Transcript Using a digital camera to quantify color variation in a

Using a Digital Camera to Quantify
Color Variation in a Population of
Mealworms
Objectives
• In this section of the workshop, participants
will:
• learn how to photograph a population under
constant conditions
• quantify color of the individuals in the
population using ADI software
• graph the quantified color data to see
emerging patterns of color variation of
individuals within the population.
STANDARDS
NGSS:
MS-LS4-4. Construct an explanation based on
evidence that describes how genetic variations
of traits in a population increase some
individuals’ probability of surviving and
reproducing in a specific environment.
HS-LS3-3. Apply concepts of statistics and
probability to explain the variation and
distribution of expressed traits in a population.
Variation in a Population of Land Snails
Peppered Moth Variation
Mixing Light and Mixing Pigment
All wavelengths of light = white
No wavelengths of light = black
All colors of pigment = black
No colors of pigment = white
I thought I was taking this picture in the
complete darkness of a closet. Evidently
not. If there was no light, the R, G, B
sensors in the camera would not register
any values: R= 0% G = 0% B = 0%
Examples of Using Digital Cameras to
Quantify Color Variation in a Population--All three investigations done by 7th graders
at Amherst Regional Middle School
1. Human Skin Color
2. Crayfish
3. Mealworms
Variation in Human Skin Color Investigation
Variation in Human Skin Color Investigation Summary
I took images of the under forearms of 20 of my students. Students used the ADI
program to get the average color of a 13068 pixel area on each of the forearms. When
the data was graphed, it approximated a normal distribution with only 20 students.
What is interesting is that if you repeat the experiment with a subgroup of 20
individuals who would be considered to have a light complexion, you still get a bellshaped curve.
After a short introduction to color and light, kids can tell from the R, G, B values of an
image that no one is white and no one is black. Everyone is shades of brown.
White = R: 100% G: 100% B: 100%
Black = R: 0%
G: 0%
B: 0%
Sample Skin Color = R: 82.75 G: 58.04
B: 41.57
I reinforce the idea that people’s skin color (before there was sunscreen, folic acid, and
Vitamin D supplements) was an adaptation which enabled people to survive. I point
out to the students that they come from a long line of WINNERS (otherwise they
wouldn’t be here!  )
Resources
http://humanorigins.si.edu/evidence/genetics/skincolor/modern-human-diversity-skin-color
http://evolution.berkeley.edu/evolibrary/article/evo_25
Variation in Color in a Population of Crayfish
Investigation Summary
- 20 crayfish were photographed.
- Students used ADI to determine the
average color of a section of the carapace
on each individual.
- The data were plotted revealing a normal
distribution.
Working Session: Using ADI to
Quantify Color Variation in a
Population of Mealworms
Set up a camera stand. Take a picture of a population of mealworms
in a petri dish. Note: if you are comparing one individual to another,
the individuals must either all be in the same photograph, or the
conditions (light, distance, camera) for taking the individual, separate
photographs must be constant.
Download ADI Software from website
Difference between highest and lowest values: 18.04
18.04 ÷ 5 = 3.6
Interval
Number of Individuals with
an average color within the
interval
21.31-24.91
1
24.92-28.52
6
28.53-32.13
8
32.14-35.74
4
35.75-39.35
1
Input data into google sheets
R
A
P
T
Variation in populations are the basis of Natural
Selection