Numbers and elementary concepts for biology students

Abstract

The validation of hypotheses in order to explain natural phenomena requires data. Many biological phenomena have been discovered and explained on the basis of qualitative analyses, but new insights often follow when they are revisited in quantitative terms. Without a quantitative description, there is no discovery at all. A parameter variation due to changes on environmental conditions is usually detected by measurements on apparatus developed according to certain physical-chemical principles. The knowledge of fundamental principles underlying the techniques used is essential for good understanding of the phenomenon in question and so it is necessary to insist on basic concepts consolidation. Recalling the properties of water and using mint leaves as biological material, spectrophotometry and tensiometry are two measurement techniques that allow us easily gathering a lot of data. The analysis of the information obtained by these two methods on similar samples may promote internalization of natural phenomena, related to the frequent mixtures of living or dead organic matter in water. In this work it is proposed an experimental activity addressed to pre-university and first year graduate students. The first step of the activity is to prepare three batches of mint leaves (biological material easy to obtain) to make an infusion, a suspension and an extract of chlorophyll from their leaves. The preparations are analysed by spectrophotometry and tensiometry. The results obtained by each technique allow us to compare some properties of the three types of samples. Although not being related a-priori, the combined analysis of the parameters measured by the two techniques provides some insight on natural mechanisms. The main goal of this activity is that students recognize the importance of elementary concepts from different scientific areas, enhancing the relevance of interdisciplinary towards the consolidation of scientific knowledge.