Danielle Sychowski #28
Artificial Selection Lab Purpose:
This lab was intended to show the process of artificial selection by choosing the tallest plants in generation 1 and crossbreeding them to whether or not tall plants would be produced in generation 2. Hypothesis:
If, after 16 days, the tallest 25th percentile of plants from generation 1 are crossbred, then the plants in generation 2 will have a taller average height after 16 days since the genes for being tall will be passed on and expressed more often than for being short. Materials: ● Wisconsin fast plant
● vermiculite seeds ● water/fertilizer mix
● water bottle with cap
● cotton wick
● 2 soil pellets
● pipe cleaners
● light box
1. Prepare water bottle for planting by cutting 1 cm below the shoulder of the bottle.
2. Fill body with water/fertilizer mix.
3. Poke a 1 cm hole in the cap and thread the cotton wick through. Place the cut off portion capdown into the bottle so that the wick is in the water/fertilizer mix. Tape the two pieces of bottle together so they are secure.
4. Fill the cut off portion with one and a half soil pellets, a layer of vermiculite, then the other half of the soil pellet. Loosely pack it down.
5. Make sure the wick isn’t poking out of the soil or it’ll dry out.
6. Place 8 seeds evenly spaced out in the soil near the edge of the bottle.
7. Put the growing system in the light box, making sure it stays watered and the water/fertilizer mix stays at a high enough level. Also be sure to check for algae growth. 8. After 16 days, measure the height of the plants (in cm).
9. In the 1st generation, only allow the plants in the top quartile to continue growing. Cut all other plants and throw them away.
10. When the taller plants flower, use the pipe cleaners to collect pollen and crossbreed the tall plants.
Sychowski 2 11. Collect the seeds from the pods after they have dried out and become yellow.
12. Give the seeds to the teacher.
13. Use the seeds for generation 2. Repeat steps 18 for generation 2. Data:
In generation 1, only the top 25% of the tallest plants were saved for crossbreeding.
Therefore, by multiplying the total number of plants by .25, that will give the number of plants saved. 152 total plants * .25 = 38 plants (but we saved 39 plants that were 12cm or taller) Mean: (total height of plants divided by total # of plants)
Generation 1: 1222.9 cm / 152 plants = 8.05 cm/plant
Generation 2: 615.4 cm/ 101 plants= 6.09 cm/plant Median: (height that is in the middle of tallest and shortest plants; can be found using Excel)
Generation 1: 7.3 cm
Generation 2: 6 cm Mode: (number that appears most frequently)
Generation 1: 4.5 cm
Generation 2: 4 cm Range: (maximum height minimum height)
Generation 1: 20.2 cm 0.5 cm = 19.7 cm
Generation 2: 14.5 cm 1 cm = 13.5 cm Analysis:
Sychowski 3 Only the 1st generation plants in the top quartile for height were crossbred in this lab. The goal was to artificially select the tallest plants from the parent generation so that the offspring generation inherited the trait of being tall, following the Mendelian Inheritance rules for height. If the plants did follow those rules, then the 2nd generation plants would have a higher frequency of the “tall” gene being expressed. However, in looking at the histograms and the mean, median, mode, and range, the 2nd generation plants are actually shorter (on average) than the parent generation. It should be noted however that the histograms do show an interesting change in heights between the two generations.
In the 1st generation histogram, the data looks almost random and seems to lack a specific pattern. It seems like there are also many more shorter plants than tall plants.
Looking at the 2nd generation histogram, a more…