Open with the phenomenon question: 'Why can a single acre of Alabama longleaf pine forest support thousands of grasshoppers, hundreds of songbirds, but only a handful of red-tailed hawks?' Tell students: today we're going to answer that with numbers, not hand-waving. Show the class the following data snapshot from a temperate forest similar to Alabama's: producers ≈ 20,000 kcal/m²/yr; primary consumers ≈ 2,000 kcal/m²/yr; secondary consumers ≈ 200 kcal/m²/yr; tertiary consumers ≈ 20 kcal/m²/yr. Ask students to notice the pattern (each level is about one-tenth the level below) and to write one prediction in their notebooks: 'What happens to the missing 90%?' Take 3 quick student predictions aloud — expect answers like 'the animal uses it,' 'it becomes waste,' 'it turns into heat.' Do NOT confirm yet; tell them we'll test their predictions today. Then flip to the second question: 'The carbon atom in the caffeine in your morning drink was, at some point, in the atmosphere, in a rainforest leaf, and in a dinosaur. How?' — foreshadow that energy flows one way but matter cycles.

1. 9m

   Trophic Levels: Producers, Consumers, Decomposers

   Content

   An ecosystem's energy budget starts with producers — autotrophs like longleaf pine, switchgrass, and pond algae — that convert sunlight into chemical energy through photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. Producers occupy trophic level 1. Above them sit consumers (heterotrophs): primary consumers (herbivores like white-tailed deer and grasshoppers) at level 2, secondary consumers (small carnivores like the eastern bluebird eating insects) at level 3, and tertiary consumers (top predators like the red-tailed hawk or alligator) at level 4. Running alongside every level are decomposers — fungi such as Armillaria and bacteria — that break down dead tissue and waste and return carbon, nitrogen, phosphorus, and sulfur to the soil and atmosphere. Without decomposers, matter would stay locked in dead organisms and the cycle would stop. Every biotic factor is coupled to abiotic factors: producers pull CO₂ from the atmosphere, plants take up NO₃⁻ and PO₄³⁻ from soil, and animals return CO₂ through cellular respiration (C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP).

   Delivery

   Anchor every trophic level to a real Alabama organism as you name it — longleaf pine, white-tailed deer, red-tailed hawk. Emphasize that 'trophic level' is a feeding position, not a species — a black bear feeding on berries is at level 2, but the same bear eating a fish is at level 3. Ask cold-call: 'Where do decomposers sit on the pyramid?' Expect the misconception that they sit at the top; correct it — decomposers act on every level. Preview that today's model will connect these levels quantitatively.

2. 8m

   Food Chains vs. Food Webs

   Content

   A food chain is a single linear path of energy: longleaf pine → grasshopper → eastern bluebird → red-tailed hawk. It is a useful teaching model but almost never accurate — real organisms eat multiple things and are eaten by multiple things. A food web is the network of interconnected chains that actually describes a community. In an Alabama longleaf pine ecosystem, the grasshopper is eaten by bluebirds, bobwhite quail, and green anoles; the anole is eaten by hawks and by rat snakes; the hawk eats anoles, quail, and small mammals. Removing one species from a food web ripples across many chains, which is why food webs — not chains — predict how ecosystems respond to disturbance.

   Delivery

   The classic misconception here is treating 'food chain' and 'food web' as synonyms. Force the distinction: chain = one path, web = the network of all paths. Ask students to name three organisms in an Alabama food web that would be affected if grasshoppers disappeared — expect bluebird, quail, anole downstream, and switchgrass upstream (less herbivory). Set up the upcoming activity where they will build a real web from index cards.

3. 12m

   Energy Flow and the 10% Rule

   Content

   Energy enters an ecosystem as sunlight, is fixed by producers, and then flows one direction — upward — through consumers, leaving as heat at every step. On average, only about 10% of the energy stored at one trophic level is incorporated into biomass at the next. The other ~90% is lost as: (1) heat from cellular respiration, (2) energy spent on movement, growth, and body heat maintenance, and (3) undigested material in feces. This is the 10% rule. Worked example: if producers fix 20,000 kcal/m²/yr, primary consumers receive ~2,000 kcal/m²/yr, secondary consumers ~200 kcal/m²/yr, and tertiary consumers ~20 kcal/m²/yr. Two immediate consequences: first, top predators occupy the smallest energy bin in the ecosystem — they do NOT have 'more' energy just because they are apex; they have the least available energy, which is why hawk populations are small. Second, energy is NOT recycled — once it leaves as heat, no organism can recapture it. Sunlight must keep entering the system for the flow to continue.

