Size of Specimens

Specimen size is an important characteristic to consider in the study of biology, particularly when examining cells, tissues or any microscopic beings.

Measuring Specimens

For measuring the size of specimens, a variety of tools are used, such as microscopes, which allows for viewing at higher magnifications.
The size of a specimen can be determined through direct measurement (e.g., using a ruler) for larger specimens, or calculated from the magnification and field of view for microscopic specimens.

Units of Measurement

Size measurements are typically provided in standard metric units, such as millimetres (mm), micrometres (µm), or nanometres (nm), depending on the size of the specimen being measured.
1 millimetre (mm) equals 1000 micrometres (µm), and 1 micrometre equals 1000 nanometres (nm), understanding these conversions can aid in comparisons between different measurements.

Estimating Specimen Size under Microscope

To estimate the size of a specimen under a microscope, you can compare its size to that of the field of view (the circle of light you see when you look through the microscope).
This comparison can be made directly if the specimen takes up the entire field of view or indirectly by estimating how many of the same specimen would fit across the field.
Also, the diameter of the field of view can be measured by placing a stage micrometer–a microscope slide with an accurately printed scale–under the lens.

Scale Diagrams and Magnification

Scale diagrams can help understand the size of a specimen. These are drawings in which the size of the specimen is compared with its actual size by a factor known as the scale, for instance, 1cm:1µm.
Further, the magnification can be calculated if both the size of the image (obtained from a drawing or photograph) and the actual size of the specimen are known. The formula is: Magnification = Size of Image / Actual Size of Specimen.

Understanding the importance of the size of specimens is crucial to appreciate the complexity and diversity in biology, from the smallest cells to the largest organisms.