Measuring Growth

We can measure the growth of an organism by measuring its

• mass

• length , height or width, and 

• area or volume.

Over a period of time. Sometimes , it is possible to measure just one part of an organism such ad , the left of a plant, but this part must grow in proportion to the number of leaves may be used as a growth indicator. Each of these growth indicators is known as a parameter of growth.

   The pattern of growth of an organism would vary with the growth parameter that is used.

    In growth studies, the parameter used would depend on the type of organism. For example we can measure the height of maize plant to estimate its growth, but we cannot use the same parameter to assess the growth of a mouse. The ease of measuring a growth parameter will Aldo determine its usage. Thus, area and volume measurements give an accurate picture of growth but are often difficult to measure and so are dearly used.

      Mass and length (height or width) are the most commonly used growth parameters since they are easy to measure. However, the results obtained may not be very accurate or reliable. For example, a seedling grown in the dark increases in heigh more rapidly than a similar seedling grown in sunlight, but it is the sidling in the sunlight that shows greater growth in terms of increase in protoplasm material. Using measurements of mass may be misleading. If an organism takes in large amounts of water its made may increase temporarily. This, however, cannot be considered as growth.

   In most growth studies mass may be measured as wet mass or dry mass. Wet mass is the  mass of the organism under normal condition. It is not a reliable indication of growth. Dry mass is  the mass of an organism after all the water in it has been removed. Although measuring growth in terms of dry mass is an accurate and reliable method, the organisms gets killed in the process. this means that it is not possible to measure growth in the same organism. To study growth by measuring dry mass, we must carry out the study on a large number of similar organisms. Growth can them be estimated by removing a given number of organisms at a time and estimating their dry mass.