   Delivery

   This is the standard's power beat — spend the time. Work the pyramid math live: 20,000 → 2,000 → 200 → 20 kcal/m²/yr. Then flip it: to support 20 kcal at the hawk level, you must have 20,000 kcal of producers — one thousand times more. Explicitly kill the misconception that 'top predators have the most energy' — they have the LEAST energy, which is exactly why they are rare. Also explicitly say: energy does NOT cycle. Heat radiated to space cannot re-enter the food web. Compare with matter (next beat) which does cycle. Do a quick check: 'If a wetland's producers fix 50,000 kcal/m²/yr, roughly how much energy is available to secondary consumers?' Expect 500 kcal/m²/yr.

4. 6m

   Biomass Pyramids and Why They Usually Match

   Content

   A biomass pyramid stacks the total dry mass of living tissue at each trophic level, usually in g/m² or kg/ha. Because biomass is the physical storage of the energy at that level, biomass pyramids almost always narrow upward just like energy pyramids — a hectare of Alabama forest may have ~20,000 kg of plant biomass but only ~2 kg of hawk biomass. There are rare inverted biomass pyramids (e.g., open-ocean phytoplankton grazed rapidly by zooplankton) where producers turn over so fast that their standing biomass is smaller than the consumers eating them — but even here the ENERGY pyramid still narrows upward, because it measures flow over time rather than a snapshot.

   Delivery

   The key idea is 'biomass = snapshot of storage; energy = flow over time.' Point out that in most terrestrial ecosystems the two pyramids look nearly identical, so students often conflate them. Emphasize the units: biomass is mass (g/m²), energy is rate (kcal/m²/yr). Ask: 'Could a biomass pyramid ever be upside down? Could an energy pyramid?' Guide them to see biomass yes (ocean plankton), energy no (would violate thermodynamics).

5. 10m

   Conservation of Matter and Biogeochemical Cycles

   Content

   Unlike energy, matter is conserved — the C, N, P, and S atoms in your body have been in this ecosystem for billions of years and will keep cycling long after you are gone. A biogeochemical cycle traces one element between biotic reservoirs (organisms) and abiotic reservoirs (atmosphere, water, soil, rock). The carbon cycle: CO₂ in the atmosphere is fixed by producers into C₆H₁₂O₆ (photosynthesis), passed up the food web as organic molecules, and returned to the atmosphere by cellular respiration in every organism plus combustion of fossil fuels. Decomposers break down dead organisms and release CO₂ back to the air and organic C to the soil. The nitrogen cycle: atmospheric N₂ is fixed by bacteria (Rhizobium in legume root nodules) into NH₃/NH₄⁺, nitrified to NO₃⁻, taken up by plants into amino acids and proteins, passed up the food web, and eventually returned by decomposers and denitrifying bacteria. The phosphorus cycle has NO atmospheric step — P moves between rock (PO₄³⁻ weathered from apatite), soil, water, and organisms (DNA, ATP, phospholipids, bones). The sulfur cycle moves S between rocks, atmosphere (SO₂), water, and organisms (amino acids cysteine and methionine). In every cycle, the same atoms move between subsystems — none are created or destroyed.

   Delivery

   The standard says students don't need every enzymatic step — focus on WHICH subsystems exchange the element. Draw the students' attention to the contrast with the previous beat: 'Energy: one-way, lost as heat. Matter: cycles, conserved.' Kill the misconception that 'matter is used up' — when a leaf decomposes, its atoms aren't gone, they're relocated to soil, decomposer biomass, and the atmosphere. Ask: 'Which cycle has no gas phase?' (phosphorus). 'Which cycle depends on bacteria to convert atmospheric N₂ into a form plants can use?' (nitrogen, via Rhizobium).

