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9th grade · Science · Unit 13 of 14

Ecosystem Stability

Ecological relationships, energy flow, matter cycles and biodiversity.

What your child practices

Practices how predation, parasitism, commensalism, mutualism and competition affect ecosystem stability, energy flow through trophic levels, carrying capacity, and how human activity and disturbances change biodiversity, with Texas examples such as Gulf Coast wetlands and invasive species.

Texas Essential Knowledge and Skills (TEKS) teks student expectation: B.13(A); B.13(B); B.13(D) · ecological relationships, energy flow through trophic levels, and how changes in biodiversity affect stability

How we explain it

Children can open this short lesson before they practice.

  1. Relationships: predation, parasitism, commensalism, mutualism and competition.
  2. Density-dependent factors depend on crowding; density-independent ones, like hurricanes, don’t.
  3. Invasive species and disturbances can upset stability; stable ecosystems recover from small ones.

Example: A barnacle rides on a whale, which is not harmed. Which relationship is this? The barnacle benefits. The whale is neither helped nor harmed: commensalism. Answer: commensalism

Ecosystem Stability in Texas

In the Texas Essential Knowledge and Skills (TEKS), this is unit 13 of 14 in 9th grade Science, after Systems in Animals & Plants and before Carbon & Nitrogen Cycles.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Texas Education Agency (TEA)

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    Hatcheries add salmon, but wild salmon still decline. One reason is…

    • habitat loss limits survival
    • hatcheries remove water
    • salmon don't eat
    • rivers are too clean

  2. Question 2

    If producers capture 10,000 kJ, about how much reaches the secondary consumers?

    • 10 kJ
    • 5000 kJ
    • 100 kJ
    • 1000 kJ

  3. Question 3

    Which human activity most reduces biodiversity worldwide?

    • Habitat destruction
    • Recycling
    • Protecting parks
    • Planting native species

  4. Question 4

    A limiting factor is something that…

    • only affects plants
    • keeps a population from growing larger
    • has no effect
    • makes populations grow forever

  5. Question 5

    Removing a top predator such as wolves can cause deer to…

    • disappear at once
    • eat less
    • become producers
    • overgraze plants, lowering biodiversity

  6. Question 6

    A logistic growth curve levels off at…

    • infinity
    • zero
    • carrying capacity
    • the starting population

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