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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.
Percent of students answering correctly (click on the item ID number to view the item and additional data)
Item ID
Number
Knowledge Being Assessed Grades
6–8
Grades
9–12
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ME095004

The sugar molecules in plants are made by the plants.

38%

42%

ME095005

The sugar molecules in plants are the result of a chemical reaction.

31%

41%

ME029006

A plant makes its food from carbon dioxide and water.

33%

40%

ME109003

Plants use sugars that they make as food.

22%

27%

ME095006

The sugar molecules in plants are made of carbon atoms linked to other carbon atoms.

25%

22%