The research on the amount of knowledge learned in the fields of Science and Biology allows us to single out concepts which pupils learn with ease, as well as concepts which pupils learn the wrong way, which causes difficulties when formulating valid concepts. Such notions learned the wrong way are called misconceptions. Misconceptions are incorrect concepts which denote wrong conceptions of certain terms, they are in contrast with scientific facts, and can be classified into several categories according to their origin. Initial and final tests conducted in the 7th grade of elementary school were used to determine the most common misconceptions. The metric analysis of the test results was done by calculating Cronbach's alpha, index of ease, science literacy, and conducting ANOVA analysis. The analysis of the initial and the final tests identified a large number of various misconceptions, most of which belong to the category of misconceptions which arise from misunderstanding of concepts and learning by heart without actually comprehending the facts. The most common misconceptions are the wrong categorization of plant species, such as putting gingko in the category of flowering plants, and the misunderstanding of processes related to plant physiology, such as osmosis and diffusion. The first misconception is the result of learning the facts by heart without actually comprehending them, whereas the second misconceptions tems from the lack of understanding of concepts. Comparison between results of the initial and the final test shows that there was no significant improvement incorrection of frequent misconceptions.