welcome to biology. increasing reliability a drug company wants to test the effectiveness of a new...
TRANSCRIPT
Welcome to Biology
Increasing reliability
A drug company wants to test the effectiveness of a new drug against asthma. How can they increase the reliability of their results?
Increasing reliability
A drug company wants to test the effectiveness of a new drug against asthma. How can they increase the reliability of their results?
Use a large test group of asthmatics (1000 +)
Have a mixed group (ages, gender & fitness levels)
Use the same number & mix in the control group
Give the control group a placebo
Run the trial over a long period
Swap the groups over and repeat the trial
Repeat the trial with another group
Get someone else to replicate the trial
Measure accurately and often changes in incidence of asthma & any side effects, etc
Milk bubbles experimentFor Part A, identify the:• Hypothesis• Independent variable• Dependent variable• Control• Variables you controlled • How you increased reliability
For Part B, you’ll need to identify these before you design & carry out your experiment
Milk bubbles experimentFor Part A, identify the:• Hypothesis – skim milk will produce smaller bubbles than full cream milk
• Independent variable – the type of milk
• Dependent variable – size of bubbles
• Control – full cream milk
• Variables you controlled – temperature, volume of milk, strength of blowing, etc
• How you increased reliability – repeat experiment, replicate experiment, etc
For Part B, you’ll need to identify these before you design & carry out your experiment
Reviewing graphs
Reviewing graphs
Title
Dependent variable 3 Grid
goes on the
Vertical axis (Y) 2 Plotted points or line or curve
Use an even scale 1
and include units
0
1 2 3 4 5
Independent variable goes on the Horizontal axis (X)
Use an even scale and include units
Interpreting graphsBubbles produced by yeast
0
10
20
30
40
50
60
70
80
0 5 10 20 30 40 50 60 70
Temperature (Celcius)
Nu
mb
er o
f b
ub
ble
s/m
in
Bubbles/min
Parts of the microscope
Parts of the microscope
Ocular lens
Objective lensArm
Stage
Iris wheel diaphragm
Light
Coarse focus
Fine focus
Using the microscope
• Changing the magnification
• Changing the focus
• Adjusting the light or contrast
Using the microscope
• Changing the magnification
• Changing the focus
• Adjusting the light or contrast
Calculating magnification
• x10 ocular lens and x4 objective lens =
• x10 ocular lens and x10 objective lens =
• x10 ocular lens and x40 objective lens =
Calculating magnification
• x10 ocular lens and x4 objective lens = x40
• x10 ocular lens and x10 objective lens = x100
• x10 ocular lens and x40 objective lens = x400
Working distance
This is the distance between the objective lens and your slide.
The higher the magnification of the lens, the larger the lens
The higher the magnification of the lens, the smaller the working distance
What you see under the microscope
Everything is reversed as well as magnified
What you see under the microscope 2
• If the object appears to be at the top of the slide it is really
You need to move the slide
• If the object appears to be at the left of the slide it is really
You need to move the slide
What you see under the microscope 2
• If the object appears to be at the top of the slide it is really at the bottom
You need to move the slide towards you
• If the object appears to be at the left of the slide it is really on the right
You need to move the slide to the right
Diameter of field of view
• Distance across centre of field
• Measured with
• Measured in
Diameter of field of view
• Distance across centre of field
• Measured with a minigrid
• Measured in micrometres (m)
Millimetres and micrometres
• 1 mm = m
• 2.4 mm = m
• 340 m = mm
• 4400 m = mm
Millimetres and micrometres
• 1 mm = 1 000 m
• 2.4 mm = 2 400 m
• 340 m = 3 400 mm
• 4400 m = 4 400 mm
Using a minigridEach square is 1 mm by 1 mm in size
The centre grid is further subdivided into 0.1 mm grid squares
Magnification and field of view 1
x40 x100 x400
Magnification and field of view 2
• As magnification increases, field of view
• As magnification decreases, field of view
Magnification and field of view 2
• As magnification increases, field of view decreases by the same factor
• As magnification decreases, field of view increases by the same factor
Magnification and field of view 3
If field of view at x100 is 1600 m, then
• Field of view at x400 =
• Field of view at x40 =
If field of view at x400 = 200 m, then
• Field of view at x100 =
• Field of view at x40 =
Magnification and field of view 3
If field of view at x100 is 1600 m, then
• Field of view at x400 = 400 m
• Field of view at x40 = 4 000 m
If field of view at x400 = 200 m, then
• Field of view at x100 = 800 m
• Field of view at x40 = 2 000 m
Size of objects under the microscope 1
If given a scale – 0 1 2 mm
Size of objects under the microscope 1
If given a scale – 0 1 2 mm
Measure object with rulerMeasure scale with rulerUse scale to convert ruler measurement
of object to real one
Size = 0.6mm = 600 µm
Size of objects under the microscope 2
If given a field of view –
Magnification x100, field of view 2000 m
Size of objects under the microscope 2
If given a field of view –
Magnification x100, field of view 2000 m
Measure object with rulerMeasure field of view with rulerUse field of view measurement to convert
ruler measurement of object to real one
Size = 1000 m
Size of objects under the microscope 3
If given a magnification –
Magnification x 200
Size of objects under the microscope 3
If given a magnification –
Magnification x 200
Measure object with rulerDivide size by magnification factor to get
real size
Size = 4cm ÷ 200 = 0.02 cm = 0.2 mm = 200 m