New Jersey Center for Teaching and Learning
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Progressive Science Initiative
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AP BIOLOGY
Investigation #1
Artificial Selection
Summer 2014
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Investigation #1: Artificial Selection
Click on the topic to go to that section
· Pacing/Teacher's Notes
· Pre-Lab
· Guided Investigation
· Independent Inquiry
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Pacing/Teacher's Notes
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Table of
Contents
Teacher's Notes
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Lab procedure adapted from College Board AP Biology
Investigative Labs: An Inquiry Approach Teacher's Manual
Click here for CB
AP Biology
Teacher Manual
Note: This investigation will be assessed in the Evolution & Classification
Unit (lab quiz located with Evolution/Classification assessments).
This investigation takes approximately 7 weeks to complete, thus it is
planned to begin during the Cell Cycle unit. However, plants required
regular watering and fertilization so please plan accordingly, keeping in
mind any school breaks/holidays.
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Pacing
Day (time)
Day 1 (HW)
Day 2 (40)
Activity
General
Description
Pre-lab
Pre-Lab
Steps 1-2
CC Day 2
HW
Set up and
CC Day 3
planting
Selecting trait,
measurements,
CC Day 11
and statistical
analysis
Day 3 (80)
Step 3-7
Day 4 (40)
Preparing bee
Prepare Bee
sticks for
Sticks
pollination
Day 5 (80)
Steps 8-10
Reference
Notes
to Unit Plan
This can occur anytime between
days 7-12
H Day 1
Pollination
H Day 2
This can occur anytime between
days 14-16. Bee sticks may need to
be constructed prior to pollination
This can occur anytime between
days 28-36, look for yellow
seedpods
Day 6 (20)
Steps 9-10
Begin drying
EC Day 4
Day 7 (40)
Step 11
2nd generation
planting
EC Day 9
This should occur after about a week
of drying seeds
Step 12-13
Reexamine trait
EC Day 19
This can occur when the new plants
are between 7-12 days old, but
should be done at the same age as
the original analysis of generation 1
Day 9 (40)
Step 14
Analysis
EC Day 20
Day 10 (20)
Assessment Lab Quiz
EC Day 21
Day 8 (80)
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Pre-Lab
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Table of
Contents
Question/Objectives
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Can extreme selection change expression of a quantitative trait in a
population in one generation?
In this lab we will:
· Investigate natural selection as a major mechanism of evolution.
· Convert a data set from a table of numbers that reflects a change in the
genetic makeup of a population over time and apply mathematical
methods and conceptual understanding to investigate the cause(s) and
effect(s) of this change.
· Apply mathematical methods to data from a real population to predict
what will happen to the population in the future.
· Investigate how natural selection acts on phenotypic variation in
populations.
· Evaluate data-based evidence that describes evolutionary change in the
genetic makeup of a population over time due to changes in the
environment.
· Design an investigation based on your observations and questions
related to the importance of a single trait in the life history of a plant.
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Pre-Lab Questions
Read the background information and answer the following
questions in your lab notebook.
1. Define natural selection and contrast it with artificial selection.
2. What will happen over time to a population exposed to artificial
selection? Give a example.
3. What does it mean to "quantify several traits"?
4. Give a brief outline of this investigation.
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Safety
When growing plants under lights, be careful to avoid
any situation where water or fertilizer could come in
contact with electrical wires.
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Guided Investigation
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Table of
Contents
Materials
·
·
·
·
·
·
·
Lighting
Growing system
Wicking
Fertilizer
Soil
Vermiculite
Fast Plant seed
· Bee sticks for pollination
· Digital cameras to record the
investigation
· Plastic magnifiers
· Laboratory notebook
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Plant Cultivation: First Generation Plants
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Step 1 Prepare growing containers.
If using plastic soda
bottles click her for
instructions
Plant Cultivation: First Generation Plants
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Step 2 Each day, check your plants and make sure that the
reservoirs are full, especially on Fridays.
As your plants grow, record your observations daily. Also try
to identify a trait that you could measure or observe reliably.
Look for variation in the plants you are growing and describe
any you see in your notebook. Observe your classmates'
plants as well.
Note: Carefully read Step 3-7 before the plants begin to flower.
Plant Cultivation: First Generation Plants
Step 3 When the plants are about 7 to 12 days old, the class
needs to choose 1-2 variable traits for artificial selection.
Several variable traits can work for this. Compare your
observations with those of other students.
You want a trait that varies between plants in a single bottle/
pot but also varies between containers. The trait should not
be something that is Yes or No, but rather something that
varies within a range. That is, look for traits that you can
score on a continuum (length, width, number, and so on).
In your lab notebook, compile a list of all the possible traits
your class identified.
