Organisms interact within and between populations. This SL lesson covers C4.1 Populations & communities and C4.2 Transfers of energy & matter.
You will model population growth, estimate size by mark-recapture, and follow energy flow and nutrient cycling through ecosystems.
Work through each screen, answer the questions as you go (some are wordy, some are calculations) and collect ⭐ stars. Press Start when you are ready.
A population is one species in an area; a community is all the interacting populations.
Populations often follow a sigmoid (S-shaped) growth curve: an exponential phase, then a slowing phase, then a plateau at the carrying capacity set by limiting factors.
Interactions include competition, predation, herbivory, mutualism and parasitism.
Energy enters ecosystems as light, is fixed by producers, and flows through trophic levels in food chains and webs.
Only about 10% of energy passes to the next level — the rest is lost in respiration (as heat), and not all is eaten or digested. This is why food chains are short and pyramids of energy always narrow upward.
Sort each organism by its trophic role.
Unlike energy, matter is recycled. Decomposers (saprotrophic bacteria and fungi) and detritivores break down dead material, returning carbon, nitrogen and other nutrients to the environment.
In the carbon cycle, photosynthesis removes CO2 and respiration, decomposition and combustion return it.
Interdependence: producers, consumers and decomposers rely on one another to keep energy flowing and matter cycling.
Match each ecological term to its correct description.
C4.1: sigmoid growth to carrying capacity; competition, predation, mutualism, parasitism
C4.2: energy flows one way (~10% efficiency); matter is recycled by decomposers
Skills: mark-recapture N = Mn/m; trophic efficiency as a percentage
Interdependence: producers, consumers and decomposers depend on one another
Press Finish to see your score.
You have worked through Theme C: Interaction — Populations & Ecosystems for IB Diploma Biology. 🎉
Your stars: 0 / 0
Next: test yourself in the Evaluate stage Confidence Quiz, then lock it in with Verify.