Animal Hands

Different functions of homologous structures


Many animals share similar body structures.  For instance, your nose, a pig’s snout, and an elephant’s trunk can all be called noses.  Though these noses have different functions and appearances, all have a similar location and structure.  Such similar features are called homologous.  Such similar features are called homologous* structures.


:     Open X-ray images 01 through 11. 


:     Briefly examine each image


The x-rays show the hands of the following animals:

Beluga Whale


Macaque Monkey


Sun Bear





Sea Lion




A structure’s shape is often related to its function.  A hand used for swimming (a fin) is shaped differently than one used for supporting and animal’s weight as it walks.  Likewise, a hand used for flying (a wing) is shaped differently than one used to manipulate objects and use tools.


Examine these x-ray images of animal hands in more detail and compare their structure. Based on the morphology (shape) of each hand, figure out its main function and determine its owner.


1. Use the animal hands (word version) data table to record your observations of the eleven hand x-rays.


:     Enhance the features of the animal’s hands.  You may want to use some of the following techniques.  Refer to the Look-up Tables and Density Slicing IPTechnique Sheets for more details.

To use this Technique…

…do this

Adjust brightness and contrast

drag the brightness and contrast sliders in the Map folder

Density Slice

Options/Density Slice

Invert Image


Enhance image with filters

use Process menu items

Switch color tables

Options/Color Tables

Adjust Color Tables

use the ↨ tool in the LUT














If the image looks worse after enhancing…

Edit/Undo to undo the last thing you did, or

File/Revert to Saved to return to the original image.


2.      Briefly describe the main features of each hand.  Here are some clues:

§         Does the hand appear to have individual fingers?

§         Does the hand show fingernails or claws?

§         Are the bones thick compared to their length?

§         How many joints does each “finger” have?

§         Can you tell the shape of the flesh covering the bone?


3.      In your table, state the function* of each hand

4.      Based on the structure and function of each hand, identify the animal shown in each x-ray


Mystery Animal

¿      Open Mystery Animal

Animals that are closely related have very similar structures.  For example, all species of birds have wings, even flightless birds.  Because of these similarities, you can figure out what kind of animal a hand belongs to even if you don’t know the exact species.


5.      Answer the Data Analysis questions on the data table.


Honors biology (complete on the back of data table or separate sheet)

  1. Based on your observations, describe how you would expect an x-ray of a bat’s wing to appear.
  2. Research the behavior of one or more of these animals to find out what other functions their hands serve.
  3. Examine the images in the Zoo Animals folder (found in the short cut to science folder). Pick one X-ray to describe.


Helpful information   (diagram of human hand parts)


*Homologous = “agreeing” in Greek

*Functions can include flying, swimming, grasping/manipulating, and walking/running




    Windows/Next Image to view each of the x-rays.  See the Windows IPTechnique Sheet for tips on working with several windows open.



§         The size of each x-ray is not related to the size of the animal

§         The heavier an animal is, the thicker its bones are.  This is a sign that the bones support weight.

§         Macaques and humans are both primates, but macaque hands have more padding for swinging on tree branches.

§         Bird bones are difficult to see in x-rays because they are very thin and light.

§         Pandas appear to have five fingers plus a thumb.  This false thumb is an extension of one of their wrist bones.  Pandas use it to strip leaves from bamboo, their main food source.

§         Sun bears are small bears.  The sun bear has a deformed front paw.

§         You may want to look at a picture of each of these