Chordate Cladogram

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Chordate Cladogram
Section 30-1
Mammals
Birds
Reptiles
Amphibians
Fishes
Nonvertebratechordates
Invertebrate ancestor
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Interest Grabber
Section 30-3

• Declining Numbers of Frogs
• Ecologists have recently noticed declining
  numbers of certain types of amphibians in a
  variety of places. Some scientists have
  hypothesized that this decline might be a result
  of toxins in the environment.
• Work with a partner to discuss and answer the
  questions that follow.

1. What characteristics of amphibians might make
them more susceptible to environmental toxins
than other types of animals? 2. Frogs reproduce
in water. Why might toxins in aquatic ecosystems
affect the reproductive success of frogs? 3. Can
you think of any other possible explanations for
the reduced numbers of amphibians observed?
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Section 3 Answers
Interest Grabber Answers
1. What characteristics of amphibians might make
them more susceptible to environmental toxins
than other types of animals? Amphibians live
both in water and on land, have moist skins that
allow the exchange of substances, and do not have
protective scales or a thick impermeable
skin. 2. Frogs reproduce in water. Why might
toxins in aquatic ecosystems affect the
reproductive success of frogs? Eggs and tadpoles
may be more sensitive to toxins in the water
during these developmental stages. 3. Can you
think of any other possible explanations for the
reduced numbers of amphibians observed? Possible
answers more predators presence of a viral,
bacterial, or fungal infection decreasing food
supply and normal fluctuations in population
size.
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Section Outline
Section 30-3

• Amphibians
• A. What Is an Amphibian?
• B. Evolution of Amphibians
• C. Form and Function of Amphibians
• 1. Feeding
• 2. Respiration
• 3. Circulation
• 4. Excretion
• 5. Reproduction
• 6. Movement
• 7. Response
• D. Groups of Amphibians
• 1. Salamanders
• 2. Frogs and Toads
• 3. Caecilians
• E. Ecology of Amphibians

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Concept Map
Section 30-3
Amphibians
means
Double life
as
larvæ they live in
adults they live on
and have special adaptations such as
are
that allow for
that provide
that allow
are
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The Life Cycle of a Frog
Section 30-3
Adult Frog
Adults are typically ready tobreed in about one
to two years.
Young Frog
Frog eggs are laid in water and undergo external
fertilization.
The eggs hatch into tadpoles a few days to
several weeks later.
Fertilized Eggs
Tadpoles
Tadpoles gradually grow limbs, lose their tails
and gills, and become meat-eaters as they develop
into terrestrial adults.
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Video
Video
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End of Custom Shows

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