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DISSECTING FROG EVOLUTION
External Anatomy
Why are trees tall? Why do zebras have stripes? Who do cheetahs have long, narrow
legs? These questions can all be answered using Darwin’s theory of evolution by natural
selection. In fact, virtually every trait of an organism can be explained using natural
selection theory. While learning the anatomy of a frog you will use Darwin’s theory to
explain why the animal and its structures take the form that they do.
For the features in the table make and record descriptive observations. Then infer
the adaptive value of the feature – attempt to describe how the feature makes the frog
better adapted for its environment.
Dorsal color
Ventral color
Location of eyes
Location of ears
Location of nostrils
Shape of head
Shape of tympanic
membrane (ear)
Vomerine teeth
Hind legs – form, length
Feet – form
Other
Part II - Explanations
In a paragraph explain why a frog looks the way it does. Why is it colored the way it is?
Why is it shaped the way it is? Why are structures located where they are? Refer to
specific structures and use the language of natural selection theory.
Student pages
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DISSECTING FROG EVOLUTION
Thoracic Cavity
Fill in the table after you have opened the frog’s thoracic (chest) cavity.
Structure/Feature
Ribs
Observations
Adaptive Value
Lungs
Pericardial membrane
Number of heart chambers
Other
Part II – Explanations
Explain why amphibians have a 3-chambered heart whereas fish only have 2 chambers.
You may need to use book or web resources to acquire some information on the topic.
Use natural selection theory to develop your explanation.
Student pages
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DISSECTING FROG EVOLUTION
Abdominal Cavity
Fill in the table after you have opened the frog’s abdominal cavity.
Structure/Feature
Shape, texture of stomach
Observations
Adaptive Value
Size of liver
Length of small intestine
Body cavity
Villi
Number of blood vessels in
mesentery
Number of eggs (in
pregnant female)
Other
Part II – Explanations
Choose 3 features from the abdominal cavity and explain why they are the way they are
in a frog. Use natural selection theory to develop your explanations.