(1) Geologic Processes. Understanding geologic processes is important for comprehending the time-scale involved in much of evolution/ecology and for developing hypotheses about the course of evolution/ecological relationships. Geologic processes are key to developing descriptions of past environments and for reconstructing the life history of the planet. (Catley et al, 2005)
(2) There are several domain general concepts students should understand. First, students should understand systems may change when components within the system change. Second, cycles remain the same unless the system in which it is a component changes. Third, cycles are systems themselves. Ecosystems rely on naturally evolved smaller-scale systems (e.g., the nitrification process in the aquaria) to achieve a function (e.g., in an aquaria, processing harmful substances from fish waste into less harmful substances), which promotes stability because the cycle repeats.
(3) High School students should be aware of the work that ecologists do: Ecologists use models to not just represent but also to conceptualize and test ideas; Ecologists make inferences based on large scales (across time and space); and ecologists work in a variety of experimental settings and use a variety of experimental techniques.
(4) Despite experiments in which students see germinating seeds and mature plants kept in the dark, this misconception seems to hold (Roth, Smith, & Anderson, 1983). Many students equate sunlight to substances like water or minerals. As a result, many students fail to recognize the essential role of sunlight in photosynthesis.
(5) In scientific usage, food refers only to those substances, such as carbohydrates, proteins, and fats, from which organisms derive the energy they need to grow and operate and the material of which they are made” (American Association for the Advancement of Science, 1993). Food is defined as those substances that provide energy and/or building materials for organisms. (CPRE-PCK)
(6) According to Rowlands (2004), children at age 10 take a “mechanical” approach to understanding what happens to food after swallowing (p. 167). They see it as “being contained inside a sack or tube in the body” and then as a “process of separation of useful parts of the food from non-useful parts, with the former being retained and the latter got rid of as feces” Teixeira (2000) says that students at that same age understand the function of the organs and have a “biological basis” for understanding the digestive system (p. 519). However, in both cases, students show no sign of understanding these changes as chemical processes in which matter is transformed from one type of substance to another during digestion
(7) Photosynthesis is “so complex and completely different from the nutrition of animals” that we should not be surprised that these concepts should be confusing for students (Wandersee, 1985, p. 593). Students are influenced by many experiences that do not support the scientific viewpoint, such as watering plants and talking about fertilizer as “plant food.” Further, humans see themselves as the highest form of life on the planet, so remembering the importance of plants can be a challenge for students. Arnold and Simpson (1980) in Driver et. al.,(1994, pg. 30) point out that students need to understand that “an element, carbon (which is solid in pure form), is present in carbon dioxide (which is a colorless gas in the air) and that this gas is converted by a green plant into sugar (a solid, but in solution) when hydrogen (a gas) from water (a liquid) is added using light energy which is consequently converted to chemical energy.” Students think of photosynthesis as a type of respiration. The terms breathing and respiration were often used interchangeably, and oxygen is equated with air. They also believe that plants exchange gases primarily for the benefit of people. Students need to understand that oxygen is simply a waste product of the process (Driver et al., 1994).
(8) Whether learning about photosynthesis, respiration, or catabolism (e.g., the building of biological molecules within cells), matter and energy are conserved. Thus, during photosynthesis the carbon atoms in carbon dioxide are rearranged to produce sugar molecules, and during respiration the carbon atoms in sugars are rearranged to produce carbon dioxide. No carbon atoms appear or disappear from existence in these processes. Energy is also conserved. Energy can be passed from one organism to another in a food chain, through decay, or dissipate through heat, but it is never destroyed. (CPRE-PCK)
(9) Part of the problem may lay in the need for a more interconnected understanding of the topic of energy. Students encounter this topic in four biological contexts that are essential to understanding feeding relations: photosynthesis, respiration, nutrition, and the interdependency of organisms. However, this version of energy is very different from that studied in physics classes. Klein (1990) asserts that the subjects comprising ecology “cannot be contained within a single disciplinary framework” (Eilam, 2002, p. 646). Concepts in ecology interact with concepts in physics such as equilibrium. Additionally, students must have a firm grasp of chemistry to understand photosynthesis, though the concept generally is covered in biology. Just as plants, animals, humans, and even the sun interact with regard to nutrition, so too do the differing branches of scientific study when we cover this broad set of topics. (CPRE-PCK)
Dr. Rebecca Jordan, Rutgers University, New Jersey (contributor)
David Mellor, Rutgers University, New Jersey (contributor)
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