Essential Science for Teachers: Life Science
Evolution and the Tree of Life Children’s Ideas
Children’s Ideas About Biological Evolution
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 6 Children’s Ideas Bibliography). Consider what evidence might refute this idea, and why a child would be likely to believe this?
1. Change in environmental conditions directly causes evolution in the affected individuals.
In order for this idea to be substantiated, you would expect to observe entire populations changing during the same generation in response to a change in the environment. For example, if a plant population were subjected to drought conditions, someone holding this idea might predict that all of the individuals in the existing population would somehow change during their lifetime to become more drought-tolerant. Children may begin to understand evolution as a process that helps living things respond to environmental change so that they can survive. Children may reason that this has to happen during a lifetime — that something has to be changed immediately in the affected individuals. Thinking about evolution in this way may be challenged once children begin to understand evolution as a process that occurs at a population level over many generations.
2. Evolution “just happens.”
For evolution to be something that “just happens” suggests that there is no specific mechanism for evolution nor any predictable outcomes. Natural selection is overwhelmingly accepted by the scientific community as the process that best accounts for evolution. Evolution through natural selection predicts that, over time, populations will become better-suited to their environments. Many children in elementary school are likely to be acquainted with the term “evolution” before it becomes a part of their science learning. Some may understand it to be a process whereby life forms change, but without knowing how this occurs. They may think that the environment causes evolution, or that change “just happens.” Once children are introduced to natural selection, their ideas will develop further. Activities involving artificial selection may help children better understand natural selection. Examples of artificial selection are highlighted in the video for Session 5.
3. Species evolve because of a “grand plan.”
This is an idea that cannot be tested using scientific methods. There is no scientifically validated evidence of a “grand plan” for evolution, just the evidence that indicates that species do evolve. The idea that there is a “grand plan” for evolution is more a matter of one’s world view than a matter of science. Children may have religious or cultural backgrounds where this belief is held.
4. Evolution is goal-oriented; species evolving later in evolutionary time are “better.”
All species that exist on Earth today can be thought of as “success stories.” Scientists do not consider evolution to produce successively “better” species. Whether a species is a bacterium with a lineage that goes back billions of years or a human being whose lineage extends back only about 2 million years, each has evolved to be suited to its own environment at any given time. This “fit” is considered to be a consequence of evolution, not a goal, and given further environmental change, any species’ survival can be challenged. Children may have a hard time believing that a process has no goal. As they learn about evolution, the phrase “survival of the fittest” may promote this way of thinking. This idea may also be a product of modern culture, where human beings are often portrayed as the pinnacle of evolution.
5. Evolution happens over a few generations.
Historically, some of the best evidence for evolution (e.g., the fossil record) reveals that observable change in a species occurs over thousands or even millions of years. Many scientists would agree, however, that because natural selection acts during each generation, evolution is happening at some level throughout a species’ evolutionary history. There are also species that may evolve much more rapidly, under certain conditions. Nonetheless, scientists would agree that evolution takes longer than just a few generations to occur. In thinking about how long an event takes, it may be hard for children to comprehend time scales that extend more than a few generations — their own, their parents, and their grandparents, for example. The fossil record may be a good place to start to help children understand that the best evidence for evolution suggests that it takes a very long time — possibly hundreds, thousands, or even millions of generations — before change is observed.
Children's Ideas Bibliography
The Children’s Ideas listed in this section of the Web site were compiled from the following research:
- Bishop, B. & Anderson, C. (1990). “Student conceptions of natural selection and its role in evolution.” Journal of Research in Science Teaching, 27(5), 415-427.
- Brumby, M. (1979). “Problems in learning the concept of natural selection.” Journal of Biological Education, 13(2), 119-122.
- Deadman, J. & Kelly, P. (1978). “What do secondary school boys understand about evolution and heredity before they are taught the topics?” Journal of Biological Education, 12(1), 7-15.
- Driver, et al. (1992). “Life and living processes.” Leeds National Curriculum Support Project, Part 2. Leeds City Council and the University of Leeds, UK.
- Engel Clough, E. & Wood-Robinson, C. (1985). “Children’s understanding of inheritance.” Journal of Biological Education, 19(4), 304-310.
- Settlage, J. (1994). “Conceptions of natural selection: A snapshot of the sense-making process.” Journal of Research in Science Teaching, 31(5), 449-457.
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.