This This isn’tisn’t preparation for preparation for

Biology 2.1Biology 2.1

AIM: Carry out a short investigation AIM: Carry out a short investigation that won’t help you prepare for that won’t help you prepare for

Biology 2.1Biology 2.1

PremisePremise

Dried apricots are low in water – no Dried apricots are low in water – no surprises there – so if you place one in a surprises there – so if you place one in a beaker of water it will take up water by beaker of water it will take up water by osmosis. No surprises there either as the osmosis. No surprises there either as the cells are still intact so water will move cells are still intact so water will move from the beaker into the apricot because from the beaker into the apricot because the water is moving from an area of high the water is moving from an area of high concentration (beaker) to an area of low concentration (beaker) to an area of low concentration (apricot) across a concentration (apricot) across a selectively permeable membrane.selectively permeable membrane.

TaskTask

Or will it? Your mission, should you choose to Or will it? Your mission, should you choose to accept it (and you will) is to demonstrate that accept it (and you will) is to demonstrate that this uptake of water will occur and then this uptake of water will occur and then explain it as succinctly and beautifully as I explain it as succinctly and beautifully as I have in the previous slide which you will have in the previous slide which you will never, never, never see again.never, never, never see again.

Please note: it would be UNREASONABLE to Please note: it would be UNREASONABLE to expect you to compare your results with those expect you to compare your results with those of your fellow scientists or compare to any of your fellow scientists or compare to any previous research, after all real scientists previous research, after all real scientists don’t do thatdon’t do that

EquipmentEquipment

You have one dried apricot and two You have one dried apricot and two friends (or maybe one dried apricot friends (or maybe one dried apricot and two other people who might and two other people who might trade results with you), a beaker, trade results with you), a beaker, water, thermometer, electric scales water, thermometer, electric scales and a next-to-useless biology teacher and a next-to-useless biology teacher who can give you “supervision” who can give you “supervision” (whatever that means).(whatever that means).

Apricots & OsmosisApricots & Osmosis

Aim:Aim: Hypothesis:Hypothesis: Independent Variable?Independent Variable? Dependent VariableDependent Variable Controlled VariablesControlled Variables Number of RepeatsNumber of Repeats MethodMethod

ResultsResults

Dried Apricot Weight Change When Placed in Water

TriTrialal

Initial Initial Weight Weight (g)(g)

Final Final Weight Weight (g)(g)

Mass Mass change change (g)(g)

Percentage Percentage weight weight changechange

Average Percentage Weight Change:

You might like to make use of the You might like to make use of the following table (or not)following table (or not)

% Mass Change vs % Mass Change vs % of Original Weight% of Original Weight

An apricot started at 10 grams and increased to An apricot started at 10 grams and increased to 20g, an increase of 10 grams.20g, an increase of 10 grams.

% mass change % mass change = weight gain / initial weight x = weight gain / initial weight x 100100

= 10 / 10 x 100= 10 / 10 x 100= 100%= 100%

% of original weight % of original weight = final weight / initial weight = final weight / initial weight x 100x 100

= 20 / 10 x 100= 20 / 10 x 100= 200%= 200%

ConclusionConclusion

Justify your conclusion in terms of the Justify your conclusion in terms of the method you used.method you used. This is about what you did to make it a fair test This is about what you did to make it a fair test

and why that means your conclusion is correct.and why that means your conclusion is correct. It isn’t about the things you cocked up or It isn’t about the things you cocked up or

would do differently if you did it again. You’re would do differently if you did it again. You’re never going to do it again so do it right in Bio never going to do it again so do it right in Bio 2.1!2.1!

DiscussionDiscussion

EvaluationEvaluation

Explain (using your vast knowledge of Explain (using your vast knowledge of osmosis) the reason for the results you osmosis) the reason for the results you obtained.obtained.

What did you results show?What did you results show?

Other guff you should know Other guff you should know after 3.5-5.5 of years of after 3.5-5.5 of years of science at Johnnies…science at Johnnies… Independent Variable (changing what? & valid range)Independent Variable (changing what? & valid range)

Dependent Variable (you’re measuring…?)Dependent Variable (you’re measuring…?) Controlled Variables (how!?)Controlled Variables (how!?) Do experiment right! (method can be changed!)Do experiment right! (method can be changed!) Why do repeats?Why do repeats? How to draw a table, graphHow to draw a table, graph Conclusion relates to purpose AND your data!Conclusion relates to purpose AND your data! Discussion uses scientific knowledge to explain Discussion uses scientific knowledge to explain

trend / pattern in resultstrend / pattern in results Evaluate it. Justify what you have said is right by Evaluate it. Justify what you have said is right by

bragging about your:bragging about your: Quantity of dataQuantity of data Wonderful independent variable rangeWonderful independent variable range Removal of sources of errorRemoval of sources of error Removal of biasRemoval of bias

Validity vs ReliabilityValidity vs Reliability Validity: the degree to which a study accurately reflects Validity: the degree to which a study accurately reflects

or assesses the specific concept that the researcher is or assesses the specific concept that the researcher is attempting to measure. We achieve validity by:attempting to measure. We achieve validity by: Having a suitable range for our independent variable (at least Having a suitable range for our independent variable (at least

five!)five!) Measuring all variables accurately (how many decimal Measuring all variables accurately (how many decimal

places?)places?) Controlling all variables not being investigated (and stating Controlling all variables not being investigated (and stating

how you controlled and measured them)how you controlled and measured them) Anything else that you might have done to remove error and Anything else that you might have done to remove error and

biasbias

A List of Controlled VariablesA List of Controlled Variables

Size of apricotSize of apricot Length of timeLength of time Concentration for each repeatConcentration for each repeat Glad wrap to prevent evaporationGlad wrap to prevent evaporation Same equipment Same equipment Temperature of repeatTemperature of repeat Apricots from same bags (controls species variation, Apricots from same bags (controls species variation,

variation in dryness)variation in dryness) Removed excess water from wet apricotsRemoved excess water from wet apricots