1. 20m

   Building an Alabama Longleaf Pine Food Web

   Groups of 3-4 students build a physical food web for an Alabama longleaf pine ecosystem using index cards as organisms and yarn as feeding relationships (arrows point from prey to predator — i.e., in the direction energy flows). Student handout — Longleaf Pine Food Web: Part 1 — Your organism cards (12 total): - Producers: longleaf pine, switchgrass, wiregrass, blueberry shrub - Primary consumers: white-tailed deer, grasshopper, gopher tortoise - Secondary consumers: eastern bluebird, green anole, bobwhite quail - Tertiary consumers: red-tailed hawk, eastern rat snake - Decomposer card: fungi & bacteria (place off to the side — connects to ALL organisms) Part 2 — Build the web. Lay the cards on the butcher paper. Use yarn taped between cards to show each feeding relationship. Arrows must point from the organism being eaten TO the organism doing the eating (energy flow direction). You need at least 15 feeding links. Feeding relationships to include (verify with your group): - Deer eats longleaf pine seedlings, blueberry, wiregrass - Grasshopper eats switchgrass, wiregrass - Gopher tortoise eats wiregrass, blueberry - Bluebird eats grasshopper - Green anole eats grasshopper - Bobwhite quail eats grasshopper, blueberry (omnivore — label both trophic roles) - Red-tailed hawk eats bluebird, quail, green anole, small mammals - Eastern rat snake eats quail, green anole, small mammals - Fungi & bacteria decompose ALL dead organisms Part 3 — Analysis questions (answer on the poster): 1. Label each organism with its trophic level (1, 2, 3, or 4). Which organism occupies more than one level? Explain. 2. Trace TWO different food chains from your web. Write them out with arrows. 3. Suppose an invasive fire ant outbreak wipes out the grasshopper population. List every organism directly affected and predict whether its population will rise or fall. Explain each in one sentence. 4. Where do the atoms from a dead hawk end up? Draw arrows from the hawk card to every place its atoms could travel next. As teacher: circulate and check that arrows point PREY → PREDATOR (a common reversal error). Push groups whose web looks like a chain — 'What else eats the grasshopper?' Groups post their web on the wall for a 2-minute gallery walk before moving on.

   Materials

   • Index cards (12 per group, pre-labeled or blank + marker)
   • Yarn or string (about 3 m per group)
   • Tape
   • Large sheet of butcher paper or poster board per group

   Example outputs

   • A food chain traced: wiregrass → grasshopper → bluebird → red-tailed hawk (with arrows drawn correctly).
   • Q3 sample: 'Bluebird ↓ (loses main prey), anole ↓, quail ↓ (loses grasshopper but still has blueberry), switchgrass ↑ (less herbivory), hawk ↓ (fewer bluebirds and anoles to eat).'
   • Q4 sample: hawk atoms flow to fungi & bacteria → soil → producers → primary consumers, showing that matter cycles even though the hawk's energy is gone.
2. 22m

   The 10% Rule: Energy Pyramid Calculations

   Individual then pair-share problem set. Give students 10 minutes to work individually, then 8 minutes to compare with a partner, then 4 minutes for whole-class debrief on Problem 4 (the trick question). Student handout — Applying the 10% Rule: Part 1 — The rule. About 10% of the energy at one trophic level is stored as biomass at the next. About 90% is lost as heat, movement, and waste. Problem 1. A patch of Alabama coastal marsh has producers (Spartina grass) that fix 40,000 kcal/m²/yr. Fill in the energy pyramid: - Producers: 40,000 kcal/m²/yr - Primary consumers (marsh periwinkle): ______ kcal/m²/yr - Secondary consumers (blue crab): ______ kcal/m²/yr - Tertiary consumers (great blue heron): ______ kcal/m²/yr Problem 2. A tertiary consumer (bass) in a Mobile Bay estuary needs 15 kcal/m²/yr to survive. Working backward, how much energy must the producers (phytoplankton) fix per year to support this bass population? - Secondary consumers must supply: ______ kcal/m²/yr - Primary consumers must supply: ______ kcal/m²/yr - Producers must supply: ______ kcal/m²/yr Problem 3. A pond ecosystem has these values: - Producers: 10,000 kcal/m²/yr - Primary consumers: 800 kcal/m²/yr - Secondary consumers: 60 kcal/m²/yr Is this pond following the 10% rule exactly? Calculate the actual transfer efficiency at each step (energy at level ÷ energy at level below × 100%). Give two realistic reasons why real ecosystems don't hit exactly 10%. - Producer → primary: ______% - Primary → secondary: ______% - Two reasons: ______ Problem 4 — Think carefully. A student claims: 'Since the red-tailed hawk is at the top of the food web, it must have the most energy of any organism in the ecosystem.' In 3-4 sentences, explain what is wrong with this reasoning and what the hawk actually has the most of (hint: think about the difference between per-individual energy and total energy at a trophic level). Problem 5. Energy vs. matter check. Complete these sentences: - Energy enters the ecosystem as ______ and leaves as ______. - Matter (C, N, P, S) does not leave the ecosystem; it ______ between biotic and abiotic reservoirs. - If humans burn fossil fuels, we move carbon from the ______ reservoir to the ______ reservoir, changing the balance of the cycle. As teacher: walk around during individual work. The most common error on Problem 2 is dividing by 10 forward when they need to multiply by 10 backward — flag it early. In the debrief, spend real time on Problem 4: this is the misconception the standard is testing.

