Fossil Record Paleontologist



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For each animal, indicate what type of movement this front limb is responsible for.

 

Animal

Primary Functions

Human

Using tools, picking up and holding objects

Whale

 swim

Cat

 Climb, catch mice

Bat

 Fly, wrap up and sleep

Bird

fly 

Crocodile

 Swim, walking in swamp

 

Compare the skeletal (bone) structure of each limb to the human arm. Relate the differences you see in form to the differences in function.

 


Animal

Comparison to Human Arm in Form

Comparison to Human Arm in Function

Whale

Whale has a much shorter and thicker humerus, radius, and ulna.  Much longer metacarpals.  Thumb has been shortened to a stub.

The whale fin needs to be longer to help in movement through water.  Thumbs are not necessary, as the fins are not used for grasping.

Cat

 Shorter, smaller, fewer phalanges, and metacarpals, larger carpal

 

 

 

 Catching mice, climbing

Bat


Longer phalanges



Flying and wrapping up to sleep

Bird

Single phalange, metacarpal

Carpal is shallow (hole in it)


Need light bones to fly

Crocodile


Long phalange, short ulna, radius, humerus



Walking and swimming in swamp

  

Homologous structures: Similar structures that perform different functions. These are seen in organisms that are closely related.



  1. Give an example of a homologous structure from this activity:

Possible answers: ulna, radius, carpal, metacarpal, phalange, humerus


Vestigial structures: remnant structures that were once important in the organism’s ancestors, but are no longer used in the same way.

Below are vestigial structures found in humans. For each, hypothesize what its function may have been.





Wisdom teeth larger jaw, replace rotten teeth

Appendix Supplies bacteria to gut to digest leaves

Muscles for moving ear used for directional hearing (hear from different directions)

Body hair body covered in lots of hair for warmth

Little toe used for balance

  1. Give an example of a vestigial structure from this activity:  

Possible answers: appendix, muscles to move ear, body hair, little toe, wisdom teeth

  1. How do homologous and vestigial structures suggest an evolutionary relationship between species? 

Homologous structures show that humans, cats, bats, crocodiles, birds, and whales all have similar bones with different functions, so they must have a common ancestor.

Vestigial structures tell us that humans have structures leftover from an ancient ancestor that are no longer used for their original purpose.

Molecular (DNA) Biology

Molecular (DNA) biologist: A scientist that studies the molecular basis of biological activity, particularly DNA sequences and biochemistry.
Below are sequences of letters that stand for portions of the genes that code for α and β hemoglobin (blood) proteins in different primates.
Compare the DNA sequences from the α hemoglobin for the thick-tailed bushed baby and humans. Circle any differences in base pairs from the human sequence and record the total differences in the data table on this page.


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