Validity vs ReliabilityValidity vs Reliability Reliability: the extent to which an experiment, Reliability: the extent to which an experiment,

test, or any measuring procedure yields the same test, or any measuring procedure yields the same result on repeated trials.result on repeated trials. We achieve this by carrying out repeats (at least We achieve this by carrying out repeats (at least

three!) and averaging the datathree!) and averaging the data

Apricot Osmosis ExperimentApricot mass in tap water  Trial Mass % changeNick 142Braden 130Tyler 177William 289Dion 208Matytthew 207Adrian 246Madoc 200Cam 190Average 199Apricot mass in salt water  Trial Mass % changeHamish 110Chris 117Hugh 131Sam 122Michael 141Masaaki 116Average 123

Apricot Osmosis ExperimentApricot mass in tap water  Trial Mass % changeJacob 229Max 172Carter 185Tim 195Ru 181Marc 180Saba 208Yuhei 196Hugh 183Chris 273Average 200Apricot mass in salt water  Trial Mass % changeGeorge 193Ben 119Ben 130Average 147

Practice PlanPractice Plan Design an experiment to find out what will

happen in terms of osmosis to celery sticks placed in different salt concentrations.

Background: concentration of salt in celery is 0.5 mol / L. You have lots of celery, 5 x 30cm sticks of celery each. Concs of salt solutions available. Distilled water, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1,1.2, 1.3, 1.4, 1.5 mol / L salt concs.

 Complete the following: Aim, Hypothesis, Variables (independent, dependent, controlled), Equipment, Method.

Observing Observing Osmosis Osmosis in a Cellin a Cell

Observing Osmosis in a Observing Osmosis in a CellCell

ProblemProblem hard to see osmosis occurring in microscopic cells.hard to see osmosis occurring in microscopic cells.

Solution Solution use a large cell like a chicken egguse a large cell like a chicken egg

Problem Problem shell impermeable to water.shell impermeable to water.

Solution Solution remove shell (dissolve in acetic acid – vinegar)remove shell (dissolve in acetic acid – vinegar)

Reaction: Calcium carbonate + Acetic acid Reaction: Calcium carbonate + Acetic acid H H22O + COO + CO22 + Calcium Acetate + Calcium Acetate

Chemists: write the formula, try to balance!Chemists: write the formula, try to balance!(Acetic acid: (Acetic acid: CH3COOH, Acetate ion: Acetate ion: CH3COO-)

Dissolve shellDissolve shell Place in waterPlace in water WeighWeigh Measure 200mL sugar solutionMeasure 200mL sugar solution Put egg in, leave 48 hours.Put egg in, leave 48 hours. Weigh, measure solution volumeWeigh, measure solution volume Expect: egg mass drop, solution Expect: egg mass drop, solution

volume increasevolume increase

Observations +30mins: Bubbles of COObservations +30mins: Bubbles of CO2 2 on eggon egg

Observations +48hrs (day 3):Observations +48hrs (day 3):

Place egg in 250mL of a hypertonic sugar solutionPlace egg in 250mL of a hypertonic sugar solutionPrediction:Prediction:Observations +48hrs (day 5):Observations +48hrs (day 5):- Egg:- Egg: Liquid VolumeLiquid VolumeObservations +48hrs (day 7):Observations +48hrs (day 7):- Egg:- Egg: Liquid VolumeLiquid Volume

QuestionsQuestions1.1. What happened to the egg? Why?What happened to the egg? Why?

2.2. What happened to the liquid volume? WhyWhat happened to the liquid volume? Why

3.3. What could you do to reverse what happened?What could you do to reverse what happened?

Elodea Elodea PlasmolysisPlasmolysis

Elodea PlasmolysisElodea Plasmolysis

Make a wet mount of elodea and add saltwater to the slide. Observe what happens to the cells after 15min. (make a control (no salt) for comparison).

Observations: Conclusions:Questions: Is plasmolysis reversible? What could you do to test this?

See: http://www.biologycorner.com/worksheets/plants_and_salt.html For a clip on cytoplasmic streaming

Isotonic Isotonic Concentration of Concentration of

Carrots Carrots Aim: to find out the isotonic Aim: to find out the isotonic

concentration of carrotsconcentration of carrots

Isotonic concentration of Isotonic concentration of carrotscarrots

Write:Write: AimAim Independent variable Independent variable

suitable range, how to change itsuitable range, how to change it Dependent variable Dependent variable

what, how to measurewhat, how to measure Controlled variableControlled variable

List each and how to measure and checkList each and how to measure and check

Carrot Mass Change in Different Salt Concentrations

Salt Salt concentration concentration (g / 100mL)(g / 100mL)

Initial Initial Weight (g)Weight (g)

Final Final Weight (g)Weight (g)

Mass Mass change (g)change (g)

Percentage Percentage weight changeweight change

Average Average percentage percentage weight changeweight change

0

0

0.5

0.5

1

1

1.5

1.5

2

2

2.5

2.5

3

3

Dummy DataDummy Data

QuestionsQuestions

What happened in distilled water? ExplainWhat happened in distilled water? Explain What happened in the saltiest concentration? What happened in the saltiest concentration?

ExplainExplain How did you identify the isotonic How did you identify the isotonic

concentration?concentration? How did you make sure the experiment was How did you make sure the experiment was

valid?valid? How did you make sure the experiment was How did you make sure the experiment was

reliable?reliable?