CTS Guide: Variation of Traits, pp 140-141- Section IV Research Summaries

Concept of Variation

  • It is common for learners to use the everyday meaning of variation, which is broader and more encompassing, when describing differences among any organism. Students who use the everyday meaning think any differences betweenliving things, including organisms of different species, is called variation and may not think it applies to organisms within the same species  (Allen, 2010).

  • A common misunderstanding of students all the way up through the undergraduate level is that they tend to recognize variation between different species but do not think there is variation between individuals of the same species (Gregory 2009).

Concept of Species

  • In a study of Spanish students, many identified species based solely on similarities in how they look (Jiménez-Tejada, Sánchez-Monsalve and González-García, 2013).

  • Researchers have pointed out that the term ‘species’ is often used in school science lessons without any explanation of what it means (Ellis and Wolf, 2010).

  • Middle school students may be familiar with the term ‘species’ from previous lessons or their everyday experiences, for example from reports about endangered species and conservation. As a result they may form their own concept of what is meant by a ‘species’, which may or may not be the scientific use of the term (AAAS 2009).

  • A study in England found that students age 5-16 knew that different breeds of dogs were all part of a group called “dogs” but showed little understanding of why they were all in the same group. By age 16 some students referred to genetics, yet showed little knowledge of the genetic basis of the concept of species (Driver et al. 1994).

Explanation for Variation

  • Some students use a teleological argument for variation believing that variation is intentional by an organism to satisfy its needs or to improve its structure or function (Gregory 2009).

  • Some students may believe that natural selection directly creates genetic variation, when in fact, it acts on existing variation within a population (Meir et al. 2007).

  • Several studies of students of all ages point to a commonly held idea that observable variation is due to the environment (Driver et al. 1994).

  • An older study of Australian 15-year-olds found that 56% thought variations in traits were due to the influence of environmental factors while 30% mentioned the influence of genes (Hackling and Treagust 1982).

Variation and Sexual Reproduction

  • Students may not recognize that variation in plants results from sexual reproduction because they do not understand that plants reproduce sexually.  Sesli and Kara (2012) developed a diagnostic test that revealed how 22.3% of the students tested thought plants could not reproduce sexually because they are unable to move and develop reproductive organs.