Homeostasis, Feedback & Interacting Systems — Practice · Grade 7 Science

Chapter: Coordination, Defense & Reproduction

What this practice covers

By the end of Homeostasis, Feedback & Interacting Systems you should be able to:

8 questions, written answer, multiple choice and numeric, each with a worked explanation.

Vocabulary used: homeostasis, feedback, negative feedback, hormone, target cell.

Problem 1

Does homeostasis require the same number at every instant?
Answer and explanation

No. Regulation can maintain functioning ranges while values vary with conditions.

Problem 2

What makes a response negative feedback in this model?
Answer and explanation

Its effect opposes the initial deviation in the regulated condition.

Problem 3

Why should a hormone model show responsive target cells?
Answer and explanation

Cells differ in their ability to respond to a particular signal; transport everywhere does not mean the same response everywhere.

Problem 4

Does return toward a model range identify the sole cause?
Answer and explanation

No. Several processes can affect the quantity; the record and mechanism must be assessed together.

Problem 5

Illustrative artificial-system record: a quantity rises from 20 to 24 units; a detector activates an output that lowers it to 21. The stated working range is 19–22 units. Explain the direction of feedback, the final relation to the range, and why these are not human clinical values.
Answer and explanation

The response opposes the rise, so it represents negative feedback. The final 21 lies within the stated working range. The units and thresholds are invented for an artificial system; they do not evaluate a learner’s body. The model illustrates a relationship while omitting the complexity of living regulation.

Identify the initial rise.

Connect the activated output with the opposing decrease.

Compare 21 with the invented range.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 6

A student says “negative feedback is bad feedback.” Correct the terminology.
Answer and explanation

Negative describes opposition to a deviation. It does not label the process morally or medically harmful.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 7

Which illustrates negative feedback?
  1. A response counteracts the original rise
  2. A number is called negative
  3. Every signal stops
  4. The deviation is always amplified
Answer and explanation

A response counteracts the original rise

The defining relationship is opposition to the initial deviation.

Problem 8

A model quantity rises to 18 units, then falls to 13. Find the response-period change.
Answer and explanation

-5 units

13−18=−5 units.

Browse all courses