Amphibians and Reptiles

Test #3

Class: Amphibia

• First vertebrates on land were in Class Amphibia

• Amphibian-means “two lives”

• About 4,000 species of frogs, salamanders, and caecilians (limbless animals that burrow in tropical forests and fresh water lakes)

Devonian Time Period

– Cycles of drought and then heavy rainfall then drought again

– Lobe-finned fish were at an advantage because the bones in their fins are like that in the arms and legs of early amphibians

– They were able to come to land to escape predators or to get food.

3 Orders of Amphibians

• 1. Urodela – “tailed ones” – salamanders

• 2. Anura – “tail-less ones” – frogs & toads

• 3. Apoda – “leg-less ones”– caecilians

Order: Urodela (Salamanders)

• 400 species• Some are entirely

aquatic and some live on land

• Most walk by bending their body from side to side

Order: Anura (Frogs and Toads)

• 3,500 species

• More specialized for living on land

• Use strong legs to hop

• Flick tongue to catch insect

What is the difference between frogs and toads?

• Frogs are in the family Ranidae and have the following characteristics:– Bulging eyes– Webbed feet and

longer legs for swimming

– Smooth or slimy skin– Lay eggs in clusters

Toads

• Toads are in the family Bufonidae and have the following characteristics:– Stubby bodies with short

hind legs for walking instead of hopping

– Warty dry skin– Poison glands behind

the eyes– Lay eggs in chains

Defense from predators

• Camouflage• Secrete mucous that

is bad tasting or poisonous

• Many with poison have a bright color to warn predators

Order: Apoda (Caecilians)

• Legless• Nearly blind• Look like earthworms

Amphibian Characteristics

• Frogs

• Tadpole --------------------------Adult• Aquatic with gills Gills & tail disappear• Lateral line Lateral line• Finned tail Develops legs

Frogs

– Frogs have air breathing lungs, eardrums, and a digestive system (carnivorous diet)

– Some frogs do not go through the tadpole phase– Some are strictly aquatic and some are strictly land– Salamanders and caecilians resemble adults when

born– Even land-dwelling amphibians need a moist habitat– Some breathe through skin and mouth b/c they have

no lungs

Frogs

– Eggs do not have a shell and dehydrate in air– Male causes female to release eggs and spills sperm

while she does this– Some incubate eggs on back, mouth, or in stomach– Some are ovivaporons (eggs hatch in uterus) and

viviparons (young develop in uterus)

• Social life– Frogs are usually quiet, but many call during mating

season• Many want to protect territory or attract females

Class: Reptilia

• 7,000 species

• Many extinct species

• Mainly lizards, snakes, turtles, and crocodilians

• Birds are closely related

Reptile Characteristics

• Scales create waterproof skin – (Helps prevent dehydration in air)

• Have lungs because they can’t breathe through moist skin

• Some turtles have gas exchange through their moist cloaca

• Most lay shelled eggs on land• Internal fertilization

Reptile Characteristics

• Called “cold-blooded” or ectothermic because they don’t use their metabolism to control their body temperature

• they regulate their temperature in other ways

• Ectotherms body temperature changes with their surroundings

Extinct Reptiles

• 1. Dinosaurs 2. Pterosaurs• lived on land flying reptiles• different sizes wings were a membrane • up to 45 m long of skin stretched from

the body wall to the tip of an elongated finger

• many were very fast• social and give parental care

Modern Reptiles

• 3 Largest Orders

• 1. Chelonia (turtles)

• 2. Squamata (lizards and snakes)

• 3. Crocodilia (crocodiles and alligators)

Order: Chelonia

• Have not changed much since the Mesozoic era

• What is the difference between a turtle and a tortoise?– Turtles are any reptile

that lives in a shell.– A tortoise is a turtle that

lives on land but enters the water for various reasons.

Order: Squamata

• Lizards- most numerous and diverse

• May have survived cold by nesting in crevices to maintain heat

Order: Squamata• Snakes- descendants of lizards

that adopted a burrowing lifestyle– Today, most snakes live above

ground– Boa’s have vestigial pelvic and

limb bones (primitive snakes)– Snakes are carnivorous– They have chemical sensors on

their tongue that helps them detect prey

– have no ear drums– feel vibrations on the ground– they have heat detecting organs

between the eyes and nostrils– they inject poison through hollow

teeth– They have loose jaws that help

swallow prey

Crocodilians (crocodiles and alligators)

• Largest living reptiles• Spend most of their time

in water breathing through upturned nostrils

• Live in warmer areas• Most closely related to

dinosaurs of all the reptiles

• Birds are the closest relatives to reptiles

What is the difference between a crocodile and an alligator?

• Crocodile:– Has a long V shaped

snout– Upper and lower jaws

are the same width so teeth show interlocking when mouth is shut

What is the difference between a crocodile and an alligator?

• Alligator:– Wide U shaped snout– Have a wider upper

jaw so that the teeth from the upper portion only show when the mouth is closed.