CTS Guide: Photosynthesis and Respiration at the Organism Level pp 106-107- Section IV Research Summaries
Plant Nutrition
Allen (2010): Garden fertilizers, labeled plant food, reinforce the idea that fertilizer is food for a plant. Some children also think plants ‘eat’ using their roots, forming an intuitive link between two pieces of knowledge: that plants absorb substances through their roots, and that plants need food to live and grow
Driver et al. (1994): Universally the most persistent notion at all ages of where plants get their food is that they take it from the environment, particularly the soil or that plant food is put into the soil. It is a common belief that plants have multiple sources of food including water, minerals, soil, carbon dioxide, and even sunlight. Starch is not considered a food for plants.
Anderson, Sheldon, and Dubay (1990): The common misconception that plants get their food from the environment and that food is taken in from the outside, is resistant to change, even after instruction.
Photosynthesis
Dimeac and Strgar (2017): Research has found that students at all levels frequently learn about photosynthesis by rote memorization of the chemical equation which ends up making learning about photosynthesis abstract, uninspiring and conceptually challenging. When students learn about the biochemical and physiological aspects of photosynthesis at the organism level, it is helpful to remind them of the ecological aspect.
Horizon Research, Inc. identified several commonly held ideas middle school students had about matter and energy in living systems, including 1) energy needed by animals is different from that needed by plants, 2) plants “want” to be eaten or to make food for animals, 3) plants make food from water and air, but it is not transformed into the plant’s body, 4) animals, not plants, break down food into simpler substances that are used for growth and repair of parts and tissues, and 5) plants photosynthesize but do not break down food (Taylor et al. 2012).
Marmaroti and Galanopoulou (2006): 33.9% of 13-year-olds could correctly identify carbon dioxide and water as needed for photosynthesis; 30.1% chose oxygen instead of carbon dioxide. In the same study, 62.3% correctly identified the products, though they had been taught that glucose (rather than carbohydrate) was the product along with oxygen. They also found students had difficulty conceiving photosynthesis as a chemical reaction.
Kinchin (2000): Active learning and metacognitive activities, including concept mapping, can support learning about photosynthesis and increase engagement. The researcher also noted the problem with using the common lab activity of testing for starch as evidence of photosynthesis. While the iodine test is easy for detecting starch, an overly narrow focus on starch as the ‘food’ made by photosynthesis is not particularly helpful, as starch is unfamiliar to students and is relatively rare in nature compared with other carbohydrates such as cellulose.
Driver et al. (1994): Some students who know that plants make their own food think they do so for the benefit of animals that eat plants. They fail to recognize that plants use the food they make through photosynthesis. Any discussion of ‘food’ is fraught with the problem of the word ‘food’ having different meanings in everyday and scientific contexts. Students may only something to be ‘food’ if it is eaten and thus some students do not think about the product of photosynthesis as food because it is synthesized, rather than eaten or taken in by the plant. Some students do not consider trees to be plants. Therefore, they may believe trees do not make their own food.
Barker and Carr (1989): 80% of 13-year-olds in their study thought plants could use heat from the sun to photosynthesize, even though they knew light was needed for photosynthesis. Other students thought plants could also use soil, minerals, water and air (in the absence of light). Light was commonly perceived to be a reactant in photosynthesis. The researchers suggest a dominant narrative about photosynthesis producing carbohydrate that plants use as a fuel (an energy source) and as a source of materials for growth. An overly narrow focus on starch as the ‘food’ made by photosynthesis is not particularly helpful, as starch is unfamiliar to students and is relatively rare in nature compared with other carbohydrates such as cellulose. These researchers used the question “Where does wood come from?” as an engaging theme to develop understanding of photosynthesis.
Stavy, Eisen, and Yaakobi (1987): Secondary school students’ understanding of photosynthesis was reviewed and the researchers concluded that “students know many bits and pieces of information about photosynthesis, but they lack a meaningful and general view of it”. For most students, the misconception that plants gain mass and grow because they take in food (usually from soil) is more intuitive and more easily believed than the idea that the increase in mass of a plant can be attributed to seemingly weightless carbon dioxide.
Roth and Anderson (1985) found that photosynthesis was seen as something plants do for the benefit of people and animals, especially in relation to giving off oxygen and taking in carbon dioxide.
Barker (1985): 54% of 13-year-olds knew that photosynthesis produces “food”, but only 19% knew that it produces carbohydrate.
In a study by Wandersee (1983) that surveyed 1,405 students ages 10–19 about the product of photosynthesis, most students selected proteins, relating them only to food for growth. Some students in this study also mentioned plants getting vitamins from the soil.
Chlorophyll
Driver et al. (1994): Students have several different ideas about chlorophyll. Some students consider chlorophyll to be a food substance, a protection, a storage product, a substance similar to blood, something that makes plants strong, or something hat breaks down starch. Students who have some notion of its function may think that it either attracts sunlight or absorbs carbon dioxide.
Dreyfus and Jungwirth (1989): As a prerequisite for learning about photosynthesis students should be familiar with the plant cell model, including the idea that some plant cells contain chloroplasts.
Bell and Brook (1984): Some secondary school students believed chlorophyll is only present to make leaves green and attractive.
