CTS Guide: Reproduction, Growth, and Development, pp 138-139- Section IV Research Summaries
Life Cycles of Plants and Animals
A study of pre-service biology teachers’ understanding about plants revealed the common misconception that seeds are produced after a fruit is formed (Yuruk, Selvi, and Yakisan, 2011).
Some students may believe a seed only comes alive once it has been planted and begins to grow because they hold a conception that there are temporary breaks in an organism’s life cycle that put it in a nonliving state. A related idea is that some students think caterpillars are alive but that when they go into the chrysalis state, they are nonliving and they become living again when they emerge as a butterflies (Allen 2010).
The 1998 National Curriculum Assessments report (Qualifications and Curriculum Authority, 1998) In the United Kingdom found that about 25% 11-year-old students were able to correctly identify all three stages of the life cycle of a flowering plant. Many of these students did not realize that all flowering plants bear fruit.
In a study that investigated 10- to 14-year- old children’s ideas about the continuity of life, most could correctly sequence pictures of seed germination, but 66% did not view the seed as alive and 19% did not understand the continuity of life from seed to seedling. Some studies indicate that children fail to consider death as part of a life cycle (Driver et al. 1994).
In a study by Tamir, Gal-Chappin, and Nussnovitz (1981) of children ages 10 to 14, 19% did not understand the continuity of life. They believed that larvae changed into pupae, which are dead, and then they became butterflies.
Food and Growth
Students of all ages think food is a requirement for growth rather than a source of matter for growth. They have little knowledge about food being transformed and made part of a growing organism’s body (AAAS 2008).
Children understand at an early age that eating or absorbing food is necessary for growth. However, they do not recognize that these materials are the material for growth and that they are transformed and taken into the body, thus making it bigger (Driver et al. 1994).
A study by Russell and Watt (1990) found that children think animals grow or stretch to accommodate the food they eat.
Embryonic Development
Some ideas about embryonic development contribute to students’ notions about what is happening inside an egg. Some children believe that a chick has always been inside an egg waiting until it was time to hatch. Others thought all the parts of the chick were in an egg when the egg was laid and that they came together in the egg (Driver et al. 1994).
In a study conducted by Russell and Watt (1989), elementary children assumed that the growth inside an egg is associated with an increase in mass within what they assumed was a closed system. They described the process of growth as creating new material rather than transforming material (yolk) that was in the egg. Only a very small minority considered some type of transformation of the contents inside the egg into a complete chick.
Process of Reproduction
·A common difficulty in understanding reproduction comes from confusion in distinguishing the differences in the purpose and process of mitosis and meiosis and where these processes occur (Flores, Tovar, and Gallegos, 2003).
Plant 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.
One study found that some children think flowers exist because people like to look at them. They also found that some children could label the parts of a flower correctly but did not seem to know how they were used in reproduction (Warwick and Sparks-Linfield, 1996).