2. Amphibians
• Amphibians are
animals that can live in
water and have lungs
and legs
• Scientists think that
amphibians evolved
from ancestors of
lungfish-like fishes
• Most of today’s
amphibians are frogs
or salamanders

3. Characteristics of Amphibians
• “Amphibian” means “double life” most
live part of lives on land and part of lives in
water
• Amphibian eggs don’t have a shell to
prevent water loss, so the embryos must
develop in a wet environment
• Are ectotherms body temp. depends on
temp. of environment (cold blooded)

4. • Thin Skin
– Skin is so thin that
amphibians absorb water
instead of drinking it
– Can easily become
dehydrated
– Can breathe with lungs,
but many absorb oxygen
through their skin, which is
full of blood vessels
– May be bright colors; often
to warn predator of poison

5. • Leading a Double Life
– Don’t just get bigger as they
grow, they change form
– After hatching, frog embryo
becomes tadpole and must live
in water
• Gets oxygen through gills and
uses tail to swim
• Later, loses gills and
develops limbs to live on land
– Change from immature form to
adult form is called
metamorphosis

6. Kinds of Amphibians
(1) Caecilians
-look like earthworms or
snakes, but have
amphibian skin
-do not have legs and
have bony scales in
their skin
(2) Salamanders
-do not develop as
tadpoles
-most lose gills and
develop lungs
-a few species keep gills
and live in water for life

7. (3) Frogs and Toads
-90% of amphibians
are frogs or toads
-toads are a type of
frogs (but spend less
time in the water)
(4) Singing Frogs
-sing to communicate
messages that help in
attracting a mate or
marking territories
-most frogs that sing
are males

8. • Amphibians as Ecological
Indicators
– Unhealthy amphibians can be
an early sign of changes in an
ecosystem
– Very sensitive to changes
– Thin skin absorbs any
chemicals in the water or air
– Lungs take in chemicals from
the air
– Climate change also affects
them because they are
ectotherms

9. • Living on Land
– 35 million years Reptiles
after they first
moved on land,
some amphibians
began to change
thick, dry skin, legs
were stronger,
eggs did not dry out
– They had become
reptiles
– Many reptiles are
now extinct most
famous are
dinosaurs

10. • Characteristics of Reptiles
– (1) Thick skin
• Forms a watertight layer that keeps cells from
losing water by evaporation
• Cannot breathe through their skin
• Depend only on lungs for oxygen
(2) Body Temperature
• Nearly all are ectotherms (cold blooded)
• Most live in mild climates
(3) The Amazing Amniotic Egg
• Egg holds fluid that protects the embryo
• Have a shell that keeps it from drying out

12. • Reptile Reproduction
– Usually reproduce
by internal
fertilization
– Reptiles do not go
through
metamorphosis
– Female lays
eggs when they
hatch, the young
look like small
adults

13. • Kinds of Reptiles
– Turtles and Tortoises
• Tortoises live on land,
turtles in the water
• Unique because of their
shells, which is used for
protection
Crocodiles and Alligators
-spend most of their time
in the water
-eyes and nostrils are on
top of their flat heads
-crocodiles have a narrow
head and pointed snout,
and alligator has a broad
head and rounded
snout

14. – Snakes and Lizards
• Most common
reptiles
• Snakes can smell
prey
-Tuataras
-live on only a few
islands off the coast
of New Zealand
-do not have visible
ear openings on
outside of body
-most active when
temp. is low