Reptiles

310 million years ago… reptiles were the first vertebrates to make the complete transition to life on land

• limited competition for the insects and plants that could be used as food on the land

• an increase in competition for food and space among all the life-forms in aquatic environments

Adaptations to Land

Amniote Egg

• The allantois stores the nitrogenous wastes produced by the embryo until the egg hatches

• an egg with a protective membrane and a porous shell enclosing the developing embryo.

-It forms a “nursery” to protect the embryo

- The egg derives its name from the amnion, the thin membrane enclosing the salty fluid in which the embryo floats.

• They yolk sac encloses the yolk, a protein rich food supply for the developing embryo

• The chorion lines the outer shell and thus encloses the embryo and all the other membranes. It regulates the exchange of oxygen and carbon dioxide between the egg and the outside environment.

• The entire amniote egg is surrounded by a leathery shell that may be hard in some species because of the presence of calcium carbonate.

-The egg is water proof, however it allows gases to flow between the environment and the chorion.

• The male places the sperm inside the female before the shell is formed. This is called internal fertilization, makes water transport of sperm unnecessary.

Waterproof Skin• dry body covering of

horny scales or plates– develops as surface

cells fill w/ keratin- same stuff as bird

feathers and fingernails

– prevent water loss – protect from wear

and tear associated w/ living in rugged terrestrial environments

– unlike amphibians who can’t be far from water or they’ll dry out

External Structural Adaptations (for land)• some limbs have toes

w/ claws – permit to climb,

dig, and move in various terrains

• others have toes modified into suctions cups – aid in climbing

• absence of limbs – snakes use scaly

skin and highly developed skeletal and muscular systems

Respiration• Well developed

lungs (not gills)– tissues

involved in gas exchange area located inside body- kept moist

in even driest environments

A.Respiration

Circulation• like amphibians have

double circulation• most have 3

chambered heart• partial division of

ventricle separates oxygen-poor blood flowing from the body from the oxygen-rich blood returning from the lungs

• alligators and crocodiles have 4 chambered hearts – separation of

oxygenated and deoxygenated blood

Excretion

• conserve water by excreting nitrogenous wastes in dry or pasty form as crystals of uric acid

Temperature Regulation• metabolism rate controlled

in part by body temperature • Ectothermic (cold-blooded) –

body temp controlled by environment

• not endothermic (warm-blooded)

• regulate their temp by behavior

– bask in sun to speed up metabolism

– hide in shade to prevent overheating

Origin and Evolution• From the studies of fossils and comparative

anatomy, biologists infer that reptiles arose from a group of ancestral reptiles called cotylosaurs, which lived about 310 million years ago.

- Fossils indicate that these four-legged, sprawling vertebrates resembled small lizards and had teeth used for eating insects

-The abundance of insects at the time may have been one reason the cotylosaurs flourished.

• during the Permian period these reptiles began to adapt to other available environments, giving rise to new forms of reptiles.

- These groups included flying reptiles called pterosaurs

• - Two groups of marine reptiles: the ichthyosaurs and plesiosaurs

• - And the thecodonts

• The dominant land reptiles came from the thecodonts.

- The small lizard-like carnivores, many of which walked on their hind legs.

• The thecodonts were the first archosaurs ( “ruling reptiles”), a group that later included the early crocodiles, the dinosaurs, and the reptiles that evolved into birds.

• The Mesozoic era is known as the Age of Reptiles.

- During this time reptiles , esp. the dinosaurs, dominated all other forms of life.

- Dinosaur means “terrible lizard” however many of the dinosaurs were small.

• Yet the incredible size of some dinosaurs distinguish the group from all other forms of life.

-One of the largest dinosaurs was the brachiosaurus, 77,00 kg.

• It was as long as a tennis court, as tall as a four-story building, and heavier than elephants.

• Over 300 genera of dinosaurs have been identified around the world. -They were adapted to a wide range of environments.• Brachiosaurus and such related dinosaurs as Diplodocus and

Apatosaurus were herbivores, plant eaters. - They probably used their long necks to reach the top of trees.• Tyrannosaurus and other carnivores, or meat eaters, walked on their

hind legs and used sharp teeth and huge claws to rip apart prey.• The scientist who studies dinosaurs are known as Paleontologists.

