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Welcome to Biology

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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?

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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

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Milk bubbles experiment For 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

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Milk bubbles experiment For 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

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Reviewing graphs

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Title Dependent variable3Grid goes on the Vertical axis (Y) 2 Plotted points or line or curve Use an even scale1 and include units 0 1234 5 Independent variable goes on the Horizontal axis (X) Use an even scale and include units

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Interpreting graphs

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Parts of the microscope

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Ocular lens Objective lens Arm Stage Iris wheel diaphragm Light Coarse focus Fine focus

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Using the microscope Changing the magnification Changing the focus Adjusting the light or contrast

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Using the microscope Changing the magnification Changing the focus Adjusting the light or contrast

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Calculating magnification x10 ocular lens and x4 objective lens = x10 ocular lens and x10 objective lens = x10 ocular lens and x40 objective lens =

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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

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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

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What you see under the microscope Everything is reversed as well as magnified

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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

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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

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Diameter of field of view Distance across centre of field Measured with Measured in

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Diameter of field of view Distance across centre of field Measured with a minigrid Measured in micrometres ( m)

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Millimetres and micrometres 1 mm = m 2.4 mm = m 340 m = mm 4400 m = mm

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Millimetres and micrometres 1 mm = 1 000 m 2.4 mm = 2 400 m 340 m = 3 400 mm 4400 m = 4 400 mm

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Using a minigrid Each square is 1 mm by 1 mm in size The centre grid is further subdivided into 0.1 mm grid squares

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Magnification and field of view 1 x40 x100 x400

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Magnification and field of view 2 As magnification increases, field of view As magnification decreases, field of view

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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

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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 =

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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

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Size of objects under the microscope 1 If given a scale – 0 1 2 mm

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Size of objects under the microscope 1 If given a scale – 0 1 2 mm Measure object with ruler Measure scale with ruler Use scale to convert ruler measurement of object to real one Size = 0.6mm = 600 µm

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Size of objects under the microscope 2 If given a field of view – Magnification x100, field of view 2000 m

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Size of objects under the microscope 2 If given a field of view – Magnification x100, field of view 2000 m Measure object with ruler Measure field of view with ruler Use field of view measurement to convert ruler measurement of object to real one Size = 1000 m

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Size of objects under the microscope 3 If given a magnification – Magnification x 200

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Size of objects under the microscope 3 If given a magnification – Magnification x 200 Measure object with ruler Divide size by magnification factor to get real size Size = 4cm ÷ 200 = 0.02 cm = 0.2 mm = 200 m

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