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STUDENT PEN NAMES: Leonardo, Wiggle13, Raphael

ASPIRE MENTORS: Matt Gilbert


OBSERVATIONS / DESCRIPTION: This inquiry looks into the external morphology of 3 types of turtles. The three types of turtles we chose to research were Sea turtles, Snapping Turtles, and Tortoises. We were curious to find out why some turtles can retract their heads and appendages while others can’t.  We wanted to compare each type of turtle’s morphology.

QUESTION: Does the length of each type of turtle’s carapace and head determine whether a turtle can retract into its shell for protection.

carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including  turtles and tortoises. In turtles and tortoises, the underside is called the plastron.

Mitchell turtle

Figure 1. This is a model of a young Green Sea Turtle.

Mason turtle

Figure 2. This is an example of a turtle that is retracting its head.

HYPOTHESIS: We think the carapace size does not determine whether or not  turtles or tortoises  retract their head into their carapace. We have observed some turtles have big carapaces and can’t retract their head.

EXPERIMENT:
1. Record information on all turtles studied.  Create a slideshow to share with a class.  Include information on habitat, diet and whether or not they can retract their    head into their shell.
2. Locate a clear photo of each type of turtle.
3.  Document the URL of each photo you find.
4. Measure the carapace, head and front appendage of each turtle using the line tool in keynote.  The line tool measures the length in “pts”.  (The ‘point’ (pt) is a unit of length, commonly used to measure the height of a font, but technically capable of measuring any length.
5. Create a chart and record data
6. Analyse your results.

EXPERIMENTAL DESIGN:
The things we are going to try to keep constant in this study are:
• We sized the photos in keynote to the same pt. size
• When choosing photos we tried to find side view images where the turtle or tortoise full carapace was showing.
• We used the same method of measuring( using the line tool in keynote)
• Consistently measured the head from the tip of the nose to the anterior edge of the carapace)

Our independent variable (the one we manipulated) was the species of turtle /tortoise
The dependent variable (responding variable) was the morphology of the species length of head and carapace of each species.


DATA:

Turtle / Tortoise Morphology Data
(measurements in pts)
Turtle / Tortoise Morphology (measurements in pts)
Data 1Data 2
Table 1. This data table includes measurements , names of turtles, and the links to where we found the pictures.Table 2. Data includes relative head size to shell . We calculated by dividing the head by the shell.

RESULTS:

Relative "Head to Shell" ComparisonRelative "Head to Shell" Comparison
ResultsGraph - Turtle
Table 3. This table includes the names of the turtles, and the percentage of the head to the shell.Figure 3. This table includes the names of the turtles, and the percentage of the head to the shell.
Average Head to Shell Retracting and Non Retracting TurtlesRetracting and Non Retracting Turtles
AverageScreen Shot 2016-05-26 at 1.49.06 PM
Table 4. This table indicates a lower head to shell percent for tortoises that are able to retract their head.Figure 4. This graph indicates a lower head to shell percent for tortoises that are able to retract their head.

 


Figure 5. Studying snapping turtle behaviour .

Figure 5. Studying snapping turtle behaviour .

CONCLUSION: Our investigation was designed to answer the  question does the length of each type of turtle’s carapace and head determine whether a turtle can retract into its shell for protection.  After researching many different kinds of turtles we thought that the carapace size did not determine whether or not  turtles or tortoises  retract their head into their carapace.  We had observed many turtles that had big carapaces and couldn’t retract their head.

Based on the data (from the tortoises and turtles we studied), we found  that the tortoises’ that could fully retract their heads had relatively shorter heads (relative to the length of their carapace) than the non-retracting turtles.  Our data, therefore does not support our hypothesis. We learned that we needed to have more data to be confident that our investigation was a “fair test”.

Future Directions

  • Look at other differences in external morphology that might influence the ability of turtles to retract into their shells. Compare aspects of the carapace to compare.  Instead of just determining the length of carapace, measure the width (perhaps the collar bone and the height of the carapace.  We could investigate whether or not their was a way to determine the area of each turtle/tortoise carapace.
  • Look at other differences in internal morphology like lung size  to see if that is a factor in determining whether or not  turtles or tortoises  retract their head into their carapace.
  • Study at least 3 pictures of each species of turtle/tortoise to find a truer average of its carapace length.  This would ensure that our experiment was a true test of our hypothesis.