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!!)