Ecosystem Stability
Aligned to HS-LS2-6 — Next Generation Science Standards.
What this lesson teaches
Healthy ecosystems stay roughly balanced because interactions push populations back after small disturbances. A large enough shock, though, can flip an ecosystem into a very different but still stable state.
Worked examples
Example 1
When wolves returned to Yellowstone, elk numbers fell, willows regrew, and beaver and songbird populations recovered, showing interactions restoring a former balance.
Example 2
Stability is not the absence of change. A healthy ecosystem's populations oscillate; it is the oscillation staying bounded that matters.
Example 3
A disturbance can be absorbed or can flip the system. A grassland that burns regularly stays grassland; one that burns too often becomes scrub.
Practice questions
- Describe evidence that a disturbed ecosystem returned to its earlier state.
- Show how a predator's decline could ripple through three other populations.
- Evaluate the claim that every ecosystem always returns to the same balance after a disturbance.
Watch the lesson
Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.
▶ Watch this lessonEn español
Estabilidad del ecosistema
Los ecosistemas sanos se mantienen más o menos equilibrados porque las interacciones regresan a las poblaciones a su nivel después de pequeñas perturbaciones. Sin embargo, un impacto lo bastante grande puede llevar a un ecosistema a un estado muy distinto, aunque también estable.
Ejemplo 1: Cuando los lobos regresaron a Yellowstone, el número de alces bajó, los sauces volvieron a crecer y las poblaciones de castores y aves cantoras se recuperaron, mostrando cómo las interacciones restauraron un equilibrio anterior.
Ejemplo 2: La estabilidad no es ausencia de cambio. Las poblaciones de un ecosistema sano oscilan; lo que importa es que la oscilación se mantenga acotada.
Ejemplo 3: Una perturbación puede absorberse o voltear el sistema. Un pastizal que se quema con regularidad sigue siendo pastizal; uno que se quema demasiado seguido se vuelve matorral.
More HS-LS2 Ecosystems lessons
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