Week 1 Lesson: Ecosystems and Energy Flow

Map

An ecosystem includes organisms and the physical conditions with which they interact. For Nina's fictional Brookside example, algae, reeds, insect larvae, small fish, and birds are living components; sunlight, water, stones, and temperature are physical conditions. A list of inhabitants is only a start. The ecological question is how a change in one part could affect another, and what evidence would establish that connection.

Follow an energy pathway

Sunlight supplies energy to algae and reeds as they grow. In a simplified Brookside sketch, an insect larva may feed on algae, a small fish may eat the larva, and a bird may eat the fish. Arrows in a food web point from the food to the organism that eats it, indicating the direction of energy transfer. The fish might also eat other organisms; a web has multiple pathways rather than one neat chain. Decomposers break down dead material and return nutrients to the environment. Nutrients can be reused, but energy is not endlessly recycled through the web.

Nina has not surveyed Brookside: the named feeding relationships are plausible teaching examples, not confirmed observations there. A sighting of a bird alone would not prove it eats these particular fish.

Test the idea

  1. Sketch algae → insect larva → small fish → bird, then add reeds and one plausible second feeding path. Label every unverified Brookside link as a hypothesis.
  2. Imagine a shaded section with less light reaching algae. Write two possible effects on the web, then explain why other food sources or movement could change the outcome.
  3. Explain in two sentences why a decomposer belongs in the ecosystem even though it is not the last step of a simple chain.

Self-check before week 2

  • I can identify living and nonliving components without calling every nearby object a feeding relationship.
  • I can read an arrow in the direction of energy transfer and distinguish energy flow from nutrient cycling.
  • I can state which Brookside links are examples and what observation would help test one of them.

Nina will carry this labeled sketch into the week 2 stream-observation exercise. Looking for habitat conditions is useful; disturbing organisms to confirm a classroom diagram is not part of the exercise.