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Name_____________________________
Activity 4: Homologous Structures
Background:
One of the classic examples of a homologous structure is a Pentadactyl (five digit)
limb.
All tetrapods (four legged animals) have limbs with five digits, at least in
some stage in development. Certain tetrapods loose some of those limbs during
development, as the bird wing shown below. So, if the bird wing does not need five
digits, why do five initially develop in the growing embryo? The most plausible
explanation is that while the five digits are not functionally necessary, they represent
a genetic artifact inherited from the ancestors of birds.
Procedure: Color the homologous structures according to the list below.
Hint:
The humerus is the upper arm bone, the ulna and radius are the middle arm
bones, the carpals are the bones in the wrist and the phalanges are the fingers.
Activity 5: Homologous, Analogous and Vestigial Structures
Define Homologous Structure:
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Define Analogous Structure:
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Define Vestigial Structure:
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Procedure: Draw examples of each type of structure in the boxes below
Homologous
Analogous
Vestigial
Activity 6: Comparative Embryology
Background:
Evolution produces changes in the anatomy of organisms.
The order
of these changes can often be seen as one examines the changes that occur
during the embryonic development of animals.
Embryos of closely related organisms
develop almost identically, especially in the early stages of development, suggesting
a common ancestor. For example:
Humans do not have gill slits by the time they
are born like fish do, but gill pouches can be seen during early human embryonic
development as well as a tail!
Procedure:
Examine the embryonic development of the 3 species below.
List at least 3 similarities that you can identify developing in all three embryos:
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Activity 7: Biochemistry
Background:
Not only can scientists determine evolutionary relationships by looking
at physical structures of different animals, they can also look at similarities between
the DNA sequences of different animals. We will learn more about his later in the
year but basically DNA codes for amino acids, when amino acids are in a specific
order they will build a protein, these proteins then are expressed to make us who
we are.
In short, the more similar the sequence of amino acids, the more closely
related the species.
Procedure: Use the amino acid sequences given to you in the table below to
answer the following questions.
Pretend each letter stands for 1 amino acid.
(Remember you are looking for similarities in the order of the letters.)
Questions:
1) Which two organisms shown in the table are most closely related? _________
and __________
2) Explain your answer to #1.
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3) Should a moth be classified as being more similar to a tuna or wheat?
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4) Explain your answer to #3.
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