Essential Science for Teachers: Life Science
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.
Children's Ideas Bibliography
The Children’s Ideas listed in this section of the Web site were compiled from the following research:
- Brumby, M. “Students’ Conceptions of the Life Concept. ” Science Education, 66 (1982): 613-622.
- Driver, et al. “Life and Living Processes.” Leeds National Curriculum Support Project, Part 2, (1992): Leeds City Council and the University of Leeds, UK.
- Stepans, J. “Biology in Elementary Schools: Children’s Conceptions of Life.” American Biology Teacher, 47 (1985): 222-225.
- Tamir, P., Gal-Choppin, R., & Nussinowitz, R. “How Do Intermediate and Junior High School Students Conceptualize Living and Non-living?” Journal of Research in Science Teaching, 18 (1981): 241-248
Session 1 What Is Life?
What distinguishes living things from dead and nonliving things? No single characteristic is enough to define what is meant by "life." In this session, five characteristics are introduced as unifying themes in the living world.
Session 2 Classifying Living Things
How can we make sense of the living world? During this session, a systematic approach to biological classification is introduced as a starting point for understanding the nature of the remarkable diversity of life on Earth.
Session 3 Animal Life Cycles
One characteristic of all life forms is a life cycle — from reproduction in one generation to reproduction in the next. This session introduces life cycles by focusing on continuity of life in the Animal Kingdom. In addition to considering what aspects of life cycles can be observed directly, the underlying role of DNA as the hereditary material is explored.
Session 4 Plant Life Cycles
What is a plant? One distinguishing feature of members of the Plant Kingdom is their life cycle. In this session, flowering plants serve as examples for studying the plant life cycle by considering the roles of seeds, flowers, and fruits. A comparison to animal life cycles reveals some surprising similarities and intriguing differences.
Session 5 Variation, Adaptation, and Natural Selection
What causes variation among a population of living things? How can variation in one generation influence the next generation? In this session, variation in a population will be examined as the "raw material" upon which natural selection acts.
Sessions 6 Evolution and the Tree of Life
Why are there so many different kinds of living things? Comparing species that exist today reveals a lot about their relationships to one another and provides evidence of common origins. This session explores the theory of evolution: change in species over time.
Session 7 Energy Flow in Communities
Communities are populations of organisms that live and interact together. The structure of a community is defined by food web interactions. The process of energy flow is the focus of this session as the interactions between producers, consumers, and decomposers are examined.
Session 8 Material Cycles in Ecosystems
Studying an ecosystem involves looking at interactions between living things as well as the nonliving environment that surrounds them. Life depends upon the nonliving world for habitat, as well as energy and materials. In this session, material cycles will be explored as critical processes that sustain life in an ecosystem.