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 Human Skin Color Crayfish 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 bell-shaped 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/skin-color/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

Input data into google sheets

R A P T Variation in populations are the basis of Natural Selection