Key Idea: Plants make their own food in the form of sugar molecules from carbon dioxide molecules and water molecules. In the process of making sugar molecules, oxygen molecules are produced as well.

Students are expected to know that:

  1. Unlike animals, plants do not take in food from their environment.
  2. Plants make their own food in the form of sugar molecules by means of a chemical reaction between carbon dioxide molecules and water molecules. Oxygen molecules are also a product of this reaction.
  3. The process of making sugar molecules involves linking together carbon atoms that come from molecules of carbon dioxide.
  4. The chemical reactions by which sugars are made takes place inside the plants. In most familiar land plants, the carbon dioxide molecules that are used come from the air that enters the plant primarily through its leaves, and that the water molecules that are used in the reaction enter the plant through its roots.

Boundaries:

  1. Although there may be limited exceptions to the generalization that unlike animals, plants do not take in food from their environment, students are not expected to be aware of those exceptions.
  2. The items do not assess knowledge of any of the chemical structures or formulas of any of the reactants or products either of the overall chemical reaction or of any of the intermediate steps, such as light-dependent and light-independent reactions.
  3. The items do not assess exceptions to the expected knowledge: that some plants, such as cacti and some other desert plants do not take in carbon dioxide through their leaves but through their stems, that some plants, such as parasitic plants, do not make their own food and obtain some or all of their food by attaching to the stems or roots of other organisms, or that in addition to plants there are other types of organisms, such as many micro-organisms, that are able to make their own food.
  4. The items do not assess the idea that light is involved in the synthesis of sugars from carbon dioxide and water.
  5. The items do not use the terms producer, consumer, photosynthesis, organic, or inorganic.
Frequency of selecting a misconception

Misconception
ID Number

Student Misconception

Grades
6–8
Grades
9–12

MEM130

Carbon dioxide is food for plants (AAAS Project 2061, n.d.).

See the Original Project

MEM123

Substances in soil are food for plants (Kuech et al., 2003; Leach et al., 1992; Simpson & Arnold, 1982; Stavy et al., 1987; Tamir, 1989, Wandersee, 1983).

See the Original Project

MEM121

Minerals are food for plants (Horizon, n.d.; Vaz et al., 1997).

See the Original Project

MEM119

Water is food for plants (Horizon, n.d.; Lee & Diong, 1999; Vaz et al., 1997, Wandersee, 1983).

See the Original Project

MEM082

Plants make sugars from minerals (Tamir, 1989) or minerals and water (AAAS pilot data 2006).

See the Original Project

MEM017

Plants use oxygen during photosynthesis (Horizon Research; Wandersee, 1983).

See the Original Project

MEM015

Carbon dioxide is absorbed through the roots of plants (Simpson & Arnold, 1982).

See the Original Project

MEM014

Plants get organic food substances such as starch and sugar (Stavy et al., 1987) or protein (Wandersee, 1983) from the soil.

See the Original Project

MEM013

Food enters a plant through the roots (Anderson et al., 1990; Roth & Anderson, 1987; Simpson & Arnold, 1982; Vaz et al., 1997; Wandersee, 1983).

See the Original Project

MEM012

Plants have multiple food sources, not just the sugars that they make from water and carbon dioxide (Anderson et al., 1990, Roth & Anderson, 1987).

See the Original Project

Frequency of selecting a misconception was calculated by dividing the total number of times a misconception was chosen by the number of times it could have been chosen, averaged over the number of students answering the questions within this particular idea.