Key Idea: All organisms need food as a source of molecules that provide chemical energy and building materials.

Students are expected to know that:

  1. Food consists of carbon-containing molecules in which carbon atoms are linked to other carbon atoms.
  2. Carbon-containing molecules serve as the building materials that all organisms (including plants and animals) use for growth, repair, and replacement of body parts (such as leaves, stems, roots, bones, skin, muscles, and the cells that make up these structures) and provide the chemical energy needed to carry out life functions.
  3. If substances do not provide both chemical energy and building material, then they are not food for an organism.
  4. Chemical energy from carbon-containing molecules is the only form of energy that organisms can use for carrying out life functions.
  5. Carbohydrates (including simple sugars and starch), fats, and proteins are molecules that are food.
  6. Light is not food because it is not made of atoms and therefore cannot provide building material, and even though substances such as water, carbon dioxide, oxygen, and various minerals provide atoms for building materials for some types of organisms, they are not food because they do not contain carbon atoms that are linked to other carbon atoms and cannot be used as a source of chemical energy.

Boundaries:

  1. The idea that there are other atoms besides carbon (mainly hydrogen and oxygen atoms) in carbon-containing molecules that are used as food is not part of this key idea.
  2. Students are not expected to know what chemical energy is other than it resides in the molecules of substances.
  3. Although students are expected to know that any molecule with carbon atoms linked to other carbon atoms could be food for organisms, they are not expected to know which of these other carbon-containing molecules are or are not food for any particular type of organism.
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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ME160001

Food is anything that is a source of both energy and building materials for plants and animals.

63%

71%

ME100002

Children need food as a source of energy and as a source of material for building or repairing body structures such as muscles.

66%

71%

ME098002

Animals and plants need food as a source of energy and as a source of material for building body parts, such as muscles in animals and leaves in plants.

60%

63%

ME161001

A solution of sugar water is a source of food because the sugar in the solution is a source of energy and building materials.

49%

60%

ME104002

Fats, proteins, and carbohydrates are sources of food for animals, but minerals are not.

52%

53%

ME149001

Milk is food for people because food is something that provides energy and building materials, and milk provides energy and building materials.

44%

58%

ME106003

Molecules made of several carbon atoms linked to each other and to hydrogen and oxygen atoms could be food for plants (item uses molecular models).

45%

55%

ME150001

Fat is a source of food for animals.

40%

51%

ME112005

The carbon dioxide used by plants comes from the air.

41%

44%

ME004012

A plant's food are the sugars that it makes--not minerals, water, or carbon dioxide.

40%

39%

ME147003

Molecules made of several carbon atoms linked to each other and to hydrogen and oxygen atoms could be food for plants.

37%

39%

ME147001

Molecules made of several carbon atoms linked to each other and to hydrogen and oxygen atoms could be food for plants.

37%

N/A

ME159001

Water is not a souce of food for plants and animals because food must contain molecules that have carbon atoms linked to other carbon atoms, and water molecules do not have carbon atoms linked to other carbon atoms.

16%

33%

Frequency of selecting a misconception

Misconception
ID Number

Student Misconception

Grades
6–8

Grades
9–12

MEM119

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

47%

36%

MEM120

Water is food for animals (Horizon, n.d.; Lee & Diong).

38%

33%

MEM121

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

25%

30%

MEM122

Minerals are food for animals (Horizon, n.d.).

25%

22%

MEM017

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

21%

22%

MEM015

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

19%

15%

MEM102

Food is a source of energy but not a source of building materials (AAAS Project 2061, n.d.).

17%

15%

MEM130

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

12%

15%

MEM003

Food is what is needed to keep animals and plants alive (Leach et al., 1992; Lee & Diong, 1999; Roth & Anderson, 1987) or grow (Anderson et al., 1990) without reference to any more specific function of food.

13%

11%

MEM067

Liquids cannot be food (Lee & Diong 1999).

14%

9%

MEM103

Food is a source of building materials, but not a source of energy (AAAS Project 2061, n.d.).

12%

11%

MEM002

Food is any material (water, air, minerals, etc.) that organisms take in from their environment (Anderson et al., 1990; Simpson & Arnold, 1982; Roth & Anderson, 1987).

11%

8%

MEM098

Food must enter an animal's body through its mouth, otherwise it is not food (AAAS Project 2061, n.d.).

10%

7%

MEM071

Oxygen supplies energy for animals (AAAS Project 2061, n.d.).

8%

6%

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.