This week’s learner guide contains the following; *How to do magnification of specimens under the microscope, *How to plot a graph, *How to do scientific drawing More specifically the following learning objectives; •Calculate magnification and size of biological specimens using milimetres as units •Measuring the cell size under microscope •Scientific drawings of cells, flower parts, animals and seeds

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WEEK #2: July 6-10, 2015

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Under the microscope

A modern light microscope

Microscopes are used to study cells. Modernlight microscopes can magnify images about 1500 times,

while electron microscopes can magnify images about two million times.

Calculating magnification

The magnification of a biological specimen is calculated using this equation:

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Source: IB Science Skills in Biology

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Source: TES education

QQuestion

A plant cell in a photograph measures 15 mm across. If the actual size of the cell is 0.015 mm,

what is the magnification in the photograph?

AYour answer:

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Plant cells seen through a microscope

Calculating actual size

The actual size of a biological specimen is calculated using this equation:

QQuestion

The nucleus in a photograph of a cell measures 3 mm across. If the magnification in the

photograph is × 500, what is the actual size of the nucleus?

AYour answer:

http://www.bbc.co.uk/education/guides/zgcxsbk/revision/4

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Source: IB Science Skills in Biology

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Drawings

These will be from specimens or photographs.

• Read the question carefully, the drawing may have to be an accurate size e.g. twice the

original.

• Make each drawing as big as the space allows.

• Use a ruler for labelling lines.

• Label in pencil.

• Use one clear continuous outline not an artistic drawing. Do not shade other than using very

light dots.

• Observe details carefully, such as number of seeds in a seed case, thickness of a layer in a

shell, etc.

Show these accurately on your drawing

Source: IGCSE Learner Guide (p 26)

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IGCSE SPECIMEN & PAST PAPER QUESTIONS FOR PRACTICE

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Source: Nov’12 P61

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Source: Nov’12 Paper 62

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Source: Nov’12 P63

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Source: 2016 SP6