Modern Reptiles• Reptiles are classified into 16 orders, 12 that are

extinct. - 4 surviving-6, 000 species• Reptiles occur worldwide except in coldest regions - Human intervention-major impact• 4 living orders of Class Reptilia: - 1. Rhynchocephalia, - 2. Chelonia, - 3. Crocodilia, - 4. Squamata

Rhynochocephalia• Only living species-

Sphenodon punctatus- the tuatara

-  Inhibit islands of coast of New Zealand

- Resembles a large lizard about 60 cm long

- Has an inconspicuous third eye on top of its head- parietal eye- functions as a thermostat- protects from overheating

- Active at low temperatures and feed at night on insects, worms and small animals

Chelonia• Order consists of about 265

species of turtles and tortoises - Tortoise are terrestrial

Chelonia (Galapagos tortoises) - Turtles- chelonians that live

in water - Body covered by a shell

made of hard plates- 2 parts- a carapace and plastron

- Shape is modified for variety of ecological demands

- retract heads, swimming - Forelimbs of a marine turtle

have evolved into flippers and freshwater turtles have webbed toes

- Migratory behavior of sea and river turtles

-return to land to lay eggs

Crocodilia• Order composed of 20 species of large lizard-shaped reptiles- crocodiles, alligators, caimans and gavials 

- Descendants of archosaurs• Crocodilians live in or near

water in tropical/ subtropical regions of the world

• - Crocodiles- nocturnal animals; Africa, Asia and Americas

• -  Alligators - China and southern U.S.

- Caimans- Central America- some in Florida

- Gavials- eat fish; long and slender snout- live only in Burma and India

• Carnivorous- hunt by stealth- features adapted for this behavior  - Eyes on head, nostrils on top of snout

-see and breathe while in water

- Valve to prevent water from entering air passage

- Parental care- both parents care for young by carrying in jaws until development

Squamata• Order consists of 5,640 species

of lizards and snakes - Loosely jointed upper jaw and

paired reproductive organs in males

- Structurally diverse• Lizards- presence of limbs• - Common lizards- iguanas,

chameleons, skinks and geckos  -  Live everywhere except

Antarctic - Special adaptations- agility

and camouflage - 2 species are venomous- Gila

monster (SW U.S.) and beaded lizard (western Mexico)

- Most prey on insects or small animals

- Blend with background - chameleons- remain inconspicuous

and fend off enemies - Horned lizards- spiked armor,

when disturbed they inflate themselves, gape, hiss and squirt blood from eyes

- Skinks and geckos- lose their tails and regenerate- autotomy- escape from predators

- Most lizards are small- .3m in length; iguanas- 1m in length

- Largest lizards- monitors- Komodo dragon (Indonesia) 3m

(9.8 ft) in length, 140 kg (308.6 lbs) - Thought to be related to snakes - have a forked tongue for sense

organs - Consume prey whole and use tail

as defense weapon

Adaptations of Snakes

Snakes probably evolved from lizards that lived above ground

found during the Cretaceous period.

Movement• A snake has a backbone

of 100 to 400 vertebrae, each of which has a pair of ribs attached.

- Providing the framework for thousands of muscles

• The interaction of bones, muscles, and skin enables asnake to move in one of three basic ways:

1. Lateral undulation 2. rectilinear

movement 3. side winding.

Movement cont.• Most commonly move by

lateral undulation. - moving forward in an S

shaped path.• In rectilinear movement,

the snake applies muscular force on its belly, not its sides.

- Scutes are scales on its belly that catch on bark orother rough surfaces (like a caterpillar).

• Some desert-dwellers snakes progress by side-winding.

Feeding

• Snakes eat animals, but lack structural adaptations common to other carnivores.

• Snakes do not see or hear well, and have no limbs, and their teeth and small mouth cannot rip and grind flesh.

Locating Prey • Snakes evolved a sense

of smell which they use to locate their prey.

- By flicking its forked tongue , a snake gathers chemicals from the environment.

• The tongue transfers these chemicals to two pits in the roof of the mouth called the Jacobsons organ where the nerves are highly sensitive to the chemicals.

Locating Prey Cont.• Some snakes inject their prey

with Toxic venom• most bite down their fangs

and inject the poison into their prey.

• Venom is chemically complex.

- The hemotoxins  are proteins that attack the circulator system, destroy red blood cells and disrupt the clotting power of blood.

- The neurotoxins work on the nervous system, by disrupting the nerve pathways which is dangerous to respiratory and heart functions.

Swallowing and Digesting Prey

• A snakes upper and lower jaws are hinged and move independently.

• when unhinged, the jaws stretch to allow the mouth to open extremely wide.

• While swallowing it whole the snake thrusts its windpipe into the throat, allowing the snake to breathe

- the process of can take several hours.

Defense • Natural selection resulted in modifications for defense.• Camouflage is beneficial for both seeking prey and

hiding from predators. - many snakes are green and blend with foliage - others are brown and hide against the bark of trees

Defense Cont.

• Some snakes defend themselves by signaling their presence.

