Texas TEKS5th GradeScience

§112.7.b.12.BPredict how changes in the ecosystem affect

Organisms and environments · b.12: Organisms and environments. The student describes patterns, cycles, systems, and relationships within environments. The student is expected to:

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What this standard means: TEKS §112.7.12.B asks fifth graders to predict how a change in an ecosystem affects the flow of energy and cycling of matter through a food web. This intervention, Texas Food Web Changes, practices that skill with short-answer questions set in real Texas habitats: a prairie drought that reduces grasses, an invasive plant crowding out gulf coast producers, and a pesticide runoff event that lowers insect numbers in a marsh. Students trace the effect from producer to consumer to decomposer, naming which organism is affected first and what change follows next, in one to three sentences. With repetition, tracing a disturbance step by step through a food web replaces guessing at the end result.

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Everything below is measured from the actual lesson and the actual file. Nothing here is an estimate.

Time to run: About 25 minutes. 7 min lesson, then 18 min of practice.
In the download: 9 printable pages: the full lesson, the worked examples, the visual models, and 6 practice questions with space to work. A teacher answer key is included at the end, so the student pages come first and it is still ready to hand out. The lesson’s worked examples do show their solutions, because that is how they teach.
Question set: The download carries all 6 questions. The page shows 3 of them as a sample.
Question format: Every question is short answer. Students show their work on the page.
Dates: Published August 6, 2026. Not revised since.

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§112.7.b.12.B

Texas Food Web Changes: Predicting What Happens Next

Predict how a change in an ecosystem affects the cycling of matter and the flow of energy in a food web.

Read the passages and examples below to learn about predicting how ecosystem changes affect energy transfer and matter cycling in a food web. Think about producers, consumers, decomposers, and what happens next when one part of the ecosystem changes.

A food web shows who eats whom in a habitat. Energy starts with producers, like grasses or algae, because they make their own food using sunlight. Consumers get energy by eating plants or animals. Decomposers, such as fungi and bacteria, break down dead matter and return nutrients to the soil or water. That keeps matter cycling through the ecosystem.

Texas prairie food web

sun
producer
consumer
decomposer

Each arrow shows which way energy moves. Follow the arrows to predict what happens next when one part changes.

When one part of a food web changes, the effects can spread. If a producer is lost, less energy enters the web, so plant-eating consumers may decline first. Then animals that eat those consumers may also decline. If a consumer becomes too common, it may use up more food, which can change other populations too. In every case, energy transfer becomes weaker or shifts to a different path.

Gulf Coast marsh food web

producer
consumer
decomposer

Arrows show which way energy moves. Trace two steps from any change to predict what happens next.

Matter cycles back to the start

Energy flows one way through a food web, but matter keeps cycling. A change at one stage changes the whole loop.

Worked exampleIf drought reduces prairie grass, prairie dogs may decline because less energy reaches them through the food web, and coyotes may then decline because they have less prey.

Worked exampleIf an invasive plant crowds out gulf coast producers, fewer herbivores may survive, and decomposers may later break down less dead plant matter from that area.

Practice questions

1
In a prairie, drought reduces the grasses. Predict two changes that may happen next in the food web, and explain why.
2
A student says this about a gulf coast food web: 'If an invasive plant crowds out native producers, decomposers stop helping because the food web breaks.' What is wrong with that idea?
3
In a Gulf Coast marsh, a pesticide runoff event lowers the number of insects living in the reeds. Small fish and frogs eat those insects, and herons and coyotes may eat the fish or frogs. Explain how this change could affect the coyote population and the rest of the food web.

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