What Is Life? Children’s Ideas

Children’s Ideas about What’s Living, Dead, and Nonliving

Below are common ideas children in grades K-6 have about this topic, compiled from research on children’s ideas about science (see the Session 1 Children’s Ideas Bibliography). For each idea, consider why a child would be likely to believe this and what evidence might refute it.

1. If it moves, it is alive.

Many things that move aren’t alive, such as cars, clouds, and flowing water. The living things that are most familiar to children are likely to be animals that move. Since they consider animals to be alive, they may associate the characteristic of movement with life.

2. If it seems to move by itself, it’s alive; if it’s moved by something else, it’s not alive.

A shadow moves by itself, but it’s not alive. Fire also moves by itself. Once children recognize that there are nonliving things that can be moved by an external force—like clouds moved by the wind, or a bicycle pedaled by a person, they may make the finer distinction that something is alive only if it can move itself.

3. If it makes light or a noise, it’s alive.

A burning candle and a flashlight make light but are not alive. A ringing bell and a piano make noise but are not alive. Younger children may believe this because they associate “doing something” with being alive.

4. It’s not alive unless it’s “doing something.”

A potato doesn’t appear to be doing anything, yet a potato is alive. If you plant a potato in a suitable environment, it will grow into a potato plant. At the cell level, all living things are constantly “doing something,” even if this can’t be detected. Children may hold this idea because they connect life with activity, particularly movement. In contrast, familiar examples of nonliving things—like rocks or books—don’t demonstrate activity.

5. To be alive, something has to “breathe.”

Not all living things “breathe” in the same way that animals do—by inhaling and exhaling. Plants, for example, do not breathe. However, the cells of all living things do take in and release gases. Children’s firsthand experience of the need to breathe and their observations of other animals may lead them to think that all living things have to breathe. The process where plants take in CO₂ and release O₂ during photosynthesis is sometimes likened to breathing, so children may equate it with breathing.

6. Growth is not a prerequisite of life.

One characteristic of life is a life span, which includes a period of growth. From a living beginning as a single cell, all life forms can be observed to grow—even organisms that are made of only one cell. Growth occurs as cells get bigger and, in multicellular organisms, as cells divide to form new cells. This idea may arise because children observe some living things when they are no longer growing. A full-grown plant, for example, may not appear to grow.

7. Objects like seeds, spores, eggs, and pupae are not alive, but they can give rise to living things.

Because seeds, spores, eggs, and pupae appear to be “doing nothing,” many children think they’re dead or nonliving while at the same time believing that they can give rise to living things. Just as all cells come from an existing cell, all life comes from something that is alive—there is no “discontinuity” of life during a life span. Seeds, spores, eggs, and pupae represent the living beginnings of a life span and have the potential for growth, development, reproduction, and death. They also demonstrate the other characteristics of life. This makes them alive. Children may believe this because they do not observe any activity in these objects, and they can’t see the developing organism inside.

8. Plants and fungi are not alive.

Because plants and fungi don’t move, some children think they aren’t alive. Nonetheless, both plants and fungi demonstrate the characteristics of life. They are built from cells, have life spans, require matter and energy, respond to their environment, and carry the hereditary material DNA. Children who consider movement a requirement for life may hold this idea. In this case they may consider animals to be the only things that are alive.

9. Plants have a different kind of life than animals.

Plants and animals differ in many ways. However, the characteristics of life apply equally to both groups of organisms. Each is made of cells, has a life span, uses matter and energy, responds to its environment, and carries the hereditary material DNA. Children may think this because the observable differences between plants and animals seem to make them “opposites” of each other. This also may be reinforced by placing the emphasis on differences while teaching about these groups of organisms.