   Materials

   • Calculator (one per student)
   • Handout printed for each student (content below)
   • Pencil

   Example outputs

   • Problem 1 answers: 4,000 → 400 → 40 kcal/m²/yr.
   • Problem 2 answers: secondary 150, primary 1,500, producers 15,000 kcal/m²/yr.
   • Problem 4 correct answer: 'The hawk has the LEAST available energy of any trophic level — only ~10% of what the level below it had. It has the highest per-individual energy needs (hence rare), but the total energy budget of its trophic level is smallest. This is exactly why apex predators are always few in number.'
3. 25m

   Carbon Cycle Model with PhET Ecosystems SimulationLab

   Pairs use the PhET simulation to observe carbon fluxes, then complete a carbon cycle diagram tracing atoms through biotic and abiotic reservoirs. Use this exact URL: https://phet.colorado.edu/en/simulations/greenhouse-effect (the 'Photon Absorption' and atmosphere modules illustrate CO₂ absorption; students will connect this to biological carbon flow using the handout below). Student handout — Modeling the Carbon Cycle: Part 1 — Simulation observations (8 minutes). Open https://phet.colorado.edu/en/simulations/greenhouse-effect and run the 'Waves' or 'Photons' view with atmospheric CO₂ set to preindustrial, then to today, then to 2100. Record: - What happens to infrared photons as CO₂ increases? ______ - Where is the extra CO₂ coming from (name TWO human sources)? ______ - Where was that carbon stored before humans released it? ______ Part 2 — Build the carbon cycle diagram (12 minutes). Draw five boxes on your handout labeled: Atmosphere (CO₂), Producers, Consumers, Decomposers, Fossil fuels / rock. Draw and LABEL an arrow for each of the following fluxes. Use the color code: - Green for photosynthesis - Red for cellular respiration - Brown for decomposition - Blue for combustion Fluxes to include (label each arrow with the process name and the molecule moving): 1. Atmosphere → Producers (photosynthesis, CO₂ becomes C₆H₁₂O₆) 2. Producers → Consumers (feeding, organic C molecules) 3. Consumers → Consumers (feeding up trophic levels, organic C) 4. Producers → Atmosphere (respiration, CO₂) 5. Consumers → Atmosphere (respiration, CO₂) 6. Producers → Decomposers (death, organic C) 7. Consumers → Decomposers (death and waste, organic C) 8. Decomposers → Atmosphere (respiration, CO₂) 9. Dead organisms → Fossil fuels (burial over millions of years) 10. Fossil fuels → Atmosphere (combustion, CO₂ — human-driven) Part 3 — Analysis (5 minutes). 1. Circle every arrow that returns carbon to the atmosphere. How many are there? ______ 2. Which single arrow is not part of the natural balanced cycle and has grown dramatically since 1850? ______ 3. Conservation of matter check: A carbon atom in a longleaf pine needle in 2025 could have been in what forms in 1825? List three plausible locations. ______ 4. Explain in two sentences: why does adding arrow #10 (fossil fuel combustion) matter, if the total number of carbon atoms on Earth is unchanged? (Hint: think about which RESERVOIR they end up in.) As teacher: this activity operationalizes conservation of matter. Pre-load the PhET tab on the projector so pairs can find the URL. Circulate and check that pairs draw BOTH directions of exchange between atmosphere and biosphere — students often draw only photosynthesis and forget respiration. In the debrief, emphasize Problem 4: matter is conserved, but WHERE we store it matters enormously for climate.

