causal pattern → causality & misconceptions → view student ideas → ecosystems examples

Student often miss indirect effects. They don't realize that if all the green plants disappeared, it would affect the entire food web, not just the organisms that eat green plants. This student realizes that the sun gives us essential warmth, but not that the energy in the entire food web depends upon the sun and green plants. Learning about energy transfer in terms of domino causality can help students to recognize indirect and extended connections in the food web.

In ecosystems, domino causality describes energy transfer while cyclic causality describes matter recycling. As we see here, students often merge the two and end up thinking that energy can be recycled. This is understandable since energy and matter "travel together" to some extent, but it leads to difficulty understanding our critical dependence on the sun and green plants for sustaining life on Earth.

How a plant can get food from the sun is mysterious to most students. Causes that are far from their effects are hard to think about and students often substitute causes that are close by or touching. Getting food from sunlight doesn't fit with any of the tangible images of "eating" that they hold. This student realizes that the sun plays a role, but thinks that it makes fertile soil, which in turn feeds plants through direct contact.

Passive causality is harder to detect than active causality. Students tend to focus on who is "doing something." As we see with this student, they often reverse the arrows in the food web to show "what eats what" instead of energy transfer. This reduces the food web to individual actions instead of an interconnected system of relationships. Domino causality makes it easier to see these relationships and patterns of energy flow.

It is hard to detect causes that we cannot see. Many students don't realize that tiny microbes are responsible for most decomposition. Instead, they attribute decomposition to aging, weathering, erosion, or obvious factors such as worms, animals or kids stepping on it, etc. This student knows that decomposition involves breaking down of particles, but seems unaware of the critical role that microbes play.

Students do realize that without decay, dead matter would accumulate and there would be a lot of it around. They don't tend to realize that matter is conserved and without the cyclic pattern of matter recycling, essential elements would be locked up in dead matter—unavailable for new life. As we see here, they don't mention this implication when describing what would happen if nothing decayed. Focusing on cyclic causality helps them to realize this.