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UNIT 1. Living organisms. THE SIZE OF CELLS. Natural Science 2. Secondary Education. UNIT 1. 1 cm 2 3 4 5 6 7 8 9 10. 1 mm 2 3 4 5 6 7 8 9 10. 1000 µm. The size of cells.

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UNIT 1

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  1. UNIT1 Living organisms THE SIZE OF CELLS Natural Science 2. SecondaryEducation

  2. UNIT1 1cm 2 3 4 5 6 7 8 9 10 1mm 2 3 4 5 6 7 8 9 10 1000 µm The size of cells How can we measure a cell? • Cells cannot be seen by the naked eye, so it is difficult to get an idea of their size or measure them. Because they are so small, cells must be measured in tiny units calledmicrometres (µm). To get an idea of how big a micrometre is, think of one of the centimetres marked on a ruler: each centimetre contains 10 mm. Now think of one of those millimetres. A single millimetre contains 1000 µ. Natural Science 2. SecondaryEducation

  3. UNIT1 15,55 µm 1cm 2 3 4 5 6 7 8 9 10 The size of cells Comparing sizes • Imagine we measure an eukaryotic cell and see that it has a diameter of about 15.5 µm. This is an average-sized cell. • How many of these cells would fit in a single millimetre? • 1,000 divided by 15.5 equals to 64.5, so we could line up 64 of these cells in a row of one millimetre • Therefore, 640 cells would fit in 1 centimetre. = 640 cells Natural Science 2. SecondaryEducation

  4. UNIT1 The size of cells Magnifying images in order to see cells • Microscope lenses magnify what we see through them many times. Normally a microscope has several lenses of increasing magnification so that we can see cells or tissue specimens in great detail. 10x magnification 40x magnification Natural Science 2. SecondaryEducation

  5. UNIT1 Two different-sized cells The size of cells Magnifying images in order to see cells • Microscope lenses magnify what we see through them many times. Normally a microscope has several lenses of increasing magnification so that we can see cells or tissue specimens in great detail. 10x magnification 40x magnification 100x magnification Natural Science 2. SecondaryEducation

  6. UNIT1 The size of cells Problemsolving and investigating, page 18, question 7 • We observe the bacteria in the photo (10,000x magnifications) and we will find out the real length of one of them. • Tocalculatethe real size of thecellwehaveto divide thesize of thecell in thephoto ( in mm) bythenumber of magnifications. • 3 centimetresor 30 mm longdividedby 10,000 magnificationsequalsto 0.003 mm or 3 micrometresisthe real size of thecell. • Howmany of these bacteria wouldfit in a millimetre? • 1000 dividedby 3 equalsto 333 wouldfitinto 1 millimetre Natural Science 2. SecondaryEducation

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