Growth may be defined as a more or less irreversible change in the structure, development of a cell, tissue or organism. Development refers to the changing in the morphology of an organism as it grows. The following are the some parameter of measuring growth;-
1. Size or Height/Length: This method of measuring the length or height of the organisms is variable if growth occurs mainly in one direction like a flowering plant. The method is advantage in that it does not injure the organism, the main growth in other direction such as width and size which can significant.
2. Total Fresh Weight: This method involves weight of whole organism at regular interval. This is an easy methods used to estimate growth in large animal including man. This method also does not involve injury to the organisms. Fresh weight measurements are influenced by variation (change) in water content of the body and therefore do not always give accurate results.
3. Volume: This methods involves placing an organism in water filled container and determine the water displacement using an overflow cam, the volume of water displaced by the organism is measured using measuring cylinder.
4. Dry weight: This method involves the killing of organism and heating it at 110oC to a constant weight to remove water. This method is more accurate since it indicates the increase in weight due to synthesis of different materials irrespective to water content.
5. Number: The method is used to measure growth in unicellular organisms as bacteria, algae and protozoa. The methods involves collecting an accounting the number of organism in a sample of fixed volume periodically.