Essential Science for Teachers: Life Science
Plant Life Cycles Plant Life Cycles: Children’s Ideas
Children’s Ideas About Animal Life Cycles
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 4 Children’s Ideas Bibliography).
Consider what evidence might refute this idea, and why a child would be likely to believe this?
1. Plants do not reproduce in the same sense that animals do.
Plants and animals both reproduce sexually with sperm and egg uniting to form the first cell of a new individual – the fertilized egg. There is an equal contribution of male and female hereditary material, just as in animals. Children may hold this idea because they associate reproduction with the act of mating in animals and they do not observe females or males in plants.
2. Plants are neither male nor female.
Plants have male and female reproductive structures. The male structures produce sperm and the female structures produce eggs. In many cases, both male and female reproductive structures occur on the same individual (in flowering plants, they are found in the flower). In other cases there are individuals of “separate sexes.” Children may hold this idea because they don’t observe what is familiar to them as a female or male and they don’t understand that plants reproduce sexually.
3. Seeds are not alive, but can give rise to a plant.
All living things arise from other living things. Seeds are formed from a fertilized egg, which is a living cell that arises from the union of two other living cells – sperm and egg. These cells themselves arise from living cells – there is no discontinuity in this process. Seeds demonstrate all the characteristics of life: they’re made of cells, they have a life span, they use matter and energy, they respond to their environment, and they carry DNA.
4. Seeds contain a tiny adult plant already formed inside.
Children may hold this idea because they do not readily observe developmental differences between a sprout and an adult – one is a miniature of the other. Seeds, however, do not contain tiny adult plants; they contain a plant embryo that has developed from the fertilized egg. In larger seeds, this embryo can be observed by dissecting the seed. Given appropriate care, the embryo can be seen to go through different developmental stages, from sprout to adult.
5. Seeds use the sun for energy to sprout.
The embryo inside a seed depends on food stored in the seed to support it until it can begin to photosynthesize as a sprout. If you take this food source away before a seed sprouts, the plant will not survive in sunlight alone. During the sprouting process, a small amount of food begins to be provided by photosynthesis. Once the sprout is established, photosynthesis becomes the sole supplier of food. Children observe that seeds sprout in the presence of sun and water. If they don’t know that seeds store food, it’s understandable that they consider the sun as the seed’s energy source.
6. Flowers are for insects to feed upon.
Children often think that one life form exists to serve another. When they observe insects feeding on flowers, this may be a conclusion. Life forms, however, do not have a “purpose”; they have functions, which may include being beneficial to other life forms. Flowers do function to provide food for many insects, but the sole function of a flower for the plant is reproduction.
7. Fruits are always sweet, fleshy products of plants.
A fruit is the ripened ovary formed from a flower. A fruit contains the seeds. Many things that children consider vegetables are actually fruits, including pea pods, cucumbers, peppers, and tomatoes. Nuts and pods are also fruits.
Children's Ideas Bibliography
The Children’s Ideas listed in this section of the Web site were compiled from the following research:
- Driver, et al. (1992). Life and living processes. Leeds National Curriculum Support Project, Part 2. Leeds City Council and the University of Leeds, UK.
- Stavy, R. & Wax, N. (1989). Children’s conceptions of plants as living things. Human Development, 32, 88-94.
- Smith, E. & Anderson, C. (1984) Plants as producers: A case study of elementary science teaching. Journal of Research in Science Teaching, 21(7), 685-698.
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.