As a class, pick a trait you want to try to affect.
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Plant Cultivation: First Generation Plants
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Step 4 Score each of your plants for the trait that your class
chose to evaluate. You may need a magnifier to do this
accurately. Don't be surprised if some plants are not very
different from one another.
Plant Cultivation: First Generation Plants
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Step 5 Calculate appropriate descriptive statistics for the class
data for the first generation: mean, median, range, standard
deviation, etc.
Plant Cultivation: First Generation Plants
Step 5 cont'd Create a histogram (such as the one below) that
shows the frequency distribution of the trait that you have
selected.
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Plant Cultivation: First Generation Plants
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Step 6 You are now ready to make selection decisions.
Directional selection tends to move the variability of a trait in
one direction or the other (increase or decrease the trait in
the next population).
Find the top (or bottom) 10% of plants with the trait in the
entire class's population (e.g., out of a population of 150
plants, the 15 hairiest plants), and mark any that are in your
plant containers. Using scissors, cut off the tops of the
remaining plants in that container (those not in the top 10%).
Note: Containers with no individuals in the top 10% will be kept as a
control population. Do not cut these plants.
Plant Cultivation: First Generation Plants
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Step 7 Just as you did in Step 5, construct a new histogram
and calculate descriptive statistics for the selected
population of plants. Record the data in your lab notebook.
Once you have finished, isolate these selected plants from
the rest of the population. Move the containers of selected
plants to another light system so that the plants can finish
out their life cycle in isolation. This population will serve as
the parents for the new generation.
Plant Cultivation: First Generation Plants
Step 8 On about day 14-16, when several flowers are
present on each of the selected plants, cross-pollinate the
selected plants with a single bee stick or pollinating device.
Fast Plants are self-incompatible - each plant must be
fertilized by pollen from another plant.
Collect and distribute pollen from every flower on every plant
in the selected population. Reserve this bee stick for only the
selected population.
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Plant Cultivation: First Generation Plants
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Step 9 Maintain the plants through the rest of their life cycle.
As the seedpods form be sure to limit each of the plants to 8
to 10 seedpods. Any more will likely result in poor seed
quality.
Once the seedpods start to turn yellow (about day 28-36),
remove the fertilizer water from the reservoirs and allow the
plants to dry for several days. After the plants and seedpods
have dried (about a week later), harvest the seedpods from
the selected population into a small paper bag for further
drying. Be sure to record observations about the plants' life
cycle in your lab notebook.
Step 10 Continue to monitor, pollinate, and maintain your
control plants throughout the rest of their life cycle. Just be
careful to keep the original population and the selected
population separate.
Plant Cultivation: Second Generation Plants
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Step 11 You should now have two populations of secondgeneration seeds: (1) a population that is the offspring of the
selected plants from generation one and (2) a population that
is the offspring of the remaining plants from generation one.
Take the seeds from the selected population and plant them
to grow the second generation of plant under conditions that
are identical to those you used for generation one.
Use new containers, or if you choose to use the previous
containers, make sure they are thoroughly clean and
sterilized with a dilute (10%) bleach solution. Use new
wicking cord and new soil.
To get your seed, break open the seedpods into a small
plastic petri dish lid.
Plant Cultivation: Second Generation Plants
Step 12 When the second-generation plants are about 7-12
days old, reexamine the plants and score for the trait you
selected. Score the plants at the same life history stage
using the same method.
Step 13 Unless you plan on growing these plants for another
generation, you do not have to save these plants. You can
discard them and clean up your growing equipment at this
point.
Step 14 Compile, analyze, and graph the class data as you
did for the first generation. What is the outcome of your
artificial selection? Be sure to record this preliminary
analysis in your notebook.
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Analyzing & Evaluating Results
Analysis Questions:
· Are the two populations/generations before and after
selection actually different?
· Are the means significantly different?
· Should you use median or mean as a measure of central
tendencies at this point in the investigation?
· Compare your two graphs from the two populations.
Consider constructing a bar graph to compare the mean
for the selected traits. Include error bars.
· What statistical test could you apply to help you define
your confidence about whether these two populations are
different?
· Compare the second population to the parent
subpopulation of generation one. How do these two
populations compare? How does this comparison differ
from your other comparison?
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Independent Inquiry
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Table of
Contents
Designing & Conducting Your Investigation
As you worked through the guided investigation, you likely
started to think about questions of your own. With
permission from your teacher, use this investigation as a
model and design an experiment to answer your question or
one of the following:
· How does this trait help the plants grow and survive?
· Does a similar pattern occur when another trait is
selected?
· Does one form or another of the trait offer an advantage in
the natural world?
· How much of the variation could be the result of
environmental differences?
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