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)
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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
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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
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1. Dinosaurs
lived on land
different sizes
up to 45 m long
2. Pterosaurs
flying reptiles
wings were a membrane
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
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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.