Handling Information for Biology Examinations

Every experiment needs: A control experiment.control To be reliable.reliable To be designed so that it is possible to draw valid conclusions from a valid experimental design.valid conclusions Well presented results and conclusions.presented Correct calculationscalculations Experiments You can move to each section by clicking on the link You can return here by clicking the symbol

A control experiment allows you to be certain that the variable that you are investigating is the variable that is causing the effect. What do you do? You do the experiment again. The Control Experiment You leave out the variable that you are investigating.

A scientist wants to know the effect of heat on the enzyme pepsin. Pepsin will turn a cloudy solution of protein clear as it digests the insoluble protein into soluble peptides Test tubes of pepsin and protein are placed in water baths at 10, 20, 30, 40 and 50ºC The time taken to clear is recorded Do a second experiment with boiled (destroyed) enzyme A Control Experiment - examples: What is needed for a control experiment? ? *click*

Investigating the production of heat from germinating peas Do a second experiment with boiled (killed) peas Investigating the effect of acid rain on the growth of seedlings ? *click* Do a second experiment using distilled water instead of the acid A Control Experiment - examples:

Reliability A r eliable experiment is an experiment that you can be sure will give you an r epeatable result every time you do it. To ensure that you have not, by chance, got a result from one of the extreme ends of the normal range of variability. Replicate ( r epeat) the experiment several times and get an average of the results. What do you do?

A v alid experimental design is an experiment where you control all the v ariables apart from the one you are investigating. If the design is v alid then you are able to draw v alid conclusions. Valid Conclusions and Valid Experimental Design

Bad wordsGood words Good Words and Bad Words Amount Quantity Size Length Width Height Volume Warmth, coldness, heat, cold Temperature Acidity, alkalinitypH Mass Volume Some descriptive words linked to variables are not acceptable

In an experiment to test the effect of temperature on enzyme activity you must control: pH The concentration of the enzyme The concentration of the substrate(s) The volume of the liquid The shapes of the containers For example (1):

In an experiment to test the effect of light on rate of photosynthesis you would need to control: pH The temperature The concentration of Carbon dioxide The volume of the watering liquid The shapes of the containers For example (2):

Results can be presented as a table, as a graph or both. To draw a table. Lines are drawn with a ruler and surround the table. There must be headings for each row or column including SI units where appropriate. There are no units in the body of the table Bubbles (number/s) Temperature (°C) Results

TypeUnitx 1000  1000 other Lengthmetre (m)kilometre (km) millimetre (mm) micrometre (µm)  1M Volumelitre (l)kilolitre (kl) millilitre (ml) Temperaturedegrees Celsius (ºC) Massgram (g)kilogram (kg) milligram (mg) tonnes EnergyJoules (J)kilojoules (kJ) millijoules (mJ) Timeseconds (s)milliseconds (ms) minutes hours, days Do not use any other units or abbreviations SI units

Experiments - Presentation For every experiment you need: to know the input variable. The variable you change. The outcome variable. The variable you measure. This goes along the x-axis. This goes along the y-axis. x y input variable outcome variable This is the top row or first column in a table. This is the bottom row or last column in a table.

Temperature (°C) Bubbles (number/s)15750 Temperature (°C) Bubbles (number/s) A Bar Chart – separate bars 1.Draw the axes 2.Mark in the labels 3.Mark the x scale 4.Mark the y scale 5.Draw the bars 6.If you have time shade in the bars

Temperature (°C) Bubbles (number/s)15750 Temperature (°C) Bubbles (number/s) A Histogram – joined bars 1.Draw the axes 2.Mark in the labels 3.Mark the x scale 4.Mark the y scale 5.Draw the bars 6.If you have time shade in the bars

Temperature (°C) Bubbles (number/s)15750 Temperature (°C) Bubbles (number/s) A Line graph Draw the axes 2.Mark in the labels 3.Mark the x scale 4.Mark the y scale 5.Draw the points 6.Join the points with straight lines

Temperature (°C) Bubbles (number/s) A Pie Chart Fraction3/246/2412/243/240/24 Simplified fraction⅛¼½⅛ Temperature (°C) 3. Draw a circle 4. Mark off the segments 5. Make a key 1. Find the total Total Calculate the fractions

Averages 1. Find the total number of bubbles Temperature (°C) Bubbles (number/s) Try this example … Find the total = Divide the total by the number of items There are 5 items in the table 30  5 = 6 Average = 6 bubbles/s 3.Don’t forget units in your answer To find the average number of bubbles … Temperature (°C) Bubbles (number/s)02832 Click here for answer

Percentages 1. Find the total number of bubbles Temperature (°C) Bubbles (number/s) What percentage of bubbles are produced at 30ºC? Find the total = Divide the number of bubbles at 20ºC by the total number 8  32 = 0.25 this is the decimal fraction 0.25 x 100 = 25% To find the percentage of bubbles at 20ºC … 3.Multiply the decimal fraction by 100 to get the percentage 25% of the bubbles are produced at 20ºC

Ratios 10ºC:20ºC 4 bubbles:8 bubbles Temperature (°C) Bubbles (number/s) Write down the ratio of the numbers To find the simple whole number ratio of bubbles at 10 degrees compared to bubbles at 20 degrees … 2. Find a number that will divide into both numbers to give a whole number – in this case 2 4 bubbles  2:8 bubbles  2 =2 bubbles:4 bubbles 3. Repeat step 2 until you cannot divide again without getting a fraction 2 bubbles  2:4 bubbles  2 =1 bubble:2 bubbles

Ratios 20ºC:30ºC 8 bubbles:14 bubbles Temperature (°C) Bubbles (number/s) Write down the ratio of the numbers To find the simple whole number ratio of bubbles at 20 degrees compared to bubbles at 30 degrees … 2. Find a number that will divide into both numbers to give a whole number – in this case 2 8 bubbles  2:14 bubbles  2 =4 bubbles:7 bubbles 3. You cannot divide any more without getting a fraction so … the simple whole number ratio is: 4 :7