• Some ward off danger by rapidly changing body shape- extending a hood like cobras

• Some hiss• Others make

mechanical noises - such as the rattle of

the rattlesnake.

Reproduction • Most male snakes rely

on the scent of female snakes of heir own species.

• Before mating, a male and female snake may glide alongside by side, with the male stroking the female with his chin and flicking his tongue over her body.

• Fertilization is internal.

Reproduction cont.• Most snakes are oviparous - female lays eggs that

hatch outside her body. - To break out a hatchling

uses a special tooth which is lost soon after.

• Other snakes are ovoviviparous

- the female carries the eggs in her body throughout development

• the young are born live. - All newborns must fend for

themselves, relying on their many specialized adaptations for survival on land.

Las Aves

Phylum Chordata Capítulo 27

Contribuciones biológicas

• Plumas• Incremento de fuerza y disminución de peso

– Patas delanteras modificadas como alas– Huesos huecos– Pico queratinizado– Endotermia– Tasa metabólica alta– Corazones grandes y alta presión– Sistema respiratorio sumamente eficiente– Visión aguda– Coordinación neuromuscular excelente

Características de las aves

• Cuerpo usualmente en forma de huso: cabeza, cuello, tronco, rabo

• Cuello desproporcionalmente largo• Apéndices pareados, los delanteros

usualmente modificados para volar• Pie con 4 dígitos (en algunos 2 ó 3)

Las aves - integumento

• Integumento delgado• Pocas glándulas epidermales• Algunas con glándula uropigial en la

base del rabo• Cuerpo cubierto de plumas; las patas

con escamas• Las plumas se mudan

Las aves - integumento

• Plumas– homólogas a las escamas de los reptiles – se originan del stratum corneum– con músculos en la pared de los folículos – cinco tipos básicos

• contorno (revisten el cuerpo y le dan forma; plumas del vuelo)• plumón (debajo de las de contorno, conservan calor)• cerda (parecidas a pelos; cerca de boca, ojos,y nares; función

variada))• filopluma (esparcidas por la superficie, función desconocida)

Las aves - esqueleto

Esqueleto completamente osificado con cavidades de aire (neumatizados)

Esqueleto fuerte peroliviano

Las aves - esqueleto

• Cada quijada con un pico – formado por alargamiento de huesos

premaxilar y dentario– cubierta queratinizada– sin dientes– modificaciones

Las aves - esqueleto

• Cráneo diápsido, usualmente cinético • Huesos del cráneo delgados y fusionados; con 1

cóndilo occipital• Quijada superior articula con el cráneo• Costillas con procesos uncinados• Vértebras

– cervicales, torácicas, lumbares, sacrales y caudales – muchas están fusionadas (no las cervicales)

• Pigostilo: fusión de las últimas 4 a 7 caudales• Sinsacrum: fusión de las últimas torácicas, las 2 sacrales y las

lumbares

Las aves - esqueleto

• Rabo corto• 1 sólo hueso en el oído medio• Esternón osificado bien desarrollado

– Con quilla: carinado– Sin quilla: rátita

• Fúrcula (clavículas fusionadas) en muchas aves carinadas; otras con clavículas rudimentarias o ausentes

Las aves - esqueleto

• Apéndices con reducción y fusión de huesos– Anterior

• 3 carpos + 3 metacarpos = carpometacarpo• 3 dígitos con número de falanges reducido

– Posterior• Tibia + tarsos proximales = tibiotarso• Metatarsos + tarsos distales = tarsometatarso

Características de las aves

• Sistema nervioso bien desarrollado, con cerebro y 12 pares de nervios craneales

• Visión más aguda de todos los vertebrados

• Audición bien desarrollada; sin pina• Olfato pobre• Pocas papilas gustativas

Características de las aves

• Corazón tetracameral: circuito pulmonar completamente separado del sistémico

• Eritrocitos nucleados y biconvexos• Endotérmicas

Características de las aves

• Siringe (caja de voz) cerca de la unión de la tráquea con los bronquios

• Respiración por pulmones levemente expansibles

• Con sacos delgados de aire entre las vísceras y el esqueleto

Las aves - digestivo

• Las aves vivientes no tienen dientes• Lengua no-muscular, corta, estrecha y triangular• Algunas con buche

almacenaje fermentaciónregurgitar enzimas

• Muchas con estómago dividido– proventrículo – secreta jugos gástricos– molleja - tritura