   Materials

   • Chromebook or laptop (one per pair)
   • Blank carbon cycle diagram handout (content below)
   • Colored pencils (green, red, blue, brown)

   Example outputs

   • Part 2 completed diagram: five reservoir boxes with 10 labeled colored arrows; arrows 4, 5, 8, and 10 all end at the atmosphere.
   • Part 3 Q2 answer: arrow #10, fossil fuel combustion — moves carbon from a very slow (rock) reservoir into the fast (atmosphere) reservoir.
   • Part 3 Q4 answer: 'The number of carbon atoms is conserved, but combustion moves atoms from the fossil-fuel reservoir (locked away for millions of years) into the atmosphere as CO₂, where it traps heat. The problem isn't creating new carbon — it's shifting the balance between reservoirs faster than photosynthesis can pull it back.'

   No-equipment fallback

   If computers are unavailable, skip Part 1 and instead show the printed 3-panel CO₂ diagram at the front of the handout (preindustrial 280 ppm, today 420 ppm, projected 2100 ~600 ppm) and have students answer the Part 1 questions from the data alone. Parts 2 and 3 run identically.

1. An Alabama pond has the following annual energy values: producers 30,000 kcal/m²/yr; primary consumers 3,000 kcal/m²/yr; secondary consumers 300 kcal/m²/yr. Using the 10% rule, calculate the energy available to tertiary consumers, and state one specific reason (not 'because of the 10% rule') why the other 90% did not reach them.

   calculationTertiary consumers receive ~30 kcal/m²/yr (300 × 0.10). Specific reasons the other 90% is lost: (1) cellular respiration releases energy as heat, (2) energy is spent on movement/growth/thermoregulation, or (3) undigested material leaves as feces.

2. A student writes: 'Because matter cycles through an ecosystem, energy must also cycle through the ecosystem.' Explain why this claim is incorrect. Use the terms heat, sunlight, and cellular respiration in your answer.

   short answerEnergy does NOT cycle. Sunlight enters the ecosystem and is captured by producers. At every trophic level, cellular respiration releases most of that energy as heat, which radiates out of the ecosystem and cannot be recaptured by any organism. Matter cycles because atoms (C, N, P, S) are conserved and reused, but energy flows one way and must be continually replenished by sunlight.

3. Which statement is TRUE about a red-tailed hawk at the top of an Alabama food web? A) It has the most available energy because energy accumulates as you go up trophic levels. B) It has the least available energy of any trophic level because ~90% is lost at each transfer. C) It receives 100% of the energy from the organisms it eats. D) It does not depend on producers because it only eats other consumers.

   multiple choiceB. The hawk sits at trophic level 4, where the smallest fraction of the original solar energy remains — about (0.10)³ ≈ 0.1% of what producers fixed. Options A and C reverse the 10% rule; D ignores that all consumer energy ultimately traces back to producers.

4. A carbon atom is currently in the CO₂ of the atmosphere over Birmingham. Trace ONE plausible year-long path it could take through biotic and abiotic reservoirs, naming at least four reservoirs it passes through. Then explain how your answer illustrates conservation of matter.

   short answerSample path: atmosphere (CO₂) → longleaf pine (photosynthesis, incorporated into C₆H₁₂O₆) → white-tailed deer (eats pine needles, C in tissues) → soil bacteria/fungi (deer dies, decomposition) → atmosphere (bacterial respiration returns CO₂). The atom itself is neither created nor destroyed — it simply moves between abiotic and biotic reservoirs, illustrating conservation of matter. (Any correct 4-reservoir path with photosynthesis + respiration/decomposition steps earns credit.)

5. Compare a food chain and a food web. Give one specific example from today's Alabama longleaf pine ecosystem to support each.

   short answerA food chain is a single linear path of energy flow (e.g., wiregrass → grasshopper → bluebird → red-tailed hawk). A food web is the network of many interconnected chains showing that most organisms eat and are eaten by multiple species (e.g., the grasshopper in our web is eaten by bluebirds, quail, AND green anoles, and each of those feeds different predators). Food webs more realistically predict how disturbance to one species affects the whole community.

• ☐Index cards (12 per group)
• ☐Yarn or string (~3 m per group)
• ☐Tape
• ☐Butcher paper or poster board (1 per group)
• ☐Calculators (one per student)
• ☐Chromebooks/laptops (one per pair)
• ☐Colored pencils (green, red, blue, brown) per pair
• ☐Printed handouts: Food Web activity, 10% Rule problem set, Carbon Cycle diagram, Formative Assessment