In Simpson and Arnold’s study (1982), only 29% of 12- to 13-year-olds, and 46% of 14- to 16-year-olds, understood the role of chlorophyll in converting light energy to chemical energy during photosynthesis.
Respiration
Maeng and Gonczi (2019): The notion that animals do respiration and plants do photosynthesis is a common belief among secondary students. Some thought plants use a process other than cellular respiration for providing energy and some thought that plants could not perform cellular respiration (and that only humans could), and some believed photosynthesis was the way plants respired.
Rogat, Hug, and Duncan (2017): Relating breathing to capturing energy from food is counterintuitive to students. The idea that there is a “burning” process in cells that uses oxygen to capture energy in food and store it in molecules an organism can use is challenging. It does not make sense to students that food can be “burned” without fire.
Wierdsma et al. (2016): Respiration may have different meanings to students in different contexts. In everyday life, the word ‘respiration’ often refers to breathing; in biology, ‘respiration’ refers to the chemical process that takes place in cells, while ‘breathing’ refers to the movement of air into and out of the lungs. Yet another term – ‘gas exchange’ refers to the diffusion of molecules of gases across an exchange surface, such as the lining of the alveoli between the blood and the air in the lungs.
Svandova (2014): A frequent student misunderstandings is that cellular respiration and photosynthesis are the same process in plants, differing only in name and in which part of the day they take place (photosynthesis during daylight and cellular respiration during the night); 77% of the oldest students in the study held this misunderstanding.
Brown and Schwartz (2009): Some students have the misconception that plant cells do not need mitochondria because “they get their energy directly from the Sun”. Furthermore, A study of preservice teachers’ conceptions of photosynthesis and cellular respiration revealed that they often compared plant functions with analogous human functions.
Driver et al. (1994): Although students have ideas about gas exchange and usually equate it with breathing, few students at any age have a complete understanding of respiration. Some students think of respiration as synonymous with breathing and therefore do not think of plants as respiring. It is also a common belief that respiration is the opposite of photosynthesis with photosynthesis occurring in the day and respiration in plants occurring at night. A study of a large sample of 15-year-olds and found that many of the students thought that respiration occurred only in the cells of leaves of plants because those cells have gas-exchange pores (stomata). They did not see things like seeds as exchanging gases. Driver and her team’s study also revealed how students fail to recognize a seed as a living thing; therefore, they do not recognize that seeds have needs similar to those of other living things.
Studies have found that although young children recognize air as being necessary for life, they have limited understanding of what happens to air once it is inhaled. Many think only organisms with lungs use air. Few students, all the way through high school, connect food with the use of oxygen (Driver et al. 1994).
Some students think plants only use oxygen (respire) in the dark (Driver et al. 1994).
Songer (1994): Several conceptual difficulties were unrevealed among college biology students about the relationship between digestion and cellular respiration. For example, some students knew that glucose came from food but did not know how it got into cells after food was digested. One student emphatically stated that the bloodstream does not deliver glucose to cells, it only delivers oxygen.
Seymour and Longden (1991): A study of 13–16-year-olds showed confusion between breathing and respiration. 57% thought respiration only took place in the lungs. Some thought that some animals, particularly invertebrates such as worms, do not respire because there are no visible breathing movements. Many of the students believed that plants do not respire, which may be associated with the perception that they do not visibly breathe in the same way as humans and other animals but was also linked to the misunderstanding that it’s because they use the process of photosynthesis instead. They also note that in order to fully understand the difference between breathing and respiration, students must accept that respiration is a biochemical process that takes place inside cells. Learning about cellular respiration may be more effective if students are guided to make connections between concepts with which they are already familiar. For example, explaining why cells (and therefore organisms) need oxygen from air and glucose from food, and how they get these fuels.
Anderson and Sheldon (1990): Even university students in the U.S. did not connect food, oxygen, carbon dioxide and energy in a coherent conception of cellular respiration. The students identified oxygen as a need of animals and used everyday language to relate respiration to breathing.
Respiration is regarded as something animals do, not plants. Haslam and Treagust (1987) found that many students, including those at the high school level, often equate respiration with breathing. Interviews with students age nine and older show they use a plant-breathing, animal-breathing model: Animals breathe in oxygen and breathe out carbon dioxide and plants breathe in carbon dioxide and breathe out oxygen. Respiration is often overlooked as an energy releasing process and many students, even college biology students, think photosynthesis is the way plants use and release energy.
When 13 to 15-year-old students were asked, “What is respiration?”, their responses were primarily about gas exchange by inhaling and exhaling air (Stavy et al. 1987).
Simpson (1984): An early study showed that students think that digestion (rather than cellular respiration) is the process that releases useful energy from food. It was thought that perhaps students incorrectly link two ideas: that digestion breaks down food, and that organisms get energy from food.
Matter and Energy in Organisms
Taylor et al. (2012): Researchers from Horizon Research, Inc. identified several commonly held matter and energy ideas middle school students had related to photosynthesis in organisms, including 1) energy needed by animals is different from that needed by plants, 2) plants “want” to be eaten or to make food for animals, 3) plants make food from water and air, but it is not transformed into the plant’s body, 4) animals, not plants, break down food into simpler substances that are used for growth and repair of parts and tissues, and 5) plants photosynthesize but do not break down food.