• Cloaca

Características de las aves

• Riñones metanéfricos • Uréteres abren a la cloaca; sin vejiga

urinaria • Orina semisólida; ácido úrico• Algunas marinas con glándulas de sal

Glándulas de sal en ave marina

Características de las aves

• Dioicas• Testículos pareados; vas deferens

desembocan en la cloaca • Algunos con órgano copulador• Hembras con ovario y oviducto izquierdo• Sexo determinado por las hembras; hembras

heterogaméticas• Ovíparas

Sistema reproductor femenino

Características de las aves

• Estrategias reproductivas– Monogamia– Poligamia: poliginia y poliandria

• Huevo amniótico con mucho vitelo y cascarón calcáreo

• Fecundación interna• Incubación externa

– precoces– altricias

Aves copulando

Desarrollo temprano de un embrión de un ave

Origen del vuelo

• Desde el suelo– Ancestro cursor que vivía en tierra

• Desde los árboles– Ancestro arbóreo

Las aves – músculos del vuelo

• Extrínsecos (se originan fuera de la parte sobre la cual actúan)

– Pectoralis• 25% de la masa del cuerpo• empuja el ala hacia abajo y hacia arriba

– Supracoracoides• eleva el ala

• Intrínsecos (se originan en la parte sobre la cual actúan)

– Musculatura de las alas reducida

Músculos del vuelo en las aves

Tipos básicos de alas

Clasificación de las aves

Clase AvesSubclase ArchaeornithesSubclase Neornithes Superorden Paleognatha

Superorden Neognatha

Subclase Archaeornithes

• Con características primitivas• Extintas• Archaeopteryx

Archaeopteryx lithographica

Subclase Neornithes

• Extintas y vivas• Esternón bien desarrollado; usualmente

con quilla• Rabo reducido• Metacarpos y algunos carpos

fusionados

Subclase NeornithesSuperorden Paleognathae

• Aves modernas con paladar primitivo• Rátitas o carinadas

– Orden Struthioniformes – avestruz– Orden Casuariiformes - emú– Orden Apteryformes - kiwi

Subclase NeornithesSuperorden Neognathae

• Aves modernas con paladar flexible

– Orden Sphenisciformes pingüino

– Orden Pelecaniformes pelícano

Subclase NeornithesSuperorden Neognathae

– Orden Ciconiiformes- flamingo, buitre– Orden Anseriformes- ganso, cisne, pato– Orden Falconiformes- águila, falcón,

cóndor– Orden Galliformes- pavo, faisán– Orden Columbiformes- palomas– Orden Psittaciformes- pericos y cotorras

Subclase NeornithesSuperorden Neognathae

– Orden Strigiformes- búho– Orden Apodiformes- picaflor– Orden Piciformes- carpintero, tucán– Orden Passeriformes- 60% de las aves

• Siringe desarrollada• Adaptados para posar en ramas• Cría altricia• Más de 5 mil especies

74

LOS REPTILES, ANFIBIOS Y PECESLos REPTILES son animales vertebrados, son ovíparos, respiran por pulmones y tienen el cuerpo cubierto de escamas.

- El cuerpo de los reptiles se divide en: cabeza, tronco, extremidades y cola.- Los reptiles se desplazan de maneras muy diferentes, las serpientes no tienen extremidades y reptan, las tortugas marinas nadan y los lagartos, andan.

Los ANFIBIOS son animales vertebrados y ovíparos, y tienen la piel desnuda.- El cuerpo de los anfibios se divide en: cabeza, tronco y extremidades. Algunos, como las ranas no tienen cola; otros, como la salamandra sí la tienen.

- Cuando las crías nacen de los huevos, son muy diferentes de sus padres. Los cambios que sufren hasta convertirse en adultos se llaman metamorfosis.

Los PECES son animales vertebrados, ovíparos, respiran por branquias y tienen el cuerpo cubierto de escamas.

- El cuerpo de los peces se divide en: cabeza, tronco, cola y varias aletas para nadar.

- Gracias a las branquias pueden respirar bajo el agua, tomando el oxígeno que hay disuelto en ella.

75

La Rana

ANFIBIOS25

76

Anfibios

26

77

Características de la Rana• Su pies es desnuda, húmeda y escurridiza. • Tienen cuatro patas de tipo mano. • Son de sangre fría y  tienen sueño invernal. • Al principio su respiración es branquial, después

pulmonar y cutánea. • Tienen circulación doble e incompleta. • Se reproducen por huevos, normalmente con

fecundación externa y al crecer sufren metamorfosis.

El huevo se forma

por

fecundación

Metamorfosis de la Rana

El huevo se transforma en un embrión

Nace el renacuajo.Tiene cola y respira por branquias

Cuando se convierte en adulto, le salen patas y cola. Respiran por pulmones y por piel

24

78

Metamorfosis de la Rana

28