deviating from the standard: integrating statistical analysis and experimental design into life...
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Deviating from the Standard: Integrating Statistical Analysis and Experimental Design into Life Science Education
Summer Workshop:: Creating a data set
Workshop – Creating a data set
Objectives:
1.Describe the scientific method2.Formulate a hypothesis3.Carry out a simple experiment to generate an experimental data set4.Identify ways that you can use this activity in your classroom
The delicious side of osmosis!
http://delightsbites.blogspot.com/2011/09/fresh-strawberry-fro-yo-healthy.html
H20
H20
H20
H20
H20
H20
H20 H20
H20 H20
H20
H20
H20H20
Increase
external
tonicity
Decrease external tonicity
H20
H20
H20
H20
The biological situation:: Water movements with osmosis
Osmolarity – concentration of dissolved substances (solutes) in a liter of liquid (solvent) (units are osmoles/liter)
Tonicity - refers to the relative abundance of impermeable solutes between two solutions separated by a barrier
Water potential balance across membranes determines direction of water movements
Ψ = water potential
Ψp = pressure potential (hydrostatic pressure)
Ψπ = solute potential = -iMRT
Ψ = Ψp + Ψπ
*all potentials have the units of kiloPascals (kPa)
Good experimental design?
Observe a phenomenon
Formulate a question
Design a testable hypothesis
Make predictions
Design and carry out experiments to test predictions and hypothesis
Compare results to predictions and hypothesis
Results support hypothesis Results do not support hypothesis
Accept hypothesis
Gather information
Gather informationModify hypothesis
Reject hypothesis
Basic experimental setup
Isotonic(6.25% sucrose)
Hypotonic(DI H20)
Hypertonic(25% sucrose)
‘Cell’6.25%
sucrose
‘Cell’6.25%
sucrose
‘Cell’6.25%
sucrose
» Allow ‘cells’ to equilibrate in their extracellular solutions for 60 minutes» Weigh ‘cells’ a second time to document changes in weight
» Construct ‘cells’» Weigh ‘cells’ to document baseline weight
‘Cell’6.25%
sucrose
Each person will do a set of cells. How should we standardize our techniques so we can minimize variability and lump the data from everyone?
Basic experimental setup
Isotonic(6.25% sucrose)
Hypotonic(DI H20)
Hypertonic(25% sucrose)
‘Cell’6.25%
sucrose
‘Cell’6.25%
sucrose
‘Cell’6.25%
sucrose
» Allow ‘cells’ to equilibrate in their extracellular solutions for 60 minutes» Weigh ‘cells’ a second time to document changes in weight
» Construct ‘cells’» Weigh ‘cells’ to document baseline weight
‘Cell’6.25%
sucrose
Wear gloves when handling the dialysis tubing!!!
Observe a phenomenon
Formulate a question
Design a testable hypothesis
Make predictions
Design and carry out experiments to test predictions and hypothesis
Compare results to predictions and hypothesis
Results support hypothesis Results do not support hypothesis
Accept hypothesis
Gather information
Gather informationModify hypothesis
Reject hypothesis
Question: How does external tonicity affect water movements across a semi- permeable membrane?
•Try to write a hypothesis and predictions for this question and our experiment
AP Biology Exam 2012 – Scientific practices
1. The student can use representations and models to communicate scientific phenomena and solve scientific problems
2. The student can use mathematics appropriately
3. The student can engage in scientific questioning to extend thinking or to guide investigations within the context of the AP course
4. The student can plan and implement data collection strategies appropriate to a particular scientific question
5. The student can perform data analysis and evaluation of evidence
6. The student can work with scientific explanations and theories
7. The student is able to connect and relate knowledge across various scales, concepts, and representations in and across domains
For Monday each person should work on their own to:
1.Organize and summarize the group data
2.Create two different graphs or visual representations of the data
3.In a couple of sentences state why you chose each graph/representation
Bonus slides!
Osmosis is everywhere!
1. In vivo● Cells
http://www.umanitoba.ca/faculties/afs/soil_science/MSSS/links/Images/cartoons/osmoregulation.jpg
Cells of the kidney
Bacteria
Osmosensory neurons in the mammalian hypothalamus
R Sharif-Naeini , S Ciura , Z Zhang & C W Bourque, 2008
Osmosis is everywhere!
1. In vivo● Cells● Organisms
Image from: http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mcb&part=A4493
Water transport in plants Body water balance by kidneys
http://www.davincisurgery.com/$assets$/7a9a5682-444e-4c22-b44e-88e33b1c1a15/Kidney-anatomic-location.jpg
http://www.scv-habitatplan.org/www/site/alias__default/296/species_of_the_month.aspx
Osmosis is everywhere!
Chinook salmon
Lives most of its life in the ocean (~1000 mOsm)
Migrates to spawn to freshwater riversLittle change in blood plasma osmolarityin the face of 100-1000 fold decrease in waterosmotic pressure
Osmosis is everywhere!
1. In vivo● Cells● Organisms
2. Applications● Reverse osmosis
● Water purification
● Desalination of seawater for drinking
(Forward) Osmosis Reverse Osmosis
http://library.thinkquest.org/C0131200/Flowchart.jpg
http://www.sabahtourism.com/sabah-malaysian-borneo/images/things-to-buy/141-Salted-fish/salted-fish.jpg
1. In vivo● Cells● Organisms
2. Applications● Reverse osmosis
● Water purification● Desalination of seawater for drinking
● food preparation and preservation!
Osmosis is everywhere!
Salting meat to prevent spoilage (by bacteria!!)
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