SkarpChapter 2 of 3
The Hidden Network Inside Every Ecosystem
Students will be able to trace one everyday example of energy flow and matter cycling through the living and nonliving parts of an ecosystem.
1. Find the Ecosystem in an Ordinary Place
An ecosystem in plain sight
A maple tree beside a sidewalk can be an ecosystem: organisms interact with each other, rain, air, soil, sunlight, and temperature.
Living and nonliving parts
Biotic components are living things, such as trees, insects, fungi, and bacteria. Abiotic components include water, sunlight, air, soil, and pavement.
A connected system
The biosphere is linked with air, water, and soil. A change in one part can affect the others.
2. Start with a Producer
The producer's role
A producer captures energy from a nonliving source. Green plants capture light energy and store some of it as chemical energy in sugars.
Matter builds the plant
Carbon dioxide from air, water from soil, and mineral nutrients provide matter for plant tissues. Sunlight provides energy, not atoms.
Use two tracing questions
Ask: Where did the energy come from? Then ask: Where did the matter come from, and where can it go next?
3. Trace Energy Through a Food Web
One pathway
Sunlight -> maple leaf -> caterpillar -> robin. The caterpillar and robin are consumers because they get energy and matter by eating organisms.
Why it is a web
A leaf can feed several kinds of animals, and a caterpillar can be prey for several predators. These overlapping routes form a food web.
Energy does not cycle
Each organism uses energy for life processes and releases heat. Energy flows onward through the system rather than returning to the Sun.
4. Pause and Sort the Evidence
A quick tracing exercise
Imagine finding a leaf with ragged edges under the maple tree and a robin searching nearby.
Sort each item into a role:
- Sunlight: source of energy for the producer
- Maple tree: producer
- Caterpillar: consumer
- Robin: consumer
- Rainwater and soil minerals: abiotic matter
Now separate an observation from an inference:
- Observation: the leaf has missing pieces.
- Inference: a caterpillar ate this exact leaf.
The inference may be plausible, but evidence would be needed to confirm it. Careful ecosystem tracing starts with what is observed, then builds the most supported explanation.
5. Follow the Leaf After It Falls
Dead material still matters
A fallen leaf may be eaten by soil animals or processed by fungi and bacteria. These organisms connect dead material back to the ecosystem.
Decomposers transform matter
Decomposition does not make matter disappear. Carbon can return to air as carbon dioxide, while other materials enter soil or decomposer bodies.
Two linked routes
A food web includes both a grazing route, such as caterpillar eating leaf, and a detrital route, where decomposers process fallen material.
6. Compare the Two Journeys
Energy story
Sunlight -> leaf sugar -> organisms -> heat. Energy enters, is transferred, and is ultimately released as heat.
Matter story
Air, water, and soil -> leaf -> animals and decomposers -> air, soil, or water -> plants. Matter changes location and form.
A useful nuance
Matter does not necessarily return quickly to the same organism. It can move through air, water, soil, and living bodies over different timescales.
7. Key Network Terms
Flip the cards to review the roles and pathways in the maple-tree ecosystem.
- Biotic component
- A living part of an ecosystem, such as a tree, caterpillar, robin, fungus, or bacterium.
- Abiotic component
- A nonliving condition or material, such as sunlight, water, air, soil, minerals, or temperature.
- Producer
- An organism, such as a green plant, that captures energy from a nonliving source and builds organic matter.
- Consumer
- An organism that gets energy and matter by eating other organisms or their remains.
- Decomposer
- An organism, especially fungi or bacteria, that breaks down dead material and wastes.
- Food web
- A network of connected feeding relationships, including both grazing and decomposition pathways.
8. Apply the Trace
Check the network
A fallen maple leaf is broken down by fungi. Which statement best traces both energy and matter?
Which statement is most accurate?
- Fungi use chemical energy from the leaf and transform its matter; some carbon can return to the air as carbon dioxide, while other materials enter soil or fungal tissue.
- Fungi recycle the Sun's energy back into the maple tree and remove the leaf's matter from the ecosystem.
- The leaf's energy and matter both move in the same closed cycle from fungi directly back to sunlight.
Show Answer
Answer: A) Fungi use chemical energy from the leaf and transform its matter; some carbon can return to the air as carbon dioxide, while other materials enter soil or fungal tissue.
Fungi are decomposers. They obtain chemical energy from dead organic matter, releasing heat through life processes. The leaf's matter is transformed and can move into fungal biomass, soil, and the atmosphere. Energy flows; matter cycles through connected living and nonliving parts of Earth.
Key Terms
- consumer
- An organism that obtains energy and matter by eating other organisms or their remains.
- food web
- A network of interconnected feeding relationships.
- producer
- An organism, such as a green plant, that captures energy from a nonliving source and uses it to build organic matter.
- decomposer
- An organism, often a fungus or bacterium, that breaks down dead organisms and wastes.
- energy flow
- The one-way transfer of usable energy through an ecosystem, with heat released during life processes.
- matter cycling
- The movement and transformation of atoms and substances among organisms, air, water, and soil.
- biotic component
- A living part of an ecosystem.
- abiotic component
- A nonliving condition or material in an ecosystem, such as water, sunlight, air, soil, minerals, or temperature.