nitrogenous waste is converted to uric acid, water is absorbed by body and a white paste is expelled from bird

6) Response

•Brain is relatively large for animal’s size•Can see color very well•Can hear quite well•Taste and smell are NOT well developed

7) Movement• Most birds fly – Which ones cannot??

• Skeleton is changed slightly to help a bird fly – near collarbone, hollow bones making skeleton more rigid. Form sturdy frame for muscles needed for flight

• Large chest muscles that power the upward and downward wing strokes

• Muscles attach to keel that runs down breastbone

which are that also that power that provide that ensure

have the followingadaptations to flight

Birds

Homologous tofront limbs in other

vertebrates

Providewarmth

Upward anddownward wing

strokes

One-way flowof O2-rich air

O2 distributionto body tissues

Wings FeathersStrong chest

muscles

Efficientrespiratory

system

Efficientcirculatory

system

8) Reproduction• Both male and female reproductive tracts open

into the cloaca

• Sex organs, which are internal, often shrink in size when not breeding

• Mating birds press their cloacae together to transfer sperm to egg (some birds have penis)

• Bird eggs are amniotic with a harder shell than reptile eggs

How does a chick get out of its shell?

•When a chick is ready to hatch, it uses a small tooth on its bill to make a hole in the shell. After much poking and prodding the shell breaks open

Groups of Birds•30 different orders•Largest is the perching birds – songbirds.

There are over 5000species•Other groups:

▫Pelicans▫Parrots▫Birds of Prey – owls, eagles, hawks▫Cavity nesting birds – woodpeckers▫Herons▫Ostriches▫Penguins

Bird Review•1) Are birds ectotherms or endotherms?

•2) What characteristics do birds have in common?

•3) How are birds adapted for flight?

•Bonus: Are robins in Iowa year round?